Shanghai Daoqin Plastics Co., Ltd.

一, plastics injection molding generate causes:
1, product separation thick degree different
2, mold inner in pressure 不足
3, mold cooling separation
4, due to cooling time 不足而 generate deformation
二, related Knowledge:
1, in plastics injection molding production products process in, is defect phenomenon in frequency rate most high, mold plastics in cooling 时发生体积 shrinkage, cooling separation surface hard 化, internal generate bubbles, 谓凹痕, is cooling slow separation in bubbles shrinkage direction generate 显眼 凹面.
2, shrinkage property large material easy generate 凹痕. need 改变 plastics injection molding molding conditions remove 凹痕时, setting conditions shrinkage small direction setting. mold temperature, material temperature degree reduce, injection shot pressure improve/increase, is attention/notes can can 会引起残余 internal stress.
3, is plastics injection molding 凹痕以不显眼 is good, therefore, if effect/influence appearance 时候, has in mold upper processing formed 腐蚀 模样, 例如纹状, and other. also has, if molding material is HIPS时, use reduce mold temperature reduce light degree has 效果. is this methods has 凹痕发生, 想修理 abrasion light products has difficult.
三, solution methods:
1, 即时: improve/increase plastics injection molding injection shot pressure, long injection shot holding pressure time, reduce material temperature degree and mold temperature degree, in generate 凹痕 方 strong/high made cooling.
2, short 期: in generate 凹痕 方补 upper 流边. in generate 凹痕 方 材 material has small 场 时, this separation thick.
3, long 期: 应彻底避免 design products thick degree 差异. easy generate add strong/high 筋, long 形状应尽 amount short.
四． 于材 material 差异:
molding shrinkage property large material, 凹痕也 large. 例如PE, PP, make need micro add strong/high 筋, generate 凹痕.
材 material molding shrinkage
PS 0.002~0.006
PP 0.01~0.02
PE 0.02~0.05
五, 参考事项:
1, temperature degree reduce to generate 凹痕时, if in mold cavity inner material also has pressure, 应该考虑 to generate 凹痕. in mold inner material in mold inner pressure pressure, what is 不一定. 接近 plastics injection molding gate separation pressure high, if material wide, is to 各 角落 pressure 传递, gate 同远离 gate pressure full pressure versus ratio versus very small 就不会 generate 凹痕, can to 不残留 internal force products. separation material in has difficult 场 时, this has high pressure, other pressure reduce generate 凹痕. this separation high pressure 残留, is products internal force large. in 理想 状态 lower material temperature degree mold temperature degree upper rise, material flow property relatively good, and injection shot in pressure 状态也变底.
2, in molding conditions 时, temperature degree, pressure, time combined 应预先 made as good table/sheet 格, 按顺序进行, can 早知道结果. time very long rear, pressure micro small 变化也容 easy 知道. attention/notes is: to temperature degree 变化时 结果, in injection material rear, and other temperature degree drop lower rear again production 时 结果.