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Project Kelvin

Supergeek

Chloe Fong Designing Our Futures: Winter warmth University of Brighton 2014


Grab a coffee, It’s about to get technical. This book was written as a supplementary book for anyone who is interested in the technical manufacturing side of Project Kelvin: A moving thermometer for older people in the shape of a plant. For the story of the development of the product, check out the Progress book.


Table of Contents

#1 Product Design Specification

05-12

#2 product schematic

13-14

#4 parts party

13-26

#5 failure mode and effects analysis

27-30

#6 design for assembly

31-34


35-36

#6 kelvin’s pot

37-38

#7 technical drawings

39-46

#8 life cycle assessment

47-50

#9 project planning


#1 Product Design Specification The holy grail of the product design process; a document that needs constant attention.

1.0 Performance

1.1 Move from open to closed position when sensor reads under 18C 1.2 Full range of movement must be made under 3 seconds 1.3 A 5 second delay between each temperature reading 1.4 Motors must be triggered within 1 second of temperature read 1.5 Motor must turn at 500rpm to get full range of motion 1.6 Kill switches must be activated at maximum and minimum heights to prevent the motor form failing

1.6.1 Kill switches must be 12mm apart

1.7 An LED will be used to indicate if the product is functioning correctly. 1.7.1 Green indicates power is on and product is functioning.

1.7.2 Red indicates a problem with the circuit

1.7.3 No light indicates no power

1.8 The electronics will be placed in the pot housing and will be tamper sealed to prevent users from opening it 1.9 Product should have an ingress protection (IP) rating of 45 1.10 Pot housing must be waterproofed to prevent users from accidently watering it 1.11 TPE over mould should allow followers to achieve full range of movement 1.11.1 Followers have a range 45 degrees

05


2.0 Environment

3.0 Product Life Span 4.0 life in service

2.1 The electronics should be sealed within the pot plant housing to prevent corrosion, rust and debris 3.1 Product will be on the market for 5 years 4.1 Should withstand 3 cycles of operation a day on average (including summer months) for at least 3 years [3 x 365days x 5 years + 3 (leap year) = 5478 cycles] 4.2 Life in service should be assessed against criteria outlined in section 1 and 2, performance and environment

5.0 Environmental Impact

6.0 Target Costs

5.1 Product should strive to have the lowest carbon footprint (measured in kilograms of CO2) without sacrificing performance criteria 6.1 The product should have an end user price under ÂŁ40 6.2 The cost of shipping and packaging should be less 15% of total production cost

7.0 Quantity

8.0 Maintenance

7.1 Product will be made in batches of 10,000 to reduce tooling costs. 8.1 Product should be maintenance free 8.2 Product should have a one year warranty

9.0 Marketing

9.1 Product should be named Kelvin 9.2 Product will initially be marketed towards the UK market 9.3 Product will launch around Christmas time to increase initial sales 9.4 Product could be marketed towards younger people buying gifts for older family members

06


10.0 Packaging

10.1 Packaging should have text mortality and its causes

to raise awareness of winter

10.2 Packaging should protect the product in transport 10.3 Packaging should be able to be stacked 11. Size and Weight

11.1 Product should be no more than 250mm in height and 120 in length 11.2 Followers should open up to 90 degrees and leaves should have a wingspan no more than 210mmÂ

12 .0 Shipping

12.1 Parts manufactured in South China, transported by truck to Hong Kong where it would be shipped to an assembly point UK by sea to be assembled. 12.2 Where possible, to reduce the cost and carbon footprint, parts will be grouped together before shipping 12.3 Parts will be shipped by CMA CGM from Hong Kong Kwai Tsing Port to Felixstowe

13.0 Manufacturing Processes

13.1 All manufacturing facilities have to comply with ISO 9000 standards. Pending revision of IS0 9001:2015 13.2 Electronics engineering, including PCB and circuit layout, as well as firmware design and programming will be outsourced to China

13.2.1 The internal circuit should be assembled in China

13.3 Delrin, Nylon and PP parts should be injection moulded in South East China 13.4 Where possible, moulds will be designed for parts of the same material

