Design for Manufacture Report Fairy Excel Gel Bottle Freddie Jordan - Joe-Simon Wood - Kishan Mistry Freddie Jordan & Joe-Simon Wood
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Contents Abstract Introduction The Excel Gel Bottle Excel Gel Bottle Dimensions Material Selection Doser Lid Cap Bottle Joining Manufacturing Mouldflow Analysis Injection Moulding Over-Moulding Doser Skeleton Lid Blow Moulding Visi-Strip Neck Detail Printing Process Adhesive Finish Tolerances & Uncertainty Assembly Cap & Seal Filling Cap Fit Bottle Flip Fitting Doser Labels FMEA Dewhurst & Botthroy Analysis Assembly line production Costing End of Life Conclusion References
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4 5 6-7 8 9 9-11 11-12 13 14-15 16-18 19 20-24 25 26 27-28 29-31 31-32 32 33 34-35 36-39 39-40 41 42 43 44 44 45 46 47-49 50 51-52 53-54 55-56 57 58
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Abstract The following report looks to identify and analyse all relevent issues regarding Design for manufacture that surround the Fairy Excel Gel Bottle. Identification of these issues will arise by looking at the whole process of the bottles creation, from polymer granules, to the supermarket shelf and ultimately the comsumers home. Along the way various issues will be addressed with analysis and reasoning as to how they have been met, overcome, as well as alternatives that are available and possibly influence the DFM process for the better. The main points to be covered include Product prototyping, materials choice and processes, costing, asssembly, design appraisals, choice of tools, tolerances, dis-assembly and end of life.
Please Note that there are 3 people in this group. Freddie Jordan, Joe-Simon Wood and Kishan Mistry. The contributors are at the bottom of each page. Pages 1-58 written and compiled by both Freddie Jordan & Joe-Simon Wood. Pages 60-65 written and complied by Kishan Mistry.
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Introduction The Fairy Excel Gel bottle has been chosen for analysis from a Design for Manufacture aspect due to its complexity in polymer moulding as well as its award winning design. It comes in a unique compact bottle comlpete with it’s own dosing cap to prevent over usage. It also utilises the use of “visi-strip” technology and allows for interasting analysis as to its formation to take place. The cap design allows for one high precision squeeze of gel to fill the doser (Fairy non-bio website ‘10) which can then be palced into the washer. The dosing system and thick gel have been specifically designed to minimise wastage and give the user more control over drips and spills. The report flows by analysis of issues surrounding DFM being realised in a hierarchical manner. Identification is first given to the parts, following that how each material and process was chosen, the realisation of prototype products through to the batch production of each component with assembly and distribution. Access to the P&G prototyping plant in Reading was available and images documenting the product at the prototyping phase are shown through-out. The assembly line for this particular P&G product is in Europe, however assembly lines and figures surrounding the product have been ascertained and discussed.
Delivery of Raw Materials Processing of Materials
Bottle Formed
Assembly
Quality Control Points
Manufacturing
PP added to blow moulding machines
PP added to Injection moulding machines. Doser PP Part formed
PP Cap formed
Overmoulded with TPE Section
TPE seal formed
Doser Formed
Cap Formed
Bottle Filled Bottle, Doser, Cap clipped together Label Applied
Distribution
Bottles crated together for shipping Transportation to storage depot Transportation to shop Sale
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Fairy Excel Bottle Identification The bottle is available for purchase in two sizes a 962ml and 667ml version. The dimensions shown are for the 962ml bottle, however, the considerations are applicable to both versions.
Doser - PP, injection moulded section with TPE overmould.
Main Bottle - PP, Blow Moulded, with co-mould transparent ‘visi-strip’.
Label - Lithography Printed with small amount of adhesive.
Cap - PP , Injection Moulded
The following taken from Wired magazine January 2010 issue identifies all of the ingredients contained within the gel. Surfactants These are the negatively charged detergent molecules that do most of the cleaning. They have a water-seeking head attached to a grease-seeking tail and together they lift the dirt off clothes. Sodium laureth sulphate is a sustainable surfactant made from coconut oil. MEA dodecylbenzene sulfonate is an oil-based surfactant (MEA stands for Methylethanolamine H3CNHCH2CH2OH).MEA palm kernelate is a sustainable surfactant made from palm oil. The human body produces its own surfactants, which it needs in order to keep the lungs working. Propylene glycol Aka 1,2-propanediol, this helps to keep all of the diverse chemicals suspended in the gel. It is most commonly used as an antifreeze. MEA borate This keeps the gel slightly alkaline, thereby protecting the enzymes. MEA borate is also found in products such as Right Guard spray. Borate can be found in wood preservative. C12-14 Pareth-7 This consists of a chain of carbon and oxygen atoms and its function is to keep all of the other ingredients suspended in the gel. 6
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PEI-ethoxylate PEI stands for polyethylene imine, which consists of chains of carbon and nitrogen atoms. It is soluble because it’s an ethoxylate (aka acetate) derivative. It acts to prevent dirt and dye molecules that have been washed off fabrics from then depositing themselves on to other fabrics Water softeners These are needed to deactivate the calcium and magnesium ions found in hard water. MEA citrate is a salt of citric acid. It is added to laundry detergents because it surrounds the calcium and magnesium ions so they cannot form insoluble scum with the surfactants, or deposit on the washing machine as limescale. Trimonoethanolamine etidronate is also good at keeping calcium and magnesium from interfering with the action of the detergents. Etidronates are also used in the treatment of osteoporosis. Glycosidase and protease These are the enzymes which digest food stains. Glycosidase removes carbohydrates; protease, proteins Disodium distyrylbiphenyl disulfonate This acts as a brightener, absorbing UV light and reemitting it as white light so that white fabrics look whiter. Used in cosmetics. Fragrances Citronellol (roses) Eugenol (spices) Geraniol (roses) Linalool (sweet) Butylphenyl methylpropional (floral) Ingredients > Aqua > Sodium laureth sulfate > MEA dodecylbenzene sulfonate > MEA palm kernelate > MEA citrate > MEA borate > C12-14 Pareth-7 > PEI-ethoxylate > Propylene glycol > Glycosidase > Protease > Disodium distyrylbiphenyl disulfonate >Trimonoethanolamine etidronate > Geraniol > Sodium sulfate > Colourant > Butylphenyl methylpropional > Citronellol > Eugenol > Linalool Freddie Jordan & Joe-Simon Wood
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Dimensions of product
24.7cm
It must be noted that all measurements of the bottle are +- parralax and ruler uncertainty.
6.2cm
9.5cm
4.0cm
13.7cm
4.9cm
5.5cm
3.5cm
10.6cm
6,5cm 8
7.7cm Freddie Jordan & Joe-Simon Wood
Materials Selection The Fairy Excel Gel bottle consists of 5 components, 4 of which are formed from polypropylene in the Bottle, Lid, Doser and Ring seal for the silicone valve. The Valve and the ring seal come as standardised parts from an external company that specialise in producing seals, the other main body components are all formed using thermo-forming methods. The polypropylene material used for each component succumbs to range of different processes to in order to be formed. The Lid and Doser components are produced using Injection moulding each with specific needs to create the component geometry. The main body of the bottle is formed using a complex Extrusion Blow moulding process. This section of the report will highlight the manufacturing processes used to create these components and highlight the issues/considerations that reside when using the process. Materials The materials of the bottle were found by reading the Standard Polymer Identification that has been imprinted on the bottle as part of P&G’s legal measures to provide the consumer with recycling information on all of their products. The bottle and the caps carry the PIC (Plastic Identification Code) of 5 which according the Society of Plastic Industry coding system (introduced in 1988) suggests that the polymer is polypropylene. Doser An interesting feature of the packaging is found in the doser cap of the bottle, the cap has two-part material construction with a rubbery textured top against the rigid polypropylene body of the doser. The squash-able cap is made from a Polyolefin TPE material. TPE – Thermo-Polymer Elastomeric. The reason for using the Softer TPE in the component is because the compressible and flexible properties of the material allows the doser to withstand the knocks the component will occur while spinning around in the washing machine drum. It increases the products repeatability factor, because if the TPE top was a rigid material like the PP bottom of the doser then there would be a huge risk of the top of the component cracking and failing under stress, thus reducing the quality of the product.
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Reasoning for using a TPE material in the design: • Protect the internal components of the washing machine. • The compressibility properties, flexibility and shape retaining properties reduce the components chance of getting internally caught on within the washing machine drum. • The fact the top of the doser cap can be squeezed means that the when in use there is a higher chance that the detergent inside the TPE cap will be emptied, because the knocks and pressure of clothes moving around inside the washing machine drum will squash on the external TPE form and squash it internally forcing the detergent out of the cap and into the clothes. If the cap were a rigid PP like the rest of the bottle then there would have been a chance that not all of the dosed detergent would get a chance to the leave the cap. • Give the user a softer looking and “feel” aesthetic to the overall product. • Increases the components repeatability factor by providing a material that is shock adsorbent and impact resistant in the common areas where the component could eventually crack and fail. • Increase overall quality and usability of the cap. The following and values and mechanical information was taken from the CES Edu Pack 2009 software: The Mechanical Properties of the TPE Material: Mechanical properties Young’s modulus * 0.0157 - 0.0249 GPa Compressive modulus * 0.0157 - 0.0249 GPa Flexural modulus 0.0157 - 0.0249 GPa Shear modulus * 0.00527 - 0.00841 GPa Poisson’s ratio * 0.48 - 0.495 Yield strength (elastic limit) * 4.78 - 7.23 MPa Tensile stress at 100% strain 2.7 - 3.24 MPa Tensile stress at 300% strain * 4.92 - 6.64 MPa Tensile strength 4.78 - 7.23 MPa Compressive strength * 5.73 - 8.68 MPa Flexural strength (modulus of rupture) * 4.76 - 5.25 MPa Shear strength * 3.82 - 7.23 MPa Elongation 522 - 796 % Elongation at yield * 522 - 796 % Hardness - Vickers * 1.43 - 2.17 HV Hardness - Rockwell M * 2.64 - 4.34 Hardness - Rockwell R * 2.64 - 4.34 Hardness - Shore D 19 - 23 Hardness - Shore A 70 - 79 Fatigue strength at 10^7 cycles * 1.91 - 2.89 MPa Fracture toughness * 1.31 - 1.43 MPa.m^1/2 Mechanical loss coefficient (tan delta) * 0.08 - 0.1 Compression set at 23°C 25.4 - 26.7 % Compression set at 70°C * 36 - 38 % Compression set at 100°C 41 - 43.1 % 10
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Tear strength 49.8 - 52.3 N/mm (Taken from CES Edu pack Software). It also needs to be noticed that the structural properties of the TPE can be altered through the use of additives and stabilisers. These can increase the Shore hardness of the material increasing it rigidity and shape retain properties. The TPE material used for the doser has a Shore hardness of about 60D this allows for a convenient mix of rigidity, flexibility and elasticity. It is important for the shore hardness of the TPE to have sufficient rigidity because by being able to maintain and withstand its shape (support itself) there is a less of need for any other structural or support features that may need to be included into the design and form of the doser if the TPE was too flexible. It is important to note that structural support such as ribs and internal framing from a different more rigid material would increase the manufacturing processes. Lid/Cap The lid of the packaging is made from form a white coloured Injection Moulded PP, the same material as the bottom of the doser cap. The Lid is interesting because although the material is the same it does have a hinge. The PP used for the Hinged Lid and the Doser bottom are the same grade out of the whole product these components have the most rigid material. The reason for this is because the lid has moveable parts (the hinge) and it also needs to fulfil the function of creating a seal to prevent the product from running out all over the table. The PP used in the lid and the doser cap is a different shore hardness than the blow moulding PP used in the bottle. The reason for this is because the lid PP provides structural support to bottle, the lid need to be strong enough to hold the other components and the bottle contents when it is standing. Also the lid needs to durable enough to withstand the stress of the lid opening and closing during each use across the hinge. Interestingly the cavities for the cap sockets have been designed to work in parallel with the PP material costs. The lid sockets are drafted slightly to ensure that the slight flex and compressibility of the PP can be forced into the sockets and create a nice, tight, solid clip shut. If the cavities for the lid closure were dead flat and vertical the cap wouldn’t have a firm shut also the tolerances would need to extremely tight to ensure the secure clipping would work. By providing a slight draft angle to the cavity and the ribs to shut the cap, the lid can compensate for excessive use. Freddie Jordan & Joe-Simon Wood
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The PP used in the lid and cap has the purpose of providing a backbone and structural support to the complete package, the lid needs to withstand the stress and pressure of the package and product to provide a secure “stand”. The PP doser cap bottom needs to be rigid to support the TPE top. The PP material comes in a clear granulated form, the white colour is achieved by adding additive colourants known in the industry as “Masterbatch”. Masterbatch are coloured granules that is made up of very dense colouring, the batch is mixed in with the clear granules at a specific ratio to give the coloured PP. The ratio for the white colour and the PP is 6%, 6% of masterbatch to the PP. The advantage of using masterbatch from a manufacturing perspective is that a base material can be purchased in bulk and can be used with a number of different components and applications. It allows to the producer’s to keep a generic stock, if the material was purchased pre-mixed as a colour then there is a higher risk of waste material and excess material (non-usable). By using the masterbatch method and having a generic bag of base material, the company can effectively save money on investment because the base PP can be used on future components. In the case of the packaging the PP base material can be brought in bulk to accommodate the moulding of the Bottle and two lids. By having excessive “virgin” base material on stand by also caters for the uncertainty of component failures during the manufacture process. For example if there is a problem with the bottling progress and the numbers of 100% produced bottles are significantly less than the amount of completed caps and lids then there is an equilibrium issue with the amount of completed packages that can be made, to compensate for the product failures the base PP reserves from the Lid and Caps can be used to replenish the bottle stock. The only aspect that needs to change is that instead of a 6% ratio of white added to the PP a percentage of blue will need to be added. If the company used premixed bags then the colourants will already be added and if any issues do happen when production rates need to be comprised from each component then the company will be left having to re-order bags and wait for deliveries which could hemorrhage cycle times and in some cases halt production. Having the option to mix master batch with base PP allows for more flexibility. It also ensures that the company can maintain supply levels at all times, in the short term they will need to order more components i.e master batch material and base material but in the long run it allows the company to keep a stock of colours and an untouched “virgin” supply of material. 12
