Shanghai Daoqin Plastics Co., Ltd.

         precision injection molding concept

         precision injection molding is processing molding injection molding products dimensions heavy degree very high, use general purpose injection molding machine, injection molding process difficult to requirements types injection molding methods.

        “ precision injection molding ” this concept, main/primary is difference 于“常规 injection molding ”, it is polymer/macromolecule material speed development, in table/sheet, electronics field/area using/adopting precision plastics parts high degree metal parts technology.

         currently for precision injection products indicators has 两:

        一 is products dimensions heavy degree, is products quality heavy degree.

        本文 main/primary from products dimensions heavy degree 方面阐述 precision injection molding. due to various material property and processing process different, can plastics made parts degree and metal parts degree and other 同起.

         molding products mold is 决定该 products can to design requirements dimensions important conditions, precision injection molding machine is ensure products in requirements dimensions scope/range inner molding, and ensure high formed product rate key/critical equipment.

         precision injection features:

         made parts dimensions degree high, small, has high degree dimensions 界限;

         products weight heavy degree high, requirements has day, month, year dimensional stability;

         mold material good, rigid property 足, type dimensions degree, light degree and sheet/plate 间 定位精 degree high;

         using/adopting precision injection machine more 换常规 injection machine;

         using/adopting precision injection molding process;

         selection precision injection molding material.

        评定 products most important technology indicators, is injection molding products degree (dimensions 公差, 形位公差 and products surface light degree). injection molding precision plastics products, from material selection, mold design, injection molding process, as technology water and other 4 large factors 进行严格 control.

         precision injection molding machine requirements products dimensions degree generally in 0.01～0.001mm以 inner, many precision injection molding also requirements injection molding machine tool has high injection pressure, high injection speed degree;

         requirements clamping system tool has large rigid property and high 锁模精 degree, 谓锁模精 degree is clamping force uniform property, can 调, stability and heavy property high, clamping 位置精 degree high;

         requirements for pressure, amount, temperature degree, amount and other can control to versus 应 精 degree, using/adopting more grade or grade injection, ensure molding process again conditions and products dimensions heavy degree and other.

         effect/influence products dimensions degree factors:

         mold degree;

         molding shrinkage;

         products use ring temperature degree, wet degree and 波动 幅 degree.

         injection molding precision molding material selection 原则

         machine strong/high degree high, dimensional stability good, resistant creep property can good, ring 境适应 scope/range 广.

         commonly used has types material:    

        POM and carbon fiber reinforced (CF) or reinforcement (GF). this type of material features is creep resistance can good, resistant fatigue, weather resistance, electrical property can good, flame resistant, add lubricant easy demolding.

        PA and glass fiber reinforced PA66, its features: impact resistant can force and wear resistance can strong/high, flow property can good, can molding 0.4mm壁 thick products. glass fiber reinforced PA66 tool has heat resistant property (melting point 250℃), its disadvantages is tool has wet property, generally molding rear need through wet 处理.

        PBT reinforcement polyester, molding time short. molding time comparison lower: PBT≤POM≈PA66≤PA6.

        PC and GFPC. features: good wear resistance, reinforcement rear rigid property improve/increase, dimensional stability good, weather resistance, flame resistant and molding processing property good.

         precision injection molding in shrinkage issues

         effect/influence shrinkage factors has types: hot shrinkage, versus shrinkage, orientation shrinkage and pressure shrink shrinkage.

         hot shrinkage is molding material and mold material solid has hot material features. mold temperature degree high, products temperature degree high, shrinkage rate increase, therefore precision injection mold temperature degree high.

         versus shrinkage due to crystallization type resin in toward process in, polymer/macromolecule crystallization 化, due to ratio decrease/reduce 而引起 shrinkage, versus shrinkage. mold temperature degree high, crystallization degree high, shrinkage rate large;但另一方面, crystallization degree improve/increase make products density increase, 线膨胀系数 decrease small, shrinkage rate reduce. therefore shrinkage rate 由两者 comprehensive function 而定.

         orientation shrinkage, due to separation in flow direction upper strong/high tensile, make in cooling large separation has heavy new 卷曲恢复 trend, in orientation direction will generate shrinkage. separation orientation degree and injection pressure, injection speed degree, resin temperature degree and mold temperature degree and other has 关. main/primary is injection speed degree.

         pressure shrink shrinkage and elastic property 复位, generally plastics tool has pressure shrink property. in high pressure lower ratio 容发生 significantly 变化. in generally temperature degree lower, improve/increase pressure molding products ratio decrease small, density increase, 膨胀系数 decrease small, shrinkage rate significantly decline. for pressure shrink property, molding material tool has elastic property function, make products shrinkage decrease small. effect/influence products molding shrinkage factors and molding conditions and as conditions has 关.

         precision injection molding mold

         mold degree, main/primary 取决于 mold type dimensions degree high, type 腔定位准确 or separation type degree is meet/satisfy requirements. generally precision injection molding mold dimensions 公差, control in products dimensions 公差 1/3 below/following.

