Shanghai Daoqin Plastics Co., Ltd.

随 injection molding parts molding processing degree requirements improve/increase, remove positive material selection and for plastics modified outer, how to positive selection molding process conditions, combined analysis products comprehensive shrinkage rate and processing process parameters between versus 互关系, and shrinkage rate generate various causes and processing factors for it effect/influence and other is very important 课题. 1实验部 separation 1.1实验 raw materials PP: 1390 type, injection grade copolymer PP, 北京燕山石化 company. 1.2 equipment injection machine: SZ-100／160NB, plastics machine injection molding parts processing; injection molding parts mold: made injection sheet/plate injection molding parts mold. 1.3 Sample specifications 200mm×100mm×4mm sheet/plate. 1.4 process conditions table/sheet 1列出PP injection molding parts molding process conditions. table/sheet 1PP injection molding parts molding process conditions project injection process parameters machine temperature degree /℃180200210220 injection molding parts pressure /Mpa6080100120 holding pressure pressure /Mpa405060 injection temperature degree /℃200210220230 injection time /s3456 holding pressure time /s30405060 injection molding parts mold temperature degree /℃50607080 cooling time /s203040502结果 and 讨论2.1 shrinkage process and mechanism fine 观察PP Sample in table/sheet 1 列各 process conditions combined lower injection can 发现, products shrinkage rate is 1％-3％, this type of shrinkage 由三部 separation formed, gate solid front shrinkage, cooling shrinkage and demolding rear shrinkage. 2.1.1 gate solid front products shrinkage PP products in gate solid front shrinkage very large degree upper 取决于 melt can force. material material 一进入 injection molding parts mold inner, due to injection molding parts mold temperature degree relatively low, melt temperature degree speed decline, melt density and viscosity in improve/increase. melt can force 取决于 holding pressure pressure large small, and in pressure lower will melt toward inner 传递 整 充模 time. this process need 一直持续 to gate solid 并封闭 is 止. therefore can is, holding pressure pressure and holding pressure time and this stage/phase shrinkage 关系极 large, holding pressure pressure large, holding pressure time long, products shrinkage rate versus for relatively low. 2.1.2 cooling process in products shrinkage from gate 开始凝 solid demolding stage/phase is cooling stage/phase. stage/phase again its it new melt mold cavity, PP products parts heavy and density again 变化. cooling process in, products shrinkage and injection molding parts mold temperature degree and cooling speed rate, cooling time has 关, cooling speed degree fast, products and 松弛, shrinkage rate can can relatively small; if injection molding parts mold temperature degree high, cooling speed degree slow, separation has separation time, shrinkage rate can can increase large. 2.1.3 demolding rear products shrinkage demolding rear PP products in room temperature lower 静置一段 time, this is is demolding rear products also has 一 自由 shrinkage process. if process conditions 设置不当, time inner also can can 发生一 自然应 force rear deformation. therefore, from products 测 总 shrinkage amount is above separation and. plastics material generate shrinkage is positive 常, how to control and products shrinkage and process factors is relatively complex research 课题, must from effect/influence products shrinkage rate process factors analysis research. 2.2影赂 shrinkage rate large small process factors 2.2.1 mold cavity pressure for shrinkage rate and stability property effect/influence in PP injection process in, melt in temperature degree and pressure lower mold cavity 并一直持续 to gate 封口, this pressure can as pressure. pressure for products shrinkage 起决定 property function, pressure high, products shrinkage small; if injection process conditions and equipment can ensure stability pressure, make products generate shrinkage 波动, effect/influence products dimensional stability. 封口之 front mold cavity pressure 取决于 holding pressure pressure, holding pressure pressure upper can as holding pressure stage/phase injection molding parts pressure, if gate time is 一定, that improve/increase holding pressure pressure must make gate pressure improve/increase, holding pressure pressure for gate pressure effect/influence upper 就反映 for shrinkage rate effect/influence, holding pressure pressure upper is injection molding parts pressure 直接反映, 图1示出 injection molding parts pressure and products shrinkage rate 关系. Shanghai plastics has company