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DIMENSIONAL CHANGES IN THE MOULDING



INFLUENCE OF PROCESS ON SHRINKAGE

MATERIALS, MOULD AND PROCESS CONDITIONS INFLUENCE SHRINKAGE.

SHRINKAGE DECREASES

with

SHRINKAGE INCREASES

with

MATERIALS

AMORPHOUS

REINFORCED

CRYSTALLINE

HIGHER WALL THICKNESS

MOULD

HIGH CONDUCTIVITY STEEL

LONG FLOW PATH

SMALL GATE AREA

INSUFFICIENT COOLING

INSUFFICIENT CLAMP FORCE

PROCESS CONDITION

HIGH CAVITY PRESSURE

HIGH INJECTION RATE

HIGH MOULD TEMPERATURE

INSUFFICIENT GATE FREEZE-OFF TIME

HIGH MELT TEMPERATURE

SHRINKAGE OF VARIOUS MATERIALS

MATERIALS

% SHRINKAGE

MATERIALS

% SHRINKAGE

Nylon 6

1 -1.5

Polycarbonate

0.8

Nylon 6- GR

0.5

Acetal

2

Nylon 6/6

1 -2

PVC - Rigid

0.5 - 0.7

Nylon 6/6 -GR

0.5

PVC - Soft

1 - 3

LDPE

1.5 - 3

ABS

0.4 - 0.6

HDPE

2 - 3

PP

1.2 - 2

Polystyrene

0.5 - 0.7

Cellulose acetate

0.5

Styrene-acrylonitrile

0.4 - 0.6

Cellulose acetate.......... butyrate

0.5

Acrylic

0.3 - 0.6

Cellulose propionate

0.5


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