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Fundamentals of design

  • A. W. Birley
  • R. J. Heath
  • M. J. Scott

Abstract

Design is an exercise embracing many considerations: mechanical perfor­mance and cost are obviously relevant, and the latter has many constituent elements, of which mass cost (or more appropriately, volume cost) is one of the most important. Data are given in Table2.1; however, manufacturing cost can modify the overall cost very considerably, and as the cost of plastics is very unstable at present, data in Table2.1 must be regarded as only approximate. Different shaping methods are employed for plastics and each has an associated processing cost depending mainly on the production quantity required. For instance, the initial capital cost of equipment for injection moulding and extrusion can be very high, whereas the cost for equipment in GRP hand lay-up may be merely the cost of a wooden former. Expensive processes can only be justified if the production quantity is large, allowing the costs to be absorbed, thus making the processing cost per item acceptable.

Table2.1

Usage and mass cost of plastics materials

 

Usage(Tonnes × 1000)

 

Plastics materials

1984

1985

1986

Price Band

Thermoplastics

    

Low density polyethylene(LDPE)/

510

580

610

A

Linear low density

polyethylene (LLDPE)

   

A/B (C8 copolymer)

High density polyethylene (HDPE)

210

250

275

A

Polypropylene (PP)

297

330

370

A (homopolymer)

B (copolymer)

Orientated polypropylene

(OPP) film

39

40

43

G

Poly(vinyl chloride)(PVC)

444

450

484

A

B (emulsion)

Polystyrene (PS)/styrenics

146

148

156

B(crystal)

B(HIPS1)

Expanded polystyrene (XPS)

31

29.5

33

C

Acrylonitrile-butadiene-styrene (ABS)

53

55

58

E

Polyamide (PA)

20

22

23

G (PA 6 and 6.6)

I (PA 11 and 12)

Poly(oxymethylene) (POM)

10

10.8

12

D/E

Thermoplastics polyesters

37

41

45

D/E (PETP2)

G (PBTP3)

PETP film

23

23.7

24.4

G

Poly(tetrafluoroethylene)(PTFE)

1.25

1.35

1.4

I

Poly(methyl methacrylate) (PMMA)

27

28

29

F

Poly(Phenylene oxide)/

Polystyrene (PPO/PS)/

6.0

5.8

G

Thermosets

    

Phenol-formaldehyde (PF) resins

49

50

49

D-F (Novolak resins)

B (Resol solution)

D/E (Resol-100% solids)

PF (moulding grades)

14

14

12

B

Amino-plasts

122

125

131

C/D (UF4 moulding powders)

C/D (MF5 moulding powders)

A-D (MF impregnation

resins and solution)

Unsaturated polyester resins (UPR)

50

51

53

E/F

Epoxides*

17

17.5

18.5

F

Polyurethanes* (PU)

91

94

100

D/E (foams)

E-G (elastomers/resins)

G (thermoplastics grades)

Notes

Price band is based on the average cost of tonne lots for the UK in 1987.

A £400-£600

B £600-£800

C £800-£1000

D £1000-£1250

E £1250-£1500

F £1500-£2000

G £2000-£3000

H £3000-£5000

I > £5000

Abbreviations

(1) HIPS High impact polystyrene

(2) PETP Poly(ethylene terehthalate)

(3) PBTP Poly(butylenes terephthalate)

(4) UF Urea-formaldehyde

(5) MF Melamine-formaldehyde.

*Epoxide and polyurethane materials are available in many chemical forms. Prices in-

dicated based on the general-purpose, rather than specialistgrades.

Keywords

Injection Moulding Weld Line Critical Crack Size Rotational Moulding Sink Mark 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

References

  1. 1.
    Rooke, D.P. and Cartwright, D.J. Compendium of Stress Intensity Factors. HMSO, London (1976).Google Scholar
  2. 2.
    Johnson, N.C. Cost comparison of rotational casting with injection moulding and blow moulding. Brit. Plast., July 1974, p. 376.Google Scholar

Further reading

  1. Ogorkiewicz, R.M. (ed.), Engineering Properties of Thermoplastics, John Wiley, New York (1970).Google Scholar
  2. Powell, P.C., Plastics for Industrial Designers, Plastics Institute, London (1974).Google Scholar
  3. Williams, J.G., Stress Analysis of Polymers (2nd edn.), Ellis Norwood, Chichester (1980).Google Scholar
  4. Powell, P.C., The Selection and Use of Thermoplastics, (Engineering Design Guides No 19), Oxford University Press (1977).Google Scholar
  5. Monk, J.F. (ed), Thermosetting Plastics: Practical Moulding Technology, Godwin [Longman Group] London (1981).Google Scholar
  6. Ogorkiewicz, R.M. (ed.), Thermoplastics: Properties and Design, John Wiley, New York (1974).Google Scholar
  7. Ehrenstein, G.W. and Erhard, G., Designing with Plastics, Hanser [John Wiley] (1984).Google Scholar
  8. Morton-Jones, D.H. and Ellis, J.W., Polymer Products; Design, Materials & Processing, Chapman and Hall, New York (1986).CrossRefGoogle Scholar
  9. Powell, P. C., Engineering with Polymers, Chapman and Hall, New York (1983).Google Scholar

Copyright information

© Springer Science+Business Media New York 1988

Authors and Affiliations

  • A. W. Birley
    • 1
  • R. J. Heath
    • 1
  • M. J. Scott
    • 2
  1. 1.Institute of Polymer Technology and Materials EngineeringUniversity of TechnologyLoughboroughUK
  2. 2.Lowe & Fletcher LtdTelfordUK

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