电热水壶手柄注塑模具设计【说明书+CAD+SOLIDWORKS】
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编号： 任务书题 目： 电热水壶手柄注塑模的设计 学院： 专 业： 学生姓名： 学 号： 指导教师单位： 姓 名： 职 称： 题目类型：理论研究 实验研究 工程设计 工程技术研究 软件开发 2013年12月13日一、设计（的内容本设计要求学生以工程实际零件电热水壶手柄注射模的设计作为设计对象，需要学生充分运用所学知识进行模具结构的设计。1、查阅资料，进行企业调研，了解现有注射模具设计的结构与工作原理，做好设计前的准备工作。2、根据给定的零件的结构特点以及尺寸参数，提出模具的设计方案（两种以上），进行比较后选出最佳方案进行设计；3、运用Pro/E、SolidWorks等CAD工具进行辅助设计，完成模具整体结构的设计；4、对模具工作部分尺寸及公差进行设计计算；5、对模具典型零件需进行选材及工艺路线分析；6、绘制模具零件图及装配图；7、编写设计说明书。二、设计的要求与数据1、在现实生活中的电热水壶手柄，自行选择一款作为设计对象，根据其结构特点、材料及尺寸完成其注射模具的设计工作；2、设计相应的模具及其主要的零部件，制定出主要零部件的工艺规程，并编制主要零部件的制造工艺；3、采用CAD设计软件（如：Pro/E、SolidWorks、AutoCAD等）对模具进行实体建模、绘制模具的装配图与零件图。4、编写设计说明书。三、设计应完成的工作1、完成二万字左右的毕业设计说明书（论文）；在毕业设计说明书（论文）中必须包括详细的300-500个单词的英文摘要；编制主要零件的加工工艺卡，进行必要的理论计算，给出计算结果；2、独立完成与课题相关，不少于四万字符的指定英文资料翻译（附英文原文）；3、绘制出所设计模具的装配图和零件图，折算A0图纸3张以上其中必须包含两张A3以上的计算机绘图图纸。四、应收集的资料及主要参考文献1. 模具设计与制造技术教育丛书编委会.模具结构设计.北京:机械工业出版社,2004.2. 杨占尧，白柳.塑料模具典型结构设计实例. 北京:化学工业出版社,2009.3. 宋满仓等注塑模具设计与制造实战M北京：机械工业出版社，2003.4. 刘航. 模具技术经济分析M. 北京：机械工业出版社，2002.5. 傅建等.模具制造工艺学M. 北京：机械工业出版社，2004.6. 冯爱新.塑料模具工程师手册.北京:机械工业出版社,2009.7. 张国强.注塑模设计与生产应用M . 北京：化学工业出版社，2005. 8. 刘文, 王国辉, 谭建波SolidWorks模具设计入门、技巧与实例M北京：化学工业出版社，2010.9. Chen,Y.-M. Computer-aided integrated design for injection moldingIntelligent Processing and Manufacturing of Materials, 1999.10. Yan, L. An Intelligent Knowledge-based Plastic Injection Mold Design SystemJ Annual Technical Conference - ANTEC, Conference Proceedings, v 3, 2003, p 3514-3518.五、试验、测试、试制加工所需主要仪器设备及条件计算机一台CAD设计软件（AutoCAD，CAXA，UG，Pro/E，Solidworks）等任务下达时间：2013年12月17日毕业设计开始与完成时间：2013年12月17日至 2014年05 月26日组织实施单位：教研室主任意见：签字： 2013年12月14日院领导小组意见：签字： 2013 年12月16日学校代码：XXXX 序 号：XXXXXXX 设 计 题目： 电热水壶手柄注塑模模具设计 学 院： XXX 姓 名： XXX 学 号： XXX 专 业： XX 年 级： XXX 指导教师： XXX XXXX年 X月II摘要 本设计为电热水壶手柄注塑模模具设计，电热水壶手柄采用ABS材料，用注塑机注塑成型。在模具设计中采用嵌入式凹模,组合式凸模，侧浇注口，塑件的外表面为模具分型面，注塑经过充模、压实、保压、倒流和冷却五个阶段。注塑完成后动,定模座分开,动模后移到指定位置，推杆推出塑件，复位杆复位好既完成一次注塑。在设计过程中采用CAD/CAM,UG,等设计软件。关键词: CAD/CAM, 塑料，注射模，注射机。Abstract: The design of injection mold die design for the card case, card case with polypropylene (ABS) materials, used injection molding machine injection molding. Embedded in the mold die design, combined punch, direct casting port, outer surface of plastic parts for the mold parting line, injection molding after filling, compaction, packing, and cooling back five stages. Injection completed action, scheduled to die seat separately, the dynamic model specified location after the move, putting plastic pieces launched, the reset lever reset the completion of an injection well only. Used in the design process CAD / CAM, PRO / E, and other design software. Key Words: CAD/CAM, Plastic, Plastic injection mold, Plastic injection目 录1 绪论11.1 塑料注射模具简介11.2 我国塑料注射模具现状12.3.1注射成型过程42.3.2注塑工艺参数43 拟定模具的结构形式53.1 分型面位置的确定53.2 型腔数量和排列方式的确定53.3 注射机型号的确定53.3.1 注射量的计算53.3.2 浇注系统凝料体积的初步估算53.3.3 选择注塑机53.3.4 注塑机的相关参数的校核64 浇注系统的设计74.1 主流道的设计74.1.1 主流道尺寸74.1.2 主流道的凝料体积74.1.3 主流道当量半径74.1.4 主流道浇口套的形式84.2 浇口的设计84.3 校核主流道的剪切速率84.3.1 计算主流道的体积流量84.3.2 计算主流道的剪切速率84.4 冷料穴的设计85 成型零件的结构设计及计算95.1 成型零件的结构设计95.2 成型零件钢材的选用105.3 成型零件工作尺寸的计算105.3.1 凹模宽度尺寸的计算105.3.2 凹模长度尺寸的计算105.3.3 凹模高度尺寸的计算105.3.4 凸模宽度尺寸的计算115.3.5 凸模长度的计算115.3.6凸模高度尺寸的计算115.4 成型零件尺寸及动模板厚度的计算115.4.1 凹模侧壁厚度的计算115.4.2 凹模底板厚度的计算115.4.3 动模厚度的计算126.1 各模板尺寸的确定136.2 模架各尺寸的校核146.3 导向与定位结构的设计147 脱模推出机构的设计157.1 脱模机构设计原则157.3 脱模力的计算157.4 推杆的直径计算及强度校核167.4.1 推杆的直径计算167.4.2 强度校核167.5 推出机构的复位168.1 冷却系统的设计原则188.2 冷却系统的简单计算19所以取4根冷却水管20结论21参考文献221 绪论1.1 塑料注射模具简介中国是制造业大国，产品是制造的主体，模具又是制造业的灵魂，模具的发展水平决定了制造的发展水平，模具又是塑料成型加工的一种重要的工艺装备，同时又是原料和设备的“效益放大器”，模具生产的最终产品的价值，往往是模具自身价值的几十倍、上百倍。因此，模具工业已成为国民经济的基础工业，被称为“工业之母”，模具生产技术的高低，已成为衡量一个国家产品制造技术的重要标志。如今塑料制品已在工业、农业、国防和日常生活等方面获得广泛应用。注塑成型是生产塑料制件最常用的制造方法之一，采用这种方法既可以生产小巧的电子器件和医疗用品，也可以生产大型的汽车配件和建筑构件，生产的制件具有精度高、复杂度高、一致性高、生产效率高和消耗低的特点，有很大的市场需求和良好的发展前景。随着塑料材料技术和注塑成型加工技术的不断进步，塑料注塑加工行业得以持续发展。塑料加工是将原材料变为制品的关键环节，只有迅速的发展塑料加工业，才可能把各种性能优良的高分子材料变成功能各异的制品，在国民经济的各领域发挥作用。模具是塑料成型加工的一种重要的工艺装备，同时又是原料和设备的“效益放大器”，模具生产的最终产品的价值，往往是模具自身价值的几十倍、上百倍。因此，模具工业已成为国民经济的基础工业，被称为“工业之母”，模具生产技术的高低，已成为衡量一个国家产品制造技术的重要标志。1.2 我国塑料注射模具现状我国塑料注射模具的发展迅速。塑料注射模具的设计、制造技术、CAD 技术、CAABS 技术，已有相当规模的确开发和应用。在设计技术和制造技术上与发达国家和地区差距较大，在模具材料方面，专用塑料模具钢品种少、规格不全质量尚不稳定。模具标准化程度不高，系列化商品化尚待规模化；CAD、CAE软件等应用比例不高；独立的模具工厂少；专业与柔性化相结合尚无规划；企业大而全居多，多属劳动密集型企业。因此努力提高模具设计与制造水平，提高国际竞争能力，是刻不容缓的。塑料注射成型是生产塑料制品的重要手段之一。在CAD技术引入注塑模设计领域后，模具设计发生了根本性的变革，同时也带来了巨大的经济效益。据国外统计，注射模采用CAD技术的比例约占所有不同模具CAD技术的75%，在我国，注塑模CAD技术也在不断地应用和推广中。 1.3 电热水壶手柄材料的选用 电热水壶手柄如图1-3，电热水壶手柄既要小巧，精致，美光又要得体。因此塑料就具有这样的性能，而塑料中的聚丙稀具有流动性好，质量轻，韧性好，耐化学性好，耐磨性好等特点。特别是聚丙烯的成行性能好，易制造出精致的电热水壶手柄。所以本设计采用ABS进行注塑。ABS塑胶原料是由癸二酸经缩聚制得的。将癸二酸和癸二胺以等摩尔比溶于乙醇中，在常压75下进行中和反应，生成尼龙1010盐。尼龙1010盐的反釜中，在240-260、1.2-2.5Mpa下缩聚制得尼龙1010。缩聚可分间歇法和连续法。亦可用精制的癸二胺与癸二酸的等摩尔比的水溶液直接缩聚而制得聚合物，然后经挤带、冷却、造粒而制得尼龙1010粒料。