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工艺注塑手册Injectionprocesshandbook一.基本理念:Basicopinion:1.什么是最佳的流动状态:Whatisthebestflowstate:流体流动状态应该是喷泉状的,最佳的流动状态是流体前端的流动速度在型腔内处处相等。由于流动方向上截面积的不同,在其变化的位置应进行注射速度的调节(注意:机床上所能设定的注射速度是指螺杆的前进速度)。Theflowstateshouldbelikefountain,andthebestisthatthespeedofthefrontmeltisthesameeverywhereinthecavities.Fordifferentareasinthedirectionthatisverticalwiththeflowway,wemustadjusttheinjectionspeed.(Attention:Theinjectionspeed,whichwecansetonthemachine,isthescrewforwardspeed)2.什么是最佳的压力,温度分布状态:Whatisthebestpressureandtemperaturestate:最佳的压力和温度分布状态是压力和温度分布在型腔内部处处相等,并且随着熔体地逐步冷却而下降并使最终产品的内应力为零。Thebestpressureandtemperaturestateshouldbelikethisthatthepressureandtemperatureeverywhereincavitiesarethesame,andmaketheforceofthepartinsidebezerofinallyasthemeltsolidified.实际压力分布状况是浇口附近最大并随着距离的增加而降低。(记住:螺杆头处的熔体和流动着的熔体前端存在压力差是使熔体发生流动的根本原因)Theactualpressurearoundthegateisthehighestandasthedistancegoesit’sgettinglowerandlower。(Remember:It’sthepressureinfrontoftheflowingmeltislowerthanincylinderthatmakesthemeltflow.)所以,综合来讲,参数设定的一般准则:(1)尽量选用高的注射速度(螺杆前进速度)(2)尽量选用高的料筒温度(3)尽量选用高的模具温度Sothegeneralprincipleswhensettingparametersare:(1)Asfastinjectionspeedaspossible(Screwforwardspeed)(2)Ashighcylindertemperatureaspossible(3)Ashighmoldtemperatureaspossible二.基本概念:Basicconception:1.收缩:Shrinkage:(1)收缩的原因:.a.热胀冷缩;.b.熔体结晶;(结晶度越高,熔体收缩越严重).c.分子取向;(一般来说,分子总是沿着流动方向取向的。对于未增强型材料,其熔体在流动方向上的收缩总是大于垂直方向;对于增强型材料,正好相反).d.状态变化Thereasonsofshrinkage:a.Changfromhottocold;b.Crystallization;(Themorecrystallization,themoreshrinkage)c.Moleculeorientation;(Fornon-strengthenmaterial,theshrinkageintheflowingdirectionismorethanthat,whichisverticalwiththeflowingdirection;andforthestrengthenmaterial,theresultisjustreverse,)d.Formchanging(2)收缩的阶段:Thestagesofshrinkage:收缩从注射开始就随着熔体的逐步冷却而开始Theshrinkagestartsfrominjectiontoforever.它包括三个阶段:a.从注射开始到保压结束;b.从冷却时间开始到脱模前;c.脱模后Itcontainsthreestages:a.Frominjectionstagetoendofholdingstage;b.Fromcoolingstagetodemoldstage;c.Afterdemold.(3)变形:Deformation变形的根本原因时收缩的不均匀。造成收缩不均匀的原因有:Therootcauseofdeformationisinhomogeneousshrinkage.Thecausesofinhomogeneousshrinkageareasfollows:a.冷却(即温度分布)不均匀Inhomogeneouscoolingb.壁厚不均匀Differentwallthicknessc.压力分布不均匀Notaveragelocationofpressurelocationd.分子取向Moleculeorientatione.脱模受力不均Inhomogeneousforceswhendemolding2.结晶Crystallization:(1)什么是结晶:Whatiscrystallization:简单的说,结晶就是指分子的有序排列Inashortword,itmeanstomakethemoleculeinorder.(2)结晶的影响因素:Factorsaffectingcrystallization:结晶的影响因素:冷却速度。冷却速度越快,结晶程度越低。