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One downside to using the master batch is that the colour matching and mixing ratios will be the responsibility of the manufacturing company and not the material supplier. Bottle The PP in used in the bottle is the same grade PP as the lid and cap, it is a grade that is can be utilised for both production methods. The only difference between the two materials is that they have been mixed with different colours and the wall thickness of the material in which the polymer has been moulded. The lid and cap are twice as thick to add structural support. The difference in the rigidity of the two component’s form is due to the difference in wall thickness and the manufacturing processes. The blowmoulding process of the bottle calls for a stretching tension on the molten polymer this means that the molecular structure of the material is succumbed to an elongation force across the bonds that weakens them increasing the material’s compressibility properties. Tensional force of the parison draw and the stretching of the air causes this. Alternatively, the Injection moulding process uses thermo forming polymers that put an immense amount of pressure on the material to form the component shape. The pressure stress on the material causes the molecular structure to form a tighter lattice (opposite to the Blow moulding Process) this means that the material’s chemical structure is denser creating a much more rigid and stable property. The stability is excellent for sue on the cap and the lid because they both need to be able to hold/support another component. The following and values and mechanical information was taken from the CES Edu Pack 2009 software: The mechanical Properties of PP are: Mechanical properties Young’s modulus 1.37 - 1.58 GPa Compressive modulus * 1.37 - 1.58 GPa Flexural modulus 1.33 - 1.61 GPa Shear modulus * 0.519 - 0.532 GPa Bulk modulus * 2.5 - 2.56 GPa Poisson’s ratio * 0.399 - 0.407 Shape factor 11.6 Yield strength (elastic limit) 31.9 - 36.4 MPa Tensile strength 22.5 - 33.5 MPa Compressive strength * 39.9 - 41.9 MPa Flexural strength (modulus of rupture) 34.4 - 51.4 MPa Elongation 52.1 - 232 % Elongation at yield 8.09 - 11.1 % Hardness - Vickers * 9.98 - 10.5 HV Freddie Jordan & Joe-Simon Wood
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Hardness - Rockwell M 59.8 - 75.8 Hardness - Rockwell R 94.9 - 104 Hardness - Shore D 64.4 - 69.3 Hardness - Shore A * 94.4 - 99.2 Fatigue strength at 10^7 cycles * 10.7 - 11.2 MPa Fracture toughness * 1.66 - 1.75 MPa.m^1/2 Mechanical loss coefficient (tan delta) * 0.0265 - 0.0278 Durability: fluids and sunlight Water (fresh) Excellent Water (salt) Excellent Weak acids Excellent Strong acids Excellent Weak alkalis Excellent Strong alkalis Excellent Organic solvents Excellent UV radiation (sunlight) Poor The material information charts from the CES Edupack software indicates that PP is very good chemically resistant material. The fact that PP is chemically inert against alkaline material is an important factor in the material selection process because the detergent that the bottle needs to hole has a PH value of 8.2. Material Joining. It is interesting to understand that the TPE material split in the doser component has been created by fusing two materials together as a single component there are no split lines or insert gaps, this is to ensure when the dosing cap is used (filled with detergent) the component is completely sealed. The fusing of the two different types of materials in the doser cap is a result of specific moulding technique known as overmoulding. Overmoulding allows for the thermo fixing of two molten polymers to heat up and adhere to each other to form one solid piece. The advantage of the having the materials fuse together is that from a production viewpoint there is no need to add another assembly procedure as in, if the component was constructed of two separate moulded pieces and inserted together. The overmoulding technique also reduces the design and development time because the design team do not need to worry about constructing complex insertion fixtures such as snap fits etc, they just need to provide enough surface coverage for the over moulded material to adhere to. If an insert method were used then the assembly process would take longer with a joining process needing to be added on the line as well as a component orientation and fitting process. Also, there would need to be extra quality checks to ensure that the component had been assembled properly. 14
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On a functional and user perspective the ability to have a fixed adhered joint reduces the risk in which a joining gap can be made. By using an insert the component adds another parameter to the form that needs to conform to a specific fitting tolerance. If there is a gap between the two material fixtures then there would be a high risk that while in use the component would fail, the TPE overmould could tear from PP under the load pressure of the detergent etc. There is also a possibility that the impact force the doser cap experiences in the washing machine may be enough to knock the two components out of place and alignment again adding to the risk of a gap and detergent leakage. By fusing the two materials together by heat and pressure there is an assurance that the components are permanently fixed. Arguably, this method of overmoulding could produce a weakened joint in the overall component compared to a being made from one material, however this can be comprised with the use of intelligently designed forms (see more on overmoulding and these forms in the manufacturing - injection moulding section).
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Manufacturing Thermo-forming Background Info The components that make up the full packaged bottle have been created from PP polymer using two different kinds of thermo-forming methods. Thermo-forming refers the process of taking a solid raw material (in this case granulated PP) and then heating it up into a molten liquid form and through the use of applying pressure and cooling, allow the molten liquid to solidify into a new specific shape. Materials used in thermo-forming processes can be categorised into two types thermo-setting and thermo materials. Thermo-setting materials are materials that can really only be shaped and converted into a solid form once, commonly thermo-set materials do not require the process of changing into a liquid state instead it involves process of compression. Compressing powdered materials to fuse chemically with each to create a larger solid. Thermo-set materials are typically used for products and components that need to withstand vast amount of heat or provide protection from potentially dangerous electronics/ wires. For the purpose of the bottle it seems logical to avoid using thermo-set materials because the heat resistant properties are not a top priority for the bottle. Thermo materials are materials that can be re-heated and formed a number of times after their initial formulation. Thermo materials have much better capacity as recyclable materials and reusable materials, which can aid the production and manufacturing process by allowing waste material to be broken down and put back into the cycle, thus reducing the amount of “loss” the product, will concede. Increasing the efficiency of manufacturing and material usage. The bottle uses PP which is a Thermo polymer. In-order to use the PP to create the desired components the polymer needs to change into a molten state (or semi-molten in-terms of Blow moulding) while in this state the material can freely “flow” between various cavities where it can cool and solidify into the final shape. In terms of the injection moulding process the “flow” of the liquid material is measured in flow rate, and it needs to be considered while designing the form of a component. The flow rate is determined by the time it takes for the PP to solidify and eventually cool. The flow rate itself is affected by many different parameters in the thermo-forming process the two most important considerations that need to be taken is the stability of the material in terms of it reaction to heat because this determines 16
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the material’s viscosity while it is flowing in it’s molten form. Another factor to take into consideration is the thickness and material of the mold (cavities) in which the material is flowing because if a material is expected to flow into a large surface area than it could physically cool at faster rate due to the heat energy transfer between the material and the tooling surface. The quicker the material cools the slower it will flow which will increase the risk of components not being fully filled by the molten material before it solidifies. Material + Surface contact = Heat energy transfer = increase in viscosity = reduced flow rate = solidification of material = mould not being completely filled. These facts need to be considered with these processes because they impact the overall mass range and section thickness available in each process. The diagram above right shows the impact of surface tension and heat loss on the filling/flow ability of a molten material. The bottom diagram also shows how the heat transfer creates slower rate by affecting the materials viscosity. In terms of moulding not adjusting or recognising these issues can lead to unfilled parts which contain areas of excess bulges. However there are ways to counter these affects which will be highlighted in the process section. On a technical perspective these issues affect the “lower limits” of section thicknesses and they a usually affect/ caused by the physics of flow. In modern manufacture most of these issues can be addressed at the CAD stage prior to any machining taking place, thus increasing the overall manufacturing efficiency and capability. The “higher limits” of section thickness and mass range in the thermo-forming processes are determined mainly by the overall geometry of the component. These “upper” limits are typically victims of material shrinkage. Shrinkage occurs because there is a lack of supportive mass for as the component fills during the manufacturing process. Shrinkage is caused by the heightening of the internal stresses in the molecular structure of the material, this can cause warping and deformation. It commonly occurs at “junction points” on the form, where there is a possibility of the material pulling in two directions.
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In regards to the Fairy Bottle the main shrinkage issue has been resolved through the use of adding the TPE piece on the cap. The material split creates a more uniform cross section around the top of the doser cap for the PP, thus reducing the chance of shrinkage. If the TPE material change and “capping” didn’t exist and the doser cap was made fully of PP then there would be a chance that when the PP filled and met at the top that it could shrink and warp because it is being pulled from all sides. The Bottle dose Cap resolves the shrinkage issue by moulding the PP with a Cavity and filling the cavity at two flow points, ensuring a more uniform filling and material flow is achieved. The cavity is then filled with over-moulding of the TPE. These section thickness limitation issues need to considered prior to the manufacturing set-up and processing because most of them can be resolved with simple form changes to the design of components or the way in which the tooling will work. It would cost too much time and money to learn through “trial and error”, most of these issues can be resolved with a flow work analysis via the Cad system.
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Mouldflow Analysis At the CAD stage mould flow analysis of how the bottle will react in the mould will take place. The images show various time of analysis that the bottle will undergo in simulation form before being moulded properly. Note - The images show parts which are not included on the bottle as P&G would not release that too us. They are simply for reference the understanding of the ways the bottle has been tested prior to manufacture. The top images simulates the filling flow of a product. It highlights in red the areas that the polymer reaches last. In the case of the bottle the injection moulding of the cap is estimated to take around 0.5 seconds. The second image highlights the warping of the product. The blue areas indicate the places that the product is least likely to bend in and the red, the most likely. For the bottle, the most likely area for warping is the centre section. This however, is delberate, so that the user is able to squeeze the contents of the bottle. The bottom image shows the areas which retain heat for the longest after the manufacturing has been finished. For the cap of the bottle it is likely that the area to cool first is the furthest from the injection point being the rim of the cap. Areas in the cap that also may cool slower are the thicker areas such as the ribs that are used to enhance the strength. Flow-mould has an impact on the overall cycle time of the product and is a constraint that must be considered when manufacturing the bottle. It defines how many can be produced in a certain amount of time. This will be discussed later in the report.
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Injection Moulding Process Injection moulding is used to create of the components for the fairy excel gel bottle, the lid and the doser cap in both instants the same injection moulding process is used but with a slight modification. The doser cap uses a process known as over –moulding or two-shot moulding in which a single component can be moulded from a combination of two different polymers. In terms of the doser it is a white PP and a clear TPE each with a different shore hardness. The lid component uses standard PP injection moulding however the tooling is interesting and slightly more complex in the way that the component is moulded with a hinge as a single piece. This method of manufacture is commonly known as moulding a “living hinge”. Aside from the specific such as the tooling and the second operation of over moulding the manufacturing process of both of the components is the same. The process basically involves the granulated polymer pellets to be liquid and force with pressure into a mould tool where the polymer cools and solidifies into a component. It works on the same principal as a syringe dispensing liquid, it forces it out. Description of Process. 1) Raw material in granulated form is placed in the hopper of the machine. In many cases the material has been left in a kiln to dry for some time before placing in the machine, this allows for any vapour on the pellets to be removed which could cause problems with the moulding process and finish of the part. 2) The material is drawn into the machine by a motor turning an Archimedes screw thread in the “barrel” of the machine. As the material is drawn in and turned it is exposed to a lot of grinding and abrasion stress which slowly causes the pellets to begin to change state. 75% of the heat for the material breakdown is generated from shearing energy of the mechanical screw. This reduces the amount of heat needed to be worked by the heating bands on the machine, the turning of the screw increases the machine’s efficiency. 3) As the screw continues to turn the granules are heated by external heating bands to temperatures around 250 degrees. There are typically 5 stages of heating bands around the barrel of standard Injection Moulding machine, the reason for this is because it allows the machine operator to control breakdown of material inside. 20
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4) Typically, bands are set up to provide a gradual rise in temperature to give an even dispersion of solid particles into liquid particles from the material. This ensures that the viscosity, thickness, mixture and general quality of polymer is maintained to the optimum standard for the part being moulded i.e. a more complex component may have deeper and complex cavities to fill, to ensure that the material could flow to these parts it would be needed to be heated to much higher temperature than a smaller component, this is to ensure the viscosity of material doesn’t increase and solidify at rate slower than the flow/fill time producing “shorts”. 5) The bands tend to heat the material up gradually and then at band 4 to 5 the material is taken to a peak point ( at 4) and dropped to the optimum flow temperature (at 5), the reason for this is because it causes the molecules to breakdown and begin to strengthen before being moulded, in layman’s terms it stabilises the polymer resin. In basic physics the temperature drop is used to initiate the start of the cooling process in which structurally the molecules will begin to form a dense lattice (when it solidifies). The “heating ramp” forces this process to initate early allowing for much more dense structure and an overall stronger part. 6) Once molten and the material has reached band 5 (the nozzle) it can be held to allow pressure and material to build up before being forced through the nozzle into the mould of the tool. All the while the machine will still be drawing material from the hopper to add the pressure. 7) The forced material is pressured into the mould, the force should allow the material fulfil the mould cavities. As the material travels through the mould it is constantly cooling down and becoming viscous which as stated before can cause some “lower limit” issues in which the flow rate is reduced increasing the possibility that the mould might not fill properly. 8) Once the material has been pressured into the mould and solidified the tool can open exposing the component. Then an pneumatic arm on the other side of the tool (non-injection side) ejects the component from one half of tool. The tool then closes together and the process begins again in another cycle.