图1-12 塑件成型的工艺性分析2.1 塑件的分析（1）外形尺寸45.47X153.90X100.05该模具壁厚1-3mm，塑件的尺寸不大，塑料的熔体流程不太长，适合于注射成型。（2）脱模斜度 ABS属于无定型塑料，成型收缩率较大，参考模具成型与技术选择该塑件上型芯和凹模斜度为。2.2 ABS的性能分析（1）ABS塑料的使用性能 综合性能好，冲击强度、力学强度较高，尺寸稳定，耐化学性，电气性能良好，易于成型和机械加工，其表面可镀铬，适合制作一般的机械零件、减摩零件、传动零件和结构零件。聚癸二酰癸二胺又名ABS，俗称尼龙1010，简称ABS，工程塑料的一种。工程塑料ABS是我国独创的工程塑料聚酰胺品种，由上海赛璐珞厂在1958年研制成功。由于工程塑料ABS具有工艺简单、设备无特殊要求、技术容易掌握、产品质量稳定以及综合性能优良等特点，因而发展迅速。工程塑料ABS是一种半透明白色或微黄色坚韧固体，具有工程塑料聚酰胺的一般共性，对霉菌的作用非常稳定，对光作用很稳定。工程塑料ABS是我国独创的一种工程塑料，用蓖麻油做原料，提取癸二胺及癸二酸再缩合而成的。成本低、经济效果好、自润滑性和耐磨性极好、耐油性好，脆性转化温度低（约在-60），机械强度较高，广泛用于机械零件和化工、电气零件。工程塑料ABS具有优越的延展性，同时具有优良的常温和低温冲击性能。工程塑料ABS在高于100下，长期与氧接触逐渐变黄，机械强度下降，特别是在熔融状态下极易热氧化降解。（2）成型性能1）无定型塑料。其品种很多，各品种的机电性能及成型特性也各有差异，应按品种来确定成型方法及成型条件。2）吸湿性极弱。含水量小于0.3%（质量），所以无需进行干燥。3）流动性好。溢边料0.03mm左右。4）模具设计时要注意浇注系统，选择好进料口位置、形式。机械加工时塑件表面呈现白色痕迹。（3）ABS的主要性能指标见下表2-1 表2-1 ABS的性能指标密度:1.03 到 1.05g/cm粘数:- 290.0 到 120cm/g- 3120 到 1502.3 ABS的注射成型过程及工艺参数2.3.1注射成型过程1） 成型前的准备。对ABS的色泽、粒度和均匀度等进行检测，由于ABS吸水性极小，成型前无需进行干燥。2） 注射过程。塑件在注射机料筒内经过加热、塑化达到流动状态后，由模具的浇注系统进入模具型腔成型，其过程可分为充模、压实、保压、倒流和冷却五个阶段。3） 塑件的后处理。处理的介质为空气和水，处理温度为6070，处理时间为1620s。2.3.2注塑工艺参数料筒温度: 后部190210中部200220前部210230喷嘴200210模具温度2040注射压力6080MPa注射周期3050S，(3)挤出成型工艺螺杆挤出温度：250，260，270，280模头温度:2002103 拟定模具的结构形式3.1 分型面位置的确定通过对塑件的结构形式的分析，分型面应选在端盖截面积最大且利于开模取出塑件的底平面上。3.2 型腔数量和排列方式的确定型腔数量的确定 该塑件为小批量，专业化生产，可采取一模四腔的结构形式。3.3 注射机型号的确定3.3.1 注射量的计算通过三维软件建模设计分析计算得注塑体积：V塑= 29cm3塑件质量：m塑=V塑 =291.05=30.45g，公式中密度参考模具成型与技术可取。3.3.2 浇注系统凝料体积的初步估算浇注系统的凝料在设计之前是不是能准确的数值，但是可以根据经验按塑件体积的0.51倍来估算。由于采用的流道简单并且较短，因此浇注系统的凝料按塑件体积的0.5倍来计算，本次设计采用PROE全3D设计，可以实际测量流道体积,故一次注入模具型腔塑料熔体的总体积为V总=V塑+ V流=2x29+5=63cm33.3.3 选择注塑机根据第二步计算出来的一次注入模具型腔的塑料总质量V总 = 63cm3，并结合模具成型与技术公式V公=V总/0.8得V公=63 cm3.。根据以上的计算，初步选定公称注射量为104 cm3 ，注射机型号为SZ-104/100卧式注射机如图3-3，其主要技术参数见下表3-1表3-1注射机主要技术参数理论注射容量/ cm3104移模行程/mm300螺杆柱塞直径/mm30最大模具厚度/mm350V注射压力/Mpa150最小模具厚度/mm200注射速率/gs-154锁模形式双曲肘塑化能力/gs-142模具定位孔直径/mm100螺杆转速/rmin-110喷嘴球半径/mm12锁模力/kN900喷嘴口孔径/mm4拉杆内间距/mm345X3453.3.4 注塑机的相关参数的校核1）注射压力校核。ABS所需要的注射压力为70100Mpa，这里取P0=80Mpa，该注塑机的公称注射压力P公=150Mpa，注射压力安全系数k1=1.11.3，这里取1.2，则：k1 P0 =1.280=96P公，所以，注塑机注射压力合格。2）锁模力校核塑件在分型面上的投影面积A塑，则 A塑=1492mm2（忽略倒角投影面积）浇注系统在分型面上的投影面积A浇，即流道凝料（包括浇口）在分型面上的投影面积A浇数值，可以按照单型腔模的统计分析来确定。A浇是塑件在分型面上的投影面积A浇的0.10.3倍。这里取A浇=0.2 A塑 。塑件和浇注系统在分型面上的总的投影面积A总，此处由于采用侧浇口，则需要测量流道投影面积模具型腔内的膨胀力F胀 P模为型腔的平均计算压力值。P模是模具型腔内的压力，通常取注射压力的20%40%，大致范围为3060Mpa。对于粘度较大的精度较高的塑料制品应取较大值。ABS属于中等粘度塑料及有精度要求的塑件，故P模取50Mpa F胀=A总P模锁模力F锁=900kN，锁模力的安全系数为k2 =1.11.2这里取1.2，则k2F胀=1.2 F胀=1.21492x30x0.001=53.7F锁=900，所以该注射机锁模力合格。对于其他安装尺寸的校核要等到模架选定，结构尺寸确定后方可进行。4 浇注系统的设计4.1 主流道的设计图4-1主流道设计如图4-1通常位于模具中心塑料熔体的入口处，它将注射机喷嘴注射出的熔体导入分流道或型腔中。主流道的形状为圆锥形，以便熔体的流动和开模时主流道凝体的顺利拔出。主流道的尺寸直接影响到熔体的流动速度和充模时间。另外，由于其与高温塑料熔体及注射机喷嘴反复接触，因此设计中常设计成可拆卸更换的浇口套。4.1.1 主流道尺寸1） 主流道的长度：小型模具L主应尽量小于150mm，本次设计中初取125mm进行设计。2） 主流道小端直径：d=注射机喷嘴尺寸+（0.51）mm=4mm3） 主流道大端直径：d=d+2L主tan(/2)6.9mm，式中=24） 主流道球面半径：SR。=注射机喷嘴球头半径+（12)mm=(12+2）mm= 14 mm5） 球面的配合高度：h=3mm4.1.2 主流道的凝料体积V主=/3L主（R+r+R主r主）=5300mm 4.1.3 主流道当量半径 Rn=（d+d)/4mm= 4mm4.1.4 主流道浇口套的形式 主流道衬套为标准件可选购。主流道小端入口处与注射机喷嘴反复接触，易磨损。对材料要求严格，因而尽管小型注射模可以将主流道浇口套与定位圈设计成一个整体，但考虑上述因素通常仍然将其分开来设计，以便于拆卸更换。同时也便于选用优质钢材进行单独加工和热处理。设计中常采用碳素工具钢（T8A或T10A），热处理淬火表面硬度为5357HRC。4.2 浇口的设计该塑件要求不允许有裂纹和变形缺陷，表面质量要求较高，采用一模四腔注射。4.3 校核主流道的剪切速率上面分别求出了塑件的体积，主流道的体积，分流道的体积（浇口的体积太小可以忽略不计）以及主流道的当量半径，这样可以校核主流道熔体的剪切速率。4.3.1 计算主流道的体积流量Q主=（V主+nV塑）/t=1.625cm/s4.3.2 计算主流道的剪切速率主=3.3q主/R主= 0.9103s-1主流道的剪切速率校核合格。4.4 冷料穴的设计冷料穴位于主流道正对面的动模板上，其作用主要是收集熔体前锋的冷料，防止冷料进入模具型腔而影响制品的表面质量，本设计仅有主流道冷料穴。由于该塑件表面要求没有印痕，采用脱模板推出塑件，故采用与球头形拉料杆匹配的冷料穴。开模时，利用凝料对球头的包紧力使凝料从主流道衬套中脱出。5 成型零件的结构设计及计算5.1 成型零件的结构设计 图5-1 图5-2（1）凹模的结构设计凹模是成型制品的外表面的成型零件。根据对塑件的结构分析，本设计采用整体嵌入式凹模如图5-1。（2）凸模的结构设计凸模是成型塑件内表面的成型零件，通常可以分为整体式和组合式两种类型。通过对塑件的结构分析，选用组合式凸模如图5-2。5.2 成型零件钢材的选用根据对成型塑件的综合分析，该塑件的成型塑件要有足够的刚度、强度、耐磨性以及良好的抗疲劳性能，同时考虑它的机械加工性能和抛光性能。又因为该塑件是小批量生产，所以构成型腔的嵌入式凹模钢材选用45号钢。5.3 成型零件工作尺寸的计算此塑件未注上下偏差，所以以下公差都是查表所得。5.3.1 凹模宽度尺寸的计算塑件尺寸的转换：相应的塑件制造公差，LM1=(1SCP)+LS1+X1P100.22=(10.015)+153.9+0.60.700.22=153.900.22mm式中，是塑件的平均收缩率，聚丙烯的收缩率为1%2%,所以平均收缩率；、是系数， 一般在0.50.8之间，此处取；分别是塑件上相应尺寸的公差（下同）；是塑件上相应尺寸制造公差对于中小型零件取（下同）。5.3.2 凹模长度尺寸的计算塑件尺寸的转换：LS1=153.90.6=153.9-1.20MM，相应的塑件制造公差3=1.2MMLS2=153.90.45=153.9-O.90MM，相应的塑件制造公差4=0.9MM.LM1=(1+SCP)+LS1+X3P100.2=(1+0.015)+92.6+=100.16000.2MM式中，是系数，一般在0.50.8之间，此处取。5.3.3 凹模高度尺寸的计算塑件尺寸的转换：HS1=100.160.2=34-0.40MM，相应的塑件制造公差0.4mm2=0,6+0.05=0.65-0.10MM,应的塑件制造公差0.1mmHM1=(1+SCP)+HS1+X1P1=(1+0.015)+100.16+0.70.400.067=12000.067MM式中，是系数，一般在0.50.7之间，此处取。5.3.4 凸模宽度尺寸的计算塑件尺寸的转换：LS=153.90.35=1200.7MM，相应的塑件制造公差0.7mmLM=(1+SCP)+LS+XP= (1+0.015)+55.65+100.160 =1000.1100.160 MM式中，是系数，一般在0.50.7之间，此处取。5.3.5 凸模长度的计算塑件尺寸的转换LS=1400.51=89.4901.02MM：，相应的塑件制造公差1.02mmLM=(1+SCP)+LS+XP= (1+0.015)+89.49+0.651.02-0.100.160 =100.160-0.100.160 MM式中，是系数，知一般在0.50.7之间，此处取。5.3.6凸模高度尺寸的计算塑件尺寸的转换HS=120.2=18.90O.4MM，相应的塑件制造公差o.4mmHM=(1+SCP)+H S+XP= (1+0.015)+30+0.60.4-0.100.160 =300.0670 MM式中，是系数，可知一般在0.50.7之间，此处取。