14.0 Aesthetics

07

14.1 Product should be styled to promote peace and calm.

14.1.1 Kelvin should blend in to different interior styles

14.1.2 It should have a colour scheme that reflects nature and relaxation


Injection Moulding


16.1.2 A leaf thermometer by Hideyuki Kumagai

09


14.0 Aesthetics (cont.)

14.2 Haptic

14.2.1

14.2.2 texture

15.0 Ergonomics and semiotics

Product should have a matte finish Leaves and stem should have the same

15.1 Packaging should be easy to open for the 90th percentile

15.1.1 Pull strength with thumb and finger grip

15.2 User should easily take the product out of the packaging 16.0 Competition

17.0 Quality and Reliability

15.2.1 Under 20 seconds

16.1 There is not direct competition, however, price point will be set on par with other decorative thermometers

16.1.1 Including Galileo thermometers

16.1.2 A leaf thermometer by Hideyuki Kumagai

17.1 Product must have a one year warranty 17.2 Product should meet requirements for CE marking 17.3 Product could be Kitemarked

18.0 Standards and Specifications

18.1 Product will comply with the EU low voltage directive 18.2 Product will have an IP rating of 45 18.3 All manufacturers will comply with ISO 9000 18.4 The following British and ISO standards will be adhered to

18.4.1 BS EN 50088:1996 (Electrical toys. Safety)

18.4.2 BS 5000 part 99 (Motor Performance)

18.4.3 BS 61558-1 (Safety of power transformers, power

supplies, reactors and similar products. General

requirements and tests

18.4.4 BS 3643-1:2007 (ISO metric screw threads.

Principles and basic data)

10


19.0 Company Constraints

19.1 None- except those outlined in point 13: Manufacturing Processes

20.0 Processes

20.1 All components are specified in metric form to ISO 4900 standards

21.0 Safety

21.1

Surge protectors in transformer to BS 61558-1 standards

21.2 EVA foam cover must be water resistant to prevent accidental watering of the product 21.3 BS EN 50088:1996 adherence as products are designed for older people, a population with lower dexterity and deterioration of general cognitive ability

22.0 Testing

22.1

User testing (see separate progress book)

22.2

Product will be randomly tested

22.2.1 0.5% of each batch will be tested for 5500 cycles to detect faults in batch

22.2.1.1 IP rating will be tested in accordance to BS EN 60529:1992 (Degrees of protection provided by enclosures) 22.2.2 Surge protection will be tested before assembly

23.0 Legal

11

23.1 use

Possible litigation lies in user electrocution with improper

23.1.1

Tampering with the electronic pot houses

23.1.2

Submerging product in water

23.1.3

Watering the product with a high power hose


Instalation requires plugging in and flicking a switch.

24.0 Installation

24.1 Product must be easy to install 24.1.1 Product must not require any previous technical knowledge install 24.1.2 A user who has never seen the product before should be able to install the product within 5 minutes

25.0 Documentation

25.1 Product should have an instruction manual 25.1.1 Type should be at a high enough point size to be read at 300mm away 25.1.2 Safety signs and warning will be printed in the user manual in accordance with BS 5499-1:2002 (Graphical symbols and signs. Safety signs) 25.2 Product packaging or documentation must have information about causes of winter mortality in older people 26.1 Recycling points should be at point of sale from launch to 5 years after obsolescence from the market

26.0 Disposal 12


#2 Product Schematic System A: Mechanical 1. Screw Thread

System b: Electrical 6. Motor

2. Push Rod

7. Temperature Sensor

3. Followers

8. Limit Switch

4. Gear 1

9. Microprocessor

5. Gear 2

4 2 1

9 10

5

6

8

7 11

13


System c: Appearance 10. PCB 11. LED power indicator 12 . Wire 13. Power Button (On wire)

14. Pot 15. Inner Stem 16. Stem Overmould 17. Leaves 18. Top of pot housing

16

19. Rubber seals

15

3

17

18

19

12 13

14 14


#3 Parts Party


1. Screw thread Dimensions: W: ISO M4 metric thread (fine pitch) L: 50mm Material Requirements: High tensile strength. Dimensional stability Material: PTFE filled homopolymer Acetal (Dupont Delrin 520MP) Rationale: Although it has a high price and slower production rates, acetal has good tensile strength, (better than some metals), dimensional stability and high flexural modulus (stiffness) . Acetal filled with PTFE makes the part self lubricating and a low friction coefficient against other parts made of the same material (Dupont, n.d.) Process: Injection Moulding DFM Considerations: Delrin has a very high thermal expansion coefficient, meaning the mould will have to allow a large amount of shrinkage. A high tolerance is needed for the threaded inner face. Need to allow a larger cycle time it also has to have a low tolerance as nut will not fit. Material testing and QC: ISO 1798 to test for tensile strength, compare to spec sheet after moulding. Test fit against gear 2 Features: Lock and Key system to stop rotation, push disk for limit switches