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The injection moulding process can generated some issues with getting the material to fully fill the mould. To increase the mould fill success rate a number of different techniques can be applied to the injection moulding process at each stage that can contribute to the overall pressure used to force the plastic. A good example of this is the use of a “switch over point”, “hold pressure”, “clamping pressure” and “back pressure”. The hold pressure is the point that the molten material is held at the nozzle before being injected, while material is still being feed into the machine. It is the action of building up a bulk of material before release. The advantage of altering the hold pressure is that it allows for more force to build up in the nozzle before being released into the mould thus increasing the pressure of the material filling the mould force filling the mould allowing the material to become more compact and meet the desired tolerances in the final component. For example if there wasn’t enough pressure there is an issue that allow the material may fill the mould it might not fill it effectively enough to produce the required density and structural qualities needed to support the component increasing the risk of material shrinkage and warp. The switch over point is the point in which Polymer in the nozzle is being used to create a hold pressure and where the injection pressure begins. If there is slow switch over point and a high hold pressure the material will be extremely dense before being injected which could cause overfilling and bulging on the final component. If the switch over point it high and the hold pressure high then there is an issue with that not enough injection pressure will be used to force the material to make a full component. The purpose of being able to play with the “switch over point” of the material in the nozzle, is so that the an optimum balance can be achieved. Clamping pressure regards to the pressure imposed by the tooling on the Injection moulding machine. By clamping the tool tighter when the material begun to fill there is a chance that added tooling pressure can compress the polymer material to spread and fill more in the tool. It is like the same effect you get when squash some plasticine in your hands the more pressure you add the further the plasticine spreads. Back pressure is the slight added force imposed on the screw, it is not a rotational pressure but a horizontal push to add to the shearing of the pellets in the nozzle. 22
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Tooling Anatomy: The injection moulding tooling is a tool that consists of two halves a Cavity and a Core half. The cavity is the side of the tool in which injection points are and where the sprue detail and component detail is machined and determined. The core is the half of the tool in which the closes the cavity side in, the core commonly has a protruded surface that needs to meet and align with the cavity. The cavity is the fixed side of the tool and contain no moving components only the indentation of component machined into it for filling. The reason for the side not contain any moving fixtures is that it is critical that this side of tool needs to align with the nozzle to allow polymer to flow into the tool and by having moving components on this side you are increasing the risk of something mis-aligning the tool through improper movement. If the tolerance on the nozzle is out by the thickness of the molten polymer then there is a huge risk of leakage and material spillage. The core side however, is constructed from a number of layers. The complete sandwich tool is know a as a bolster, typically the bolster will house the ejection moulding pins to remove the component from the tool. The ejection pins are connected by a separate pneumatic arm on the other side of the machine and the pins are aligned to travel through the core of the tool. The pin are pushed through the tool to force the product out when the tool is open. The tolerances on the ejector pins need to be carefully considered because if they are out by 0.001 of a mm there is a high chance that they will leave a witness mark on the product. The reason for the tool being split into tool is two fold it allows certain geometries of components to be moulded and it also allows undercut components to be released. The core side is usually associated with all of the moving components because then all the tolerances and “shut=Off” geometries are kept to side of tool making it easier for the engineer to adjust, alter and set up. During the process the tool works by closing, taking the material, applying “clamping pressure” to ensure filling and the opening to release the material. As the tool opens the eject pins are forced forward pushing the component out of the mould.
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Eject pins are needed because as the polymer material solidifies and cools in the pressure it compresses which causes an issue on areas of tight angles and undercuts and steep sides because the material can “hug” and get itself stuck in the tool. The ejector pins help force the component off the mould and also ensure that the component isn’t left in the tool for too long to cause it contract and “shrink” too much. One common problem with tooling and injection moulding is to do with the heat generated from the mechanical energy output of the opening and closing of the tool while it has been continuously running. The running of the tool will constantly generate heat which will affect the cooling and solidification of the polymer in the mould to produce a fully rigid component. To counter this problem some tools need to be equipped with cooling mechanisms. Cooling occurs through the use of running temperature controlled water through other internal cavities of the tool. By cooling the tool you can increase the rate in which the molten liquid will turn solid which is great way to compensate for the generation of heat from continual use. Cooling allows injection moulding machines to run effectively for 24/7. Common production tools are machined from tall steel for their high strength. Tall steel ensures that the tool can have a long life before wear occurs. Because the tool is constantly opening and shutting on itself there is huge chance that it can begin to wear away which can cause deformation of certain areas of the tool. This internal wear can distort the tolerances, the wear can also effect the surface finishing of the internal tooling. To counter wear the tool can be chemically enhanced with polishing processes and electrolysis plating processes in which a harder material can be impregnated onto the tool increasing its durability and wear-ability. The tool manufacture itself is commonly created by using subtractive machining methods such as CNC machining. If a higher tolerance is need on parts that other processes such as EDM can be used, Electrode Discharge machining is a very intricate process in which the material is eroded away from the steel. CES Edu Pack 2009 describes this process: “In ELECTRO-DISCHARGE MACHINING (EDM) the work-piece is held in a jig submerged in a dielectric fluid such as kerosene. A power supply generates rapid electric pulses that create a discharge between the 24
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work piece and an electrode (a shaped graphite form) at the point of which the two are closest. The discharge creates a plasma causing the melting (and probably the vaporization) of a minute bite of material, slowly eating into the work piece; the debris is swept away by the dielectric fluid. EDM is remarkable for its ability to shape difficult materials, provided they are conductors, and do so with great precision.” Tooling draft Angles. The Fairy Non Bio Gel injection moulding components have been designed for effective production by having rounded drafted edges. The form of the doser cap and the lid cap have little to no straight edges this is because straight edges make the component extremely difficult to “slip” off the tool after injection. If the cap and the lid were 90 degree angled edges with sharp corners, there would be a huge risk of the components getting jammed in the tooling when the material shrank and tightened. Draft provide a run way to slide off of because there is less surface area for the component to make contact within the tool when it opens unlike having a deep straight cavity. Tooling issue – filling correctly To increase the quality of flow of the polymer the tooling can also include venting marks with allows air to escape from the pressurised cavity of the tool. Without an air release pockets can be formed in the polymer as it solidifies which can produced distorted shapes and brittle weakened material. Venting on hard to reach areas also aids the flow of the polymer because the air would be racing to be released through pressure. Over-Moulding Over moulding is the process of adding two different materials on to one component. In terms of the Fairy bottle the doser uses the method of overmoulding to give the benefits of TPE and PP combination. The overmoulding process works the same as injection moulding except instead of injecting one material the process is repeated a second time with a second material. The doser is manufactured in two separate components, this means there needs to be two tools for one complete component.
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Doser Skeleton. First of all a “skeleton” is moulded, this is the PP base of the doser. The skeleton base consists of a number of features and considerations in its manufacture. One of the main considerations is the supportive lip for the TPE overmould to latch onto. The lip provides a guide and added surface area for the TPE fuse and weld to, with out this ledge then there would be an issue with a weakened joining of a flexible and rigid material. The lip also acts a flow guide for the TPE when it is eventually injection moulded. If the lip wasn’t present than the TPE would have nothing to flow into and would cover the whole component. The skeleton PP base is moulded from two injection points which are controlled by a T shaped sprue. The sprue creates an injection flow gate that allows the polymer to flow evenly down either side of the component allowing for much more formulation production, reducing the risk of “short” and uneven thicknesses and forms. The sprue is trimmed away from the component to allow the gap for the TPE to fill. As well as the lip two small “bracers” are included on the lid of the dosing cap, these little notches have two effects on the product, one is that it provides the component with its two flow points to ensure and even spread and flow of material and secondly it acts a structural support for the TPE to prevent it from sinking on itself, the braces keep the overmould up and stable. They also act as another gripping factor to the TPE to ensure a strong binding and fusion has been achieved. The TPE top is added by taking the skeleton PP component and trimming off the sprue leaving on the white base and the opened cavity hole of the component with the two bracers protruding out. The component is then loaded onto another tool and the injection process is repeated except with TPE loaded into the machine and with the skeleton PP part already in the machine tooling. When the TPE polymer flows into the mould it will flow into the open cavities of the top of the doser and then instead of flowing into the bottom half of the doser it will flow into the contact surfaces of the inserted PP piece. The molten TPE will then fuse with the PP surface creating a solid join. The TPE then cools and the tool will open up and eject the full component. The Doser has been effectively designed well for 26
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manufacture because it has surface lips and shuts off on the base/skeleton PP component to ensure that the TPE will not overflow. It also has structural bracers to ensure the TPE will maintain its shape and adhere effectively. It is interesting to see that both the tools for the skeleton PP and the TPE overmould have the same ejector pins. The reason for this is that tooling can easily managed at the CAD and development stage it also maintains consistency through moulding process by ejecting from the same place there are no issues that could affect other areas of the form. Internal/External Detailing. The Doser component does have some internal detailing on it that is interesting because it resides on one of the vertical surfaces of the cap. To achieve the detailing of the numbers a movable internal piece of the tool is used that pops up and down. The reason for having a moveable piece that pops up and down is because it allows for the writing details to emboss out of the struts without risk of the undercuts of the tooling causing the component to get stuck. The moveable piece of the tool has been designed to pop out as the tool begins to open this ensure that the polymer which has filled is still hot and flexible enough to come out and not get stuck. The popping component of the tool also forces the doser cap up from the tooling surface making the ejection easier. The white PP base also has a very matte colouring and texture, this is achieved by adding extra finishing techniques to the internal cavities of the tooling. One way to get a matte effect is to coat the tool with a vapour blast of sand. The surfaces that require a matt finish are exposed to a high pressure blast of small abrasive grit. The Lid The Lid component is also injection moulded however it differs from the doser cap in the way that the tool needs to compensate for the fact a hinge is moulded with the component as a solid piece. The advantages of moulding a living hinge in a component is that it doesn’t require any assembly during the production line and that the whole component can be produced with just one process. The lid components already utilises some of design issues involved with designing a component that is optimised for injection moulding processes, such has having a rounded (no sharp corners) draught angled form that makes it easy to eject from the tool. The lid also makes use of location notches to help locate the lid onto Freddie Jordan & Joe-Simon Wood
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the neck of the bottle, it also has under hangs that have been put in place to make the bottle a complete snap fitting package again making the assembly extremely easy to be integrated into automatic machines. The flip of the lid component makes use of structural ribs to brace the form and shape of the flip top. This is to reduce the amount of sinking that could occur from poor mould flow in these areas while moulding. The ribs also provide a security support in that it ensures if the consumer puts any pressure on the lid it is less likely to snap or crack on the extra weight. The lid is moulded with the flip top open this ensures that there is no fusion of the material and that the thin wall thickness that makes the hinge is easily maintain and controlled during the mould process. What is interesting in the cat that the lid need to open is that the lid has it own insert. The reason for the insert is because it allows the component to have high quality matt “sand blast� finish on the core side of the tool as well as maintaining the matt finish on the external base (through the sand blasting of the cavity tool). The thin wall section for the hinge is created by the lid insert having a slightly raised surface causing the material to flow over at thinner rate. The insert also ensures the hinge is not damaged during ejection and that whole component is supported while cooling. The tool is moulded the inside out, in the way that the lid component is moulded in the opposite direction to the main base . The external matt finish of the base is moulded in the cavity tool yet the external matt finish of the flip lid is moulded in the core, this is achieved with the use of an insert. Shown in centre picture. PP is a great material to be used for living hinges because it has good fatigue resistance and can be moulded into thin sections, which are durable and stable.. Living Hinges provide a low cost, low maintenance way of producing hinged components, simply because the hinge doesn’t need to be assembled in anyway its all one piece. The edges of the flip lid have been designed to have a slight angle to them; the reason is to do with fitting and the tolerances involved. On the inside of the flip lid there is also a circular clip element which is slightly drafted (to compensate for wear), the draft circular form allows a location clip for the nozzle of the bottle to sit in. The 28
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edge of the flip lid and also slightly draft to increase the surface contact with the rest of the lid creating a much tighter seal and flexible tolerance differentiation as compared to a straight edge. This is essentially for producing a flip top that doesn’t flip open every-time you move the bottle. To reduce sprue and waste material “Hot tips” can be used with the injection moulding process. Hot tips are a means of keeping the polymer still molten in the nozzle while the tool opens it prevents the sprue from hardening and being ejected with the component. Hot tips allow for constant moulding because it keeps the polymer at the optimum heat prior to the last point of injection, allowing for a constant molten flow. Blow Moulding Process Blow-moulding is another thermo-forming process and it is used to create the hollow body of the bottle. Unlike Injection moulding blow moulding uses air pressure to force material around a die, the air pressure forces the material to form internally against the walls of a hollow mould thus allowing for hollow components to be produced. However similar to injection moulding the process does involve the breakdown of granulated material into molten liquid, the only difference is that the molten material is not just forced into a mould a semisolid piece, the material needs to be hollowed. The process has been chosen for the production of the bottle because it is the quickest and easiest way to produce a hollowed component out of polymer. Other techniques such as rotational moulding would not take to long and would incur a lot problems in trying to maintain a uniform wall thickness all around the bottle. Blow moulding simply uses the pressure of the air-flow to determine the wall thickness and formation of the bottle. The material from the machine is hollowed through the use of a die, the die sits on the end of the injection/ extrusion nozzle. The die can be either a diverging or converging shaped die depending on the size and form of the neck of the bottle. In the case of the Fairy bottle a converging pin in the die forcing the plastic to form around and flow outwards,. The hollow section of the plastic is maintain by a small amount of air blowing down the internal center (this ensures the polymer doesn’t touch itself on the internal walls causing it to flatten and collapse). The hollow stream being produced by the die and pin from the extrusion nozzle is know as a parison. Freddie Jordan & Joe-Simon Wood
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The die and pin can be moved in the manufacturing process to produce a fluctuating parison, this is useful when bottles have irregular wall shapes that require more filling in certain areas. The parison is run out of the machine down to a length that is substantial enough to cover the tool. The tool is then clamped shutting the parison internally. A hot knife cuts the parison from the extrusion nozzle and the whole tool shift over to the blow pin which forces it self into the neck of the tool and blows a forceful amount of air into the bottle causing the parison to bloat and expand all around the edges of the tool. The material cools and solidifies with the air still adding pressure to the material forcing on the walls. Once the material has hardened the blow pin pops out of the tool and the tool opens releasing a fully hollow bottle. The process then repeats with the open tool shifting back to the next parison and closing on it. The form of the bottle’s neck has been kept relatively simple in design and the development team have made the bottle a snap fitted product. The benefit of having a simple neck is that the actually bottle manufacturing process can be simplified to the use of just Extrusion Blow moulding. Typically, most bottles with threaded necks for twist caps (such as drinks bottles) require very high tolerances and detailing around the neck to ensure that the angles of the thread, the size and the quality of the thread are moulded to give a secure fit with the opposite thread on the cap. To ensure that these tolerances are essential generally extrusion blow moulding cannot be used on its own accord because the creep issues and uncertainties that crop up with trying to mould from a moving parison. So to counter this issue, drink bottle manufacture consists of using both an extrusion blow-moulding process and an injection moulding process to create the one bottle via Injection Blow Moulding. Injection blow-moulding has the benefits of producing a higher surface finish around the neck of a bottle especially when a thread is required. However Injection blow-moulding is a two-step process in which it takes an injection moulded “perform� and heats it up while applying air pressure to expand the perform into the mould of the bottle. 30
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The high tolerance of the neck is achieved by using injection moulding to create the pre-form then blow moulding is used to expand the body. The pressure from the injection moulding process forces the material to flow more efficiently around the neck area than it would of done in a typical Extrusion Blow moulding technique. The Fairy Non-Bio gel bottle however has been designed with complications of neck manufacture in mind and as such has developed a relatively simple snap-on feature. This means that the bottle can reduce the standard manufacturing time of a threaded (typically capped) bottle, because the bottle doesn’t need to compensate for tight tolerances it doesn’t require the need of the injection moulded pre-form process. The simple neck design means that the bottle can be easily integrated into the Extrusion Blow moulding technique which halves the typical process time, tooling time, tooling costs and run costs of a standard “threaded” bottle; Mainly because it only requires one continuous process to be made, as opposed to two. By considering the manufacturing aspects at the design stage the Fairy excel Bottle has innovatively managed to use Design for Manufacture to reduce costs and increase production, it shows that looking into these details pays off! Visi-strip Process. The bottle itself has an added feature on it, in the form of a “visi-strip”. The strip has the functional role of providing the consumer with a window into how much detergent is left in the bottle. The strip itself is produced by introducing another injection nozzle into the machine, the second nozzle add another material just before the parison is formed at the extrusion head. The parison is then extruded with a strip down the side of it. The second strip of material is integrated into the parison at timed intervals this ensures that the strip doesn’t flow all over the bottle but only in a specific region i.e. not all up the neck. The bottle is then blown in the normal away expect with the clear and blue pp stripped parison. The reason the strip maintains a uniform thickness around the bottle is due to the different grade PP used and the fluidity of the clear against the base blue. Also the strip has been geometrically placed at the point on the bottle where the least amount of stretching will occur, down the witness lines of the tool (tool joining) and not on the larger rounded surface.
