塑料注塑成型加工

塑料注塑成型加工塑料注塑成型加工向明四川大学高分子研究所高分子材料工程国家重点实验室良好的注塑件质量获得的条件良好的注塑件质量获得的条件l适合的注塑设备l适宜的螺杆结构l良好的材料预处理工艺l合适的注塑工艺条件l合理的模具结构塑料注塑基础塑料注塑基础l注塑加工涉及的过程1、塑料胶粒的软化和塑化（螺杆塑化过程）螺杆结构的设计必须保证得到均匀一致的熔体2、塑料熔体计量螺杆转速，背压3、塑料熔体向锁闭型腔注射锁模力比型腔压力高20%，熔体以均衡的方式充填模具型腔，以避免内应力的产生 多级注塑、充模流动行为、型腔压力分布、熔体PVT性质4、冷却熔体凝固并保持模具型腔形状 均匀的模具表面温度，避免制件翘曲、保证尺寸精度5、制件顶出塑化过程塑化过程最大计量行程最大计量行程屏障螺杆屏障螺杆关于塑料的特征关于塑料的特征l分子量l熔体指数lPVT性质l剪切稀化行为l热稳定性l收缩行为l最大流动比l吸湿性PVT性质性质材料的收缩特性材料的收缩特性l温度引起的体积变化结晶高分子29%无定型高分子8%l压力引起的体积变化10-15%Poly-merDensityRoomTemp.Processtemp.degreecDensityprocesstemp%ageinjectionutilisa-tioncapacityPermissibleresidencetime-min.Max-flowratiofor1mmwallthicknessScrewcushionmmShrinkage%OutputratiorelatedtoPsScrewrpmrelatedtoPsABS1.05220-2600.9640-80100-1404-60.4-0.70.830.83CA1.29170-2501.1050-805-830030.4-0.7NANAPOM1.42192-2151.1630-8015100-2302-62NANAPMMA1.18220-2601.0935-804-8100-1302-60.4-0.80.940.74PPO1.06250-290NA30-808100-1403-40.4-0.7NANAPA6/61.14220-2800.9540-805100-2302-4NA0.580.50PC1.22280-3101.0850-802-360-10040.7-0.80.670.57PES1.37330-400NANANA60-1204-50.60.950.83PBT1.31220-270NA40-803-4125-1854NANANAPPS1.5-2.1300-360NA50-802-4120-1504-60.2NANAPETP1.38260-3001.250-802-450-9041.3-1.50.80.74PS1.05220-2700.9525-902-4150-20040.451.001.00HDPE0.95220-2800.7410-851702-61.5-20.730.94LDPE0.92180-2800.7410-952002-6NA0.821.05PP0.91250-2750.7310-8517041.2-2.20.630.86RPVC1.3-1.6170-190NA25-8020600.5-0.2NANASPVC1.1-1.14180-200NA20-801518041.2NANASAN1.08240-2700.9940-805-6140-18040.50.961.12TPU1.20180-225NA40-80305031-1.15NANA剪切变稀行为剪切变稀行为螺杆压缩区的剪切稀化螺杆压缩区的剪切稀化喷嘴的剪切稀化喷嘴的剪切稀化热稳定性热稳定性Kx最大射胶体停留时间=-x成型周期型腔体积注塑过程注塑过程l充模过程85-98%注塑行程l切换过程l压实过程l冷却过程注塑过程中的收缩行为注塑过程中的收缩行为加工过程对收缩的影响加工过程对收缩的影响不同材料的收缩率不同材料的收缩率MATERIALS%SHRINKAGEMATERIALS%SHRINKAGENylon61-1.5Polycarbonate0.8Nylon6-GR0.5Acetal2Nylon6/61-2PVC-Rigid0.5-0.7Nylon6/6-GR0.5PVC-Soft1-3LDPE1.5-3ABS0.4-0.6HDPE2-3PP1.2-2Polystyrene0.5-0.7Celluloseacetate0.5Styrene-acrylonitrile0.4-0.6Celluloseacetate.butyrate0.5Acrylic0.3-0.6Cellulosepropionate0.5收缩收缩收缩与翘曲收缩与翘曲收缩与结晶收缩与结晶收缩与加工过程收缩与加工过程收缩与取向收缩与取向收缩与冷却收缩与冷却充模与冷却充模与冷却均衡流动均衡流动调整均衡性调整均衡性调整均衡性调整均衡性与模具和机台相关的注塑缺陷与模具和机台相关的注塑缺陷l缩痕壁厚设计不均匀可通过注塑压力、保压压力、注塑速度调整l尺寸变化冷却不均匀，调整保压压力、时间、强化冷却均匀性l翘曲l熔接缝l降解l重量变化POSITIONSPEEDPRESSUREFILLING PHASEAlso known as Speed phase.Selectendof1ststepandstartof2ndstep.SetSPEED1Trytosethigh.Only one pressure setting is required during FILLING PHASE.Pressure Setting should be more than actual filling pressure.as relief valve should not be actuated.If it is actuated,then speed control will be lost.Filling pressure depends on resistance to move the melt.It depends on flow ratio and viscosity of melt.Also known as Speed phase.There may be no.of steps available on machine.Selectendof2ndstepandstartof3rdstepSetSPEED2Lowerspeedforcrossingnarrowpassage/gateSteps are position controlled.Selectendof3rdstepandstartofSWITCHOVERPOINT.Thispointisataround80-95%oftheinjectionstroke.SetSPEED3Reducetolowersinkmark/increasetoshiftweldline.PRESSURE PHASE-Holding phase.There may be no.of steps available on machine.TimercontrolstheHoldingpressurestepsifavailableonmachine.Holdingpressuretimeforstep1issetonatimer,Set SPEED low value say up to 35%not more.This can be one step of speed for different Holding steps.Speed set is low,as there is less or no space to move the melt.Holdingpressure1setjustenoughtofillcavitywithoutoverpacking.Steps are timers controlled.Holdingpressuretimeforstep2issetonatimer,Holdingpressure2setjustenoughtofillcavitywithoutoverpacking.Holdingpressuretimeforstep3issetonatimer,Holdingpressure3setjustenoughtofillcavitywithoutoverpacking.