Mould Design Part One

Mould Design Raja Aziz Raja Ma’arof Institute of Production Design and Manufacturing UniKL IPROM July 2007-2008

Plastic Product Design Plastic product Ordered volume / mould life Volume per batch delivery

Plastic product technical details Material Shrinkage Tolerance Fitting condition with other parts

Number of cavities Injection machine selection Plastic mould design…

Design criteria Type of mould Cavity layout Gating design Runner & sprue design Cooling channel design Ejection design Venting design Mould tooling material

Plastic Mould Design Design details Two- or three plate? Standard / hot / cold runner? In-line / symmetrical / star? Standard / pin-point /tunnel / flash / tab / disc? Circular / semi-circ / rectangular / trapezoid / etc? Standard / U / spiral?

In-mould product design

Water / oil / air?

MOULD DESIGN

Design criteria Type of mould Cavity layout

Plastic Mould Design Design details Pins / stripper ring / plate / air / slider?

Gating design Cooling channel design Ejection design

Venting design

Parting lines / inserts / core / ejector pins / plates? Plain tool steel / through hardening / case hardening / heat treatable / nitriding steels?

Mould Material Shrinkage value / draft angle / surface quality? In-mould product design

MOULD DESIGN

Injection plastic material


Material  Application

(where will it be used?)  Engineering / precision / consumer  Brand (Bayer, etc.)

Shrinkage
Tolerance


 Use

standard tolerances  Minimize the use of controlled tolerances


Fitting condition (single or assembly)  Static:

minimize contact points, hence controlled tolerances  Dynamic

Plastic injection machine Fixed side

Hooper Screw component Heating element

Clamping plate




Standard machine




Machine with two plastic material inputs

Shrinkage & draft Material

Inj. Pr, Ps (bar)

Hold Pr, Pn (bar)

Mass tempt (ºC)

Mould tempt (ºC)

Shrinkage Draft (%) (%)

Polystyrol

1200…1500

(0.3…0.6)x Ps

150…280

10…50

Ca. 0.45

1.5

ABS

1000…1500

(0.3…0.6)x Ps

180…240

50…85

0.4…0.7

-

Polyethylene

1200…1500

(0.3…0.6)x Ps

140…350

20…60

1.5…2

0.2…2

Polypropylene

1200…1800

(0.4…0.8)x Ps

150…260

20…60

1.2…2.2

1.5

Polycarbonate

1300…1800

(0.4…0.6)x Ps

230…320

85…120

0.7…0.8

1

polyvinylchloride

800…1600

(0.3…0.5)x Ps

140…210

20…60

0.5…0.7

1.5

Injection plastic material (2)


Semi-crystalline  PE,




PP, POM, PA6, PA66, PBT

Amorphous  PS,

ABS, PC, PMMA, PPE, ABS/PC, PVC-U, PVC-P, etc.




Amorphous/ Semi-crystalline  PET

(Polyethylene terephthalate)

Injection plastic material (3) Item

PE

PP

PS

ABS

PC

POM

PMMA

PA6

A / SC

SC

A

A

A

A

SC

A

SC

ρ1 (gm/cm3)

0.92 0.96

0.91 0.93

1.05

1.06 – 1.19

1.20

1.42

1.18

1.14

ρ2 (gm/cm3)

0.72 0.76

0.72 0.74

0.95

0.95 – 1.05

1.08

1.16

1.09

0.98

no

no

no

4/100

3/120

no

4/80

4/80

Nozzle (°C)

220 300

220 300

220 280

210 260

300 320

195 215

200 - 250

230 240

Mould* (°C)

20-60

20-70

15-30

40-80

80-110

40-120

40-80

60-100

50200

50-200

50-100

50-100

100-150

50-100

100-300

20-80

0.6

1.0

Predrying (h/°C)

Screw ** (bar)

Max screw 1.2 1.2 1.2 0.6 0.6 0.7 vel. (m/s) SC = semi-crystalline; A = Amorphous ρ1 = Density at room temperature; ρ2 = Density at processing temperature *Mould surface temperature; **Screw back pressure

Injection plastic material (4) Item

PA66

PPE

PET

PBT

ABS/PC

PVC-U

PVC-P

CA

A / SC

SC

A

A/SC

SC

A

A

A

A

ρ1 (gm/cm3)

1.14

1.05-1.1

1.35

1.30

1.15

1.35

1.1-1.4

1.2-1.3

ρ2 (gm/cm3)

-

-

-

-

-

-

-

-

Predrying (h/°C)

4/80

2/110

4/140

4/120

4/80

no

no

3/70

Nozzle (°C)

280290

280-300

250-290

250-260

250-270

180-210

160-220

170-200

Mould* (°C)

60100

80-120

120-140

60-80

70-90

30-60

30-50

40-80

20-80

30-100

50-100

50-100

50-100

50-300

50-100

50-100

1.0

0.6

0.5

0.7

0.4

0.2

0.5

0.6

Screw ** (bar) Max screw vel. (m/s)

SC = semi-crystalline; A = Amorphous ρ1 = Density at room temperature; ρ2 = Density at processing temperature *Mould surface temperature; **Screw back pressure

Injection plastic material (5) Groups

Consumer goods

Closures

Covers

Applications

Parts with low surface quality and dimensional requirement, simple toys

Screw caps, lids and closures for pharmaceuticals and cosmetics

Vacuum cleaner housings, bumpers, instrument panels, lawn movers, power drills

Floppy disks, CD jewel cases, video cassettes, slide frames

Typical materials

PS, PP, PE

PE, PP

PS, PP, ABS/PC

PS, ABS

Flow path to wall thickness

100-150:1

30-100:1

100-150:1

100-150:1

Quality requirements

Low

Medium

Medium

Medium

200-250

350-400

350-400

350-400

Required mould cavity pressure (bar)

Engineering packaging

Injection plastic material (6)


Screw barrel RPM

ShotWeight[g] x 60 RPM = Coolingtime[sec] x Plast.Flow[g/R] x Correctivefactor




Plasticising time Plasticing

time[s]

=

Plast.Flow

ShotWeight [g] x 66 [g/R] x Corrective factor x

RPM

Injection plastic material (7)


Follow-up pressure, PF (with regards to mould cavity pressure, PMC) Material PE, PP, PS, PA SAN, ABS, PPO, PET, PBT PMMA, PC, POM,ABS/PC


PF PMC x 1.25 PMC x 1.3 PMC x 1.35

Clamping Force, FC [kN] = PMC[bar] x Part projected surface[cm2]/100  FC = PMC[bar] x Part projected surface[mm2]/10,000  FC

Cavity calculation Volume required: 2,000 monthly
Production data


 One

shift  Eight hours per shift  22 days per month


Production allocation  Two

days per month  Injection machine cycle time approx 50 sec.

Cavity calculation (2) No. of Cycle Time: 2days x 8hrs per day x 3600sec per hr / 50sec = 1152
No. of cavities: 2,000 u / 1,152 Cycle Time = 2 cavities