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The key to maintain the visi-strip thickness is to allow the position of the strip to be at the least stretching point of the bottle i.e not the front and back of the bottle’s surface where most of the contours of the form occur but on the sides, which remains quite uniform from the top to the bottom. Neck detailing/testing and prototyping. During prototyping the tooling for the bottle is not just a single dual sided symmetrical closure. The tool has been split into section which each have the capability of including numerous inserts in them. The reason for the inserts at the prototyping stage is to allow for a quick change of geometry for development which needing to machine new tool for iterations, the tool is commonly split into the middle (main body) Base (bottom) and Top (thread/neck). During prototyping insert can be produced using advanced metallurgy prototyping tooling such as metallic laser sintering, like an EOS machine. SLS metallic matching is an additive layer technology that allows extremely high detailed components to be fused from metallic powder, these components can include under hangs etc. The SLS process is excellent in producing intricate insert that are needed to mould detailed neck components. The splitting of the blow-moulding tool means that the new insert can be dropped directly into the tool and moulded almost immediately. The splitting of the tool and usage of inserts are also used on a production level because it provides another way of countering the effects of tooling wear. By splitting the tool if a neck tolerance begins to wear fast all that is needed is a quick dismantle of the tool and a replacement of the insert, not a complete replacement of the tool. TO replace the tool completely would mean having to machine can complete new tool from scratch when it is much easy to just replace the worn insert with a new one. Like injection moulding, the blow-moulding tool can also be plated, polished and sand blasted to provide a range of different surface finishes depending what is required. The Fairy bottle tool has been lightly sand blasted to provide the bottle with a matte “soft� feel effect.
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One of the issues with Extrusion blow-moulding is that a lot of flash is produced around the neck area and along the sealing line sat the bottom of the bottle. This excess material needs to trimmed off after being produced and this is why there a re large irregular witness line in these areas. In production the flash can be taken off by machines by tumbling or just die cutting / grinding presses. The waste material however can be recycled and ground down. Printing Process The labels for the bottles are printed onto sheets of paper via a process known as rotogravure printing. The process involves an image being etched onto a metallic sheet that is attached to the surface of a printing drum, the drum then rolls around through a coloured ink as paper is fed. When the ink filled surface of the drum rolls round it leaves an imprint on the paper. The printing process require that each colour on the label needs to be printed with its own drum and specific coloured ink well which means for the Fairy label the paper needs to pass through at least 5 drums to meet all of the coloured specs. Because rotogravure printing requires rollers it can be easily integrated into a production line and is extremely fast to keep on continual production. Once a full sheet of labels have been printed onto the paper’s surface, the sheet is rolled over layer of adhesive spread that coast the underside of paper. The sheet is then rolled into a die cutting press that has a die cutter plate matching the geometry of the oval label. The die cutter then applies clasp down onto the paper forcing the paper cut. The best way to understand this process is to think of a cookie cutter impressing itself onto cookie dough. The excess waste paper is removed leaving only the oval labels to collected and got ready for the adhesion assembly to the bottle.
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Adhesive application Consideration as to the nature of the adhesive used to hold the label on each side of the bottle must be noted. As well as the bottle shape, colour and finish, the label is an important factor in the sale ofthe product. Below is a table of synthetic sealing adhesives.
Adhesive
Description and applications
Anaerobic
Single Component, thermosetting, acrylic-based. Cures by free radical mechanism at room temperature. Applications - Sealant Structural assembly. Two- Component thermoset, consisting of acrylic-based resin and initiator.hardener. Cures at room temp after mixing. Applications - Fiberglass, sheet metal in aircraft. Single component., thermosetting, acrylic, cures at room temp on alkaline surfaces. Applications - Rubber to plastic, plastic and cosmetic cases. Includes a variety of widely used adhesives formulated form epoxy resins, curing agents, and filler/modifiers that harden upon mixing. Applications - Aluminium bonding applications, lamination of wooden beams etc. One or two components, thermosetting liquid, based on solicone polymers. Curing by room temperature vulcanisation to rubbery solid. Applications - Seals in cars, gaskets, bonding of plastics.
Modified Acrylics Cyanoacrylate Epoxy
Silicone
It is most likely that the label on the bottle has been stuck on using an epoxy adhesive. The adhesive would be be added after the paper has been printed onto. The paper would then have to be cut and stuck onto the bottle. This is covered in the next section on die cutting. Surface preparation In order for adhesive bonding to succeed, part surfaces must be extremely clean. The strength of the bond depends on the degree of adhesion between adhesive and adherend, and this depends on the cleanliness of the surface (Groover ‘07). In most cases. additional processing steps are required for cleaning and surface preperation, however, in terms of the Excel bottle given the way it is manufactured (blow moulding) no surface cleaning will be needed. The surface produced by the process is clean enough to ensure the label sticks properly. Application Methods There are many techniques that can be used to apply adhesive to a product, such as, Bushing, Flowing, using manual rollers, silk screening, spraying and automatic applicators. In the case of the bottle the most probable method is the use of automatic rollers. Diagrams shows how labels feed through rolling machine and adhesive is applied (adapted from Goover ‘07). Label
Backing Roll
Coating Roll Adhesive
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Advantages of bonding the label in this type of way is that many can be completed at the same time. The product can then be cut and applied to the bottle. The process is applicable to a wide variety of materials can be applied to different sizes of label for the different bottle, covering of the entire surface is quick and easy. Limitations include weak bonding. The bond is not strong enough for securing any items that need strong bonding. The label to the bottle just needs to be stuck on. It can be removed if pulled at, but it is not necessary that it is secured in a manner that it is not removable. The correct adhesive must be used and the cleanliness of the surface myst be maintained. Consideration must also be given to the curing time. In the case of the bottle this is not long as the amount of adhensive is small.
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Surface Finishes A surface is what we touch when we hold an object (Groover ‘07). Surfaces are important in any product. This is for a number of different reasons 1) Aestehtics - Smooth generally being mroe appealing 2)Safety - Protection of product 3) The frictiomn and wear of a product can depend on surface finish. 4) Mechanical and physical properties eg surface flaws. 5) Assembly of parts - a roush surface will be darher to fit through a hole than a smooth one. In the case of the Surface finish of the Excel bottle, surface fnish has been considered very carefully. Here is a breakdown of the finishes Doser - PP - Smooth on outside & inside TPE - Matte more textured surface finish. Cap - PP - Smooth on outside More of a matte finish on the inside. Bottle - Smooth on both inside and outside. When considering the surface finish of the bottle the characteristic of the surface must be indentified, surface texture and integrity can be discussed and the relationship between the manufacturing process and the resulting surface. The surface of a product depends heavily the manufacturing process it has been through. There are way of finsihing product after manufacturing, eg, spraying a car. However, in the case of the bottle how it is manufactured will give rise to the surface finish. Since the processes of manufacturing the bottle and doser include injection and blow moulding.the surfaces can be determind by the finish of the moulds. The moulds have to be highly polished, and the smoother the inner sections , the smoother the outside of the bottle and doser will be. The image to the left showing the mould for the bottle demonstrates how the inner section has been highly polished resulting in a smooth finish on the outside. Although appearing smooth and feeling smooth, on a microscopic level the surface texture is likely to be uneven. The diagram below depicts this. (taken from Groover pg.80 ‘07).
Crater (flaw)
Lay Direction Crack (flaw)
Waviness height Waviness spacing
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Surface texture consists of the repetitive and/or random deviations from the nominal surface of an object which is defined by four features 1) Roughness - Small finely spaced deviations fromthe nominal surface. 2) Waviness - deviations of a much larger spacing, usually due to work deflection, vibration, heat treatment etc. 3) Lay - the prominant direction or pattern of the surface texture. 4) Flaws - irregularities the occur occasionally in a product. (Points taken from Groover ‘07). Surface roughness is measureable. Using stylii (either spherical or truncated) it can be measured. Although we were unable to get hold of technical data such as this for the excel bottle, general test that the product would have undertaken before going to market would have been to check the surface finish. An example of possible roughness finish has been shown here, it is an extreme case of irregularity however depicts the necessary points to descirbe surface roughness. Vertical deviations
Actual surface
y
Nominal Surface
x lm P&G drawings for the surface finish of the bottle would show engineering drawings with the surface finish evident. An example here, taken from Groover shows how this would be represented. Maximum waviness height Maximum waviness width. 0.002-0.5 0.030 Maximum roughness 63 Minimum roughness 32
Cutoff length Lay symbol max roughness spacing
0.010
Lay Symbol
Surface Pattern
X M C R P
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Description Parallel to line representing surface Perpendicular to line representing surface Angluar in both directions to line reprsenting surface Multidirectional Circular
Radial relative to centre of plane Lay is particulate, non-directional or protuberant.
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Surface integrity (the study and control of subsurface layers) in terms of the Excel bottle is something that needs to be considered however is not as important as the outside smooth surface. After taking the bottle apart, it can bee seen that in the inside there are surface blemishes tha are quite obvious. Under the rim there is a large portion of plastic that is untrimmed. This is of no significance in terms of the outside of the bottle but does mean that the top inner surface is slightly thicker. For the placing of the cap onto the bottle during assembly this is essential. Thsi means the inside unfinished plastic gives the bottle the rigidity it needs, so in terms of DFM, sometimes flaws are helpful if you can predict systematically where they are going to be and use them to your advantage. When shining the bottle into the light as the seond image shows, the surface flaws can be seen. Running down the centre of the bottle the plastic is slighlty thicker, this is where during the blow moulding proccess it has merged toghet more tightly where the 2 halves of the mould join. This once again give rise to a stronger mid-section which is usefeul for bottle durability.
Visi-strip
Around the area where the ‘visi-strip’ is flow lines can be seen. From the outside these are impossible to see, but looking closer there is a pool-like finish. This is reminisant of a circular lay type finish as shown in the table on the previous page. The diagram below depicts this.
The depiction highlights how the flow of the material has formed around the visistrip. The outside smooth surfaces are not affected by this, due tot he polishing of the moulds. but it is something to think about in terms of DFM issues on the inside of the bottle. Futher issues surrounging the surface finishing are those of the sprue marks left on the TPE section of the Doser, along with the type of PP (07) that has been moulded into the top section. These give slightly raised profiles and the injection point being direcly on top of the TPW section means that it cannot be hidden and a smooth surface finish on that part cannot be maintained.
