Injection Moulding Basics

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InjectionInjectionMouldingMoulding


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Moulding machineMoulding machine


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Basics of InjectionBasics of Injection

MouldingMouldingHopper

Screw & Barrel

Nozzle

Clamping unit


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Calculated by multiplyingtheprojected area of the cavity

(cavities), including runner system by the maximum internalpressure (hold pressure).

Clamping pressureClamping pressure


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Clamping pressureClamping pressure

POMPOM

PAPA

LCPLCP

PETPPETP

PCPC

PMMAPMMA

PPPP

PEPE

ABSABS

PSPS

3 - 4 T/inch3 - 4 T/inch22

3 - 5 T/inch3 - 5 T/inch22

4 - 6 T/inch4 - 6 T/inch22

4 - 6 T/inch4 - 6 T/inch22

3 - 5 T/inch3 - 5 T/inch22

2 - 4 T/inch2 - 4 T/inch22

1 - 4 T/inch1 - 4 T/inch22

1 - 4 T/inch1 - 4 T/inch22

3 - 4 T/inch3 - 4 T/inch22

2 - 3 T/inch2 - 3 T/inch

22


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Drying PrinciplesDrying Principles

Non-hygroscopic Polymers :e.g. P/S, P/E, P/P, POM

Drying require only to remove surface moisture.Hygroscopic Polymers :

e.g. P.A., P/C, PBTP, PETP, PET-G

Use Dehumidified air drier or Vacuum oven


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Water content & lowering of molecular weight:

0

10

20

30

0 0.05 0.1 0.15 0.2 0.25

Water content of pellet (wt%)

Loweringofm

olecular

weight(%)

Moulding temp.300 cMoulding temp.300 c

PolycarbonatePolycarbonate


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30% GR PET30% GR PET

Influence of Moisture on impact strength


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Drying time &Drying time &

temperaturestemperaturesMaterial Moisture level Temp (

oC) Time (Hrs)

PA 0.2 80 2 4

PBTP 0.04 120 3 4

PETP 0.02 130 3 4

P/C 0.02 120 4 6

POM 0.2 80 1 2

LCP 0.01 135 2 4PPS 0.04 150 4 6

ABS 0.1 80 2 4


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Moulding temp. & lowering of molecularMoulding temp. & lowering of molecular

weight:weight:

100

1000

10000

350 340 320 300 280

Moulding temp (deg.C)

L

oweringofm

ol.wt.(Mv)

35 min35 min

20 min20 min

5 min5 minResidencetime

Residencetime

PolycarbonatePolycarbonate


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Hold-up-timeHold-up-time

Toughened Nylon 6.6


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Temperature profileTemperature profile


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Injection and HoldInjection and Hold

PressurePressure

Injection pressureInjection pressure - Dynamic filling phase (under velocity- Dynamic filling phase (under velocitycontrol), moves the screw and push the material intocontrol), moves the screw and push the material into

the mould, (around 95% of the part volume).the mould, (around 95% of the part volume).

Hold pressureHold pressure - Quasi-static feeding phase (under- Quasi-static feeding phase (underpressure control), packing the part to compensate forpressure control), packing the part to compensate for

the change in volume from a liquid to a solid.the change in volume from a liquid to a solid.

V-P switch pointV-P switch point

- In crystalline material, use distance- In crystalline material, use distance

rather than with pressure, as would typically be donerather than with pressure, as would typically be done

for an amorphous materialfor an amorphous material..


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Hold pressure time Vs

part weight and shrinkageDelrin* 500


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Hold-on-timeHold-on-time

POMPOM

PAPA GR-PAGR-PA

MR-PAMR-PA

PBTPBT

GR-PBTGR-PBT

PETPET LCPLCP

TEEETEEE

88 secssecs/mm/mm

55 secssecs/mm/mm 33 secssecs/mm/mm

33 secssecs/mm/mm

44 secssecs/mm/mm

33 secssecs/mm/mm

44 secssecs/mm/mm 0.50.5 secssecs/mm/mm

4-84-8 secssecs/mm/mm


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Tool at 400C Tool at 900C

Influence of ToolInfluence of Tool

TemperatureTemperature

Outer layer insufficientlycrystallised

Optimum structure


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Shrinkage behaviourShrinkage behaviour


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Gate PositionsGate Positions


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Gate Size and DesignGate Size and Design


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Effect of Gate diameterEffect of Gate diameter

on the qualityon the qualityNylon 6.6


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Runner Size and Design


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Venting designVenting design


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Moulding tolerancesMoulding tolerances


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RegrindRegrind


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Forcrystalline materials. (With amorphous materials, the

main differences are shorter hold on time, but much longer

cooling time.)

Moulding cycle-TimeMoulding cycle-Time


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A Polymer for Every ApplicationA Polymer for Every Application

Injection Moulding Basics

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