Plastics Processing Methods - An easy guide

The right process for the job - reducing costs by the right choice!

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1. Thermoplastics Processing Methods

• Thermoplastics are materials which soften when heated and can then be formed whilst soft. After cooling they becoming rigid take up the applied form. The softening and forming processes are reversible. Thermoplastics are probably the most widely used type of polymer. The group includes most of the "commodity" plastics such as polyethylene, PVC, polypropylene, nylons (polyamides) and polystyrene.

  Thermoplastic Processing Methods
  Processing Method	Equipment Cost	Tooling Cost	Cycle Time	Precision	Economic Quantity
  Extrusion	A	B	D	A	D
  Injection Moulding	A	A	A	A	A
  Blow Moulding	A	B	A	B	A
  Rotational Moulding	B	C	C	B	B
  Thermoforming	B	C	B	C	B

  Key
  	A	B	C	D
  Costs	High	Moderate	Low
  Time	<1 min	1-3 min	>3 min	Continuous
  Precision	Good	Moderate	Poor	Not applicable
  Quantity	> 10K	100 to 10K	<100	>5Km

2. Polymers and Processing Methods

• Not all thermoplastics can be processed by all the methods. This table is a guide to what thermoplastics can be processed by each method.
  

  Polymers and Processing Methods
  Process	Extrusion	Injection Moulding	Blow Moulding	Rotational Moulding	Thermo-forming
  Material
  ABS	Yes	Yes	No	Yes	Yes
  EVA	No	No	No	Yes	No
  PA	Yes	Yes	No	Yes	No
  PC	Yes	Yes	Yes	No	Yes
  PE-LD	Yes	Yes	Yes	Yes	No
  PE-HD	Yes	Yes	Yes	Yes	No
  PMMA	Yes	Yes	No	No	Yes
  POM	Yes	Yes	Yes	No	No
  PP	Yes	Yes	Ye	No	Yes
  PS / PS-HI	Yes	Yes	Yes	Yes	Yes
  PVC-U	Yes	Yes	Yes	Yes	Yes
  PVC-P	Yes	Yes	Yes	Yes	Yes
  SAN	Yes	Yes	Yes	No	No

3. Thermosetting Processing Methods

• Thermosetting materials are materials that are formed whilst warm or hot but once formed they set in the formed shape. Cooling and reheating do not make thermosetting materials go soft again. The forming process is not reversible. Thermosetting materials were the first type of polymer to be produced e.g. Bakelite, but are still widely used for many applications. Typical thermosetting materials are phenol formaldehyde resins, urea formaldehyde resins, epoxy resins and most rubbers.

  Thermoset Processing Methods
  Processing Method	Equipment Cost	Tooling Cost	Cycle Time	Precision	Economic Quantity
  Compression Moulding	B	A	B	A	A
  Transfer Moulding	B	A	B	A	A
  Injection Moulding	A	A	A	A	A
  Liquid Casting	D	C	C	B	C
  DMC and SMC	B	A	B	A	A
  RIM and RRIM	B	B	B	B	B
  GRP (Hand Lay-up)	D	C	C	C	C
  GRP (Spray and Match Die)	B	B	B	B	B
  Filament Winding	B	C	C	C	C
  Pultrusion	B	B	D	B	D

  Key
  	A	B	C	D
  Costs	High	Moderate	Low	None
  Time	<2 min	2-5 min	>5 min	Continuous
  Precision	Good	Moderate	Poor	Not applicable
  Quantity	> 10K	100 to 10K	<100	>5Km

4. Features and Processing Methods

Features and Processing Methods
Process	Extrusion	Injection Moulding	Blow Moulding	Rotational Moulding	Thermo-forming
Feature
Equipment Cost	High	High	High	Moderate	Moderate
Tooling Cost	Moderate	High	Moderate	Low	Low
Cycle Time	Continuous	<1 min	<1 min	>3 min	1-3 min
Economic Quantity	>5Km	>10K	>10K	100 - 10K	100 - 10K
Precision	Good	Good	Moderate	Moderate	Low
Wall Thickness Control	Yes	Yes	No	No	No
Open-ended Hollows	No	Yes	Yes	Yes	Yes
Enclosed Hollows	No	No	Yes	Yes	No
Very Small Items	No	Yes	No	No	No
Complicated / Intricate Shapes	Yes	Yes	Yes	No	No
Large Enclosed Volumes	No	No	Yes	Yes	No
Inserts	No	Yes	No	Yes	No
Moulded-in Holes	No	Yes	No	No	No
Threads	No	Yes	Yes	No	No

If in doubt contact a please contact Tangram Technology for further information.

Last edited: 29/03/04

© Tangram Technology Ltd. 1998

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