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Ways of measuring surface roughness include 1) Comparison with test surfaces, 2) Stylus electronics 3)optical techniques. Tesing by comparing the finish of the bottle to others that have been produced is the easiest way to measure if the standard is high and consistant. Howver, when producing the bottle for the first time more accurate measurements may need to be taken, to ensure all that are manufactured there after are of the same quality. The use of stylii are the best way of measuring finish. A profilometer can be used which may contain either a spherical or a truncated stylus, typically with a diamter of 0.005 mm (Groover ‘07). The sylus can be moved across the product surface horizontally and as it does so, it measure the vertical imperfections. The diagram below depicts this. Transversing direction
Vertical motion of stylus
Stylus tip
Surface
Optical techniques include testing the light reflectance of the surface, light scatter or diffusion. They are generally only used on products when surface contact is undesirable. In the case of the bottle the best way of testing the surface would be with the use of the stylus. The finish is not overly important as the product is only used fr containing a substnace and thrown away as soon as it is used, however integrity needs to be maintained to refect the quality of the brand. Tolerances & Uncertainty Through out the manufacturing and assembly stages, tolerances of the materials used along with uncertainty of their measurements must be considered. Overleaf various measuresments of the bottle have been undertaken. It must be remembered however, that these measurements are subject to the accuracy of the micrometer. The tolerances have to be considered in the snap fitting of the cap and the doser to the bottle. If the plastic shrinks too much, it will no longer fit. The moulds have been designed with this in mind. These issues have been mostly covered in the previous sections of manufacturing and assembly. The pictures have been taken to clarify the understanding behind tolerances and fits and to demostrate the ability to realise the most important, in terms of the bottle manufacturing and assembly.
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Assembly Process - Hiearchical Task analysis of how bottle is assembled. The bottle consists of 5 components. Due to the nature of the bottles shape and its contents various DFM issues arise during assembly. The following HTA looks at giving a quick overview as to how each part is put together during the assembly stage.
1
2
3
4
5
6
The images above show the basic assembly procedure for the product. Each stage is detailed below 1. Seal to encase fluid is placed into the cap. 2. Main bottle is orientated parallel with filling nosel and contents filled. 3. Cap is pressed onto bottle. 4. Bottle is flipped 5. Doser is added to bottle. 6. Label is applied and bottle is complete. The following pages look to detail all DFM issues surrounding each stage of the assembly cycle addressing the complications faced along the way. It must be noted that the assembly of the product was unable to be viewed due to the assembly lines being located in Europe. Assumptions will be made based on the nature of the product as to the most accurate way of assembly.
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Stage 1 - Cap & Seal Assembly To begin with the silicone seal is inserted into the cap. For this stage to occur the caps lid must be closed, this is completed by factory workers which, at the stage of ensuring the lid is closed also check the quality of the lids manufacture. The assembly machines first of all orientate the cap to sit flat on the surface of the conveyer. The lids orientation on the X-axis is not important, so long as when it passes by the instrument used to force the seal in they are parrallel. This is shown by the diagram below.
The seal is held in place and as it meets the central section of the cap is pushed down with a force of around 100N. This causes the hole it is being pressed into to flex out, allowing it to become sandwiched. The nosel that was holding the deal is removed and the product continues down the assembly line. Mulitple parts can under-go this assembly at once, in the case of the Fairy Excel Gel bottle 6 can be completed at once. The time for this processes is approximately 5 seconds, from the time the part is orientated to the correct angle and placed at the correct spacing, to the deal being injected and the part being complete. This insert is critical to the success of the product. the image shown to the bottom right illustrates what can happen if the part is not sealed properly. This was a test that was carried out to view what would happen should the seal be placed in not aligned properly.
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Stage 2 - Filling of bottle During the filling stage because of the design of the product it has to sit in a puck. Shown in the image below is the bottle as it stands on it flat edge. This edge stands the bottle at a 60 degree angle to the horizontal plane. This means the the filling nosel which is perpendicular to the horizontal plane cannot effectively fill the bottle.
Parallel
60 degrees
As in the previous stage the bottle is to be orientated first into its correct position. This is done by all bottles being stood onto a conveyer belt, as the belt moves around they are moved by runners into the correct position. The bottle then drops down into a puck, and the rim is not parrallel to the horizontal plane meaning the nosel can inject the gel.
From a DFA perspective it may be possible to insert the nosel into the product regardless of the 60 degree angle, however, the product ,due to the pressure of the gel entering is likely to topple. It would be right side heavy and become unbalanced. It is for this reason the assembly process is not completed like this.
An important DFA aspect to account for is the accuracy of the nosel when flling the bottle. The nosel must be right over the rim of the bottle, directing the gel straight down, otherwise the assembly must be haulted for spillages. It is also important to note the flow rate of the fluid into the bottle. In this case each bottle (962ml) takes around 5 seconds to fill. With the total time from moving the bottle in, to shifting it out around 8 seconds, due to the nosel havign to be inserted and taken out again. High pressure is used and the use of the piuck means the bottle will not topple due to this pressure. An important DFM issue to note is why the bottle has been deisgned with the 60 degree angle. It is not neccessary to the product and during the assembly process means more machinery and parts are needed to line then up correctly. It is reasoned that P&G wish to keep the angle to the bottle as a USP. Keeping USP’s is in the companies intertest to maintain the high quality brand the product is to reflect. Freddie Jordan & Joe-Simon Wood 43
Stage 3 - Fitting of Cap Whilst still in the puck, the cap is applied to the bottle. In much the same manner as the way the seal was inserted into the cap, force is used to flex the cap over the rim of the bottle and into place. The use of the puck has benefits in that the product is very unlikely to topple over during the various application of forces and nor is it likely to move out of alignment with the parts that are being attached. The image shows how the rim of product also contains a pyramid type insert. This has been moulded in the manufacturing stage, to allow the cap to be removed if necessary. It assists the assembly process by the fact that the cap has the same pyramid shape missing. meaning that to ft together properly the two must align correctly.
The rim around the lower edge of the bottle also assists the application of the lid correctly to the bottle. The oval shaped nature of the product means that the lid can only be fitted in two orientations, leaving error of application unlikely. In this instance the assembly rotation is 360 and 360 for the alpha planes and 180 for he Beta plane. The Cap being positioned the wrong way around is cut out by the addition of the indents on the bottle. Shown here, on the top side (in the photo) one indent represents the front of the bottle and two that back, meaning correct orientation of the way the cap fits is gauranteed.
Stage 4 - Flipping the bottle. The bottle, now that the cap has been applied has to be flipped to place the dosing cap on the top. The bottle is flipped by the use of a rotating system. The bottle enters the system, which spins around and put the bottle out at 180 opposite to how it began.
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Stage 5 - FItting the Doser. The process for this is much the same as adding the cap. The flex of the PP is used to clip the doer to the bottle. The doser is held, and forced down over the bottle. The orientation at this stage does not matter. The oval shape constrains the design to only fitting in two ways, either of which due to the bottles similarity is acceptable. The use of the puck is again needed at this stage as the doser fits the bottle at an angle that is not parrallel to the machinery holding the doser horizontally.
These images demostrate the way the two parts fit together. The left showing the grooves in which the doser snaps under, and the right the doser as it apears from an ariel shot with its four snap fit clips highlighted. The doser unique component as it is the only part of the bottle that can be removed and replaced. For this reason the four ckips have been used. During an idustrial assembly process, the doser could fit the lid so tightly it cannot be removed, however, through clever DFM and DFA the four clips allow not only assembly machinery to attach the doser tightly enough it doesn’t fall off during distribution, but also allows the user to remove and replace as frequently as needed.
1
2
3
1. The diagram pictures the dosing cap from the side being forced down into place by the assembling machinery. 2. Dipiction of flex involved in material that allows for it to deform, the clasps to come lose from the undercut and be removed. 3. Ariel view of the 4 clasps. The very slight undercuts allow for loose enough fitting for it to be removed and tight enough for it to remain in place when not.
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Stage 6 - Application of labels When applying the labels to the front and back of the bottle a roller system is used. The bottle moves through the two rollers, as it does so, the label is smoothed onto the bottle. This type of application means that any unwanted air bubbles are forced out. If the bottle was to be stamped from either side when the labels applied, it could flex and cause air bubbles under the label.
Roller
Roller
Bottle Ariel view of label assembly process
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Function Modes and Effects Analysis Function Modes and Effects Analysis (FMEA) looks at mitigating failures in a product before it has been produced. Consideration to all aspects that may fail allows an increase in product functionality and user satisfaction. By tracing the effects of component failures through sub-systems to system failures modes, the impact of possible failure modes at all levels can be assessed, and preventive or corrective meaures taken. (Molloy ‘98). Failure modes and Effects Analysis plays a key role in determining what prototyping is required for a product during its development. (Baxter ‘95). Steps to completing an FMEA analysis :
1. Failure Modes identification - Using level 2 & 3 from the PFA possible reasons for failure of the individual functions are identified. 2. Cause of failure - Identify the causes of the possible failures discussed. 3. Occurrence of failure - Each failure is ranked as to its liklihood of failure. 4. Failure effects - Identification of the effects of the possibel failures and how it will affect the customer. 5. Failure severity - Ranking as to each of the failures severity and possible consequence for customer. 6. Design verification - The methods of detection that can be undertaken to ensure the failure can be identified. 7. Failure detection - Ranking of the liklihood of detection based on the ease of the detection method that has been outlined. 8. Risk Priority number - Severity Ranking x Occurrence Ranking x Detection Ranking. The summation of all the information calloected on product failure (Baxter, ‘95). The higher the RPN the more attention is required as the risk to the manufacturer is greater.
9. Recommended action - Actions that be undertaken before a product goes to market to ensure the discussed failures are mitigated. In steps 3, 5 and 7 when ranking is required. The scale used will be 1-10 with 1 being the lowest liklihood and 10 being the highest. The FMEA is an important tool as it allows design teams to increase their knowledge of what risks products could encounter and highlights how to avoid making mistakes during the design process. The FMEA ensures that no flaws are overlooked and the possible embarressment of product recall will never have to occur. This also gives a huge benefit to the company the designers are working for as a reputation for good quailty produce is obtained. A full FMEA can run into hundreds of pages. Shown here are a range of possible failures with their effects and how to avoid the flaws. Not all possible points a re covered. QA : Quality Assurance.
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Bottle topples over at end of assembly process.
Bottle does not stand correctly on lid.
At end of assembly contents will not pour correctly.
Assembly cannot be completed.
Conveyers on assembly line fail
Pouring insert does not fit properly.
Assembly cannot be completed. Parts get caught up in assembly process.
Doser cannot snap fit onto bottle correctly
Incomplete assembly.
9
Machinery moving bottle becoming out of sync due to running inaccurately.
Distance between bottles on assembly line becomes inaccurate
Label does not stick to bottle correctly.
10
Bottle topples over causing assembly line to hault.
Filling processes cause bottle to become un-balanced
8
Something caught in conveyer.
10
10
4
Loose conveyer parts.
Gluing assembly not functioning correctly. Label is incorrect size for bottle. Lid and insert not lining up correctly. Not enough pressure supplied to snap parts together.
QA :Check parts during manufacture. QA :Check assembly line. QA :Check assembly line.
7 6
QA : Check flow of glue.
QA :Check parts during manufacture.
QA : Check machinery parts. QA : Check for stray parts on conveyer.
QA :Check parts during manufacture.
3
7
6
7
Parts are released but not secured correctly.
8
Incorrect lid manufacture.
7
7
7
5
7
6
2
6
6
7
QA : Check machinery parts.
5
Loose machinery parts. Incorrect Doser tolerances
5
5
420
490
150
490
324
160
240
336
420
245
210
350
280
7
Testing : Conveyer speed.
QA : Check bottle and filler are in line.
QA : Check filling speeds
6
7
4
Detection Method
Detection
Faulty Conveyer.
Bottle is out of line with filler
FIlling pressure is too fast.
Cause
Occurance
10
7
10
Effect
Severity
Failure Mode
RPN
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Test the pressure rate pushing parts together.
Check the distances between assembly of insert and bottle.
Ensure manufacturing of parts is of highest standard before assembly process begins.
Test the pressure rate of the filling process.
Ensure manufacturing of parts is of highest standard before assembly process begins.
Look along conveyer for anomolous parts.
Check conveyer parts.
Ensure manufacturing of parts is of highest standard before assembly process begins.
Ensure all parts are of correct tightness.
Check the velocity of the conveyer.
Check the distances between products to ensure filler and bottle line up.
Test the pressure rate of the filling process.
Recommended Action
Failures Modes & Effects Analysis Conclusion From the matrix the areas of most importance when assembling the bottle can be deduced. . The top 3 in need of attention are as follows :
Label does not stick to bottle correctly. RPN - 490 Pouring insert does not fit properly. RPN - 490 Doser cannot snap fit onto bottle correctly - 420 Although all slightly varying in terms of RPN value, it is not really acceptable to consider each error as being more important than another. Conveyer assembly failure for instance only has a RPN value of 160. This is due to it only happening in extreme cases, perhaps, only because of power failure but none the less should not be overlooked. The reason why these three failures above are most likely to occur are because of random system errors. Random system erros are those that cannot be predicted or accounted for immediately. Many people believe that there are no such thing as random errors, only unexplained systematic errors. The cause for these problem could also be outlying errors which are most generally caused by humans incorrectly handling or operating the assembly of the product.
Error
To clarify, random errors are those that are unexplained. Systematic are those that can be predicted and avoided and outliers are anamolous results mostly caused by human error. Given time random erros can be understood and become systematic ons, whilst outliers are always going to be anolmous reasons for failure. The graph below summarises these different errors.
