Common injection molding defects of polypropylene



Surface porosity

Fault analysis and Troubleshooting:

(1) When the size of runner and gate is small, the surface porosity is easy to occur. The size of runner and gate should be enlarged properly.

(2) The plastic wall is too thick. The wall thickness should be reduced as much as possible in the design.

(3) If the molding temperature is too high or the injection pressure is too low, there will be pores on the surface of plastic parts. The molding temperature should be reduced and the injection pressure should be increased.


Flow mark

Fault analysis and Troubleshooting:

(1) The melt and mold temperature are too low. The barrel and die temperature should be appropriately high.

(2) The injection speed is too slow. The injection speed should be increased appropriately.

(3) The nozzle aperture is too small. The nozzle with larger diameter should be used instead.

(4) There is no cold hole in the mold. Cold material hole should be added.


Silver bar silk

Fault analysis and Troubleshooting:

(1) The content of moisture and volatile matter in raw materials is too high. The raw materials should be pre dried.

(2) Poor exhaust of mould. The exhaust hole should be added to improve the exhaust performance of the die.

(3) Poor contact between nozzle and die. The position and geometric dimension of the two should be adjusted.