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Injectiion Molding Machine Molding condition

Injectiion Molding Machine Molding condition

Jul 27,2020
1.Resin temperature
When molding NOVADURAN, resin temperature should be generally about 240℃~265℃. Liquidity will be better as the temperature rises, but extremely high temperature will accelerate heat degradation which will end up with physicality deterioration of the molded article. 
2.Injection and pressure keeping
(1) Pressure 
Injection pressure can be considered as the fill pressure (primary pressure) and the hold pressure (secondary
pressure). Generally the fill pressure will be set stronger than the hold pressure. When low-temperature solidification, crystalline resin like NOVADURAN will cause a big shrink, therefore the hold pressure is necessary for filling up and is closely related to the molding shrinkage. Increasing the hold pressure is effective to resolve sink and void problem, but if it increase too much, it might cause burr, so the attention is required.

(2) Injection speed
In the case of thin molded product or multi-cavity molded product which severe size precision is required,faster injection speed is better. In contrast, slower injection speed is better for thick molded product. Also, the program control of injection speed is effective to resolve the jetting and the flow mark.

(3) Injection time
Setting will differ by the molding machine, but basically should be considered as below. 
 injection time (filling time + pressure keeping time) > gate sealing time
Gate sealing time is the time when resin stops flowing by solidification at the gate part. If pressure keeping is put away before the gate is sealed, molten resin will backflow from the gate by the tool internal pressure, which will cause measurement and physicality variability, and warpage, sink, and void problems, because of decrease in molded product's filling density (packing property). To estimate the gate sealing time, measure the weight of molded product by gradually increasing the injection time, and look for the injection time when the weight of molded became a certain amount and stop changing. 
CST188/630 Injection Molding Machine
3.Back pressure
The measurement might become instable by the gas and the air generated from molten resin when plasticization. To stabilize the measurement and improve the kneading effect, put the screw back pressure (5 ~10kg/cm2 ) on. However, if the back pressure is too strong, it might degrade the plasticization ability. 
4.Mold temperature
Generally, 60℃ to 80℃ is suitable for mold temperature of NOVADURAN, and this is the most important  point in the molding condition. If high cycle molding is intended, molding in temperature of about 20℃ to 30℃ is possible by using chiller temperature controller, but require attention because it might cause deformation by the residual strain inside the molded product, and dimension change by aftercontraction might be bigger depending on the usage environment (high temperature atmosphere). It is effective to raise the mold temperature to about 120℃, when dimension stability is required since assumed to use under a high temperature atmosphere, or high level of surface gloss is necessary.