injection moldinginjection molding- process description · pdf fileinjection moldinginjection...

Injection Molding-Injection MoldingProcess Description

ver. 1

ME 4210: Manufacturing Processes and Engineering Prof. J.S. Colton © GIT 2009

1

Overview

• Equipment• Process


2

EquipmentEquipment

Cl M ld B lClamp MoldHopper

Barrel


3

EquipmentEquipment


4

KrausMaffei at Ford 4000 tonnesKrausMaffei at Ford - 4000 tonnes

5ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2009

Machine schematic


6

Mold


7

MoldMold


8

Modular moldsModular molds


9

Mold schematic


10

Moldspruerunner

cavitygate

sprue nozzlep

sidefront ejectionpin


11

pin

Process


12

ProcessProcess

• Pellets placed in hopperPellets placed in hopper• Pellets fall into barrel through throat

P ll t k d t f lid b d• Pellets packed to form solid bed– air forced out through hopper

• Pellets melted by mechanical shear between barrel and screw


13

ProcessProcess

• Melted plastic forms shot in front of• Melted plastic forms shot in front of screw

b k l ti– screw moves back as plastic moves forward (reciprocating screw)


14

Process

• Screw moves forward to inject plastic j pinto mold cavity

P t l d lidifi• Part cools and solidifies– next shot is made


15

ProcessProcess

• Mold opens• Mold opens• Ejection pins move forward to eject part

• Mold closes• Process starts again• Process starts again


16

Solid bedSolid bed

• Pellets crushed together• Pellets crushed together• Air ejected


17

Melting zoneMelting zone

• Solid bed melted by mechanical shear• Solid bed melted by mechanical shear

barrelbarrel

screw flightsolid bed

secondarymixing flow

screw flight


18

Homogenization zoneHomogenization zone

• Melted polymer is homogenized thermally and color-wise.y


19

Injection pressureInjection pressure

• Typically 15,000 psi• Ranges from 3 000 to 40 000 psiRanges from 3,000 to 40,000 psi• Hydraulic pressure is about 10x less


20

Process timeClose mold

InjectionOpen and eject

part jp1

533

35

Part cooling

Pack and hold

15


21

Pressure historyy

Mold closed time

Cycle time

50

ject

ionCooling

Mold closed time

2 st c

losi

ng

Inje

ctio

n

Pack

ze o

ff Par

t ej

25 Fas

Gat

e fre

ez

33 3515500

Time (s)


22

Time (s)

Temperature historyTemperature historyCooling

200

ject

ion

part

100

st c

losi

ng

njec

tion

Pack

ze o

ff Par

t ejp

gate

Fas I

Gat

e fre

ez

33 3515500

Time (s)


23

Time (s)

Gates and freeze offGates and freeze-off

Filling &Packing

Cooling


24


25

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