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Materials for Inspiration Design 3 2013/14 DES09135 Trimester 1, Project 1 Sensor Controlled Tap Product Design Specification

Gavin Housley/40063497

PDS Issue Number 1.0.6 21/10/20


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Semi-transparent HDPE cover for LED strip allows protection and access to LED's for maintenance

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LED Temperature Display Strip

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Tap Sensor Module

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Brief Design a bathroom or kitchen. The manufacturing process for the main body of the tap must be metal casting however other processes and materials may be considered for secondary components. The operation for the tap is to use a motion detecting sensor and an LED system is to be incorporated in order to display temperature control. The tap is to be situated in a bathroom and the design should reflect this appropriately. The main concern of the design is to promote water conservation in urban settings. Due to current global climate, heat spells and drought are becoming increasingly more common. The design should be able to be situated in more upmarket situ however control the water waste. The use of the sensor controls will allow for water control while material and form will inform the price and situ of the tap.

Tap design in situ

Performance The tap is controlled by an infrared sensor module. Heat will be controlled with a lateral motion such as swiping hands to the left across the sensor to lower the water temperature, swiping right will raise the temperature. The temperature of the water will be displayed on an LED strip on the top back of the design. This strip will contain 3 LED’s and emit the colours blue (cold), white (roughly room temp and red (hot).


The LEDs will be contained within a frosted HDPE case to prevent water damage and allow for the entire strip to glow with the predominant colour.

Sensor controlled tap diagram

LED display diagram

The tap is designed to reduce water use so the sensor will only work when there is an object in motion within its field of view. When the object is removed from its field, or becomes stationary, the tap will stop the water flow after three seconds. This is a key component to the tap design. The sensor is placed in such a way that an item must be under the nozzle in order to allow water flow. This conserves water as there will be no flow as the user is brushing their teeth, only when the toothbrush is under the tap head. Also, when washing hands, the flow is only allowed when the user requires it, not while drying hands or applying soap etc.


Sensor position in relation to design brief

Flow rate will be set at 0.1 litres per second. This rate provides enough force to sufficiently wet or fill while not being so powerful as to create splash back. The sensor control box will be positioned under the shelf the sink is attached to. It is imperative that this unit be accessible in case of malfunction so it will be made of sheet aluminium in order to provide a high degree of finish/desirability.

Cost The aim will be to place the product in the upper end of the pricing scale for domestic taps. Research has shown that this bracket is between £150 and £180. The Die casting allows for a relatively large number of units to be produced quickly while nickel-chrome plating gives a desirable finish. Research has shown that a tap of similar standards will cost between £140 and £240 depending on height, spout reach, number of components and brand, which is why a similar amount can be charged for this product. The initial die cost must be factored into the price. As a magnesium alloy is the material of choice, it allows a quick working time with reduced equipment and energy costs. These savings are then passed onto the customer as they are receiving a unique design with a sophisticated level of performance and operation while still maintaining a high street price without stepping into the specialist markets. The cost has been estimated by comparison to the manufacturing process of other examples, number of components, final finish and performance.


Manufacture The main body of the design will be cast using Die Casting. Specifically Gravity Die Casting. Die casting was chosen over Investment or Sand Casting because: -

Higher production rate than Investment Casting or Sand Casting. Initial set up cost is higher than Investment due to die tooling however this will be cancelled out with the production rate. Lower volume of waste/ more recyclable waste produced than Investment Casting. Reduced cross section can be created which could not be with Investment or Sand. Relatively good surface finish from process. A secondary finish will be applied after the casting to prevent corrosion so casting finish is not of the greatest importance. Die Casting allows for high dimensional accuracy. The accuracy is not that of Investment however is still very high. The internal form will be created using a sand core which can be removed easily after the casting. Gravity (low pressure) Die Casting will be used as the alloy chosen for the product has a low viscosity and a quick casting time, eliminating the need for pressure casting and reducing cost and energy.

