1)从注塑成型问题诊断探讨产品、模具与工艺设计的优化.广州.051611

从注塑成型问题诊断探讨产品、模具与工艺设计的优化ReviewingPart,MoldandProcessDesignOptimizationfromthePointofViewofTroubleshooting徐昌煜CharlesHsu2011年5月15和16日于广州骏星酒店试模及量产时，经常遭遇的问题包括银纹、波纹、虎皮纹、流痕、气痕、缩痕、熔接痕、应力痕、黄化、脆裂、变形、周期时间长等，使得材料、能源、机器、设备、时间、人力及金钱浪费、良率偏低、甚至无法交货。若无正本清源之道，只有走上败亡之途。试模和量产中80%的问题源自设计不当，产品、模具与工艺设计是救亡图存、反败为胜的关键。强度、应力、降解与污染(60分钟)对材料施加外力时，材料产生阻力而变形。换言之，材料受外力而在内部积蓄应变能。在变形的初期，以分子内原子间的距离变化或分子间距离的变化来应对，之后逐渐无法应对而发生各种构造变化，如部分分子向外力方向，或分子链从结晶中拉出等。这时，部分能量则因材料的粘性效应而变为热能逃出。若继续对材料做功，材料则形成新表面以便放掉能量，这就是破坏，而这时的材料的限界阻力就是强度。强度Strength外力有:(1)拉伸、(2)压缩、(3)剪、(4)弯曲和(5)扭转，这些是由外力的方向差产生的。外力ExternalForceFF拉伸剪弯曲扭转当外力施加于材料时，材料内部产生一种阻挡这外力的内力。每单位面积的内力叫做应力。外力F，应力σ时：A是内力作用面的截面积。材料的强度系以每单位面积可以承受的内力即应力表示。AF应力和强度StressandStrength拉伸应力、拉伸应变和弹性模量1121121112llldddEllllAFwhereF:tensileforce拉伸力A:areawhereFapplies拉伸力所施之面积(紅色)σ:tensilestress拉伸应力ε:tensilestrain拉伸应变E:modulusofelasticity弹性模量μ:Poisson’sratio泊松比Fδl1d2d1l2μ=(unitlateralcontraction)/(unitaxialelongation)lbccc'''''nmcaAFGwhereF:shearforce剪力Aa’c’m’n’:areawhereFapplies剪力所施之面积:shearstress剪切应力:shearstrain剪切应变G:shearmodulus剪切模量剪切应力、剪切应变和剪切模量δγcc'aa’bdγFm’n’lrBByxyzydASECB-BIEMrdAyIIyMAx12whereσx:bendingstressinthexdirectionx方向弯曲应力M:bendingmoment弯曲力矩I:momentofinertiaofAwithrespecttozaxis惯性力矩A:cross-sectionalarea断面积(断面线处)whereE:modulusofelasticity弹性模量EI:flexuralrigidityofthebeam梁之弯曲刚性弯曲应力mndxxTJGdArGrdAGrrdATGrdxdGrGAAAooo2)()(mndxabcdooooc’dArroTorsionandTorque扭力与转矩WhereG:shearmodulus剪切模量:shearstrain剪切应变r0:outsidediameteroftheshaft轴外径r:dA形心至轴之中心线之距离Φ:theangleoftwistwhichisproportionaltothedistancexofthecross-sectionfromthefixedend扭转角(与断面和固定端的距离x成正比)Θ:Θ=dΦ/dx,theangleoftwistperunitlengthoftheshaft单位轴长之扭转角T:torque(appliedcouple)转矩(所施之力偶):shearstressondAdA上的剪切应力:shearstressattheoutersurfaceoftheshaft轴外径表面之剪切应力J:polarmomentofinertia极惯性力矩mndxabcdooooc’dArro0TorsionandTorque扭力与转矩Residualstressisaprocess-inducedstress,frozeninamoldedpart.Itcanbeeitherflow-inducedorthermal-induced.Residualstressesaffectapartsimilarlytoexternallyappliedstresses.Iftheyarestrongenoughtoovercomethestructuralintegrityofthepart,thepartwillwarpuponejection,orlatercrack,whenexternalserviceloadisapplied.Residualstressesarethemaincauseofpartshrinkageandwarpage.残余应力是制程中凝固在成型品中的应力。它可能是流动引起的或热引起的。残余应力对产品的影响与外力产生的应力相似。如果它们大到足以克服产品结构的完整性，产品在脱模时就会变形，而在之后受到外力时开裂。残余应力是收缩翘曲的主因。