2. Push Rod: Dimensions: L :2mm, W : 4mm, H :24mm Material Requirements: Material must be stiff as it is carrying the load of the followers and the leaves. Material: Nylon 6 -glass bead filled (higher flexural modulus than 6/6) (Curbell Plastics, n.d) Rationale: Can be placed in the same mould other components. Glass beads will also make the part stiffer Process: Injection Moulded DFM Considerations: Shrinkage, larger cycle time Material Testing and QC: Test assembly with push rod, pivot pin and followers for 7500 cycles (4 cycles a day on average x 365 days x 5 years life in service =7300)

16


3. Followers: Dimensions: L:2 W:42 H:2 Material Requirements: Material must have a low friction coefficient against the push rod. Should also be stiff as it bears the load of the leaves. Material: Delrin 520MP Rationale: Nylon/Acetal parts reduce wear. Can be in the same mould as other Delrin parts. Process: Injection Moulding DFM Considerations: Shrinkage, larger cycle time Material Testing and QC: Test assembly with push rod, pivot pin and followers for 7500 cycles (4 cycles a day on average x 365 days x 5 years life in service =7300

4. Gear 1 (attached to motor): Dimensions: face width: 2mm, pitch diameter 14mm, number of teeth: 32 Bore to fit motor Material Requirements: High Flexural modulus. Low friction coefficient to reduce wear against other gear. Dimensional stability after cooling as teeth need to fit Material: Nylon 6: glass bead filled :Zytel 101(higher flexual modulus than 6/6, Dupont, 2014) Rationale: Tough, hard wearing, low friction coeffiencet. Maoa et al (2009) found that a combination of nylon and acetal reduces wear in gears. They also found that Nylon as the driver gear performs better than using acetal as the driver gear. Nylon also has better adhesion to the motor compared to Delrin 520MP Process: Injection Moulding DFM Considerations: Nylon has a high thermal expansion coefficient, meaning the mould will have to allow a large about of shrinkage. Large cycle time. Material Testing and QC: Create a jig with the dimension of the final piece. Check parts against jig 17


Gear 2 (with inbuilt nut): Dimensions: face width: 2mm, pitch diameter 14mm, number of teeth: 32. Bore ISO M4 nut threads. Bore diameter 4.08 (to reduce friction with m4 thread) Material Requirements: high flexural modulus as a bent gear will cause product to malfunction. Low friction coefficient to prolong life and efficiency. Dimensional stability after cooling as gears need to fit. Ideally self lubricating to prevent jamming. Threaded face must have a high tensile strength and dimensional stability to move threaded rod. Material: PTFE filled homopolymer acetal (Dupont Delrin 520MP) Rationale: Tough, hard wearing, low friction coefficient. There are other materials that also have these properties (such as PEEK) but they are more expensive, can be injection moulded with other Delrin parts (Cubell, n.d.) Process: Injection moulding DFM: Delrin also has a high expansion coefficient and high shrinkage Material Testing and QC: Create a jig to check dimensions after shrinkage

18


6. Motor (bought in component) Part Number: DS-13SS050 Manufacturer: Dong Shun Motor Co. Ltd. Rationale: 500rpm motor, geared. bi-directional, small size, low MOQ: 1000 pieces. Location: Southeast China

Drawings from manufacturer’s website

7.9.&10.Temperature sensor, microprocessor and PCB (Outsourced bought in components) Manufacturer: Edadoc Co Ltd Rationale: As the design, layout and specific selection of components require highly specialised knowledge, training and experience. These component merchandising and firmware engineering will be outsourced to a Chinese manufacturer. Location: Southeast China

Drawings from manufacturer’s website

8. Limit Switches: Bought in component Part Number: MX-1201 Manufacturer: Dongguan Electronics Co. Ltd.

City

Bailing

Location: Southeast China Note: Limit switches must be 12.5mm apart. It’s locations will be drilled out on the PCB to aid assembly accuracy. 19


20


14. Pot Dimensions: See technical drawing Material Requirements: Must be waterproof for IP 45 rating. Should look high end to justify price of ÂŁ40. Material Choice: Terracotta with PU glaze on the inside. Rationale: Terracotta does not require expensive tooling so the initial start up cost is minimised. Although it would cost more per unit in the long run, it gives an overall higher end appearance and increases the perceived value of the product. Process: Jolleying DFM: Jolleying is one of the most cost and time efficient methods of mass production. It is used