Casting is a manufacturing process by which a molten material such as metal or plastic is introduced into a mould, allowed to solidify, and then ejected in its final form. Casting is used for making parts of complex shape that would be difficult or uneconomical to make by other methods, such as cutting from solid material. Die Casting (also known as Permanent Mould Casting) is a process in which the molten material is forced into a mould, usually made of steel. This process is usually accomplished by using high pressure injection systems. Depending on the casting material, the other process of gravity moulding can be used. Gravity Die Casting is a manufacturing process that involves pouring molten material into a mould in order to produce metal parts which are built to tight tolerances. The molten materials can be Aluminium, Magnesium, Pewter (or other so called white or pot metals), Zinc or an alloy of Zinc mixed with an amount of copper and aluminium. Basically, any metals that have a lower melting point than steel can be used for Gravity Die Casting. The mould used in Gravity Die Casting is nearly always built of steel. This steel is usually hardened and polished to a high mirror finish before it is put to use. An alternative to steel moulds are graphite moulds which are used with less frequency due to the difficulty and health risks involved with machining graphite. Gravity casting is usually used when the finished product is more visually based then structurally based which is why this method is a favorite of artists and even some jewelers. The loss of strength is due to the lack of pressure used in this process. If strength is required but still want to use gravity casting, more of the molten metal will need to be used which will increase the weight.


Gravity casting machine

With all Die Casting process, draft angle is imperative to the manufacturing process. With the tap design, the draft has been used as a design consideration and exploited in order to both produce a tap that can be manufactured and one with a unique form.

Although it is possible, with the right research and structure, to have products manufactured in the UK for a similar price, but with the advantage of a far greater degree of control, it is cheaper to transport them on a freight ship than it would be to transport within the country on a lorry.

Material The primary metal for the die casting will be a Magnesium alloy with the commercial name AZ91D The percentage of the alloy composition is as follows:


8.3-9.7% Aluminium 0.15% Manganese min. 0.35-1.0% Zinc 0.10% Silicone max. 0.005% Iron max. 0.030% Copper max. 0.002% Nickel max. 0.02% max. other (each) balance the rest with Magnesium. Magnesium alloy AZ91D is the primary choice for casting: -

Magnesium is the lightest structural material at 1.8gms/cc. Âź the weight of steel and 2/3 the weight of aluminium.

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Relatively low melting point at 595 degrees Celsius. Aluminium has a melting point of 660 and pure magnesium is 648 degrees. Lower melting point means reduced embedded energy in the product production. Casting takes place usually at between 625 and 700 degrees.

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The casting time is 4 times less than that of aluminium. The material will harden within the mould much more quickly.

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The die life is between 3 and 4 times of that if aluminium alloy is being used. Greater die life means less material required and more importantly, less machining required, a huge cost in the casting process.

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Magnesium is a very abundant metal. Magnesium supplies are all but inexhaustible.

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30% weight reduction in comparison to aluminium.

Magnesium dries up quickly because of its natural lubrication and rapid heat dissipation. This allows for fast machining after casting to apply finishing touches such as threading or additional boring. Magnesium does require an additional degree of protection in the melting bath. Magnesium produces a permeable skin between the bath and the molten alloy. This allows oxygen bubbles to form and burn within the molten metal, creating flaws and impurities. A gaseous nitrogen layer is pumped into the bath in order to negate this effect. This secondary process would not be required with aluminium alloy however is justified due to lower casting time and lower melting point of the magnesium alloy. The magnesium alloy AZ91D was chosen over other magnesium alloys due to its high level of purity and its excellent corrosion resistance. AZ91A and AZ91B can be made from secondary metal which


would reduce the cost of the alloy however due to their poor corrosive resistance; they are not fit for purpose for a bathroom tap. During casting, it is not uncommon for 50% of the AZ91D alloy to be cast and the other 50% to become scrap. However with this particular alloy, its low impurity content means it can be reused with great efficiency while retaining its initial properties. If impurities and inclusions were to be part of the alloy during recycling it would cause the corrosive resistance and strength/ductility to become significantly hampered by each, respectively. If the recycling process is properly monitored, recycling at the point of casting can be rigorously controlled and highly effective. The AZ91D alloy can be recycled, even with impurities and inclusions, so long as the final product has been understood in terms of the limitations of the recycled materials. AZ91A,B,D

AZ91C,E

Property

F Temper

F Temper

T4 Temper T6 Temper

Tensile strength, MPa (ksi)

230 (33)

165 (24)

275 (40)

275 (40)

Tensile yield strength, MPa (ksi)

150 (22)

97 (14)

90 (13)

145 (21)

Elongation in 50 mm (2 in.), %

3

2.5

15

6

Compressive yield strength at 0.2% 165 (24) offset, MPa (ksi)

97 (14)

90 (13)

130 (19)

Ultimate bearing strength, MPa (ksi)

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415 (60)

415 (60)

515 (75)

Bearing yield strength, MPa (ksi)

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275 (40)

305 (44)

360 (52)

Hardness, HB

63

60

55

70

Hardness, HRE

75

66

62

77

Charpy V-notch impact strength, J 2.7 (2.0) (ft.lbf)