5.4 成型零件尺寸及动模板厚度的计算5.4.1 凹模侧壁厚度的计算 凹模侧壁厚度与型腔内压强及凹模的深度有关，根据型腔布置，模架初选230x300的标准模架，其厚度计算如下：T=30mm式中：a=29.49mm（型腔内高度） E=2.1105MPa p=35MPa c查表所得5.4.2 凹模底板厚度的计算TH=39.06mm式中：b=27.74mm（型腔内宽度） E=2.1105MPa p=35MPa 查表所得5.4.3 动模厚度的计算动模板厚度和所选模架的两个垫块之间的跨度有关，根据前面的型腔布置，模架应选在250mmx270mm这个范围之内，垫块之间的跨度大约为154mm。那么，根据型腔布置及凸模对动模板的压力就可以计算得到动模板的厚度，即T=0.54L()=77.4mm为了垫板不因弯曲应力过大而变形 ，所以动模板80mm。式中，是动模板刚度计算的需用变形量，；L是两垫块之间的距离，约为154mm；L1为动模板的长度，取270mm，A是型芯投影到动模板上的面积A=1968.6 模架的确定与导向结构设计图6-1为CI典型的模架结构图。 图6-1根据本设计模具型腔布局的中心距和凹模嵌件的尺寸可以算出凹模嵌件所占的平面尺寸130mm170mm，又考虑凹模最小壁厚，导柱，导套的布局等，再同时参考中小型标准模架的选型经验公式可确定选用模架序号CI-2325-A120-B70-C80，模架结构为CI型。6.1 各模板尺寸的确定1)A板尺寸。A板是定模型腔板，塑件高度为100.16mm，凹模嵌件深度65.79mm，又考虑在模板上还要开设冷却水道，还需要留出足够的距离，故A板厚度取120mm。2)B板尺寸。B板是型芯固定板，按模架标准板厚度取70mm。3)C板（垫块）尺寸。垫块=推出行程+推板厚度+推杆固定板厚度+（510）mm=7883mm，初步选定C为80mm。经上述尺寸的计算，模架尺寸为230mm250mm，模架结构形式为CI型的标准模架。其形外尺寸：宽长高=250mm280mm320mm。6.2 模架各尺寸的校核 根据所选注射机来校核模具设计的尺寸。1） 模具平面尺寸为250mm320mm345mm345mm（拉杆距离），校核合格。2） 模具高度尺寸320mm，200mm320mm350mm（模具的最大和最小厚度），校核合格。3） 模具的开模行程S=H1+H2+（510）mm=34+88+（510）mm=132mm300mm（开模行程），校核合格。6.3 导向与定位结构的设计注射模的导向机构用于动、定模之间的开合模导向和脱模机构的运动导向。按作用分为模外定位和模内定位。模外定位是通过定位圈使模具的浇口套能与注射机喷嘴精度定位;而模内定位机构则通过导柱导套进行合模定位。锥面定位则用于动、定模之间的精度定位。本模具所形成型的塑件比较简单，模具定位精度要求不是很高，因此可采用模具本身多带的定位机构。7 脱模推出机构的设计7.1 脱模机构设计原则（1）保证塑件不变形损坏，正确分析塑件对凹模或型芯的附着力的大小及其所在部位，有针对性的选择合适的脱模方法和脱模位置，使推出重心与脱模阻力中心相重合。型芯由于塑件收缩时对其包紧力最大，因此推出的作用点应尽量靠近型芯，同时推出力应该作用于塑件刚度和强度最大的部位，作用面也应该尽可能大一些。（2）力求保证良好的塑件外观，顶出位置应尽量设在塑件内部或对塑件外观影响不大的部位，在采用推杆脱模时尤其要注意这个问题。7.2 推出方式的确定本塑件采用推杆脱模机构。推杆脱模机构是最简单、最常用的一种形式，具有制造简单、更换方便、推出效果好等特点。推杆直接与塑件接触，开模后将塑件推出。塑件中心用4根推杆。推杆端面应和塑件成型表面在同一平面或比塑件成型表面高出0.050.10。7.3 脱模力的计算因为矩形塑件内壁长宽尺寸与壁厚之比10mm，所以此塑件为薄壁矩形塑件。F=0.1A=0.1388=10393.4mm式中 E-塑料的弹性模量（1300MPa）；L -型芯或凸模被包紧部分的长度（119）；-脱模斜度（）；S -塑料成型的平均收缩率（1.5%）；f-摩擦系数，一般取0.5；t-塑件的壁厚(1.5)；-由与f决定的无因次数，；-塑料的泊松比（0.32）；A-塑件在与开模方向垂直的平面上的投影面积（388）。7.4 推杆的直径计算及强度校核7.4.1 推杆的直径计算D1=K()1/4=1/4=6.394mm取D1=7.4mm；式中-推杆长度（133.5）；-推杆数量，取4；E-推杆材料的弹性模量（）；k是安全系数，取k=1.5。7.4.2 强度校核所以合格。式中，是推杆材料的许用压应力（），查塑料模设计手册。7.5 推出机构的复位脱模机构完成塑件的顶出后，为进行下一个循环必须回复到初始位置，目前常用的复位形式主要有复位杆复位和弹簧复位。本设计采用复位杆复位。7.6 推杆与模体的配合推杆和模体的配合性质一般为H8/f7或H7/f7，配合间隙值以熔料不溢料为标准。配合长度一般为直径的1.52倍，至少大于15mm，推杆与推杆固定板的孔之间留有足够的间隙，推杆相对于固定板是浮动的。8 冷却系统的设计8.1 冷却系统的设计原则（1）动、定模要分别冷却，保持冷却平衡。（2）孔径与位置，一般塑件的壁厚越厚，水管孔径越大。（3）冷却水孔的数量越多，模具内温度梯度越小，塑件冷却越均匀。（4）冷却通道可以穿过模板与镶件的交界面，但是不能穿过镶件与镶件的交界面，以免漏水。（5）尽可能使冷却水孔至型腔表面的距离相等，当塑件壁厚均匀时，冷却水孔与型腔表面的距离应处处相等。当塑件壁厚不均匀时，壁厚处应强化冷却、水孔应靠近型腔，距离要小。（6）浇口处加强冷却。（7）应降低进水与出水的温差。（8）标记出冷却通道的水流方向。（9）合理确定冷却水管接头的位置。（10）冷却系统的水道尽量避免与模具上其他机构发生干涉现象，设计时要通盘考虑。8.2 冷却系统的简单计算（1）单位时间内注入模具中的塑料熔体总质量W1）塑料制品的体积 V2）塑料制品的质量 M3）由于塑件80%部分的壁厚为1 mm，20%部分的壁厚为1.6mm，可查表，取综合冷却时间t冷=15s，取注塑时间t注=1.6s，脱模时间t脱=8s，则注塑周期：t= t冷+ t注+ t脱=15+1.6+8=24.6s。由此得每小时注射次数：N=(3600/24.6)次=146次 4）单位时间内注入模具中的塑料熔体的总质量：（2）确定单位质量的塑件在凝固时所放出的热量Q5 查表4-35直接可知聚乙烯的单位热流量Q5的值的范围在（590-690）KJ/kg 之间。故可取=590KJ/kg。（3）计算冷却水的体积流量qv 设冷却水道入口的水温为,出水口的水温为，取水的密度，水的比热容为C=4.187/(kg),则根据公式可得：Q=3.8410-5（4）确定冷却水路的直径d 当Q=3.8410-3m3/min时，为了使冷却水处于湍流状态，取模具冷却水管的直径 d=6mm。（5）冷却水在管内的流速 V=1.715m/s（6）求冷却管壁与水交界面的膜传热系数 h 因为平均水温为3.5，查手册可得，则有=2.85KJ/m（7）计算冷却水通道的导热总面积 A A=0.0038（8）计算模具所需冷却水管的总长度 L L=0.202M=202mm（9）冷却水路的根数X设每条水路的长度为=125mm.则冷却水路的根数为 X=4所以取4根冷却水管结论通过这次的塑料模具设计，使我对于塑料模具有了更加深入的了解，对模具的设计过程有了清晰的认识。塑料模具的设计过程就是一次在总结前人经验的基础上不断创新的过程。在具体操作设计的时候，我发现有很多需要的理论、数据、参数等都是在课本上找不到的，很多情况下都只能凭借设计者自己的经验进行，由此可见实践对于我们设计人员的重要性。并且通过具体的操作，不仅让我学到了许多新知识，还让我重新拾起了许多已经淡忘的知识，如CAD、机械制图、公差等。总之，这次课程设计让我获益良多。首先，感谢院领导和XXXX老师对我们毕业生的高度关注和支持，以及对毕业答辩的精心安排。最后，感谢杨老师在毕业设计过程给我的鼓励和帮助。参考文献l 1 叶久新，王群、M 北京：机械工业出版社,2008l 2李建军，李德群., 2005l 3 邓明M 北京：机械工业出版社，2006l 4 何忠保，陈晓华，王秀英M 北京：机械工业出版社，2000l 5 许发樾M 北京：机械工业出版社，2003 l 6 塑料模设计手册编写组.塑料模设计手册M.北京:机械工业出版社,2002l 7谭建荣、张树有、陈国栋、施岳定主编，图学基础教程，高等教育出版社，1999l 8邵立新、夏素民、孙江宏等主编，UGNGINEER Wildfire 3.0中文版标准教程，清华大学出版社，2007；附图：模具2D3D装配图22编号： 毕业设计外文翻译 （原文）题 目： Injection Molding Guide 学院： 机电工程学院 专 业： 机械设计制造及其自动化 学生姓名： 梁松强 学 号： 1000110123 指导教师单位： 桂林电子科技大学 姓 名： 彭晓楠 职 称： 副教授 2014年5月26日桂林电子科技大学毕业设计（论文）说明书用纸 第26页 共25页Injection Molding GuideINTRODUCTIONObjectiveThis document provides guidelines for part design, mold design and processing of styrenic block copolymer (SBC) TPEs. The GLS product families that include styrenic TPEs are Kraton compounds, Dynaflex TPE compounds and Versaflex TPE alloys.SBC RheologyOne major characteristic of SBCs is that they are shearing dependent. A material is shear dependent when its viscosity is higher at low shear rates (such as extrusion) and lower at high shear rates (as in injection molding). Therefore, SBC compounds will flow more easily into thin areas of the mold at high shear rates. The shear thinning behavior of SBCs should be considered when designing injection molds and also when setting mold conditions during processing.Figure 1.The effect of shear rate on the viscosity of GLSstyrenic TPE compounds (measured at 390F (200C).To obtain information