21

to make symmetrical parts. Due to the firing and drying, tolerances are low, which will give the part a hand-made style and is acceptable as the pot is a cosmetic part. The holes for the power cable, LED and temperature sensor will be cut out after Jolleying and before firing. A waterproof PU coating will be used on the inside of the pot to achieve the IP rating. Wall thickness will not be uniform but the interior surface will be smooth. Ridges in the interior walls of the pot will hold gear disks in place. Jolleying only allows parts with rotational symmetry so the idea of a logo engraving would not be possible. However the logo could be heat transferred onto the pot Material Testing and QC: Test for waterproofing as per IP code by the European Committee for Electro Technical Standardization.


17. Leaves: Dimensions: As per CAD file. dimensions H:2mm W:20 D:5mm

Snap fit

increasing its desirability. There is also a cut out for the followers to fit in.

Material Requirements: Must be the same finish as stem mould. Low density to decrease load on followers.

DFM considerations: Production rate can be increased as both leaves are identical, limiting assembly errors and decreasing the initial start-up cost as only one mould is needed.

Material: TPE Rationale: By using a flexible material, the overmoulded stem can be snap fitted into the structure of the leaf (see next page overmould). It also increases the overall realism of Kelvin,

Material testing and QC: Snap fit will be tested against other parts to eliminate errors. Features: Snap fitting (see image)

22


15. Inner Stem Dimensions: As per CAD file. Start radius 5mm end radius 1.5mm (flat cap). Uniform tapering. Material Requirements: Material needs to bind to overmould, cost should be low as there are not as many tolerance or structural requirements as mechanical parts. As it will be over moulded , the mould temperature has to be higher than the overmould Material Choice: Polypropylene Rationale: The material was chosen in conjunction with the overmould (TPE Dynaflex G2711) for best adhesion and a lower mould temperature. (GLS Corp, 2004) Process: Injection moulded DFM: Part is hollow, 2 part injection moulding along centreline of front plane. Uniform wall thickness of 1mm. Material Testing and QC: Cannot be tested before over moulding, obvious warping and deformities will be eliminated by eye in factory.

23


16. Stem overmould: Dimensions: As per CAD file. Height 140mm, Start radius 8.8mm, end radius 2.5mm Material requirements: Must be flexible (shore D rating 5 or under to allow movement of followers) Moulding temperature must be lower than stem and tube Material: Thermoplastic Elastomer (TPE) Dynaflex G2711 Process: Injection moulded (overmould) Rationale: Originally selected Hystrel RS (Dupont), however the melting and injection temperatures were quite high, and would melt or warp the substrate (core of stem) so Dynaflex was chosen due it it’s low moulding temperature. The data sheet also specifies that it bonds well with PP. Over moulding TPE guidelines includes creating interlocking sinks in the substrate part, (GLS corp, 2004) but as the part is completely over moulded, has small dimensions, and the shape of curvature , there is no need for interlocking sinks. Material Testing and QC: Assemble with CAM system , inner core and leaves. Build a jig to push the rod up 12.5mm for 7500 cycles and check for tears on overmould. Features: There is a ridge at the base to seal the pot housing. It also makes assembly easier.

24


18 &19. Top of Pot housing, gear disks and O ring Dimensions: Top plate diameter 68mm H: 2mm Bore hole: 1mm, gear disk diameters: 66mm, 66mm. H: 2mm Bore: 1mm. Key mechanism: 2x1x1 Material Requirements: Waterproof. Rubber gaskets added to seal housing to IP 45 standards Material: Top Plate-EVA, Gear disks and key mechanism- PP, O ring: rubber Rationale: The top plate can be easily manufactured with die cutting to reduce costs. As key mechanism needs to be added, PP can be easily injection moulded, both disks can be made in the same mould to reduce cost and lead time. Process: Die cut top plate, Injection moulded disks. DFM: O rings are recommended to stretch at a minimum of 1% and a maximum of 5% and recommendation of 2%. The ring sizes will be cut 2% smaller than bore with 1% tolerance. Material testing and QC: Test to IP45 standards BS EN 60529:1992

25


26


Mechanical

#4 Failure Mode and effects analysis Brace yourself, it’s long.

