Injection moulding

Question 1

Injection moulding steps

Answer 1

1. plastification
2. injection
3. packing/cooling
4. demold/ejection

Question 2

Sandwich moulding principle

Answer 2

• two separate screw feed systems

- allows multiple polymers to be injected into one mould to make one part

Question 3

Sandwich moulding steps

Answer 3

1. Short shot of skin polymer melt injected into mould
2. injection of core polymer melt until cavity is nearly filled
3. skin polymer melt injected again, pushing the core polymer

Question 4

Mould features

Answer 4

• air extraction channels
• insert
• injection gate

Question 5

SCORIM principle

Answer 5

• apply microscopic shears to molten material in a mould during solidification
• minimum of two gating points within a mould cavity between which melt shearing pressure can be applied
• divides the feed in two, independently pressured streams

Question 6

SCORIM packing modes

Answer 6

1. pistons moved back & forth at same frequency but 180 degrees out of phase
2. pistons are moved back and forth at same frequency and phase
3. pistons held down at static pressure

Question 7

SCORIM advantages

Answer 7

• enhanced polymer matrix or fibre alignment
• elimination of mechanical discontinuities i.e. weld lines
• elimination/reduction of defects resulting from thick-sectioned components
• reduction in detrimental effects of a change in moulded section thickness