regarding the viscosity of an individual grade, refer to the Product Technical Data Sheet, available at or contact your GLS representative.PART DESIGNGeneral Part Design ConceptsWhen designing a TPE part, there are a few general rules to follow: The part wall thickness should be as uniform as possible. Transitions from thick to thin areas should be gradual to prevent flow problems, back fills, and gas traps. Thick sections should be cored out to minimize shrinkage and reduce part weight (and cycle time). Radius / fillet all sharp corners to promote flow and minimize no-fill areas. Deep unventable blind pockets or ribs should be avoided. Avoid thin walls that cannot be blown off the cores by air-assist ejection. Long draws with minimum draft may affect ease of ejection.Flow Length and Wall ThicknessThe maximum achievable flow length is dependent on the specific material selected, the thickness of the part, and processing conditions. Generally, GLS compounds will flow much further in thinner walls than other types of TPEs. The flow to thickness ratio should be 200 maximum; however this is dependent on the material and the part design. High flow GLS TPE compounds (such as Versalloy) have been used successfully to fill flow ratios up to 400.The measurement of spiral flow offers a comparative analysis of a materials ability to fill a part. The spiral flow test is performed by injecting a material into a spiral mold (similar to a ribbon formed into a spiral). The distance the material flows is measured in inches. In this case, the spiral flow test was conducted using two different injection speeds (3 in/sec and 5 in/sec). The typical spiral flow lengths for the various GLS product families are summarized in Table 1. With specific compounds, flow lengths of up to 40 inches (at 5 in/sec injection speed) are possible.Table 1. Typical Spiral Flow Lengths for GLS Compounds*SeriesFlow length, in3 in/sec5 in/secDynaflex D13-1518-20Dynaflex G12-2218-30Versaflex 9-1613-26*Spiral flow tests performed using 0.0625 in thickness and 0.375 in width channel at 400F.For spiral flow information about a specific grade or additional details about the spiral flow test procedure, please refer to the GLS Corporation TPE Tips Sheet #7, available at or by contacting your GLS representative.UndercutsThe flexibility and elastic nature of TPEs allows for the incorporation of undercuts into the part design. Because of their excellent recovery characteristics, GLS compounds are capable of being stretched and deformed, allowing them to be pulled from deep undercuts (Figure 2). If both internal and external undercuts are present on the same part, slides or core splits may be necessary. Parts with internal undercuts (e.g. bulb shaped parts) may be air ejected from the core by use of a poppet valve in the core. Minor permanent elongation (3% - 8%) due to deformation may occur during ejection.Figure 2. An example of TPE parts with large undercuts.Gate and Knit Line LocationsThe product engineer should indicate the areas of the part that are cosmetic and those that are functional and include this information on the drawing. This will help the mold designer to determine the allowable gate and knit line locations.AnisotropyThermoplastic materials that have different properties in the flow direction versus the cross-flow direction (90 perpendicular to the flow direction) are characterized as “anisotropic” materials. Properties that may be affected are shrinkage and tensile properties. Anisotropy is caused when the polymer chains orient in the direction of flow, which leads to higher physical properties in the flow direction. Wall thickness, injection speed, melt temperature and mold temperature are a few variables that affect anisotropy. Depending on the processing conditions and mold design, most GLS styrenic TPE compounds exhibit a degree of anisotropy.ShrinkageDue to their anisotropic nature, GLS styrenic TPE compounds shrink more in the flow direction than in the cross-flow direction. Generally, SEBS compounds have higher shrinkage and are more anisotropic than SBS compounds. Typical shrinkage values for SEBS-based compounds are 1.3% - 2.5%, whereas those for SBS based compounds are 0.3% - 0.5 %. Softer SEBS compounds (below 30 Shore A) will shrink more than harder 6 materials. Some grades, such as Dynaflex G7700, G7800, and G7900 Series contain filler, which reduces their shrinkage.The shrinkage values reported by GLS are determined using a 0.125” thick plaque. It should be noted that shrinkage is not an exact number, but a range value. This range can be affected by the part wall thickness, melt temperature, mold temperature, injection speed, hold/pack pressures