Item

Potential Failure Potential effects of Mode failure

S Cause

O

D

Screw thread

Jams

push rod will not move, motor will not stop

8 debris, rust

4

2

Sticks

push rod will not move, motor will not stop

Fall out of Position

Movement will be distorted, might pierce outer shell

6 Product is dropped by user

1

1

Yield

Leaves will not move

7 Large impact on stem, possible from standing on the product of sitting on it

2

1

Jammed Pivots

Leaves will not move

7 debris, rust

4

1

Snap

Movement will be distorted, might pierce outer shell

6 User drops it

3

1

Gears

Jam

Motor will overheat, product will not move

8 debris, rust, wear

5

1

Motor

Burn out or Short out

Plant will not move, 7 Loose wires, corrosion, loss of primary function power surge

2

1

Temperature Sensor

Burn out

No temperature input, no movement

7 Loose wires, corrosion, power surge

2

4

Limit switch

Short out

Motor will not stop, causing thread to overshoot

7 Loose wires, corrosion, power surge

2

4

Jam

Motor will not start

6 debris, rust

2

4

Seize

Motor will not start

6 debris, rust

2

4

Push Rod

Electrical

Followers

Burn out

27


RPN

Recommended Action

Standard/Testing

Action taken

New S

New O

New D

New RPN

64

Lubricate plastic part

BS 3643-1:2007 (ISO metric screw threads. Principles and basic data)

Delrin 520MP (self lubracating)

8

1

2

11

6

bind to connection disk

Use moulding Use Resiweld Epoxy guidelines by DuPont (DuPont, no date)

6

0

2

8

14

Material choice: Delrin

As above

Delrin 520MP (self lubracating)

7

1

1

9

28

Material choice: Delrin

As above

Delrin 520MP (self lubracating)

7

1

1

9

18

Material choice: Delrin

As above

Delrin 520MP (self lubracating)

6

1

1

8

40

Material choice: As above Teflon filled Delrin

1x nylon wheel, 1 delrin wheel

6

3

1

10

14

Encase all electronics in pot housing, and tamper seal, Ingress Protection code 45

Test for Encased in pot waterproofing as housing per IP code by the European Committee for Electro Technical Standardization

5

2

1

10

56

As above

Compliance with BS EN 50088:1996 (Electrical toys. Safety)

As above

6

1

2

12

56

As above

As above

As above

6

1

2

12

As above

As above

As above

6

1

2

12

48

As above

As above

As above

4

1

2

12

48

As above

As above

As above

4

1

2

12 28


Appearance

Electrical (cont.)

Still the Fmea...

Item

Potential Failure Mode

Potential effects of failure

S

Cause

O

Microprocessor

Burn out

Product will not move according the temperature

7

Overheating

1

PCB

Corrosion

Product will not function

7

Flux residue

2

Transformer

Over heating

Fire risk due to negative feedback (drawing more power)

9

Transformer overloading 3

Power surge from socket

Blows all the components

8

National grid, lighting storms

3

LED

Burn out

No visual feedback of product function

1

End of life cycle

2

Pot

Scratch

Cosmetic damage

2

Shipping, point of sale, at the user’s home

7

Dent

Might dislodge gears

7

Shipping, Dropping, hitting against other items

4

Shatter

System will not fit together, product will not work

8

Being dropped from a significant height

2

Tear

Cosmetic, product will no longer look like a plant

4

User trying to force leaves

2

Break off at connection

Cosmetic, product will no longer look like a plant

4

Overuse of joint due to constant temperature change

4

Scratch

Cosmetic

2

Wear and tear

6

Water damage

Electrocution

10 User thinks the product is an actual plant and waters it

Leaves

Stem All All

29

2


D

RPN

Recommended Action

Standard/Testing

Action taken

New S

New O

New D

New RPN

5

35

None

5

70

Ask for evidence of manufacturer QC

Pass of test (BS EN 60068-2-83)

Manufacturer selected with ISO:9001 certificate. Explicit instructions

6

1

3

18

1

27

Inbuilt surge protection

Make sure component As above complies with EC Low Voltage Directive

9

1

1

9

6

144

Inbuilt surge protection

BS 61558-1 (Safety of power transformers, power supplies, reactors and similar products. General requirements and tests)

8

1

1

8

1

2

None

1

14

Originally designed using PP copolymer, however, pot material choice changed after user testing to increase desirability.

1

28

1

16

1

8

None

1

16

Material choice: DuPont TPE

1

12

None

10

200

Waterproof Plant

As above

Design to GE injection moulding guidelines

Material chosen

2

2

1

4

Ingress Protection code standard test. BS EN60529:1992

Green top to warn user. Ingress Protection rating of 45.