         can processing property and rigid property, in mold structure design in, type 腔数不宜 more, sheet/plate, sheet/plate, type 腔壁都 need thick 一, 以避免 parts in high temperature, high pressure function lower 发生剧烈 elastic property 形变.

         products demolding property, mold need amount less type 腔数, less short runner and ratio mold has more high light degree, this has demolding.

         precision mold material, selection machine strong/high degree high alloy 钢. made as type 腔, 浇道 材 material need 经 严格 hot 处理, selection hardness high (molding parts need to HRC52 left right), wear resistance good, resistant property strong/high material.

         precision injection machine features and selection

         technology parameters features:

         from injection pressure 方面划 separation, machine: 147 ～177MPa; precision machine: 216 ～243MPa; ultra-high pressure machine: 243～392MPa.

         precision injection molding machine must high pressure is:  

        (1) improve/increase precision products degree and quality, injection pressure for products molding shrinkage has most obvious effect/influence. injection pressure to 392MPa时, products molding shrinkage is 零. this products degree mold control or ring effect/influence. 实验证明: injection pressure from 98MPa improve/increase to 392MPa rear, machine strong/high degree improve/increase 3%～33%.

        (2) can decrease small precision products thick, improve/increase molding long degree. 以PC is 例, machine injection pressure 177MPa, can molding 0.2～0.8mm壁 thick products, precision machine injection pressure in 392MPa时 can molding thick degree in 0.15～0.6mm between products. ultra-high pressure injection machine can obtain long ratio more large products.

        (3) improve/increase injection pressure can separation injection speed rate 功效. to injection speed rate, has 两 办 method: is improve/increase system most high injection pressure;二 is renovation screw parameters, improve/increase long ratio. precision injection machine injection speed rate requirements high.

         precision injection machine in control features:  

        (1) for injection molding parameters heavy degree (again property) requirements high, using/adopting more grade injection control:

        a. more grade control;

        b. more grade speed degree control;

        c. more grade holding pressure control;

        d. more grade back pressure control;

        e. more grade screw speed control.

        位移传感 device degree requirements to 0.1mm, this can control amount 行程, injection 行程以 and material thick degree (injection shot 监控点), ensure injection amount 准确, improve/increase products molding degree. material and nozzle temperature degree control need 精确, rise temperature ultra- 调 amount need small, temperature degree need small. precision injection molding using/adopting PID control, make temperature degree degree in ±0.5℃ between is 宜.

        (2) quality requirements, plastics uniform property not only effect/influence to injection molding parts molding quality, also effect/influence to melt plastics through gate 时 受 retardant force large small, is to uniform 塑化, design specialized screw and use specialized increase technology can less.

         another, machine temperature degree 也应精确 control, in screw, machine temperature degree more using/adopting PID control (ratio/proportion, micro separation, separation), degree can control in ±l℃ inner, basic can meet/satisfy precision injection molding requirements, if using/adopting FUZZY control methods, more combined precision injection molding.

        (3)工 as temperature degree control need high temperature 变化导致 injection pressure 波动, must for as using/adopting add hot, cooling ring plant/unit, temperature stability in 50～55℃ is 宜.

        (4) holding pressure pressure effect/influence, holding pressure for degree parts effect/influence large, 准确 说, holding pressure can relatively good shrink, decrease small parts deformation, control parts degree, holding pressure pressure stability 决定 塑 parts molding degree, screw 终止位置不变 is holding pressure 效果 决定 factors.

        (5) for mold temperature degree control requirements cooling time same, mold type temperature degree low products thick degree need ratio temperature degree high products thick degree dimensions large. 如POM, PA type material, mold temperature 50℃时 thick degree is 50～100μm products, in 80℃时 thick degree decrease small to 20～40μm, 100℃时 decrease small to has 10μm. room temperature for precision products dimensions has effect/influence.

         precision injection molding machine liquid pressure system:

        油路 system need using/adopting ratio/proportion pressure 阀, ratio/proportion amount or 伺服变 amount ratio/proportion system.

         in pressure clamping machine in, clamping separation and injection separation separation 开.

         due to precision injection molding machine tool has high speed property, is must strong/high liquid pressure system reaction speed degree.

         precision injection molding machine liquid pressure system, more need separation machine electrical liquid 仪一体 chemical industry 程.

         precision injection molding machine structure features:

         due to precision injection machine injection pressure high, this need strong/high clamping system rigid degree. 动, sheet/plate degree control in 0.05～0.08mm scope/range inner.

         requirements for low pressure mold and clamping force large small degree control. is clamping force large small need effect/influence mold deformation degree, most need effect/influence to made parts dimensions 公差.

        启, speed degree need fast, generally in 60mm/s left right.

        塑化部 parts: screw, screw 头, ring, material and other, need design formed can force strong/high, 均化程 degree good, injection efficiency high structure 形式; screw 驱动扭矩 need large, can grade speed.

        无论何 types precision injection molding machine, most 终都必 must can stability control products dimensions heavy degree and quality heavy degree.