注塑工艺培训讲座.pptx

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、制件顶出塑化过程最大计量行程屏障螺杆关于塑料的特征分子量熔体指数PVT性质剪切稀化行为热稳定性收缩行为最大流动比吸湿性PVT性质材料的收缩特性温度引起的体积变化结晶高分子29%无定型高分子8%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剪切变稀行为螺杆压缩区的剪切稀化喷嘴的剪切稀化热稳定性Kx最大射胶体停留时间=-x成型周期型腔体积注塑过程充模过程85-98%注塑行程切换过程压实过程冷却过程注塑过程中的收缩行为加工过程对收缩的影响不同材料的收缩率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收缩收缩与翘曲收缩与结晶收缩与加工过程收缩与取向收缩与冷却充模与冷却均衡流动调整均衡性调整均衡性与模具和机台相关的注塑缺陷缩痕壁厚设计不均匀可通过注塑压力、保压压力、注塑速度调整尺寸变化冷却不均匀，调整保压压力、时间、强化冷却均匀性翘曲熔接缝降解重量变化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.均衡热交换均衡凝固熔接缝改变熔接缝位置成型周期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热塑性工程塑料的加工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、化学的变化通常,加工窗口越窄,制件的不合格率越高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模具浇道冷料井:直径与浇道或流道直径相等深度为1.5D流道90度转弯处须设定冷料井浇道太大会延长成型周期为此有如下的改造方法流道保证最大的流动面积和最小的冷却作用流道直径取决于流道长度流道上的冷料井和排气口多型腔模具的流道流道尽可能短,保证各型腔平衡充模浇口浇口位置是模具设计、熔体流动、制品最终用途等综合因数决定的。设计浇口的基本原则：1、大型制件所设计的多浇口应尽量靠近，以增加熔接缝强度2、浇口直径应保证足够的充模压力和速度浇口长度应尽可能短3、侧面进胶保证熔体注于型腔壁或模芯上而避免射流出现4、避免气体包裹，浇口位置应保证充模流动将气体压向排气口5、浇口位置应保证熔体从制件厚端向薄端流6、浇口应远离制件承受冲击和应力的部位（浇口部位可能的过度填充引起的内应力）7、为了减少射流、浇口散射花纹、浇口变色，浇口应和流道垂直直浇口用于制件大、后、流动径深大的制件，此时要求注塑压力最大、浇口凝封时间长。直浇口应位于制件最厚处，浇口尺寸可为壁厚的两倍环型浇口用于要求同心度、并不允许熔解缝存在于环筒上的圆筒型制品扁浇口扇型浇口为减少射流和浇口喷射纹如果存在喷射纹和高内应力，加大冷料井（一般可为流道直径的2-3倍）薄膜浇口解决大型薄板的翘曲方型浇口解决具有冷料井流道不能间接接近浇口的困难解决浇口内应力和喷射问题收缩率影响因素壁厚变化，充模压力熔体及模温注塑速度PVT性质描述材料在熔体和固态下，在注塑温度、压力下的体积变化行为型腔排气减少焦烧避免充模速度的降低而引起的充模不满排气口位于型腔最后充模点尽量位于分模线上对于大型薄壁制品，每隔2550mm，开设一个排气口顶杆、模芯、冷料井排气可作为分模线排气不易实现部位排气口选择的位置注塑工艺充模速度快速充模用于流动长度大薄壁部位的填充有利于表面光洁度慢充模用于直浇口、扁浇口，可避免浇口喷纹、喷射和射流对厚制品慢充模可以减少缩痕和空洞程序充模的应用在开始充模时，慢速可以避免浇口喷射、材料焦烧充模到一定的时候，加快充模，维持恒定的熔体前端速度在充模末期，降低充模速度，以获得良好的制件质量注塑压力寻求得到最好制件质量、外观、成型效率的最低注塑压力保压压力注塑压力的40-80%质量问题焦烧变色射流浇口流痕缩痕喷射纹浇口过小溶接缝强度浇口位置的缺陷保压保压压力恒定保压时间正确设定浇口和流道的不适当凝封在充模完成并充分保压后凝封不适当时：过度填充、反流关于收缩熔体在型腔中冷却时的体积收缩结晶高分子最高可达29%无定型高分子8%熔体的可压缩性10-15%冷却的体积收缩大于可压缩性所以收缩不可避免，只有靠保压过程中的不断补充熔体来减少。不均匀收缩冷却不均匀取向大的方向收缩大注塑速度和保压速度的优化控制可以缓解缩痕气辅成型技术薄壁注塑技术制件壁厚小于0.6mm,流动长度与壁厚之比大于200高透明薄壁制件PP熔体温度最高可达280-320模温5-15常用PP材料，BASEL公司740T智能卡基片制造ABS树脂BAYERLUXTRANM305高流动高注塑温度OneofthekeyprocessconditionsthatinfluencesshrinkageisthepackingpressuremagnitudeandthepackingtimeasillustratedinFigure9.Asthematerialcoolsinthemold,itshrinks.Packingpressureisusedtoaddmorematerialtotheoldcavitytohelpcompensateforthisshrink-age.Ifthepackingpressureishigherorthepackingtimeislonger,morematerialcanbepumpedintothecavitytohelpcompensateforshrinkage,whichdecreases.热塑性工程塑料的加工缺陷的发现目测表面、外观质量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重量比较尺寸稳定性观察内应力的表征加工缺陷表观缺陷外观、尺寸、重量变化、制件发脆等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黑点原因downtimetoolongbarrelswitchedoffoveralongperiodoftimepoorpurgingofbarreldirtyplasticizingunitinadequatenozzledeadedgesingate/runnersystemgranuleimpuritiesdegradationbyotherresinspick-upofdegradedmaterialfromcylinderwallduringcooling气泡injectionpressuretoolowinadequatefunctioningofbackflowvalvesuck-backtoolongplasticizingtoofastairtrapinthehopperfeedimproperfeedvolatilesandtrappedgasmouldtemperaturetoolowthintothicktransitionmeltoverheating1.controlholding/injectionpressure2.increasebackpressure3.increasemouldtemperature4.checkbackflowvalve5.allowforadequateventing6.enlargegate7.shortenlandlength流痕injectionspeedtooslowortoofastinjectionpressuretoolowholdpressuretoolonginadequatemouldcoolingmouldtoohotaroundgatemouldtoocoldgatetoosmallwronggatelocationgatelandlengthtoolongwronghotrunnersystemmelttemperaturetoolow1.adaptinjectionspeed2.addalargecoldslugarea3.addcoldwellsattheendofrunnersystems4.controlnozzleheatbetter:ifnecessaryaddberylliumcoppertip(notrecommendedforFRresins)5.shortenoreliminatestandardspruebushing:useahotspruebushing6.cleanflowmustexistfromthecylinder,adaptor,nozzleandtip:avoidandeliminateanydeadpocketsorsections胶烧problemswithbackflowvalveinjectionspeedtoofastbackpressuretoohighinadequateventing:entrappedairfrictionalburningcheckspruediametermelttoohotortoocold:maycreateshear起层injectionspeedtoohighmelttoohotpoorlymeltedIncompatiblecolourdyescrosscontaminationwithotherpolymerstoomuchuseofrecycledmaterial变色飞边射流纹路缩痕缺料银丝热塑性工程塑料加工的隐性缺陷收缩率、翘曲后收缩率大空洞ZIPPER不熔颗粒及熔体不均匀性熔接痕强度低模温设定不正确引起的性能劣化其他加工条件引起的性能劣化飞边引起的缺口效应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！