Injection Molding
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Short Shot of PE Injection Molded Products (Venting Type)
Fenómeno do problema
PE products repeatedly have short shots at a fixed position; they still cannot be filled completely after increasing pressure and speed, and are easily accompanied by flash.
Análise das causas
That position happens to be the last filling point of the cavity and has poor venting; during filling, the compressed air has nowhere to go, forming back pressure that prevents the melt from filling completely; if venting is not solved and injection pressure is blindly increased, the trapped-air problem will only be converted into new defects such as flash and burning.
Solução
①Use the short shot method to confirm the last filling point; ②Open/clean vent grooves at that location; ③Adjust the gate position if necessary; ④Decelerate injection at the end; ⑤Check whether the clamping force is too large and closes off the venting.
Conclusão principal
For repeated short shots at a fixed position in PE, check venting first rather than pressure: using the short shot method to locate the last filling point and opening vents at the correct position is the fundamental cure; pressure is not a panacea — if trapped air is not removed, the higher the pressure, the more defects, and it also accelerates mold wear.
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