Injection Molding
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Repeated material shortage at a fixed point in PP '2079851475616104452 (venting type)
Fenómeno do problema
The product repeatedly lacks material at a fixed position; even with the injection pressure and speed already raised very high, it still cannot be filled, unlike ordinary over-pressure material shortage.
Análise das causas
This position is the last fill point of the cavity with poor venting; the back pressure of the trapped gas prevents the melt from filling; it is often misjudged as insufficient pressure and pressure is raised blindly, which instead triggers other defects such as flash.
Solução
①Use the short-shot method to confirm that this point is indeed the last fill point; ②open/clean vent grooves at the shortage location; ③adjust the gate position when necessary to change the last fill point; ④reduce the injection speed at the end to leave time for venting; ⑤check whether the clamping force is excessive, closing the vents.
Conclusão principal
For repeated material shortage at a fixed point, suspect venting before pressure: use the short-shot method to locate the last fill point, and opening vents at the correct position is the real cure; blindly raising pressure only turns a trapped-air problem into a flash problem.
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