射出成型之设计教程.ppt

成型工艺设计原理分析,注射成型生产过程,注射成型生产过程概述,2023/5/22,Page3,注射成型生产过程,注射成型周期,注射成型是一个循环的过程。在注射成型过程中，注射机以循环方式进行一序列操作。一个成型周期即是注射机的完全操作。,2023/5/22,Page4,注射成型生产过程,注射成型周期,周期时间充填时间35%保压时间1015%冷却时间3060%开模时间1020%,2023/5/22,Page5,22秒,1,9,10,2,注射成型生产过程,典型模具材料的热特性,注射成型过程,充填Filling模具闭合，螺杆快速向前移动，将熔融塑料射入模穴保压Packing(保持Holding)模穴填满，保压开始，冷却开始,2023/5/22,Page7,注射成型生产过程,注射成型过程,冷却Cooling保压完成，浇口凝固关闭，冷却继续螺杆快速后移，开始为下一次注射塑炼塑料开模Opening冷却完成，模具打开,2023/5/22,Page8,注射成型生产过程,注射成型过程,充填Filling保压Packing与冷却Cooling 开模Mold opening 顶出Part ejection 闭模Mold closing,2023/5/22,Page9,注射成型生产过程,压力-体积-温度(PVT),01充填Filling13保压Packing34冷却Cooling45开模Mold opening56顶出Part ejection,2023/5/22,Page10,注射成型生产过程,粘度与剪切速率,2023/5/22,Page11,高剪切速率导致低粘度,注射成型生产过程,成型各阶段,Filling，计量的充填模穴 Pressurization，建立模穴压力 Compensation，挤入额外的塑料以减少收缩,2023/5/22,Page12,注射成型生产过程,成型各阶段,充填阶段:充填阶段时塑料被射出机的螺杆挤入模穴中直到正好填满。当塑料进入模穴时，塑料接触模壁时会很快地凝固，这会在模壁和熔融塑料之间形成凝固层。加压阶段:虽然所有的流动路径在充填阶段都已经充填完成，但其边缘及角落都还有空隙存在。为了完全充填整个模穴，所以必须在这个阶段加大压力将额外的塑料挤入模穴。补偿阶段:塑料从熔融状态冷凝固到固体时，大约会有25%的高收缩率，因此必须将更多的塑料注入模穴以补偿因冷却而产生的收缩。,2023/5/22,Page13,注射成型生产过程,特殊注射成型方法简介,Co-injection(sandwich)molding,共注射（三明治）成型共注射成型包括相续或同时注射两种或多种不同塑料进入一个模穴内，塑料形成薄板而凝固。塑料可以是相同材质，只是颜色不同。若使用不同材质的塑料，塑料间必须能相容，也就是接合性良好、熔融温度相近等。共注射成型生产有叠片结构的产品，核心材料在皮层材料之间埋入。这种创新的成型方法提供使用每种塑料的最佳特性或更改成型产品性能的固有弹性。,2023/5/22,Page15,共注射成型的四个阶段：(a)射入模具的皮层熔融塑料短射(以暗绿色显示)；(b)核心熔融塑料射入；(c)直到模穴几乎填满；(d)再一次射入皮层塑料，清除核心塑料远离注道,特殊注射成型方法简介,Fusible core injection molding,熔芯注射成型熔芯注射成型方法可用右图的有复杂内部几何的中空产品举例说明，该方法在塑料产品内部形成一个核芯。在成型后，核芯将会自身熔化或者化学溶解，以它的外部几何作为塑料产品的内部形状。,2023/5/22,Page16,熔芯注射成型,特殊注射成型方法简介,Gas-assisted injection molding,气体辅助注射成型利用惰性气体N2将模穴部分充填塑料推满，且内部中空并全面均匀保压产品，产品冷却后再将压缩氮气排出回收。由于产品中空，可使成型时间缩短，节省材料。达到“省工省料”。由于产品厚度可全面打薄、局部加厚，可使产品“很轻很壮”。由于保压气体几乎无压力损失，压力小而平均，可使产品“平滑方正”。,2023/5/22,Page17,(1)部分塑料充填；(2)气体辅助充填；(3)气体辅助保压；(4)排放回收气体,特殊注射成型方法简介,Injection-compression molding,注射压缩成型压缩注射成型方法是传统的注射成型的延伸。将预先设定好体积的塑料熔体射入一个开放的模穴之后，随即闭合模具，塑料即被压缩，如右图所示。当塑料要被注射的时候，压缩也能发生。该方法的主要优点是产品尺寸稳定性好，基本无内应力，所需锁模力低（比常规注射成型方法低20%50%）。,2023/5/22,Page18,注射压缩成型,特殊注射成型方法简介,Lamellar(microlayer)injection molding,薄片（微层）注射成型该方法使用一个双注射料筒的喂料块和层增殖器来结合熔融流体。它用不同的微层来生产多树脂的产品，如右图所示。用分层结构结合不同的树脂提高许多性能，例如气体防护性能、尺寸稳定性能、热阻隔性能、光透明性能等。,2023/5/22,Page19,薄片（微层）注射成型,特殊注射成型方法简介,Live-feed injection molding,多动式喂料注射成型多动式喂料注射成型方法在多塑料入口处应用振动压力引起熔胶振动，如右图所示。当在模具内由于塑料凝固而使不同的分子层或纤维取向建立时，活塞的运动将留在浇口处的塑料熔化。该方法可被改进用于常规注射成型，主要用来消除缝合线、减少凹痕和大空隙的形成、控制大分子和纤维的取向。,2023/5/22,Page20,多动式喂料注射成型,特殊注射成型方法简介,Low-pressure injection molding,低压注射成型低压注射成型本质上是传统注射成型的最佳化延伸(如下图)。以适当的螺杆每分转速、背压和螺杆前进速率达成低压力来控制熔融温度和注射速率。它也可用大浇口或多个相续开闭的阀浇口来减少流动长度。以一个通常慢而受约束的注射速率除去保压阶段。低压注射成型的优点在于成型产品所需的锁模力和压力降低、应力降低、模具费用减少。,2023/5/22,Page21,低压注射成型,特殊注射成型方法简介,Push-pull injection molding,推拉注射成型推拉注射成型方法使用带有两个传统注射系统的注射机和一个带有两个浇口的模具，迫使塑料在主注射单元和辅助注射单元之间来回流动，如下图所示。该方法用来修复缝合线、空洞和裂缝、控制塑料分子和纤维取向。,2023/5/22,Page22,推拉注射成型,特殊注射成型方法简介,Reactive molding,反应成型反应成型系将两种低分子量、高反应性、低粘度液体（单体）以高压射入混合室中混合，再射入模穴中成型，并于模穴中产生聚合反应，也就是聚合与注射一起进行的成型方法。