p.145,“C-MOLDDesignGuide”残余应力ResidualStressTheprocessconditionsanddesignelementsthatreduceshearstressduringcavityfillingwillhelptoreduceflow-inducedresidualstress.Likewise,thosethatpromotesufficientpackinganduniformmoldcoolingwillreducethermal-inducedresidualstress.Forfiber-filledmaterials,thoseprocessconditionsthatpromoteuniformmechanicalpropertieswillreducethermal-inducedresidualstress.在型腔充填期间能够减少剪切应力的工艺条件和设计要素可以减少流动引起的残余应力。同样地，举凡促进充分保压和均匀冷却者可以减少热引起的残余应力。至于添加纤维的材料，举凡增进机械性均布者可以减少热引起的残余应力。p.145,“C-MOLDDesignGuide”残余应力ResidualStress流动引起的残余应力Flow-inducedResidualStressUnstressedlong-chainpolymermoleculestendtoconformtoarandom-coilstateofequilibriumattemperatureshigherthanthemelttemperature(i.e.,inamoltenstate).Duringprocessingthemoleculesorientinthedirectionofflow,asthepolymerisshearedandelongated.Ifsolidificationoccursbeforethepolymermoleculesarefullyrelaxedtotheirstateofequilibrium,molecularorientationislockedwithinthemoldedpart.Thistypeoffrozen-instressedstateisoftenreferredtoasflow-inducedresidualstress.无应力的长链高分子在熔点以上倾向于任意卷曲的平衡状态。制程中被剪切和拉伸的高分子依流向排列，如果高分子在充分松弛前被凝固，分子排列便被锁在成型品中，此一凝入的应力就是流动引起的残余应力。p.145,“C-MOLDDesignGuide”Becauseofthestretchedmolecularorientationinthedirectionofflow,itintroducesanisotropic,non-uniformshrinkageandmechanicalpropertiesinthedirectionsparallelandperpendiculartothedirectionofflow.因为伸张的高分子沿流向排列，所以流向和垂直流向的机械性质不同而收缩率也不同。p.145,“C-MOLDDesignGuide”流动引起的残余应力Flow-inducedResidualStress热引起的残余应力Thermal-inducedResidualStressThermal-inducedresidualstressoccursduetothefollowingreasons:•Materialshrinksasthetemperaturedropsfromtheprocesssettingstotheambientconditionsreachedwhentheprocessiscomplete.•Thematerialelementsexperiencedifferentthermal-mechanicalhistories(e.g.,differentcoolingratesandpackingpressures)asthematerialsolidifiesfromthemoldwalltothecenter.热引起的残余应力的起因如下：•制程从设定温度降到室温时材料收缩。•当材料从模壁向型腔中心固化时，材料单元经历了不同的热力过程(如不同的冷却率和保压)。p.147,“C-MOLDDesignGuide”•Changingpressure,temperature,andmolecularandfiberorientationresultinvariabledensityandmechanicalproperties.•Certainmoldconstraintspreventthemoldedpartfromshrinkingintheplanardirections.•改变压力、温度和分子/纤维排列产生不同的密度和机械性质。•某些模具的拘束阻止了成型品在面向的收缩p.147,“C-MOLDDesignGuide”热引起的残余应力Thermal-inducedResidualStressThesinglebiggestcontributortothepoorperformanceofthemoldedpartisanexcessivelossofmolecularweight.---Thesecondlargestcontributoriscontamination.成型品功能不足的单一最大原因是分子量过度减损。---第二大原因是污染。TheMaterialsAnalyst,Part27:ContaminationspringsfromcostpressuresIMM–December1999成型品功能不足的原因ContributorstothePoorPerformanceofTheMoldedPartLongerpolymerchainsmeanhighermolecularweight,increasedchainentanglement,andimprovedproperties.Thepropertythatbenefitsthemostfromhighermolecularweightisimpac