Systematic Outlier
Random Outlier Time
FMEA is most effective when being used by a design team. If failures are overlooked an FMEA will not mitigate all possible circumstances of failure. The FMEA carried out is small in comparison to the extent that would be needed to fully analise all of the possible failures, but does give insight into the most important functions that would need attention if the product was to go to market.
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Dewhurst and Boothroyd Analysis To ensure that the Excel Gel bottle is assembled in the quickest and easist way possibel a Boothroyd and Dewhurst “Design for Assembly” technique has been undertaken. The Design for dis-assembly looks at the parts of the product and asks 3 pertinant questions :1) During operation, does the part move relative to all other parts already assembled? 2) Must the part be of a different material from all other parts already assembly? 3) Must the part be seperate from all other parts for assembly or dis-assembly? If the answer to any of the questions is no that part becomes a candidate for elimination. The idea behind undertaking this type of analysis is that it will reduce the amount of parts the system needs to have in order to function in the desired manner. This will reduce manufacturing and assembly time. With minimal parts the energy used to produce the product as well as the energy embodied in the components will be lower. This will lead to savings at the transport stage as it is lower in weight and at the disposal stage as the reduced part means less processes will have to occur in order for the product to be recycled. All of the stages downstream from manufacturing and extraction will be affected. Weight (Kg)
Component
1 2 3 4 5 6 7
Doser Bottle Cap Label
PP TPE PP PP TPE Front Back
Qu 1 Qu 2 Qu 3 Qty
0.008 0.002 0.038 0.014
Y Y Y
N N
Y Y
N
Y
N
Y Y
0.001 0.001 0.001
Y
N
Y
N
Y Y
Y
N
Y
1 1 1 1 1 1 1
Possible Qty 1 0 1 1 1 1 1
Reasoning
Saving (kg)
Needed to hold contents Unnecessary Part Needed to hold contents Need to protect contents
0 0.002 0 0
Needed to pour contents Needed to display Needed for information
0 0 0
Dewhurst & Boothroyd Analysis
Completion of the Boothroyd and Dewhurst analysis allows the potential part count to be lessened form 7 to 6. The reason for stating that the TPE section can be removed, is that it serves to real purpose to the bottle or the way the doser cap functions. It has been included purely for aesthetic purposes. However, the removal of this part does not reduce the assembly phase for the product it does reduce the types of materials and removes a manufacturing process. Thus, overall improving the rate at which a bottle could be made and reducing the cost and less complex moulding tools are needed. The analysis has been completed as a theoritical way P&G, if needed could reduce costs and manufacturing time. However, it is not thought that any of this to a company of P&G’s stature is worrying. The TPE, soft over-moulded section is considered a USP and removal of that would conflict with P&G’s brand values.
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The Assembly line This section aims to document the timings of the manufacture and assembly, give insight into the companies used in the production of the bottle and look into the the assembly line. Zeller is situated in France, whilst Alpla in Germany. The logistics of JIT production must be taken into account very carefully between the two manufacturers, with Alpla having limited storage. The caps and dosers must arrive at the correct time to make sure efficient assembly time can be maintained. Companies used in the manufacture of the bottle Zeller
Alpla Bottle Blow moulded
Injection moulded PP Cap
Cleaned
Filled
Valve inserted and checked
Silicone valve produced
Skeleton Doser
Slit punched
Checked and Cleaned
Injection mould ring
TPE Overmould
Components cleaned and checked
Checked and Cleaned
Shipped to Alpla
Sealed with lid Tested All parts assembled Labelled Packed
Assembly
Manufacturing
Shipped
Process Blow Mould Bottle Injection Mould Cap Injection & Overmould Doser Print Label Apply Adhesive Bottle moves into Puck Puck moves down conveyer Bottle Filled Bottle Moves down conveyer Cap Applied Bottle moves down Conveyer Bottle Flipped Bottle moves down conveyer Doser Fitted Bottle moved down conveyer Label Applied Conveyer to packing Total
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Timings (s) 1 1.5 3 1 1 5 5 3 5 1 5 2 5 1 5 2 5 51.5 Seconds
Looking at the total from the table, a bottle from manufacture to assembly can be produced in 51.5 seconds. This is assuming that the polymer is preheated in the hoppers of the moulders. It more than likely to take around double the time due to packing being undertaken by people and quality assurance checks along the way. Running 24.7 this would produce around 700-1000 a day. The product is likely to be produced in batch runs of 25,000 to 50,000 products for distribution around Europe, including shipping to the UK. Batch production is estimated as supposed to Mass due to the product not being the market dominator in fabric cleansers. It is only supplied as the store orders it on a JIT basis.
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Bottle
Conveyer with pucks
Filling
Cap Applied
Flip Bottle
Bottle now stands freely on cap
Puck no longer needed.
Fit Doser
Apply Label
Package & distribute
The diagram indicates how the bottle moves around the assembly line. What happens at each stage has been previously spoken of. Conveyers move the bottle around, with various machinery, such as filling tools, and tools that place the cap on operating at specific stages. This type of assembly alludes to a product flow layout way of production. The part moves through the various assembling machines. Each machine operates a single part which is moved into place with the bottle as it travels along the conveyer. For this type of manufacture fixed position is not necessary, as that involves larger objects. It could possibly be done in a process layout way, however this slows the movement of the manufacturing and assembly. It would cause the assembly to slow down and would not be as sucessful as product flow.
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Costing The cost of manufactuting any product is made up of four main attributes. The cost of the part, the cost of processing, the cost of assembly and the costs associated with the running of the manufacturing system producing the product and the factory it is made in. (DFM costing hand out). Manufacturing Cost = (raw materials/parts) + Labour, tooling & Equipment) + Assembly + Overheads Given the sensitive nature of IP on the product, specific costing values were not able to obtained. The chart below looks at theoretically implementing a costing breakdown. It aims to highlight the areas of costing invovled with manufacturing,. Taking into account both fixed and variable costs. Variable costs are ones that increase as the number of parts increases, whilst fixed costs are those that are incurred irrespective of the number of parts that are made. When viewing the table it must be noted that the total costs are per each bottle. (Table adapted from Costing lecture notes).
Component
Variable Costs Fixed Costs Materials Processing Assembly Total Variable Mould Mould Total Fixed Total Tooling Tool Life Cost costs Cost (labour)
Doser Bottle Cap Gel
0.06 0.06 0.06 0.07
0.10 -
0.10 -
0.06 0.06 0.26 0.07
Total Direct Costs
0.25
0.10
0.10
Overhead Costs
0.04 (15%) 0.29
0.18 (180%) 0.28
0.28 (280%) 0.38
Total Cost
150k 150k 250k -
0.01 0.01 0.02 -
0.07 0.007 0.028 -
0.45
0.04
0.49
0.50
0.02 (50%) 0.06
0.52
0.95
150k 150k 250k -
1.01
Assumptions that were made were that the only assembly and processing for the cap, per bottle cost £0.10 each. This is because it is the only part that requires physical checks by humans. All other parts can be overseen during the assembly stage and need no physical interaction unless there is a problem. The table also infers that there are no fixed costs for the Gel, however there are costs involved with storing it and packing it, however, in this breakdown have been assumed negligible. The total cost per bottle is around £1.00 (£1.01). This has been used to calculate a return of investment chart, which is shown overleaf.
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Development Costs
Cost
R&D Prototyping IP Product Testing Tooling Total
200,000 200,000 500,000 150,000 500,000
Reasoning Overheads, managment, labour Visualisation, prototype moulding European Intellectual Property Testing of product attributes All tools needed for moulding
1,550,000
Manufacturing
£1.00
25% of total manufacuting cost - material, design, volumes, process etc 15% of total manufacuting cost - Process, mahinery, tooling, accuracy etc 10% of total manufacturing cost - Type, layout, time, control etc 50% of total manufacturing cost - Indirect labour, quality, dispatch etc £1.00 is assummed per bottle as RRP is £3.99 & mark up is 400%
Profit RRP
£3.00 £3.99
Profit (x4 mark up is assumed) Recommended Retail Price
5 Year Sales UK Europe Total Sales Income from Sales (RRP x Total Sales) Profit
1
Part Cost Processing Cost Assembly Cost Overheads
(Income - setup & maintenance & cost per part)
0.25 0.15 0.10 0.50
2
3
4
400,000 600,000 1,000,000
5
600,000 1,000,000 1,600,000
1,000,000 1,700,000 2,700,000
1,500,000 2,500,000 4,000,000
2,200,000 3,500,000 5,700,000
Total 5,700,000 9,300,000 15,000,000
4,000,000
6,400,000
10,800,000
16,000,000
22,800,000
60,000,000
1,450,000
3,250,000
8,100,000
10,450,000
17100000
45,000,000
The return on investment chart shows the possible income over a 5 year period in both the UK and Europre. It goes more in-depth at looking at the development costs. It must be remembered that during development CAD software along with CAM methods are used at an expensive price per hour, (£40-60). The 2 charts aim to document the theoretical price points for the various stages of maunfacture. Only so much can be considered as it is not know the true value of the costs, however, probable costs have been assumed as accurately as possible. Further costing considerations have been extraced from BS 8887-1 Design for manufacture, assembly, disassembly and end-of-life processing (MADE) – Part 1: General concepts, process and requirements and are shown in the appendix.
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End of Life & Dis-assembly Whilst designing the bottle, end of life must also be considered. From a DFM point of view the easiest way to include consideration as to what will happen to the bottle after it has been finished with is to make it easy to disassemble. Ways this has been done for the Excel bottle are Manufacturing the cap so that it snap fits to the bottle. Manufacturing the Doser so that it snap fits to the bottle. Manufacturing the label so that it can be peeled off the bottle easily. The table and graph shown below indicate the values of energy consumption the product uses at each stage of life-cycle. These values have been calculated using the Cambridge eco-selector. The results are energy used per bottle. Further calculations are needed to see how much a batch run of the bottles uses. For a batch run of 50,000 the total of energy embodied in the polymer is to be 5.06MJ x 50,000. This equates to 253000MJ of energy. To reduce this, the product can be recycled at end of life, meaning some ofthe embodied energy is regained. The assumption made during this LCA was that the product does not use any electricity, for example the electricity needed to wash the clothes. In the Appendix, a Procter and Gamble LCA has been completed in which they have included the electricity used in the cycle. It shows a saving in energy at the use phase due to the way the gel has been manufactured. The contents of the gel formulate a washing solution that means clothes can be washed on a cooler cycle. “A reduction of consumed electricity of approximately 40% was reported for a reduction of the wash temperature from 40oC to 30oC (Ariel, UK conditions, 2006).
0.013 MJ
0 MJ
0.0125 MJ
0.531 MJ
5.06 MJ
End Of Life
Use
Transport
Manufacture
Phase
Materials
Energy used over product lifetime
The fact that the cap and doser are the same size, regardless of bottle size, means that schemes could be introduced encouraging re-use of these parts. The Doser is a product that is only needed once. Yet everytime you buy the bottle you get a new one, meaning you get up to around 4 per year. 1 Doser is capable of lasting 5 years. An option to improve this would be a bottle that comes without the doser. It would dramatically reduce the energy used and also means that P&G do not need to manufacture and assemble as many. There could be two versions to buy on the shelf, one bottle with, or one without. There could also be the option to iriadicate it completly and purchase the Doser seprately, although this may compromise P&G USP of having it inclusive in the shape of the bottle.
Material Manufacture Transport Use End of Life Total End of Life (potential/burden) Total (including end of life)
Energy (MJ) 5.86 0.531 0.0125 0 0.013 6.41 0 6.41
Energy (%) CO2 (kg) CO2 (kg) 91.3 8.3 0.2 0.0 0.2 100 0.0
0.197 0.0425 0.000891 0 0.0078 0.242 0 0.242
81.7 17.6 0.4 0.0 0.3 100 0.0
Energy and C02 emissions per bottle
Graph showing energy consumption at each stage of product lifecycle
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BS 8887-220:2010 Design for manufacture, assembly, disassembly and end-of-life processing (MADE). The process of remanufacture. Specification discusses various ways in which a product can be designed with dis-assembly at the the end of life stage taken into consideration. The diagram below has been exctracted from the standard and looks at product life-cycle examining which way is best to be most environmentally friendly.
Remaunfacture
Re-use
Assembly
Raw Material Extraction
Materials
Use
Part Manufacture
DisAssembly
Re-purpose
Recycle
More environmentally preferable
Recondition
Different use
Dispose
The Extract below is taken from BS8887:2007 “Design output for manufacture, assembly, disassembly and end-of-life processing (MADE). It documents the checklist that can be followed in order to enable the energy and emissions impacts of demanufacturing and recycling to be minimised. The cehcklist is as follows a) Materials & manufacture • Minimise non-biodegradable materials. • Use compatible materials • Maximise standardisation of component variations. • Select materials with simialr component life to match design life of assembly. • Avoid composite materials employing adhesives. • Group harmful materials in seperate, accessible modules • Avoid combingin ageing and corrosive materials • Minimise number of peice parts, either within the product or sub-assembly as designed, or by redesigning the product or subassembly, or by using different manufacturing methods which allow the product or sub-assembly to be made in fewer pieces or in one piece. b) Joining • Minimize the number of fixings and fasteners and standardize • the types and sizes. • Subject to security and safety considerations, use joining • technologies and methods which enable easy separation of • components and materials.