0.79 (0.58) 4.1 (3.0)

1.4 (1.0)

Finish The product will be finished using Nickel-chrome. This process involves electro plating nickel onto the cast products surface then electro plating chromium on top of that. The nickel plating provides the smoothness, much of the corrosion resistance, and most of the reflectivity. The chrome plating is exceptionally thin, measured in millionths of an inch rather than in thousandths i.e. it will have no structural property. Nickel-chroming must be a precise process as flaws in the barrier layer (the finish) would result in accelerated corrosion of the coated material, magnesium AZ91D. This is due to the direction of electron flow between materials. With galvanisation, zinc sacrifices electron in order to protect the steel on which it is layered and is known as “sacrificial layering�. Provided there is still zinc present on the steel surface, corrosion will be limited. With chroming, the opposite occurs. If the barrier is perforated, the magnesium AZ91D will actually transfer electrons to the chrome, accelerating the


corrosive rate of the main metal. Chroming is a highly refined and understood industrial process meaning it is heavily controlled and very well tested.

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The position of the tap will be in a bathroom and water will be present. Using nickelchroming over simple chroming adds an extra degree of corrosion resistance. Due to the small depth of the chrome finish, millionths of an inch, the process will yield not structural advantages to the product. Before the chrome can be attached, a rigorous cleaning process must be applied to the surface to be chromed. Magnesium alloy will be an excellent base for the chroming as it is easily machined down to a fine finish if required and impurities and dirt can be easily removed. The use of electro plating creates one seamless surface while the use of nickel before chrome creates a smooth surface. These elements provide a finish that is easy to maintain, no cracks or crevices for dust to accumulate. The surface is very stable and does not react with chemicals. Proof of this concept is chroming used on car part where numerous everyday chemicals are applied to the part yet it maintains its brightness and finish. The chroming does provided a degree of resistance to wear and tear and will last if treated properly however perforations in the finish will damage the structure of the product so it is vitally important the during transport, care is take. The additional packaging to secure and protect the product will raise the overall price of the product but the final result will justify this increase.

Quality Quality Standards ISO 9001 International Quality Management Systems Requirements


ISO 28000 Supply Chain Security Management Systems ISO 10005/10006/10007 Quality Management Systems BS EN ISO 14065:2012 Greenhouse gases. Requirements for greenhouse gas validation and verification bodies for use in accreditation or other forms of recognition BS 5750 British Quality Assurance EN 29000 European Quality Assurance

Use of magnesium AZ91D for Die Casting standards BS ISO 16220 Magnesium and magnesium alloys BS EN1753 Magnesium and magnesium alloys BS 2970 MAG3 Properties of Magnesium alloys BS 4L 101 Procedure for inspection, testing and acceptance of magnesium-based ingots and castings ASTM (US) B94 Standard specification for Magnesium alloy Die Casting AMS 4490 Magnesium alloy castings

Use of Nickel-chrome electroplating finish BS EN ISO 2064 Metallic and other inorganic coatings. Definitions and conventions concerning the measurement of thickness ISO 1456 &1457 (1,2,3,4) Electrodeposited coatings of nickel plus chromium and of copper plus nickel plus chromium BS EN 12540 Corrosion protection of metals. Electrodeposited coatings of nickel, nickel plus chromium, copper plus nickel and copper plus nickel plus chromium BS 4641 Requirements for electroplated coatings of chromium on ferrous and non-ferrous metals

CE Mark This signifies that the product conforms to health, environmental, and safety regulations and makes the product legal to be sold in the European Union. The CE mark makes a buyer's job much easier as it helps a buyer find quality assurance. The CE Directory makes a buyer's job even easier.


Design Registration See attachments

Packaging Volume of material used

= 150 350 mm3 = 150.350 cm3

Density of Magnesium

= 1.8 g/cm3

Total weight

= 270.63 g = 0.271 kg

Weight of finish

= 15% of 0.271 kg = 0.041 kg

Additional tubing and sensor unit and LED Total weight to be shipped

= 2.5 kg = 2.812 kg

The packaging will be a simple cuboid with the dimensions of 250mm x 150mm x 70 mm. Within this space there will be addition bracing for the tap parts which will form extra sections for smaller fixtures and fitting such as brackets for control box, valves for hot/cold inlet etc.