10

0

10

0

30


#5 Design for assembly Kelvin will be assembled in 2 parts, the pot sub assembly and the stem one. The two systems interlock with the snap fitting at the base of the stem overmould.

31


Stem Assembly: The stem assembly also consists of layers, but the process has a longer lead time due to over moulding. The CAM pivot system is its own sub assembly within this assembly. The overmould on the connections are hollowed out to reduce shrinkage problems. One: Assemble CAM system (push rod, followers and pivot pin) Two: Fit CAM system inside the inner tube from the bottom Three: overmould stem and connectors Four: Snap fit the leaves onto connectors Then snap in the top of the pot housing and place and fix onto the pot assembly and voila, a Kelvin is born.

32


Layer one: motor mount, the PCB (with limit switches and microprocessor soldered on), LED and wire.

33

Layer two: The lower gear disk will be sandwiched between the motor and gear 1. The screw thread is inserted from the bottom (due to key system) the whole system will be placed in the pot. Gear 2 is then screwed on. (see assembly drawing)


Layer 3: Top gear disk

Layer 4: The top disk will not be put on until assembled with stem subassembly

Pot assembly The sub assembly will be put together in layers. There are shelves in the interior wall of the pot part, which allows the gear disks to sit flush in their correct positions.

34


#6 Kelvin’s pot Most of the manufacturing processes to make Kelvin are industry standard Injection moulded parts, for details on how each has been optimised for its manufacturing process; look back at the parts party section. One of the processes that is less common is Jolleying (yes that the actual name), used in the production of the pot. Jolleying is a process for hollow, symmetrical ceramic parts. The theory of it is based on a potters wheel. A clay liner (an extruded slug)is placed in a spinning mould, and a template of the cross section is then put into the rotating mould, a blade on the top cuts of the excess. Jolleying can only be used to make symmetrical

parts, but the wall thickness does not have to be uniform, making the lip of the pot easier to make. However there are some disadvantages that need a work around, the tolerances for Jolleying is low, at about 1% due to firing and cooling, but the good news is, some manufacturers, for a higher price will increase the tolerance. Compared to injection moulding, the initial tooling cost is lower, but in the production process is slow as pots need to be fired and cooled. A manufacturer could be sourced in the UK to limit losses from transporting fragile goods. (Lefteri, 2012)


Tools needed for Kelvin’s profile


#7 Technical drawings

37


The Technical drawings sadly could not fit into this booklet. They will be available on request. Alternatively, if you are marking this book they will be handed in separately.


39


#8 Life cycle assessment

The life cycle analysis was done to assess the environmental impact of Kelvin. At the point of the analysis, Kelvin still had a plastic pot, so the details might not be as accurate.


This one is long too... Information from CES Edupack

Part one: Goal Definition 1.1 Goal

1.2 The intended audience

The goal of the assessment is to: •

Complete a Life cycle Inventory to assess the environmental impacts of producing a form changing thermometer

To use data collected in point 1 to evaluate material selection choices

To use data collected in point 1 to make design changes to reduce the environmental impact

Potential investors for the launch of the product who are conscious of the environmental impact of the product

Environmentally conscious retailers who want to stock the product

Designers who want to optimised the product to lower environmental impact

Part two: Scope 2.1 Function of the product

41

The primary function of the product is the alert older people, aged 65+, of ambient temperature drop in their indoor environment as they have a diminished physiological ability to sense temperature drop (keatinge, 2002) The product has the form of a potted indoor plant as research has shown that indoor plants can promote wellbeing (Lohr, et al, 1996) The leaves of the plant will close up when the room temperature drops under 18C, the NHS recommended indoor temperature (NHS, n.d.). This will act as a visual cue to evoke behavioural changes, such as turning the heating on, or putting on a sweater.


2.2 The scope of the assessment

In this assessment, the manufacture, production processes and assembly of the plastic parts will be assessed and quantified. As the product consists of many parts, parts for each material with the same process will be analysed by volume, they are as follows: 1

Polypropylene (PP),Injection moulded: The inner core of the stem, the core of the leaves, the pot

2

Thermoplastic Elastomer (TPE), Injection moulded: the overmould for the leaves and stem

3

Nylon 6, glass bead filled, connection disk,

4

Acetal Homopolymer, PTFE filled (Delrin), injection moulded: Gear with inbuilt nut, threaded rod

5

Ethylene Vinyl Acetate, foamed and die cut: Top of plant pot

Injection moulded: Gear on motor,

The electronic parts such as the motor, microprocessor, and PCB board will not be assessed as they have strict functional requirements. This study will be divided into five stages: raw materials, production processes, transportation, product use and end of life.

