The Reason Of The Defect Of Plastic Injection Molding And Its Remedy​

- Oct 30, 2017 -

The reason of the defect of plastic injection molding and its remedy

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1. Characteristics of defect of injection molding


The injection molding process is not complete because the cavity is not filled with plastic or the injection process lacks some details.


2. Possible causes of problems


(1) insufficient injection speed.


(2). Plastic shortage.


(3) the screw does not leave the screw padding at the end of the stroke.


(4) change of operating time.


(5). The temperature of the ejection cylinder is too low.


(6). Insufficient injection pressure.


(7). The nozzle part was sealed.


(8) the heater outside the nozzle or the ejection cylinder does not work.


(9). The injection time is too short.


(10). Plastic is attached to the hopper throat wall.


(11). Injection molding machine capacity is too small (i.e. injection weight or plasticizing capacity).


(12). Mold temperature is too low.

(13). There is no anti-rust oil for cleaning the mould.


(14). The stop ring is damaged and the molten material is in reverse flow.


3. Remedies


(1). Increase the injection speed.


(2) check the amount of plastic in the hopper.


(3). Check whether the injection schedule is properly set and change if needed.


(4) check whether the check valve has worn or cracked.


(5) check whether the operation is stable.


(6) increase the melt temperature.


(7) increase back pressure.


(8). Increase the injection speed.


(9). Inspect the nozzle hole for any foreign or unplasticized plastics.


(10). Check whether the energy output is correct with the ammeter in all the heater layers.


(11) increase the screw forward time.


(12). The cooling amount of the hopper throat area, or lower the temperature after the cylinder.


(13) use a larger injection molding machine.


(14). Properly elevated mold temperature.


(15). Clean the anti-rust agent in the mould.


(16) check or replace the check ring.