Shipping is a primary concern for any manufacture, especially if the product is being made offshore. For a container with internal dimensions of 2200mm x 2250mm x 5340mm, a total of 9765 units could fit with a total weight of 27 459.18kg Ergonomics


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Distance from tap base to aerator, horizontally: 160mm Height of aerator from base, vertically: 90mm Distance of sensor from base, horizontally: 150mm Height of sensor from base: vertically: 90mm

The design requires the user to engage with whichever practice they are undertaking more fully before engaging with the tap. For example, they will put tooth paste on the brush before turning the tap on instead of wetting the brush, leaving the water running, then applying the paste. Even if they require wetting the brush first, the timer means significantly less water is used. Having a greater distance horizontally means the sensor can be placed further toward the user and closer to the aerator. The LED temperature display is located at the back of the tap as the users eye line will be vertically in line with their hands and this position allows them to glance upward to check the temperature.

Offshore Manufacture Offshore or over-seas manufacture is an integral part of manufacturing process and product development today. The production costs and delivery costs are generally lower due to the exchange rate and differences in international living wages. There are inherent risks with offshore manufacture such as: -

Loss of control


Due to the distance between yourself and the factory, intermittent checks cannot be completed as the product is being produced. You may receive the full order and one aspect of every unit could be incorrect. -

Maintaining and managing working relationships The distance, cultural and language barrier present a problem when attempting to maintain relationships. The manner in which problems are resolved in one country is completely different to that of the next and may cause offence.

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Unauthorised use of intellectual property The distance and different market means intellectual property could in infringed and designs could be copied/stolen.

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Standards Standards vary from market to market. There are international standards and manufacturers should be aware of the standards of the market into which the product will enter. However there is still an opportunity for the failure to uphold these standards which, in the worst case, would mean receiving a shipment that is not fit for sale. The distance between designer and factory also means inspection is difficult and costly.

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Impact of design practice There is a distancing between design and manufacture and a loss of potential experience which could later inform the design process with a greater knowledge of manufacturing process and material properties.

Business ethics Transparency is essential to business. It must be maintained in relation to taxation, both locally and internationally, material sourcing, recycling, industrial process, intellectual property and internal structure. Only if transparency would disrupt the working process, endanger an individual’s privacy or threaten the profitability of the business (in terms of trade secrets/internal discoveries) would it be revoked. Offshore manufacture will be adopted to increase profitability, streamline and speed up the manufacturing process and increase global networking and company relationships. It is imperative that companies be researched and understood before any business is undertaken. Living wages, safe and decent working conditions and management structure must be considered before a transaction is completed.

Sustainability


Creating a sustainable process is not only beneficial to natural resources but also to business. If materials are environmentally sourced and recycling is used wherever possible, while maintaining standards, the company can both be proud of its environmental contribution and be rewarded by the savings that reuse provides. In many cases investing in new technologies for sourcing and manufacture may prove initially expensive but will, in the long run, pay for them and streamline the processes as well as reduce carbon emissions, reduce resource consumption and promote a sustainable future. Material and process choice will be informed by sustainability. Materials that are in larger abundance or are easily replenished will be chosen over rare materials unless there is a performance issue in which case the material choice will be appropriately analysed. It is also an interest to choose materials that have lower embodied energy costs from basic state to finished product. It must be noted that these new processes and resources will always be a major consideration for the company both now and in the future. The company will however, not put its financial stability at risk in order to experiment with unproven practice as its employee’s and reputation are primary concerns at the present. If, in the future, a situation presents itself to experiment while maintaining employee security, then that opportunity will become a priority.

References Making It: Manufacturing Techniques for Product Design, 2nd Edition. Chris Lefteri Sustainable Materials, Process and Production, The Manufacturing Guide. Rob Thompson http://www.jim.or.jp/journal/e/pdf3/47/04/1047.pdf http://www.brunel.ac.uk/__data/assets/pdf_file/0007/295108/G-Liu-2007-No-12.pdf http://mg.tripod.com/asm_prop.htm http://www.keytometals.com/article75.htm http://www.keytometals.com/Article78.htm http://www.toolingu.com/definition-500255-54059-draft-angle.html http://www.efunda.com/materials/alloys/alloy_home/show_alloy_found.cfm?ID=AISI_Type_316&p rop=all&Page_Title=%20Metal%20Alloys%20Keyword%20Search%20Results http://chemistry.about.com/od/alloys/a/list-of-alloys.htm http://www.ampcometal.com/en/index.php?page=gravity http://2.bp.blogspot.com/-N-Ldi5xg5Q/UUgCFxUwGfI/AAAAAAAAAsA/QoiS_4hVeks/s1600/Periodic+Table.png http://www.matweb.com/search/MaterialGroupSearch.aspx?GroupID=180


Tap Design for 3rd Year Materials