and also the time between molding and measuring. As a result, prototyping is strongly recommended for parts with close tolerances to better quantify the realistic shrinkage of a specific grade of material in a specific application.For shrinkage values for specific grades, please refer to the product Technical Data Sheet, available at or by contacting your GLS representative.MOLD DESIGNTypes of MoldsGLS SBC compounds can be molded in two- and three-plate molds. Both conventional and hot runner tool designs have been used with GLS compounds. Self-insulating hot runner tool designs are not recommended due to the potential for material degradation in the stagnation zones. Two-shot molds and insert molds can also be used. If a family mold is required, the cavity volumes should be similar, otherwise over packing and flashing of the smaller cavity may occur.Steel SelectionGLS styrenic TPEs are generally non-abrasive and non-corrosive. The selection of tool steel will depend on the quantity and quality of parts to be produced. For high volume production, the initial expense of quality tooling is a sound investment.A wide variety of tool steels are available for injection mold construction. Table 2 lists the properties of common tool steels and the typical mold components for which they are used. Soft metals, such as aluminum and beryllium copper, can be used for prototype parts or short production runs up to 10,000 parts.Table 2. Typical Tool Steel for Injection Mold ConstructionSteel TypeSteel PropertiesMold ComponentP-20Pre-hardened, machines well, high carbon, general-purpose steel. Disadvantage: May rust if improperly stored.Mold bases, ejector plates, and some cavities (if nickel or chrome plated to prevent rust).H-13Good general purpose tool steel. Can be polished or heat-treated. Better corrosion resistance.Cavity plates and core plates.S-7Good high hardness, improved toughness, general-purpose tool steel. Machines well, shock resistant, polishes well. Disadvantage: Higher cost.Cavity plates, core plates and laminates, as well as thin wall sections.A-2Good high toughness tool steel. Heat-treats and polishes well.Ejector pins, ejector sleeves, and ejector blades.D-2Very hard, high wear characteristics, high vanadium content, somewhat brittle. Disadvantage: Difficult to machine.Gate blocks, gibe plates to prevent galling, gate blocks to prevent wear.420 SSTough corrosion resistant material.Heat-treats and polishes well.Disadvantage: High cost.Cavity blocks, ejector pins, sleeves, etc.Some part designs may benefit from the use of higher thermal conductivity materials such as beryllium copper. This material is less durable than steel and may hob or wear faster than steel if used at the parting-line. Beryllium copper can be used for inserts, slides or cores to increase heat transfer rates and reduce cycle times. In cases where there is a long draw core, a fountain-type bubbler may be beneficial.Mold Surface Treatment, Finishing and TexturingMost GLS materials replicate the mold surface fairly well. To produce a glossy surface, a polished mold is required and an unfilled grade should be used. A highly polished tool and a transparent material are required to produce a part with good clarity. If a matte finish similar to that of a thermoset rubber is required, a rougher mold texture should be used (or a GLS product such as GLS Versalloy TPV alloys, which naturally produce a matte surface). In general, an EDM surface will produce a good texture and may improve release from the tool during part ejection. Matte surfaces can also help to hide any flow marks or other surface defects. Vapor honing, sand or bead blasting and chemical etching are also used to produce textured surfaces with varying degrees of gloss and appearance. To aid in release, the cavity or core may be coated with a release coating such as PTFE impregnated nickel after it has been given a sandblast or EDM finish.Sprue and Sprue Puller DesignThe sprue should have sufficient draft, from 1 to 3 to minimize drag and sprue sticking. Longer sprues may require more taper (3 - 5), as shown in Figure 3. Typically, the sprue diameter should be slightly larger than the nozzle diameter. An EDM finish is acceptable for most styrenic TPE materials. Permanent surface lubricant treatments have also been used successfully.Sprue puller designs vary with the hardness of the material. The different sprue designs possible and their relative dimensions are shown in Figures 4 through 7. In addition, Table 3 shows the typical hardness range for which a particular sprue design is applicable.Table 3. Typical Sprue Designs for Various Hardness ValuesTypical TPE Hardness RangeMost Common Sprue Puller