2.3 Category Indicators

The following indicators will be used to quantify the damage to the environment caused by the production of the product: Indicator

Rationale

Energy (MJ) Only 11.3% of energy produced in the UK (Department of Energy and Climate Change, 2013), and 17% in China (Worldwatch Report, 2007) is from renewable sources. Since non-renewables sources produce greenhouse gasses such as CO2 , the energy used to produce parts is detrimental to the environmental

Carbon DioxideCO2 (kg)

CO2 is a greenhouse gas, causing global warming by trapping heat within the atmosphere.

Table 2.1.1: Rationale of Indicators

42


2.4 Assumptions

The following assumptions are made •

Nylon used is Dupont Zytel 101

Acetal used is Dupont Delrin 520MP

TPE used is GLS Dynaflex G2711

Where data is not provided by manufacturer datasheets, generic data will be taken from the same class of polymers.

Part Three: Inventory analysis 3.1 Raw materials

In order to produce an inventory analysis of the raw materials, the masses of each material must first be calculated. Material

Volume (m3)

Density (kg/m3)

Total Mass (kg)

PP

0.000005295145

946

0.005

TPE

0.0000021449

1000

0.002

Nylon

0.000002583119

1140

0.003

Delrin

0.0000031241157 1410

0.004

EVA

0.00001960984

45

0.001 Table 3.1.1 : Total masses for materials

PP

TPE

Nylon

Delrin

EVA

Energy (MJ)

0.35

0.18

0.33

0.49

0.079

CO2 (kg)

0.011

0.0079

0.02

0.027

0.0021

Table 3.1.2: Raw Materials

Dupont plastics have a distributor in Guangdong province (Yun Tian Shi Trading Co.), where the injection moulding factory is situated. Raw materials will be delivered to the factories from their South China distributor to reduce the environmental impact of transporting raw materials across the country.

43


3.2 Production Processes

The processes for PP, TPE, Nylon and Delrin and EVA foam are all injection moulded. PP

TPE

Nylon

Delrin

EVA

Mass (kg)

0.005

0.002

0.003

0.004

0.001

Process

I n j e c t i o n I n j e c t i o n I n j e c t i o n I n j e c t i o n Injection moulded moulded moulded moulded moulded

E n e r g y 0.087 (MJ)

0.038

0.062

CO2 (kg)

0.0029

0.0046

0.0065

0.062

0.014

0.0047

0.0011

Table 3.2.1 Production Processes

PP has the highest energy consumption; however this is due to the higher volume of plastic. Nylon requires the most energy per kg produced, due to its high viscosity. However, the material cannot be changed due to the requirement of dimensional stability and resistance to wear. The amount of PP can be greatly reduced by making the inner core hollow. To assess the environmental impact of the functional unit as a whole, the sum of all values are calculated Total Energy (MJ)

0.263

Total CO2 (kg)

0.0198

Table 3.2.2 Total values for production processes

The value above corresponds to one unit of the product. If the product was to be mass produced, over a longer period of time, the amount will significantly increase.

3.3 Transport of goods

Assuming that the parts will be injection moulded in Shenzhen, Guangdong, China, transported to Kwai Tsing container terminals in Hong Kong by truck, and sea freighted to Felixstowe, Suffolk. From

To

Tr a n s p o r t Distance E n e r g y CO2 (Kg) type (km) (MJ)

Shenzhen

Hong Kong

Truck

25

0.00032

2.3e-0.5

Sea freight

2e+4

0.049

0.0035

0.049

0.0035

Hong Kong Felixstowe Total

Table 3.3.1 Environmental impact of transporting parts

44


Due to the fact that Kwai Tsing harbour is one of the busiest cargo ports in the world, and Felixstowe one of the biggest in the UK, many containers will travel the same route on a day to day basis. To reduce the overall environmental footprint of the transport, shipping containers could be shared with other goods with the same destination. It would also become more cost effective. Assembly in the UK can reduce the space taken up for packaging in the container. It also reduces the potential ability to damage the product in the container.

