Shanghai Daoqin Plastics Co., Ltd.

injection molding parts mold in cooling to room temperature rear, dimensions shrinkage this type of property can is shrinkage property. due to shrinkage not only is resin hot cold shrink, but also also and formed factors has 关, therefore formed rear parts shrinkage is formed shrinkage. 　　

1, formed shrinkage formed shrinkage main/primary performance in lower 列几方面: 　　

（1）塑 parts dimensions shrinkage due to hot cold shrink, parts demolding elastic property 恢复, property deformation and other causes 导致塑 parts demolding cooling to room temperature rear its dimensions shrink small, is type design must 考虑予以补偿. 　　

（2） shrinkage direction property formed separation direction 排列, make parts 呈现各 toward property, material direction （即平行 direction ）则 shrinkage large, strong/high degree high, and material 流直角 direction （即垂直 direction ）则 shrinkage small, strong/high degree low. another, formed due to parts 各部位 density and filler distribution 不匀, make shrinkage 也不匀. generate shrinkage make parts easy warpage, deformation, cracks, especially in and injection formed 形时则 direction property more is obvious. therefore, mold design 时应考虑 shrinkage direction property parts 形状, material direction shrinkage rate is 宜. 　　

（3） rear shrinkage parts formed 形时, due to formed pressure, 剪切应 force, toward property, density 不匀, filler distribution 不匀, mold temperature 不匀, hard 化不匀, property deformation and other factors effect/influence, 引起一 series force function, in viscous 流态时不 can full 部消失, parts in force lower formed 形时存 in residual stress. demolding rear due to force toward balanced and conditions effect/influence, make residual stress 发生变化而 make parts again shrinkage is rear shrinkage. generally parts in demolding rear 10 small inner most large, 24 small rear basic type, most rear stability need 经30-60天. usually thermoplastic property plastics rear shrinkage ratio hot solid property large, and injection formed ratio compression molding formed large. 　　

（4） rear shrinkage has parts property can and process requirements, formed rear 需进行 hot 处理, rear 也会导致塑 parts dimensions 发生变化. mold design for high degree parts 则应考虑 rear shrinkage and rear shrinkage 误差并予以补偿. 　　

2, shrinkage rate 计算塑 parts formed shrinkage can use shrinkage rate table/sheet 示, 如公式（1-1） and 公式（1-2） 示. 　　(1-1) Q实=（a-b）/b×100 (1-2) Q计=（c-b）/b×100 　　式 in: Q实—实际 shrinkage rate （%） 　　Q计—计算 shrinkage rate （%） 　　

a —塑 parts in formed temperature degree mono toward dimensions （mm） 　　

b —塑 parts in room temperature lower mono toward dimensions （mm） 　　

c — mold in room temperature lower mono toward dimensions （mm） 　　

实际 shrinkage rate is table/sheet parts 实际 发生 shrinkage, its value and shrinkage versus very small, therefore mold design 时以Q计 is design parameters type and type dimensions. 　　

3, effect/influence shrinkage rate factors in formed not only different product types plastics its shrinkage rate same, but also different 批 同 product types plastics or 同 一塑 parts different its shrinkage value 也经常 different, effect/influence shrinkage rate main/primary factors has lower several 方面. 　　

（1） plastics product types various plastics has its shrinkage scope/range, types type plastics due to filler, molecular weight and ratio and other different, its shrinkage rate and toward property different. 　　
（2）塑 parts features parts 形状, dimensions, thick, has parts, parts amount and for shrinkage rate large small has very large effect/influence. 　　（3） mold structure mold separation type and add pressure direction, system 形式, and dimensions for shrinkage rate and direction property effect/influence relatively large, especially in and injection formed more is obvious. 　　
（4） formed process 挤塑, injection formed process generally shrinkage rate relatively large, direction property obvious. preheating 情况, formed temperature degree, formed pressure, maintain time, material and hard uniform property for shrinkage rate and direction property has effect/influence. 　　如 upper mold design according to various plastics 说明书 in provide shrinkage rate scope/range, 并按塑 parts 形状, dimensions, thick, has parts 情况, separation type and add pressure formed direction, mold structure and material 口形式 dimensions and 位置, formed process and other factors comprehensive 考虑选取 shrinkage rate value. for or injection formed 形时, 则常需按塑 parts 各部位 形状, dimensions, thick and other features different shrinkage rate. 　　 another, formed shrinkage also to formed factors effect/influence, main/primary 决定于 plastics product types, parts and dimensions. therefore formed adjustment formed conditions can 够适当 改变塑 parts shrinkage 情况.