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DIMENSIONAL CHANGES IN THE MOULDING
INFLUENCE OF PROCESS ON SHRINKAGE
MATERIALS, MOULD AND PROCESS CONDITIONS INFLUENCE SHRINKAGE.
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SHRINKAGE DECREASES with |
SHRINKAGE INCREASES with |
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MATERIALS |
AMORPHOUS REINFORCED |
CRYSTALLINE HIGHER WALL THICKNESS |
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MOULD |
HIGH CONDUCTIVITY STEEL |
LONG FLOW PATH SMALL GATE AREA INSUFFICIENT COOLING INSUFFICIENT CLAMP FORCE |
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PROCESS CONDITION |
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HIGH CAVITY PRESSURE HIGH INJECTION RATE |
HIGH MOULD TEMPERATURE INSUFFICIENT GATE FREEZE-OFF TIME HIGH MELT TEMPERATURE |
SHRINKAGE OF VARIOUS MATERIALS
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MATERIALS |
% SHRINKAGE |
MATERIALS |
% SHRINKAGE |
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Nylon 6 |
1 -1.5 |
Polycarbonate |
0.8 |
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Nylon 6- GR |
0.5 |
Acetal |
2 |
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Nylon 6/6 |
1 -2 |
PVC - Rigid |
0.5 - 0.7 |
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Nylon 6/6 -GR |
0.5 |
PVC - Soft |
1 - 3 |
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LDPE |
1.5 - 3 |
ABS |
0.4 - 0.6 |
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HDPE |
2 - 3 |
PP |
1.2 - 2 |
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Polystyrene |
0.5 - 0.7 |
Cellulose acetate |
0.5 |
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Styrene-acrylonitrile |
0.4 - 0.6 |
Cellulose acetate.......... butyrate |
0.5 |
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Acrylic |
0.3 - 0.6 |
Cellulose propionate |
0.5 |
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