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The Extract below is taken from BS8887:2007 “Design output for manufacture, assembly, disassembly and end-of-life processing (MADE). It documents the checklist that can be followed in order to enable the energy and emissions impacts of demanufacturing and recycling to be minimised. The cehcklist is as follows a) Materials & manufacture • Minimise non-biodegradable materials. • Use compatible materials • Maximise standardisation of component variations. • Select materials with simialr component life to match design life of assembly. • Avoid composite materials employing adhesives. • Group harmful materials in seperate, accessible modules • Avoid combingin ageing and corrosive materials • Minimise number of peice parts, either within the product or sub-assembly as designed, or by redesigning the product or subassembly, or by using different manufacturing methods which allow the product or sub-assembly to be made in fewer pieces or in one piece. b) Joining • Minimize the number of fixings and fasteners and standardize • the types and sizes. • Subject to security and safety considerations, use joining • technologies and methods which enable easy separation of • components and materials. c) Coatings/finishing • Avoid secondary finishing such as painting, coating or plating. • Choose durable materials in preference to protective coatings. d) Recycling • Provide convenient access to valuable and reusable parts. • Provide clear identification of replacement/repair modules. • Protect sub-assemblies against soiling, corrosion and erosion. • Code or otherwise identify parts to facilitate recycling and • audit trails to production data. For plastic parts above 50 g, • mark in accordance with BS EN ISO 1043 and • BS EN ISO 11469. • Code or otherwise identify materials, including surface • coatings and alloys, to facilitate recycling and audit trails to • production data. • Provide all information to assist recycling in documentation, • whether in print or electronically. The standard also lists many other considerations that can be applied to the bottle such as when specifying manufacturing processes consider the materials, energy, water and hazardous materials usage as well as the product usage.
Conclusion To conclude this report, the discussed aspects of the product have allowed insight into the various design for manufacture issues surrounding the Excel Gel Bottle. Information on various manufacturing techniques has been aqcuired and analysed. Throughout consideration has been given to the manufacturing of the product, the assembl, processing methods, material identification, assemby routes, costing estimates, appraisals of existing designs, tools, tolerance, surface finhes, dis-assembly, environmental impact and end of life processing.
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References Standards EN 20286-1:1993 System of limits and fits - Part 1: Bases of tolerances, deviations and fits. EN 20286-1:1993 System of limits and fits - Part 2: Tables of standard tolerance grades and limit deviations for holes and shafts. BS 8887-1: 2006 Design for manufacture, assembly, disassembly and end-of-life processing (MADE) – Part 1: General concepts, process and requirements People Would like to thank all of the members of the prototyping work shop at the P&G London Innovation Centre for allowing us to visit the site view the machines, tools and the general practices they perform. The P&G LINC Pack Dev Department. Joe Wood – for his knowledge gained on a years placement working in the Pack Dev department at P&G. Freddie Jordan – generally applying common sense and intensive research into DfM issues and considerations. Books Boothroyd, G (1994) “product Design for Manufacture & Assembly” - Marcel Dekker, NY Groover, M. (2007) “Fundamentals of Modern Manufacturing Materials, Processes and Systems” John Wiley & Sons Inc. UK Lee, N (2000) “Plastic blow moulding handbook” - Chapman & Hall, London Lee, N (1998) “Blow Molding Design guide” - Hanser, Germany. Lefteri, C. (2007) “Making It: Manufacturing Techniques for Product Design” Laurence King Publishing UK. Molley, O. Tilley, S. Warman, E. (1998) “Design for Manufacturing and Assembly Concepts, Architectures and Implementation” Chapman and Hall UK. Redford, A. Chal, J. (1994) “Design for Assembly Principles and Practice” McGraw-Hill International UK. Swift, K. Booker, J. (2003) “ Process Selection: From Design to Manufacturing” Butterworth Heinemann UK. Web: These sites were last checked and accessed on 18th March 2010. http://www.protomold.co.uk http://www.adv-puck.com/about.cfm http://www.alpla.com/index.php?lang=en http://www.ebottles.com/resins.asp http://www.environment-green.com/Plastic_Recycling.html http://www.coldisthenewhot.com/html/rate-and-review/index.php?3 http://www.info-pg.com/cgi-bin/info-pg/showproduct.pl?lang=en_UK&id=2380-1
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BLOW MOULDING PROCESS About blow moulding and the process To manufacture the body of the container the process co-extrusion blow moulding has been used. This process allows two types of material to be extruded at the same time, which produces the visi strip down the side of the bottle. SEE VISI STRIP ON BOTTLE PICTURE Blow moulding is the process for forming a hollow shaped object by ‘blowing’ a thermoplastic molten tube called a parison in the shape of a mould cavity. The process has two fundamental phases. First a perform (or parison) of hot plastic resin in a tubular shape is created. Secondly a pressurised gas, usually air is used to expand the hot perform and press it against a female mould cavity. The pressure is held until the plastic cools. There are two types of extrusion blow moulding: Continuous This is where the parison is continulaly extruded. The parison is then either transfered from the die to the mould either by means of arms or by moving the moulds to the parison. Intermittent (or Short Extrusion) This is where a reciprocating screw, almost identical to that of Injection-moulding is used. The resin is plasticised while the screw rotates and retracts, charging the shot in front of the screw. The screw is rammed forward pushing the plastic through the head and out the die head tooling as a parison. The mould then closes over the parison at this point and air is then blown into the mould. This is a rapid process compared to continuous blow moulding. Blow moulding process of the container: • Plastic granules are added to the hopper • The granules then enter the barrel • The granules are moved along the barrel via the rotating screw • The plastic granules are heated to plasticity • The molten plastic in under force due to the screw and is being pushed towards the die • A parison emerges from the hot tip/die • The mould then moves over the parison and closes • The hot knife cuts the parison to length • The closed mould with the parison moves back to its starting position • The blow nozzle is inserted/comes down on the mould and blows air into the mould, it is held there for a second • While this is happening another parison is extruded • The mould is released, the part drops out onto the conveyor • The mould then moves over to the parison and closes • The process carries on ADD PICTURES OF MACHINE
Co-extrusion Blow Moulding This is where two materials are extruded through the same die at the same time, first the main material is extruded and the second material is then injected near the die so that when the parison emerges from the die the two materials are as one. ADD DIAGRAM OF PARISON AND COEXTRUSION What needs to be considered? When designing the bottle the following factors were taken into consideration: The shape of the bottle The overall bottle weight The wall thickness of the bottle Overflow capacity Neck dimensions, whether it will be capped with thread or friction fit cap The substance it will hold Whether a pigment will be added or not
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User ergonomics Filling Packaging and shelf height Presentation labelling using sleeves or prints for example This then leads to mould design and construction, which needs to be done before production of the bottle can begin Identification of the front and back of the container as well as the top and bottem The reasons why blow moulding been chosen Extrusion blow mouling is the favoured process in manufacturing the bottle due to the following factors: • It has low tooling, unit and running costs compared to that of injection moulding which costs two times more and stretch blow moulding which can cost considerably more • It is sustainable only for high volume production runs • It can produce high quality, uniform think walled parts • It can produce high quality surface finish that can be gloss, textured or matt • It has a very rapid cycle time typically 1-2 minutes • A versatile process, variety of shapes and materials • Containers can be moulded with integrated handles and multiple layered walls • It can produce thin walled and strong containers • Low labour costs • Production can be fully automated • Materials generally used for this process can be directly recycled • Produce a large range of containers sizes from 50ml to 220 litres (IM – limited from 3ml to 1lite, SBM limited from – 50ml to 5litres) For example the neck of the bottle is a simple snap fit design SEE FIGURE, it has not been threaded, a threaded bottle neck is produced using injection blow moulding as it allows for higher/tighter tolerances this done Typical plastics for injection blow moulding are: Polypropylene (PP) High Density Polyethylene (HDPE) Typical plastics for extrusion blow moulding are: Polypropylene (PP) Polyethylene (PE) Polyethylene Terephthalate (PET) Poly Vinyl Chloride (PVC) Typical plastics for stretch blow moulding are: Polyethylene (PE) Polyethylene Terephthalate (PET) Alternative processes Since the bottle has been made from PP, other processes that could be used to make bottle could be Rotational moulding, Injection blow moulding, and stretch blow moulding. However rotational moulding is not used because it is used to produce large hollow containers such as bins and Injection & stretch blow moulding have greater tooling costs. 3D printing could also be used however it can only produce rigid forms which is not ideal as one of the functions for the bottles it for it to be easily squeezed. This is so that its contents can be dispensed more efficiently. Alternative materials Seeing as the production method for the bottle is extrusion blow moulding this process is also good for PP, PE and PVC. However these plastics have not been used due to the fact that their properties for the job of the container are not necessary and hence would not be efficient use of the material. Glass could also be used to make the bottle shape; though this is not really the best choice of material due to the fact it requires more energy to work with. Using glass would also increase transportation cost due to the weight of the material also you cannot
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User ergonomics Filling Packaging and shelf height Presentation labelling using sleeves or prints for example This then leads to mould design and construction, which needs to be done before production of the bottle can begin Identification of the front and back of the container as well as the top and bottem The reasons why blow moulding been chosen Extrusion blow mouling is the favoured process in manufacturing the bottle due to the following factors: • It has low tooling, unit and running costs compared to that of injection moulding which costs two times more and stretch blow moulding which can cost considerably more • It is sustainable only for high volume production runs • It can produce high quality, uniform think walled parts • It can produce high quality surface finish that can be gloss, textured or matt • It has a very rapid cycle time typically 1-2 minutes • A versatile process, variety of shapes and materials • Containers can be moulded with integrated handles and multiple layered walls • It can produce thin walled and strong containers • Low labour costs • Production can be fully automated • Materials generally used for this process can be directly recycled • Produce a large range of containers sizes from 50ml to 220 litres (IM – limited from 3ml to 1lite, SBM limited from – 50ml to 5litres) For example the neck of the bottle is a simple snap fit design SEE FIGURE, it has not been threaded, a threaded bottle neck is produced using injection blow moulding as it allows for higher/tighter tolerances this done Typical plastics for injection blow moulding are: Polypropylene (PP) High Density Polyethylene (HDPE) Typical plastics for extrusion blow moulding are: Polypropylene (PP) Polyethylene (PE) Polyethylene Terephthalate (PET) Poly Vinyl Chloride (PVC) Typical plastics for stretch blow moulding are: Polyethylene (PE) Polyethylene Terephthalate (PET) Alternative processes Since the bottle has been made from PP, other processes that could be used to make bottle could be Rotational moulding, Injection blow moulding, and stretch blow moulding. However rotational moulding is not used because it is used to produce large hollow containers such as bins and Injection & stretch blow moulding have greater tooling costs. 3D printing could also be used however it can only produce rigid forms which is not ideal as one of the functions for the bottles it for it to be easily squeezed. This is so that its contents can be dispensed more efficiently. Alternative materials Seeing as the production method for the bottle is extrusion blow moulding this process is also good for PP, PE and PVC. However these plastics have not been used due to the fact that their properties for the job of the container are not necessary and hence would not be efficient use of the material. Glass could also be used to make the bottle shape; though this is not really the best choice of material due to the fact it requires more energy to work with. Using glass would also increase transportation cost due to the weight of the material also you cannot
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squeeze a glass bottle to squeeze out its contents, which is a feature of the Fairy bottle. Overall it is more efficient to use a polymer. Shape of the bottle P&G have designed the bottle in the shape of a pebble. The doser becomes the top of the bottle and the cap becomes the bottom. This is purposely done so that the contents (the gel) is always near the cap so that it can easily be squeezed out, it also stops the user from having to shake the bottle to access its contents. There is no technical or scientific reason for doser to be at an angle other than that it enhances the aesthetics of the bottle, it also indicates the design innovation of the bottle. Bottle Features Neck The neck of the bottle has been designed with an under cut to allow the cap to be snap fitted on, it also has two stops opposite each other to stop the cap from rotating. Manufacturing the neck in this way requires less work in manufacturing the mould and is simpler to implement than a screw thread, which requires greater tolerances. SEE FIGURE PP logo The PP logo is moulded into the bottle to indicate the type of material that has been used. This allows for identification of the polymer for the end of life of the Fairy bottle for recycling. SEE FIGURE The step around the bottle shoulders below the neck is there to indicate where the cap sits once mounted this provides a seat for the cap. SEE FIGURE The single slot and the double slot on the shoulder of the Fairy bottle are font and back indicators for the labelling process, the single slot indicates the front of the bottle and the double slots indicate the rear. SEE FIGURE The under cut on the base of the bottle is there to allow the doser to snap fit on the bottle. The rounded edges from the front to the back on the bottom of the bottle are there so that when you twist the doser, it pops of easily. SEE FIGURE Mould construction/Design Before blow moulding can begin the mould has to be created. When designing the mould for blow moulding it must be accurate, efficient, durable and cost effective. During the construction of the mould the following factors need to be taken into account: Mould cooling • Conduction of heat in the wall of part and mould (This is dependant on resin type, temperature and wall thickness) • Conduction of heat in mould wall (This is dependant upon mould material thermal properties, porosity and mould cooling layout geometry) • Convective transfer of heat in cooling fluid Wall thickness differences lead to cooling rate differences and in turn can cause warping and mould in stress. Slower cooling allows more stress relaxation however moulds to cold can cause condensation this spoils the surface finish and retards cooling. Cooling of flash is important to help effectively trim the part. In addition the shoulder and bottoms of bottles are usually thicker than the walls and require more cooling lines. Cooling of the blow pin is necessary to produce well-formed threads and eliminates warping that could ovalise the openings. Cooling of flash grippers and other part removal equipment need cooling to prevent sticking. Cutting and welding the parison (Parts of the mould that weld the ends and sometimes the interior portions of the parison together) Venting - this allows air inside the mould to escape as the parison inflates. Accomplished by carefully providing passageways out of the cavity. Alignment pins - Bolts and bushings are used to ensure accurate positioning of the mould halves as they are closed. The position of the ejectors pin for removing the part from the mould The material and method of construction are also chosen for the sustainability for the desired end product production quality and for the resin type. Detail of the moulds is important because the moulds must produce containers of the same volumetric and dimensional accuracy. Efficiency in processing results from a mould that cools the molten extrude into a form as free from warping as possible in as short
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PRODUCTION Production rate This depends to great extent on the efficiency with which the plastic material is heated and cooled. The time taken/required to cool the part primarily determines the rate of production and controls to a great extent the quality of the part being produced. The production rate of the Fairy bottle is ... bottles a minute. This means a bottle can be blow moulded every ... seconds and filling only takes ... seconds. The doser and bottle cap are produced by ‘global closure systems’ (Zeller) and then shipped to ‘Alpla’ (a German company) factory where the bottle is manufactured, filled, assembled (the cap, dose and lables are stuck on) and packaged. Alpla use a puck production process to allow for integration of oddly shaped bottles and containers to their assembly line. The puck is a type of jig/holder made specifically for the bottle being manufactured. It allows the bottle to be incorporated to the current production line, without having to change much, which would increase costs. In this instance because the Fairy bottle is at an angle SEE FIGURE the filling nossel would have to be inserted at an angle which is not efficient so the puck is used to make the bottle stand straight, this allows filling to be done more efficiently without having to alter the angle of the filling nozzles. During the production of the bottle, quality control also takes place. Lasers are used to check the thickness of the walls after the bottle is released from the mould and moves down the line. Prior to the filling, the bottle is pressure tested to check for any holes before the gel is poured in. If the bottle fails any of the checks it is removed from the line either by a get of air or a flicking arm.