均衡热交换均衡热交换均衡凝固均衡凝固熔接缝熔接缝改变熔接缝位置改变熔接缝位置成型周期成型周期The predominantly material causes involved in failure were:The predominating process faults were:Environmental Stress Cracking,Excessive moulded-in stresses,Cyclic Fatigue,Voiding,Notch Sensitivity,Poor weld lines,Chemical Attack and;Stress Cracking,Adverse Orientation,UV Degradation,Material contamination,Thermal Degradation,Longer Residence time in the machine,Creep,Wrong material selection or poor part design,Buckling,Wrong material selection or poor part design工程塑料的加工缺陷及解决方法工程塑料的加工缺陷及解决方法热塑性工程塑料的加工热塑性工程塑料的加工l材料加工在材料应用中处于举足轻重的地位特定用途材料选择依据材料性能的准确测试但在实际的过程中,加工过程并不能完整的将材料性能表达到具体的制件上特定用途材料选择加工条件l如果选择的工程塑料的加工窗口过窄,塑料会在加工过程中发生力学、物理、化学的变化l通常,加工窗口越窄,制件的不合格率越高l一般在塑料加工过程中，制件的质量控制主要通过将其与已知性能的好样品进行比较热塑性工程塑料的加工缺陷的发热塑性工程塑料的加工缺陷的发现现l目测表面、外观质量l力学性能测试材料性能和加工条件对制件使用性能的影响l重量比较l尺寸稳定性观察l内应力的表征加工缺陷加工缺陷l表观缺陷外观、尺寸、重量变化、制件发脆等l隐性缺陷导致材料过早失效热塑性工程塑料加工的表观缺陷热塑性工程塑料加工的表观缺陷l黑点原因downtimetoolongbarrelswitchedoffoveralongperiodoftimepoorpurgingofbarreldirtyplasticizingunitinadequatenozzledeadedgesingate/runnersystemgranuleimpuritiesdegradationbyotherresinspick-upofdegradedmaterialfromcylinderwallduringcoolingl气泡injectionpressuretoolowinadequatefunctioningofbackflowvalvesuck-backtoolongplasticizingtoofastairtrapinthehopperfeedimproperfeedvolatilesandtrappedgasmouldtemperaturetoolowthintothicktransitionmeltoverheating1.controlholding/injectionpressure2.increasebackpressure3.increasemouldtemperature4.checkbackflowvalve5.allowforadequateventing6.enlargegate7.shortenlandlengthl流痕injectionspeedtooslowortoofastinjectionpressuretoolowholdpressuretoolonginadequatemouldcoolingmouldtoohotaroundgatemouldtoocoldgatetoosmallwronggatelocationgatelandlengthtoolongwronghotrunnersystemmelttemperaturetoolow1.adaptinjectionspeed2.addalargecoldslugarea3.addcoldwellsattheendofrunnersystems4.controlnozzleheatbetter:ifnecessaryaddberylliumcoppertip(notrecommendedforFRresins)5.shortenoreliminatestandardspruebushing:useahotspruebushing6.cleanflowmustexistfromthecylinder,adaptor,nozzleandtip:avoidandeliminateanydeadpocketsorsectionsl胶烧problemswithbackflowvalveinjectionspeedtoofastbackpressuretoohighinadequateventing:entrappedairfrictionalburningcheckspruediametermelttoohotortoocold:maycreateshearl起层injectionspeedtoohighmelttoohotpoorlymeltedIncompatiblecolourdyescrosscontaminationwithotherpolymerstoomuchuseofrecycledmateriall变色l飞边l射流l纹路l缩痕l缺料l银丝热塑性工程塑料加工的隐性缺陷热塑性工程塑料加工的隐性缺陷l收缩率、翘曲l后收缩率大l空洞ZIPPERl不熔颗粒及熔体不均匀性l熔接痕强度低l模温设定不正确引起的性能劣化l其他加工条件引起的性能劣化l飞边引起的缺口效应l残留内应力提高生产效率-减少成型周期-低模温-高内应力-应力开裂检查内应力检查内应力ABS冰醋酸，甲醇SAN甲苯/异丙醇（1/5）PA6，PA66氯化锌饱和水溶液，50POM硫酸，50PC甲苯/异丙醇（1/3）结语结语在正确选用材料的前提下，热塑性工程塑料加工中的缺陷是造成制件失效的主要原因。可以通过优化加工条件、模具设计的改善、以及材料的流动特征及冷却凝固行为的控制，来避免加工过程产生的缺陷减少制件的失效破坏。谢谢！