十字联编的聚合体结构通常得到改良的机械性能、较好的热和环境抗力。主要的反应成型方法包括reaction injection molding（RIM反应注射成型）和复合物成型，如resin transfer molding（RTM传递模塑法）和structural reaction injection molding（SRIM结构反应注射成型）。,2023/5/22,Page23,反应注射成型原理图1.原料槽(主要原料和硬化剂)；2.旋转叶片；3.计量加压泵；4.模具；5.加热器；6.锁模装置；7.喷嘴；8.混合器；9.清洗液；10.真空泵；11.马达；12.阀；13.空压机,特殊注射成型方法简介,Structural foam injection molding,结构发泡注射成型结构发泡注射成型生产由外部实体皮层包围内部发泡芯层所构成的产品，如右图。该方法适合于在最终使用中遭受弯曲载荷的大而厚的产品。发泡注射成型产品可用低压和高压生产，生产过程中使用氮气或化学发泡剂。,2023/5/22,Page24,典型的结构发泡塑料横截面,结构发泡注射成型过程,特殊注射成型方法简介,Thin-wall molding,薄壁成型术语“薄壁”是相对的。传统的塑料产品一般都是24mm厚。而当产品厚度在1.22mm范围时薄壁设计被称作“advanced”，产品厚度低于1.2mm时，薄壁设计则被称作“leading-edge”。薄壁成型的另外一种定义是以流动长度对壁厚之比为基础，典型的薄壁比率应用范围从100:1 到 150:1 或更多。薄壁成型在便携式通讯仪器和电脑设备中更为流行，要求塑料外壳更薄更轻，但仍然如传统产品一样提供相同的机械性能。,2023/5/22,Page25,特殊注射成型方法简介,GE Plastics,Plastic Injection MoldingTroubleshooting,e,Injection Molding Troubleshooting,Warpage,Burning,Gloss,Voids,Shorts,Shrinkage,Flash,Splay,Streaking,Overpacking,Fingerprinting,POLLING SLIDEWhat is the first step in the troubleshooting process?A.Change a parameter you think may be the causeB.Observe the process and settings attempting to get a better understanding of the problem.C.Make sure the hopper is full.D.Reboot the machine.,Correct answer is B,Injection Molding Troubleshooting,What is the first thing you do to your process when a problem occurs?,We Believe.It is POOR Processing or Tooling!,Customer Assume.IT MUST BEBAD MATERIAL!,Injection Molding Troubleshooting,Sinks,Caused by materialshrinkage and is more likely in heavy sections.Can also be due to flow obstructions or mold hotspots,Injection Molding Troubleshooting,Sinks,Ways to Minimize Sink Marks,Reduce Injection Speed Reduce Mold Temperature Increase Injection Pressure Profile Injection Speed Increase Injection Hold Time,Cool Melt TemperatureProvide Adequate VentingHave Proper Nozzle Orifice Enlarge Runner And Gate Gate Into Heavy Sections,Injection Molding Troubleshooting,Voids,Voids are Caused by shrinkingof molten material when outsidewalls have solidified.,Injection Molding Troubleshooting,Voids,Ways to Minimize Voids,Check the Part Design Check Feed Rate Increase Injection Hold Time Increase Injection Speed Increase Mold Temperature,Check Melt TemperatureIncrease Back PressureMaintain Sufficient VentingIncrease Runner/Gate DimensionsIncrease Injection Pressure,Injection Molding Troubleshooting,Short Shots,A Short Shot IsA Part That Is NotCompletely Filled,Injection Molding Troubleshooting,Short Shots,Ways to Minimize Short Shots,Check for Nozzle RestrictionIncrease Injection PressureIncrease Stock TemperatureIncrease VentingIncrease Mold TemperatureEnlarge Gate and Runner,Injection Molding Troubleshooting,Flash,Flash is the condition wherebymolten material flows beyond thenormal confines of the mold,Injection Molding Troubleshooting,Flash,Not Enough Clamp Injection Pressure