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a time as possible. An efficient mould also reduces the number of parts that are rejected due to design imperfections. Durability is needed for a long mould life because moulds are constantly closed under pressure, which can eventually wear down the mating surfaces. Also the pinch off sections also can be abraded by the material the mould cuts and welds There are two ways to produce a mould, CNC machining or Casting. CNC is the process where a computer is used to cut out the desired shape in a block of metal, it is more accurate and has a better finish compared to that of casting. Casting is the process, which uses sand and molten metal to produce the desired mould shape. PICTURE OF MOULD LABELLED The choice of production method depends upon the expected run-length of the product, the number of cavities necessary, and the surface irregularity of the product. Castings are typically not as durable or as thermally efficient as moulds cut from solid blocks. In this instance the mould for the Fairy bottle is created by CNC using both a block of Aluminium alloy and Steel as the choice of material. The aluminium mould is created for the prototyping stage and is used because it has a high thermal conductivity, it is lightweight, corrosion resistant and it easy to work with and machine. However the drawback to using aluminium is that it is soft and can be easily damaged, hence the reason it is used for prototyping and not for the full manufacturing stage. During this stage the tolerances, shape, material choice, pressure, temperature and cooling calculations are all tested and varied to get the best results for the final product. Any changes that need to be made to the final design are done during this stage. Colour is also added to see what affects it could have on the final product. The mould is created using a 5 axis CNC milling machine. The shape is rough cut which can take up to 10 hours. The cutting head is then changed and the inside of the mould is smoothed out for a matt, textured or gloss finish look on the final product polishing is done buy hand in the mould. This can take a further 10 hours. SEE FIGURE CNC is the chosen production method for the Fairy bottle mould because it is more accurate and the quality of finish is much better than that of casting. However CNC production does waste a lot of material, though collecting and recycling the waste material will easily solve this. The steel mould is created for the full manufacturing stage. Steel is used because it is corrosion resistant, it has extreme toughness, low thermal conductivity, excellent surface texture can be obtained through etching process and can be fabricated by both machining and casting. Machining is difficult because of the high hardness of steel but this means the service life of the mould can be up to 10million cycles. Steel is also used where high wear is expected These areas include the mounting plates and bars, guide elements and pinch off inserts. As well as auxiliary parts such as the blow pins (for removing the part from the mould), needles and shear surfaces. Material The choice of material for the Fairy bottle is PP, this is used because it is one of the plastics that work well with blow moulding. It has good barrier properties against oxygen and carbon dioxide, has good resistance to mineral oils, solvents and acids and it is available as an amorphous (transparent) and as a semi crystalline (opaque & white) thermoplastic material. Amorphous PP has ductility but less stiffness and hardness. Semi-crystaline PP has good strength, ductility, stiffness and hardness. PET can also be used in other manufacturing processes such as; • Injection moulding • Injection blow moulding • Extrusion • Stretch blow moulding • Vacuum forming • Fibre spinning
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Appendix Cost Considerations taken from BS8887-1:2006 Design for manufacture, assembly, disassembly and end-of-life processing (MADE) – Part 1: General concepts, process and requirements. 7 Cost considerations 7.1 General The design brief includes the target price for the product in accordance with Clause 5. The designer shall ensure that the overall product cost is consistent with the target price derived from the design brief, Pt, allowing for any required contribution, as shown in the following equation: Pt + Pc= [(Cdev + Cmkt)/Qat] + Cmat + Cma + Cde where: Pc is that portion of the selling price contributing to the manufacturer’s overhead cost and the required profit; Cdev is the cost of developing the product (for total anticipated quantity); Cmkt is the cost to market (including direct sales, delivery etc.) (for total quantity); Cmat is the cost of materials, components, etc. (per unit); Cma is the cost of manufacturing and assembly (per unit); Cde is the cost of disassembly and end-of-life processing (per unit); Qat is the anticipated total quantity of the product. NOTE 1 It is often necessary to make trade-offs between technical needs and commercial needs, typically between unit cost vs. unit features and development costs vs. development timescales. If trade-offs have to be made, this should be done as early as possible in the costing process. NOTE 2 Although operating costs have necessarily to be considered by the designer (see Clause 11) they do not constitute part of the calculation. 7.2 Development costs (Cdev) The cost of the product development project shall be estimated taking into account the following constituent costs. a) Project planning and estimating effort. b) Project management effort. c) Patent agent research and patent related costs. d) Effort in finalizing the design brief (see Clause 5). e) Effort in using the design tools (see Clause 6). f) Concept phase effort (see 6.2.2). g) Realization phase effort (see 6.2.3). h) Technical documentation effort (see 6.2.4) (including user documentation). i) Industrial design effort (see Clause 8). j) Detail design effort (see Clause 9). k) Design verification effort (see Clause 12). l) Prototype hardware build (materials and man-hours). Pt + Pc= [(Cdev + Cmkt)/Qat] + Cmat + Cma + Cde m) Hire of specialist equipment for development/ testing and/or test house fees. n) Overheads for facilities needed (where these need to be explicitly accounted). o) Software development. p) Software testing. q) Regulatory compliance testing (where relevant).
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r) Independent product evaluation or involvement of a Notified Body. s) Packaging design and development. Estimation of the cost of individual tranches of work, or sub-programmes, shall be undertaken by the staff responsible for those areas. Estimates shall be based as far as practicable on actual data gathered from similar previous development work. NOTE 1 The resources required (i.e. number of staff) is dictated by development timescales, which might have a limit stated in the design brief. Alternatively the development timescale should be established by working back from the deadline by which the product is to be launched in order to capture the desired market share, making allowance for the time required for manufacture and distribution etc. NOTE 2 The designer should consider options for reducing development costs, for example through variety reduction, simulation, rationalizing and standardizing commonly used components (such as fasteners), use of off-the-shelf mechanical hardware, subassemblies, electronics, software etc. 7.3 Marketing, sales and support costs (Cmkt) The costs of taking the product to market shall be estimated taking account of the following. a) Product launch (one-off). b) Marketing costs, including publicity in the press, promotional expenses, direct advertising. c) Fees to agents. d) Discounts to distributors. e) Sales. f) Export (including exchange rate variability). g) Distribution. h) After sales support. i) Staff training. j) Warranty. 7.4 Materials costs (Cmat) The costs of materials required to make the product shall be determined and typically comprise the costs of: a) electronic/electrical components; b) mechanical components; c) structural items such as housing/frame/chassis/etc.; d) bought-in subassemblies and assemblies; e) raw materials; f) special processing of parts, for example painting, plating, passivation; g) consumable materials necessary for assembly/processing; h) packaging materials; i) unit based licences, for example software, patents. NOTE Parts costs can be heavily dependent on the quantity purchased. One or more purchasing specialists should be involved in establishing best prices for the items listed. 7.5 Manufacturing, assembly, disassembly, end-of-life processing costs 7.5.1 Manufacturing and assembly costs (Cma) The manufacturing and assembly costs shall be estimated taking into account the following. a) Piece part manufacture.
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b) Piece part inspection/test. c) Assembly and associated processes. d) Sub-assembly and assembly testing. e) System integration. f) Product/system testing, functional and safety. g) Specialist equipment. h) Subcontractors packing and storage. NOTE The non-recurring costs of making production tooling, jigs and fixtures, test harnesses, test equipment etc., should also be included if these have not be taken account of as part of the development. 7.5.2 Disassembly and end-of-life processing costs (Cde) End-of-life processing costs (if any element of these is borne by the manufacturer) shall be estimated taking account of the following. a) Transport and collection. b) Disassembly. c) Disposal of harmful or toxic components (e.g. batteries). d) Reprocessing or re-cycling parts. e) Other disposal costs.
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Basic Injection Moulding Overview – As described in Process Selection from Design to manufacture. The following information has been extracted from K.G Swift’s and J.D Booker’s Process Selection book. The Book provides general information regarding the manufacturing processes. Injection Moulding – Materials• Mostly thermo-plastics, but thermo-sets, composites and elastomers can be processed. Process Variations• Injection Blow Moulding – allows small hollow parts with intricate neck detail to be produced. • Co-injection – For products with rigid cores pre-placed in the die before injection or simultaneous injection of different materials into same die. Economic Considerations – • Production rates are high, 1-50/min, depending on size. • Thermoset parts usually have longer cycle time. • Lead times can be several weeks due to manufacturing if complex dies. • Material utilization is good. Scrap generated in sprues and risers. • If material permits, gates and runners can be reused resulting in lower material losses. • Flexibility limited by dedicated dies, die changeover and machine setup times. • Economical for high production runs, typically 10,000+. • Full automation achievable. Robot machine loading and unloading common. • Tooling costs are very high. Dies are usually made from hardened tool steel. • Equipment costs are very high. • Direct labour costs are low to moderate. • Finishing Costs are low. Trimming is required to remove gates and runners. Design Aspects – • Very complex shapes and intricate details possible. • Holes, inserts, threads, lettering, colour, bosses and minor undercuts possible. • Uniform section thickness should be maintained. • Unsuitable for the production of narrow necked containers. • Variation in thickness should not exceed 2:1. • Marked section changes should be tapered sufficiently. • Living hinges and snap features allow for part consolidation. • Placing of parting line important, i.e. avoid placement across critical dimensions. • The clamping force required proportional to the projected areas of the moulded part. • Radii should be as generous as possible. Minimum inside radii = 1.5mm. • Draft angle ranging from less than 0.25 to 4 degrees, depending on section depth. • Maximum section, typically = 13mm. • Minimum section = 0.4mm for thermo-plastics, 0.9 mm for thermosets. • Sizes ranging 10g – 25kg in weight for thermoplastics, 6 kg maximum for thermosets. Quality Issues • Thick sections can be problematic. • Care must be taken in the design of the running and gating system, where multiple cavities used to ensure complete die fill. • Control of material and mould temperature critical, also injection pressure and speed, condition of resin, dwell and cooling times. • Adequate clamping force necessary to prevent the mould creating flash. • Thermoplastics moulded parts usually require no de-flashing; thermoset parts often require this operation. • Excellent surface detail obtainable. • Surface roughness a function of the die condition. Typically, 0.2-0.8 um Ra is obtainable. • Allowances of approximately + or – 0.1mm should be added for dimensions across the parting line. Blow Moulding Information – Process Selection: From deisgn to Manufacture K.G.Swift, J.D Booker.
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Materials• Most thermoplastics. Process Variations – • Extrusion blow moulding: more applicable to asymmetrical parts, integrated handles possible. • Injection blow moulding: parison injection moulded and then transferred to blow moulding machine. For small parts with intricate neck details. • Multiple parison: can create multi-layered parts. This requires close control since uneven parisons produce waste. • Parisonless blowing: similar to dip coating followed by expansion into the mould. • Stretch blow moulding: the simultaneous axial and radial expansion of a parison, yielding a biaxially orientated container. Economic considerations – • Production rates between 100 and 2500/h, depending on size. • Lead times a few days. • Integration with extrusion process to produce parison provides continuous operation. • There is generally little material waste, but can increase with some complex geometries using extrusion blow moulding. • Full automation readily achievable. • Flexibility limited since moulds are dedicated. • Setup times and changeover times relatively short. • Production volumes of 1000, but better suited to very high volumes. • Tooling costs moderate to high. • Equipment costs moderate to high, especially for full automation. • Direct labour costs low. One operator can manage several machines. • Finishing costs low. Some trimming required. Design aspects • Complexity limited to hollow, well rounded, thin walled parts with low degree of asymmetry. • Asymmetrical mouldings, e.g. off-set necks possible with movable blowing spigots. • Undercuts, bosses, ribs, lettering, inserts and threads possible. • Corner radii should be as generous as possible (>3mm). • Placing of parting line important, i.e. avoid placement across critical dimensions. • Holes cannot be moulded-in. • Draft angles not required. • Maximum section = 6mm. Thick sections may need cooling aids (carbon dioxide or nitrogen gas). • Minimum section = 0.25mm. • Sizes ranging 12mm in length to volumes up to 3m cubed. Quality issues. • Poor control of wall thickness, typically + or – 50 per cent of nominal. • Creep and chemical stability of product important considerations. • Residual stresses, e.g. non-uniform deformation, may relax in time causing distortion of the part. • Good surface detail and finish possible. • The higher the pressure the better the surface finish of the product. • Allowances of approximately + or – 0.1 mm should be added for dimensions across the parting line.
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