Shanghai Daoqin Plastics Co., Ltd.

十 large molding processing tips/techniques

一 injection molding 厂 in 实践操 as in, from for 无定形 plastics experience 出发, relatively short holding pressure time and relatively long cooling time, but also this type of methods used for POM（ polyoxymethylene (POM) ）, PA（ nylon ）, PBT, PET（ polyester ） and other semi crystallization property plastics. 本节讨论 调 machine selection combined holding pressure time 时 一 key/critical factors.

in holding pressure lower 会发生 what?

一旦 mold cavity by filling, plastics separation 子就开始 crystallization, separation 子链开始 has 序排列, formed relatively high density. this process from outer 围开始, in in 心结束（见图）. and polyoxymethylene (POM) 一样, this process 引起 体积 shrinkage can to 14％, need in holding pressure lower again toward in melt. if, will formed small 孔（ micro 孔）, this small in more for plastics products property generate effect/influence.

 
how to holding pressure time is short

use this type of methods manufacturing products 经常发生 shrinkage, deformation, 凹痕, 空隙, has mechanical properties 也会变差, dimensions can can 会发生 very large 变化. as has 时会试图 through increase cooling time 弥补, this milli 无意义 延 long cycle time.
for use reinforcement material products, its holding pressure time effect/influence types methods is in most thick 处切开. abrasion light rear 切割面 can use 检查空隙 and bubbles, this as can use large or light micro 镜 执行. types more methods is 准备切 sheet/slice （见图 sheet/slice ）. use this type of methods, make is most small defect can use micro testing to.
use reinforcement material products defect can very easy through most thick 处 断面 进行 testing. if, upper 会出现一 similar bubbles structure, large 断面显 micro sheet/slice upper can to by plastics 包裹而暴露 in external fiber. types methods is 准备抛 light sheet/slice micro sheet/slice, from in can obvious testing to bubbles.
has holding pressure time can through in injection molding machine upper for many products 进行称 heavy to （详见描述）. for/regarding to mold, this is its in 实际操 as conditions lower holding pressure time most good methods.
most holding pressure time can through comparison method obtain （见 table/sheet ）. this type of methods suitable for to thick mold, it 并未考虑 to temperature degree, formed additives or material, mold filling time and other other factors effect/influence. thick small mold holding pressure time short, thick large mold holding pressure time long.

 
 
positive 确 调校程序

is make parts property can to most 佳, holding pressure time application heavy method 确定, cooling time 应设置 is most small value （略 high 于塑化 time ）. this requirements must design gate 位置（参见Plastverarbeiter 46[1995]6 and 7 第2部 separation and 第3部 separation ）. positive pressure value material selection material different, in 60MPa and 100MPa间变化.