TypesFigure50 Shore ATapered, Pin, Z-Type3, 4 and 640-70 Shore AUndercut55-40 Shore APine Tree7Hot sprue bushings and extended nozzles may also be used with GLS compounds. In many molds, the sprue is the thickest wall section in the mold and will control the minimum cooling time. The use of a hot sprue, which may be viewed as an extension of the machine nozzle, can sometimes reduce cycle time. Extended machine nozzles may also be used to reduce sprue length and size. When hot sprues are used, the machine nozzle tip should be a free-flow nozzle rather than a reverse tip.Figure 3. Tapered Sprue Puller Figure 4. Z-Pin Sprue PullerFigure 5. Undercut Sprue PullerFigure 6. Sucker Pin Sprue Puller Figure 7. Pine Tree Sprue PullerConventional Runner Configuration and DesignA balanced runner configuration is critical to achieve uniform part quality from cavity to cavity. In a balanced runner system, the melt flows into each cavity at equal times and pressure. The runner balance can be designed by using computer mold-flow analysis programs and verified by performing short-shot studies.An unbalanced runner may result in inconsistent part weights and dimensional variability. The cavity closest to the sprue may be over packed and flashing may occur. As a result of over packing, parts may also develop high molded-in stresses, which lead to warpage. Examples of balanced runner systems are shown in Figures 8 and 9.Figure 8. Example of Balanced Spider Runner Figure 9. Example of Balanced Cross-RunnerFigure 10 shows different runner cross-sections and their associated efficiency. Full round runners have the least resistance to flow and surface area, allowing the material to stay molten longer. The second most efficient runner cross-section is the modified trapezoid. This runner geometry most closely simulates a full round runner but only requires machining in only one plate. Figure 11 shows typical ball cutter dimensions and the corresponding modified trapezoid runner sizes. Figure 12 illustrates typical runner dimensions.Figure 10. Typical Runner Cross-SectionsFigure 11. Modified Trapezoid Runner SizesFigure 12. Runner Design and DimensionsCold slug wells should be used at each runner transition (turn). Cold slug wells serve to remove the leading edge of the melt. The slug well associated with the sprue should be large enough to trap the cold material formed in the machine nozzle during the mold-open cycle. Typical slug well dimensions are approximately 1.5 to 2.0 times the diameter or width of the feed runner.Runner KeepersRunner keepers or sucker pins provide undercuts to keep the runner on the desired plate but should not restrict material flow through the runner. Figures 8 and 9 show typical locations for runner keepers and sucker pins. Figure 13 illustrates an example design of a runner keeper.Figure 13. Runner Keeper designGate Design and LocationMost conventional gating types are suitable for processing GLS styrenic TPE compounds.The type of gate and the location, relative to the part, may affect the following: Part packing Gate removal or vestige Part cosmetic appearance Part dimensions (including warpage)The type of gate selected is dependent on both part and tool design. The gate location is equally important. To prevent the chances of jetting, locate the gate entrance in an area where the flow will impinge on a cavity wall. For automatically degating tools, the highly elastic nature of softer TPEs makes submarine gate designs or three plate tools with selfdegating drops more difficult. Higher hardness and filled grades usually have lower ultimate elongation and therefore are more easily degated. To assure the gates will break at a specific location, they should have a short land length to create a high stress concentration.Tab/Edge GatesTab or edge gates (Figure 14) most commonly utilize a conventional sprue and cold runner system. They are located along the tool parting line. A small undercut can be placed where the gate meets the part to minimize gate vestige caused by degating. Advantages of edge gates are ease of fabrication, modification and maintenance. The 14 gate depth (D) should be 15% - 30% of the wall thickness at the gate entrance. Common practice is to start “steel safe”. A good starting point for the gate width should be 1.0 - 1.5 times the gate depth. The gate land should be equal to or slightly longer than gate depth. The gate size may also depend on the part volume. The gate area may be inserted to facilitate gate maintenance or modification.Figure 14. Tab or edge gate Figure 15. Submarine GateSubmarine or tunnel gates are self-degating. During part ejection, the tool steel separates the part and the runner. Figure 