Injection Molding Process
The injection molding process parameters of two kinds of commonly used plastic reference,
A, high density polyethylene (HDPE)
Barrel temperature feeding zone 30 ~ 50 C (50 DEG C)
From 1160 to 250 C (200 DEG C), from 2200 to 300 C (210 DEG C), from 3220 to 300 C (230 DEG C)
From 4220 to 300 C (240 DEG C), from 5220 to 300 C (240 DEG C), the nozzle 220 ~ 300 C (240 DEG C)
Temperature is suggested in brackets as the basic set value, travel utilization rate was 35% and 65%, mold flow length and wall thickness ratio of 50:1 to 100:1
Melt temperature 220 to 280 DEG C, barrel temperature of 220 DEG C, mold temperature of 20 to 60 DEG C
With good flow property of injection pressure, avoid the use of high injection pressure 80 ~ 140MPa (800 ~ 1400bar); except for some thin wall packaging container can reach 180MPa (1800bar).
Holding pressure contraction degree is high, need long time on the product pressure is maintained, the dimensional accuracy is the key factor, the injection pressure is about.30% ~ 60%
Back pressure 5 ~ 20MPa (50 ~ 200bar); back pressure too low place is easy to cause the weight of the product and the dispersion.
High injection speed injection speed of thin-wall packaging containers need, secondary injection speed is often applied to the plastic products of other classes.
Screw speed high screw speed (line speed is 1.3m/s) is permitted, as long as meet the cooling time before the end of the completion of the plasticizing process can; screw torque requirements for low.
Measurement of travel of 0.5 ~ 4D (minimum to maximum); metering stroke4D for the melt dwell time is long enough to provide the residual material amount is very important for 2 ~ 8mm, depending on the measurement of travel and the screw diameter.
injection molding cost is depending on the molding process
The recovery rate can reach 100% recovery.
The shrinkage rate of 1.2 ~ 2.5%; easy to twist the high degree; shrinkage;never shrink after 24h (after shrinkage)
The gating system point gate; heating hot runner hot runner, insulation, cast in suit; cross-sectional area is relatively small, the thin section products have enough machine stoppage time without the need to use other materials for cleaning work of specialized PE temperature rise;
Barrel equipment standard screw, three section type screw standard us on the packaging container products, mixing section and shear section geometric shape special (L:D = 25:1), through the nozzle, a non-return valve.
Two, polypropylene (PP)
Barrel temperature feeding zone 30 ~ 50 C (50 DEG C)
From 1160 to 250 C (200 DEG C), from 2200 to 300 C (220 DEG C), from 3220 to 300 C (240 DEG C)
From 4220 to 300 C (240 DEG C), from 5220 to 300 C (240 DEG C)
The nozzle 220 ~ 300 degrees (240 degrees C)
Temperature is suggested in brackets as the basic set value, travel utilization rate was 35% and 65%, mold flow length and wall thickness ratio of 50:1 to 100:1
Melt temperature 220 to 280 DEG C, barrel temperature of 220 DEG C, mold temperature of 20 to 70 DEG C
With good flow property of injection pressure, avoid the use of high injection pressure 80 ~ 140MPa (800 ~ 1400bar);
Except for some thin wall packaging container can reach 180MPa(1800bar).
Holding pressure to avoid product shrinkage wall, take a long time for the product of holding pressure (about cycle time; 30%) about the injection pressure 30% ~ 60%.
Back pressure 5 ~ 20MPa (50 ~ 200bar).
The injection speed high injection speed of thin-wall packaging containers need (accumulator); secondary injection speed is often applied to the plastic products of other classes.
Screw speed high screw speed (line speed is 1.3m/s) is permitted, as long as meet the plasticizing process cooling time before the end of May.
Measurement of travel of 0.5 ~ 4D (minimum to maximum); metering stroke4D for the melt dwell time is long enough to provide is very important
Residue volume ranged from 2 to 8mm, depending on the metering stroke and screw speed.
Pre drying is not needed; if the storage condition is not good, at a temperature of 80 DEG C dried 1H can.
The recovery rate can reach 100% recovery.
The shrinkage rate of 1.2 ~ 2.5%; contraction degree is high; won’t shrink after 24h (after shrinkage).
The gating system point gate or multiple point gate; heating hot runner hot runner, insulation, cast in suit; the position of gate WIP thickest point, or prone to large shrinkage.
injection molding China company needs optimize the parameter from time to time to reduce the cost and keep same quality.
Machine stoppage time without the need to use other materials for cleaning work of specialized PP temperature rise;
Barrel equipment standard screw, three section type screw standard use on the packaging container products, mixing section and shear section geometric shape special (L:D = 25:1), through the nozzle, a non-return valve.
You may know more about injection molding by going to https://en.wikipedia.org/wiki/Injection_moulding