3.4 Product use

The parts that consume energy during product use is not included in the

3.5 End of Life

The leave, stem core and the overmould cannot be recycled as overmouldings cannot be separated. Another material that was initially considered was Dupont Hystrel RS, a TPE made from 60% recycled plastics. However due to its high melting temperature, it cannot be moulded onto PP as it would deforms its inner core.

scope of this Assessment.

Delrin is a Polyoxymethylene, which is 100% recyclable. It is currently marked with a 7, other plastic, whether or not the plastic is recycled is dependent on the individual council. As nylon is also 100% recyclable and also marked 7, there could be a recycling bin at retailers that stock the product, which when filled could be brought to a disassembly point and each part can be recycled. PP is a widely recycled plastic, it is marked with a 5 according to ISO 11469:2000. However due to the fact that only the pot can be recycled, and it is also a housing for electronic parts, with a target audience of 65+, it is less hazardous if the user brings the product back to the point of sale for recycling. Although not included in the assessment, the electronic parts could also be stripped for precious metals if the product the collected to be recycled as a whole. There are ready made sheets of biodegradable EVA foam available from manufacturers, which would lessen the burden on landfills. As the foam is bought in sheets, injection moulding will not be needed, instead the foam will be die cut. Another way to reduce the environmental impact of the product is to blend virgin pellets and recycled pellets in the injection moulding process. 45


Part 4: Conclusion and steps forwards The total energy used and CO2 produced per product is as follows: Stage

Energy (MJ)

CO2 (kg)

Raw materials

0.015

0.068

Manufacture

0.263

0.0198

Transport

0.049

0.0035

Total

0.327

0.0913

Table 4.1 Total environmental impact per product

The following are steps that can be made to lessen the impact the product has on the environment. 1. Hollow out the top part of the PP inner stem to reduce its mass 2. Create a central collection point for end of life recycling 3. Use a mixture of virgin and recycled pellets in the injection moulding process 4. Use pre-made, biodegradable EVA foam sheets which can be die cut

46


#9 Project Management


Planning design is an art by itself, because there are so many variables that cannot be predicted or justified. The Gantt chart on the next pages is representative of what was planned to happen, and in reality , none of that happened as there were many attempts and failures in the process of getting kelvin to work. For more information, check out the other book: Progress, which is a chronological narrative of what actually went down. Alternatively, there is also a diary sketchbook called Kelvin’s diary.


Week Number Tasks Materials research FEA Find Manufacturers Samples Make first prototype (proof of principal Design coating and form factor CAD Research manufacturing processes Optimise for mass production (DFM/A) Surface finishes PDS Design Pot Pot manufacturing processes Make visual prototype FMEA Animate prototype Packaging colour scheme Structural packaging development User testing ergonomics of packaging opening Semiotics of packaging Packaging graphics Packaging Text LCA IP Liability Marketing Layout and graphics 49

1

2

3

4

5

6

7


easter Break 8

9

10

11

12

13

14

15

16 17 18

50


References

Department of Energy and Climate Change, 2014. DECC Departmental Improvement Plan, London: Department of Energy and Climate Change. Dupont , n.d. Engineering Polymers for gears from Dupont. s.l.:Dupont. Dupont, 2014. DyPont Zytel 101 NC010. s.l.:Dupont. Dupont, 2014. Zytel 101. s.l.:Dupont. Dupont, n.d. Delrin Design Guide. s.l.:Dupont. Dupont, n.d. Dupont Delrin acetal resin Moulding Guide. s.l.:Dupont. Edadoc Co. Ltd, n.d. About Us. [Online] Available at: http://www.edadoc.com/cn/about/a.html [Accessed 21 03 2014]. GE Plastics , n.d. GE Engineering Thermoplastics. s.l.:GE Plastics. GLS Corp., 2004. Overmoulding Guide. s.l.:GLS. IDES , 2009. Dynaflex G2730. s.l.:IDES. Mao, K. L. W. H. D. W., 2009. Friction and wear behaviour of acetal and nylon gears. Wear, 267(1), pp. 639-645. Walker, J., 2005. Machining nylon and acetal. s.l.:Product Focus . Wellman Engineering Plastics, 2009. Resins Design Guide. Johnsonville: Wellman. World Watch Institute , 2007. State of the World 2007: Our Urban Future, Washington DC: World Watch Institute. The Following British Standards are also referenced: BS EN 605529:1992, BS ISO 1798, BS 500088, BS 615581, BS 3643, ISO 49000, BS 60068-2-93, BS 5499 :1, BS 11469 :2000

Supergeek  

The technical side of Project Kelvin.

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