15 shows a typical design of a submarine gate. Cashew type submarine gates should not be used for medium to soft hardness compounds due to their high coefficient of friction and high elongation.Fan GatesA fan gate is a streamlined variation of a tab gate (Figure 16). The fan gate distributes material into the cavity more evenly; thus it is normally used in parts that require a high degree of flatness and absence of flow lines. It also minimizes the possibility of gate pucker or part warpage.Figure 16. Fan gateSprue or Direct GateThe sprue or direct gate is often used on prototype parts because it is inexpensive. This type of gating is not recommended for GLS styrenic compounds because of their high elongation. In addition, the sprue will need to be trimmed thus appearance quality of the part is usually poor. If sprue gating is selected, care should be taken to keep both the sprue length and diameter as short and small as possible.Diaphragm GateThe diaphragm gate is used to maintain the concentricity of round parts. It allows even flow into the cavity and minimizes the potential for knit lines. Due to anisotropic shrinkage, flat round parts using center or diaphragm gating may not lay flat. A ring gate may also be used on the outside of a circular part.Table 4 compares the advantages and disadvantages of the various gate types discussed in this section.Table 4. Advantages and Disadvantages of Various Gate TypesGate TypeAdvantageDisadvantageEdge/Tab/Fan Gate Appropriate for flat parts Easy to modify Post-mold gate/runner removal is difficult Poor gate vestigeSubmarine Gate Automatic gate removal Minimal gate vestige More difficult to machineDiaphragm Gate Concentricity Appropriate for round parts No knit lines Scrap Post-molding gate removalPin gate (3-plate) Automatic gate removal Minimal gate vestige Localized cooling Requires floater plate More scrap Higher tool costValve gate (Hot runner systems) Minimal gate vestige Positive shut-off Minimizes post pack Higher tool cost Higher maintenance Only for hot runner systemsGate LocationStyrenic TPE compounds are anisotropic, thus they have different physical properties in the flow direction versus the cross-flow direction. Depending on the products intended usage, these property differences could be critical to the performance of the final part. As a result, the anisotropic nature of the styrenic TPE needs to be taken into consideration when determining the gate location on the part.The material flow may be estimated by eye or by using flow analysis programs. For higher shrinkage grades, the part may shrink near the gate, which causes “gate pucker” if there is a high molded-in stress at the gate. Parts shaped like a handle grip may warp toward the gate side of the part. Locating the gate at the top of the part minimizes this problem. Using two gates on opposite sides of the part can also address the issue, but it will result in two knit lines. If filling problems exist in thin walled parts, adding flow channels or minor changes in wall thickness can alter the flow. In some cases, it may be necessary to add a second gate to properly fill the parts.The gate should be placed so that the flow path is as short as possible. Locating the gate at the heaviest cross section of the part can improve packing and minimize voids or sinks. If possible, the gate should be positioned so as to avoid obstructions (flowing around cores or pins) in the flow path.The flow path of the material should minimize the possibility of formation of knit lines and flow marks. Upon injection, the material should impinge off the cavity wall to reduce the possibility of jetting. To minimize the effect of molded-in stress (at the gate) on part performance, the gate should be located in noncritical areas of the part. Also, the gate location should allow for easy manual or automatic degating.Mold VentingMold venting is critical to the quality and consistency of the finished part. Venting is required to allow the air in the sprue, runner and cavity to leave the tool as the melt flows into the cavity. Inadequate venting may cause short-shots, poor surface appearance, or weak weld-lines. Potential air traps in the part design can be predicted by flow simulation software. Once the tool has been built, short-shot studies can be used to find the critical venting areas.Vents should be placed at the last place to fill and in areas where weld lines occur. The typical vent size for GLS compounds is 0.0005” - 0.0010” (0.012 mm - 0.025 mm) with a 0.040” - 0.060” (10 mm 15 mm) land. Past the land, the vent depth should be increased to 0.005” - 0.010” (0.12 mm - 0.25 mm) to provide a clear passage for the air to exit the tool (Figure 