Too High Obstruction in The Mold Injection Speed Too Fast Melt Temperature Too High Improper Feed Rate Damaged Mold,Injection Molding Troubleshooting,Overpacking a Part,Overpacking results from forcing too much material into the mold.The consequences of overpacking are heavier parts and molded-in stress.,Injection Molding Troubleshooting,Warpage,A Warpage is caused by Uneven Wall Thickness Unequal Cooling Rate Unequal Pressure Anisotropy(Uneven Shrinkage Cause Warp),POLLING SLIDEWhich of the following can affect warp in a part?A.Mold temperatureB.Type of material.C.Gate locationD.Uneven wall sections(thick,thin).E.All the above,Correct answer is E,Injection Molding Troubleshooting,Warpage,Ways to Minimize Warpage,Change Mold TemperatureIncrease or Reduce Injection PressureIncrease Holding or Cooling TimeReview Part DesignChange Gate LocationIncrease Gate and Runner Dimension,Injection Molding Troubleshooting,Burn Mark,Gas Burn is caused by thecompression of trapped air and gasses at elevatedtemperatures and pressures,Injection Molding Troubleshooting,Gas Burn,Improper clamp tonnage Lack of adequate venting Injection speed too fast Injection pressure too high Melt temperature too high,Injection Molding Troubleshooting,Poor Ejection,Caused By:Roughness or undercuts Overpacking Inadequate knockout pins Poor cooling,Injection Molding Troubleshooting,Gate Blush,Blush is the Result ofMelt Fracture Material temperature too low Injection speed too slow or too fast Improper gate design Mold too cold Material viscosity too high,Injection Molding Troubleshooting,Jetting,Stock Too ColdMold too coldInjection Speed Too FastGates Too SmallWrong Gate Location:(Directly into Wall or Pin),Injection Molding Troubleshooting,Fingerprints,Cavity Pressure Too Low,Injection Molding Troubleshooting,Weld Lines,Weld lines Occur When Two or More Melt Fronts Merge.Typically,These Will Be MeltFronts from Different Gates,or a Single Melt Front Forcedto Split Around an ObstructionSuch as a Core pin.,Injection Molding Troubleshooting,Splay(Silver Streaking),Splay or silver streaks are caused by volatiles within the melt.These can be due to moisture,degraded material,contamination or excessive decompression.,Injection Molding Troubleshooting,Splay(Silver Streaking),Stock Temperature Too High Shear Burning at Gate Trapped Volatiles-Vent Mold Excessive Moisture Contaminated Material Degraded Material,Injection Molding Troubleshooting,Color Deviation,Injection Molding Troubleshooting,Color Deviation,Stock Temperature Too High Shear at Gate or Runner Lack of Packing Mold Temperature Too Low Not Sufficient Drying,Injection Molding Troubleshooting,Dark Spots due to Thermal Damage,Black Specks,Injection Molding Troubleshooting,Pick Up of Degraded Material at Barrel Wall Stock Temperature Too High Barrel Too Large for the Part Not Sufficient