Injection_moulding_basics.pdf
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Injection Moulding
Moulding machine
2
Basics of Injection Moulding Hopper Clamping unit Screw & Barrel Nozzle
3
Clamping pressure Calculated by multiplying the projected area of the cavity (cavities), including runner system by the maximum internal pressure (hold pressure).
4
Clamping pressure
POM PA LCP PETP PC PMMA PP PE ABS PS
3 - 4 T/inch2 3 - 5 T/inch2 4 - 6 T/inch2 4 - 6 T/inch2 3 - 5 T/inch2 2 - 4 T/inch2 1 - 4 T/inch2 1 - 4 T/inch2 3 - 4 T/inch2 2 - 3 T/inch2 5
Drying 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 6
Polycondensation - Water
+ Water
Hydrolytic degradation - High temperature in the presence of water, result in the break- up of the molecular chain 7
Polycarbonate Water content & lowering of molecular weight: Lowering of molecular weight (%)
30
20
10
Moulding temp.300 c
0 0
0.05
0.1
0.15
0.2
0.25
Water content of pellet (wt%)
8
30% GR PET Influence of Moisture on impact strength
9
Drying time & temperatures o
Material
Moisture level
Temp ( C)
Time (Hrs)
PA PBTP PETP P/C POM LCP PPS ABS
0.2 0.04 0.02 0.02 0.2 0.01 0.04 0.1
80 120 130 120 80 135 150 80
2–4 3–4 3–4 4–6 1–2 2–4 4–6 2–4 10
Polycarbonate Moulding temp. & lowering of molecular weight: 35 min
1000
20 min 5 min 100 350
340
320
300
Residence tim e
Lowering of mol. wt. (Mv)
10000
280
Moulding temp (deg.C)
11
Hold-up-time Toughened Nylon 6.6
12
Temperature profile
13
Injection and Hold Pressure Injection pressure - Dynamic filling phase (under velocity control), moves the screw and push the material into the mould, (around 95% of the part volume). “Hold” pressure - Quasi-static feeding phase (under pressure control), packing the part to compensate for the change in volume from a “liquid” to a “solid”. “V-P” switch point - In crystalline material, use distance rather than with pressure, as would typically be done for an amorphous material. 14
Hold pressure time Vs part weight and shrinkage Delrin* 500
15
Hold-on-time
POM PA GR-PA MR-PA PBT GR-PBT PET LCP TEEE
8 secs/mm 5 secs/mm 3 secs/mm 3 secs/mm 4 secs/mm 3 secs/mm 4 secs/mm 0.5 secs/mm 4-8 secs/mm 16
Influence of Tool Temperature
Tool at 400C Outer layer insufficiently crystallised
Tool at 900C Optimum structure
17
Shrinkage behaviour
18
Gate Positions
19
Gate Size and Design
20
Effect of Gate diameter on the quality Nylon 6.6
21
Runner Size and Design
22
Venting design
23
Moulding tolerances
24
Regrind
25
Moulding cycle-Time For crystalline materials. (With amorphous materials, the main differences are shorter hold on time, but much longer cooling time.)
26
A Polymer for Every Application
Moulding machine
2
Basics of Injection Moulding Hopper Clamping unit Screw & Barrel Nozzle
3
Clamping pressure Calculated by multiplying the projected area of the cavity (cavities), including runner system by the maximum internal pressure (hold pressure).
4
Clamping pressure
POM PA LCP PETP PC PMMA PP PE ABS PS
3 - 4 T/inch2 3 - 5 T/inch2 4 - 6 T/inch2 4 - 6 T/inch2 3 - 5 T/inch2 2 - 4 T/inch2 1 - 4 T/inch2 1 - 4 T/inch2 3 - 4 T/inch2 2 - 3 T/inch2 5
Drying 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 6
Polycondensation - Water
+ Water
Hydrolytic degradation - High temperature in the presence of water, result in the break- up of the molecular chain 7
Polycarbonate Water content & lowering of molecular weight: Lowering of molecular weight (%)
30
20
10
Moulding temp.300 c
0 0
0.05
0.1
0.15
0.2
0.25
Water content of pellet (wt%)
8
30% GR PET Influence of Moisture on impact strength
9
Drying time & temperatures o
Material
Moisture level
Temp ( C)
Time (Hrs)
PA PBTP PETP P/C POM LCP PPS ABS
0.2 0.04 0.02 0.02 0.2 0.01 0.04 0.1
80 120 130 120 80 135 150 80
2–4 3–4 3–4 4–6 1–2 2–4 4–6 2–4 10
Polycarbonate Moulding temp. & lowering of molecular weight: 35 min
1000
20 min 5 min 100 350
340
320
300
Residence tim e
Lowering of mol. wt. (Mv)
10000
280
Moulding temp (deg.C)
11
Hold-up-time Toughened Nylon 6.6
12
Temperature profile
13
Injection and Hold Pressure Injection pressure - Dynamic filling phase (under velocity control), moves the screw and push the material into the mould, (around 95% of the part volume). “Hold” pressure - Quasi-static feeding phase (under pressure control), packing the part to compensate for the change in volume from a “liquid” to a “solid”. “V-P” switch point - In crystalline material, use distance rather than with pressure, as would typically be done for an amorphous material. 14
Hold pressure time Vs part weight and shrinkage Delrin* 500
15
Hold-on-time
POM PA GR-PA MR-PA PBT GR-PBT PET LCP TEEE
8 secs/mm 5 secs/mm 3 secs/mm 3 secs/mm 4 secs/mm 3 secs/mm 4 secs/mm 0.5 secs/mm 4-8 secs/mm 16
Influence of Tool Temperature
Tool at 400C Outer layer insufficiently crystallised
Tool at 900C Optimum structure
17
Shrinkage behaviour
18
Gate Positions
19
Gate Size and Design
20
Effect of Gate diameter on the quality Nylon 6.6
21
Runner Size and Design
22
Venting design
23
Moulding tolerances
24
Regrind
25
Moulding cycle-Time For crystalline materials. (With amorphous materials, the main differences are shorter hold on time, but much longer cooling time.)
26
A Polymer for Every Application
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