Thecoolingspeedaffectsthecrystallization.Thefastercoolingspeedthemorecrystallization(3)结晶对产品性能的影响:Howdoescrystallizationaffecttheparts:结晶度越高:密度越高收缩越大光洁度越好强度越高韧性变差Themorecrystallization:ThehigherdensityThemoreshrinkageThebettersurfaceThestrongeroftheparts3.粘度:(1)什么是粘度:Whatisviscosity:粘度是流体本身的一种性能,它的大小是流体流动性能的一种衡量。数值越大,流体的流动性能越差。Viscosityisacharacteroftheflowingmaterial.Itsvalueisusedtomeasuretheflowingcharacter.Thebiggervalueitis,theworseflowingcharacteritis.(2)粘度的影响因素:Whataffecttheviscosity:a.温度Temperatureb.剪切速度Shearratec.压力Pressure千万注意:往往粘度是三者共同作用的结果。不同的材料对温度,剪切速度和压力的敏感程度是不同的,并且在不同的注射速度下哪一个起主导作用也是不同的Attention:Thethreefactorsaffecttheviscositytogetherallthetime.Differentmaterialaredifferentlysensitivetotemperature,shearrateandpressure,andwhichfactorwillbethemainfactorindifferentphaseisalsodifferent.通常:(A)对温度敏感:PA;PCNormally:Sensitivetotemperature:PA,PC对剪切速度敏感:POM;PP;PESensitivetoshearrate:POM,PP,PE对压力敏感:PP;PESensitivetopressure:PP,PE(B)在高速注射的情况下,剪切速度起主导作用(所以,对于薄壁产品或含薄壁部分的产品宜采用高速注射)。Inhighinjectionspeedsituation,theshearrateisthemainfactor.(Sousehighinjectionspeedforthinwallthicknessparts)4.止回阀:Non-returnvalve:a.止回阀的功能是什么:Functionofnon-returnvalve:在注射,保压时防止熔体倒流,从而给予熔体我们所需的压力和速度。Topreventthemeltflowingbackwheninjectionandpacking.b.怎么判断止回阀或料筒损坏Howtorecognizethenon-returnvalveisbroken:初步判断:经常性的出现料垫不稳,或无料垫。Recognizepresumedly:Meltcushionisnotstableusuallyornocushion.准确判断:延长保压时间,如果出现零料垫则说明止回阀损坏或料筒损坏。Recognizeprecisely:Prolongtheholdingtime,ifthereisnomeltcushion,thenon-returnvalveisbrokenorthecylinderisbroken.c.怎么区别止回阀损坏还是料筒损坏Howtorecognizethenon-returnvalveisbrokenorthecylinderisbroken:方法一:换上新的止回阀,延长保压时间依然没有料垫,则说明料筒损坏。Method1:Changeintoanewnon-returnvalve;prolongtheholdingtime,ifthereisstillnomeltcushion,itmeansthecylinderisbroken.方法二:放大料垫,延长保压时间依然没有料垫,则说明止回阀损坏;反之则说明料筒损坏。Method2:Makethemeltcushionbigenough;prolongtheholdingtime.Ifthereisstillnomeltcushion,itmeansthenon-returnvalveisbroken;ifthereismeltcushion,itmeansthecylinderisbroken.三.基本参数:Basicparameters:1.注射速度:Injectionspeed:(1)什么是注射速度:Whatisinjectionspeed:通常我们所设定的注射速度是指螺杆前进的速度。但是真正重要的是熔体在型腔里前进的速度,它与流动方向的截面积大小有关。Theinjectionspeed,whichwecansetonthemachine,isthescrewforwardspeed.Butwhatisveryimportantisthemeltforwardspeedincavities(2)怎么确定注射速度:Howtosettheinjectionspeed:作为原则,注射速度应越快越好。Asarule,theinjectionspeedshouldbethefasterthebetter.它的确定取决于熔体的冷却速度和熔体粘度:冷却速度快的或粘度高的熔体采用高的注射速度。注意:冷却速度的快慢取决于材料本身的性能,壁厚以及模具温度高低。Theinjectionspeedisdeterminedbythecoolingspeedandtheviscosityofmelt:Tothemelt,whichcoolingspeedisveryfastandtheviscosityishigh,we‘dbetterusefastinjectionspeed.Attentionthatthecooling
本文标题:注塑工艺手册
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