Drying Material Contamination Machine Downtime Too Long Damaged Barrel and Screw,Black Specks,Injection Molding Troubleshooting,Cold Material,A Flow Mark,Dull or Milky Spot Near the Gate due to Cold Material,Injection Molding Troubleshooting,Cold Material,Drooling at Nozzle Nozzle Too Cold Nozzle Temperature Control Problem Nozzle Opening Too Small Screw Pull Back Too Small Back Pressure Too High,Injection Molding Troubleshooting,Delamination分层,The separation of a moldedpart into layers.This can becaused by contamination orby improper processing ofblends or alloys.,Injection Molding Troubleshooting,High Shear at Gate,Runner&Nozzle Injection Speed Too High Mold Temperature Too Low Material Contamination,Delamination,十大成型加工技巧,保压时间太短不良表面的修复错误的浇口位置；浇口的位置 错误的模具温度 错误的熔融温度模具供料系统过小 翘曲塑料颗粒料中的水分 与热流道有关的问题制品的模垢,成型参数变化重点之一：保压,保压分析,什么是合理的收缩相关术语收缩最佳化最佳化的步骤精确调整,什么是合理的收缩水准?可以在帮助中找到材料典型的收缩水准如果使用的材料没有收缩数据对照材料种类、填充物种类、粘度和热数据仅搜索收缩等级,保压分析,Conventional packing有一到两段恒压用两段时与profiled packing相似当机器没有能力进行profiled packing时使用如果产品肉厚变化比较大时使用该保压方法可能是比较好的Profiled packing 压力随时间而变化,Conventional和Profiled Packing,Profiled Packing可达成的效果,使产品的体积收缩(volumetric shrinkage)分布更均匀当塑料冷却凝固时体积收缩由作用于塑料上的压力决定压力越大收缩越小在产品上总是存在压力梯度的随时间降低压力一直降到浇口处为零,何时采用保压曲线当机器有能力时当产品肉厚变化不大时当翘曲很重要时,Profiled Packing,Constant,Decay,Packing Time,CoolingTime,Actual Injection Time,Time,Pres.,Moldflow的定义,Packing,Holding,Cooling,Actual Injection Time,Time,Pres.,Machine的定义,保压术语,最佳化产品充填流道平衡冷却 确定初始保压压力以机器最大锁模力的80%作为保压压力最大值(公式单位为公制),制作保压曲线,以恒定保压压力运行保压分析初始的保压时间取希望得到的保压时间与冷却时间的总和此分析确保浇口已经完全凝固如果冷却分析已经运行过，在此分析中使用相同的保压时间与冷却时间的总和,制作保压曲线,查看结果来绘制曲线初始体积收缩分布从收缩综合报表中取得资料与典型收缩数值做比较确定恒定压力、恒定保压时间、压力衰减时间和冷却时间采用以下项目随时间变化的轨迹 温度(temperature)凝固层比率(%frozen layer)注入点的压力(pressure of injection location node)、浇口或产品上的nodes和elements的压力,制作保压曲线,采用衰减的保压压力运行多层保压分析(Multi-laminate packing)检查体积收缩分布对整个产品或产品中的某一部分缩放volumetric shrinkage必要时修改profile使用注入点、浇口或产品上的nodes的压力轨迹调整profile,制作保压曲线,制作保压曲线,Decay起始点由EOF达到 No Flow Temp.的时间决定(Transition Temp.+20deg.C),Decay结束点由浇口凝固时间决定。最好查看凝固层比率或温度随时间的变化轨迹。,确定最佳的曲线,寻找在EOF处的时间,Node 2EOF,6.6 sec.,寻找浇口凝固的时间,对beam gates，检查浇口处的%Frozen Time series和XY graph对shell element gates，检查时间的XY graph和contour,时间为 11.15 sec.约等于11.2 sec.,计算和填写Profile,Pressure Time MPa Sec40.00.040.04.2(CPT)0.04.6(DT)0.07.2(CT)Note:Actual Injection time 2.4 SecCPT=6.6 2.4=4.2DT=11.2 6.6=4.6CT=16-(4.2+4.6)=7.2(Tot.hold time仍然是16 sec),前后结果对比,对最后充填区域的调整调整constant-pressure持续时间 缩短，volumetric shrinkage升高 延长，volumetric shrinkage降低,对浇口区域的调整改变压力衰减率 变慢，volumetric shrinkage降低 变快，volumetric shrinkage升高,对中间充填区域的调整斜坡“Step”衰减率 增加，volumetric shrinkage降低 减少，volumetric shrinkage升高,精确调整Packing Profile,Exercise,Snap Cover，两个模穴材料：Bayer USA Lustran LGA-SF(ABS)给定充填分析结果由使用者确定packing pressure和time以constant pressure设定和运行第一个packing analysis查看结果，制作profile运行profiled packing查看结果检查 ShrinkageTime Series of Pressure修改profile以得到更好的结果 以time series of pressure作指导,