17). Venting in areas below the parting line can be accomplished by allowing the ejector pin to be 0,001 loose on each side (Figure 18). Venting of ribs or pockets can be achieved by venting down an ejector pin, or with the use of porous mold steels. Ejector pin vents are self-cleaning, but they should be wiped once a day to remove buildup. Porous plug vents need to be replaced, or dismantled and cleaned when they become clogged.Figure 17. Mold vent design Figure 18. Venting through an ejector pinPart EjectionPart ejection is more difficult in long draw areas. A 3 - 5 draft per side on all long draw areas is recommended. Ejector pins should be located at runner transitions and in areas of the part where appearance is not critical. The diameter of ejector pins should be as large as possible to minimize push-through marks. Larger pins also allow for easier ejection of warmer parts, which can reduce cycle time. Ejector blades, ejector sleeves and stripper rings can be used for part ejection. Air ejection and the use of poppet can help strip large undercuts, providing the material has room to deform when the air is applied. Mold surface texturing and special mold surface treatments can also help to pull the parts from the “A” half. Advancing cores are used usually when ejecting large internal undercuts.Mold CoolingThe mold should have adequate cooling to optimize cycle time. The use of mold materials with high heat transfer, such as beryllium copper, can be used to cool slides or inserts. Commercially available fountain-type bubblers may also help to cool long cores. Separate chillers for the movable and stationary sides are suggested. This allows the processor to use differential cooling to help retain the parts on the movable (“B”) plate. Connecting cooling lines from the A to the B plate should be avoided. Special cooling for cores and slides is also an option to improve cooling efficiency.HOT RUNNER SYSTEMSThe differences between hot runner systems; cold runners and hot sprues are summarized in Table 5. GLS SEBS compounds are quite heat stable and are used successfully in hot runner tools today. Selecting a particular type of hot runner system is influenced by the product design and production requirements. There are many hot runner component and tool manufacturers available. If possible, utilize a system or component supplier with experience in styrenic TPEs. SBS compounds can crosslink (forming gels) if they are held at high temperatures for too long a period of time, therefore hot runner tools are not recommended for these materials.Manifold DesignTable 5. Comparative Assessment of Hot Runner SystemsSystem TypeAdvantageDisadvantageCold runner Lower tool cost Easily modified Enables use of robotics Typically governs cycle time Potential for cold slugs Potential for sprue sticking Scrap (though regrindable)Hot Sprue orExtended Nozzle Faster cycle Minimizes scrap Easily maintained Better temperature control Higher tool cost Potential heat degradation for SBS compoundsHot Runner No runner scrap Faster cycle time Precise temperature control Highest tool cost Purging Material degradation MaintenanceExternally heated systems are best. Internally heated manifolds are not suitable for TPEs. These systems typically have hot spots and stagnation zones that cause partially solidified material to cling to the cooler manifold walls. For maximum flexibility, the design should be naturally or geometrically balanced. Rheological balancing is possible, but only for a specific grade or rheometric curve. Internally heated manifolds are not suitable for TPEs these systems typically have hot spots and stagnation zones that cause partially solidified material to cling to the cooler manifold walls. All passages should be highly polished circular cross sections with gentle bends to minimize the possibility of stagnation zones. In order to maintain high shear, minimize residence times and promote flow, the passages should have a diameter of 0.250” to 0.375”. Individualized zone controls for the hot runners are recommended and allow the operator to adjust the balance slightly to make the parts more uniform.Hot Runner System GatesValve GatesValve gates offer the best solution for high production parts where surface quality is critical, such as medical and cosmetic products. Since valve gates leave only a slight ring on the part, gate vestige is minimized. Further improvement can be obtained by positioning the valve recessed below the part surface or concealing the gate in the part detail for aesthetic products. An example of a hot runner system with a valve gate is shown in Figure 19.Image provided by Mold-Masters Limited, Dura is a registered trade-mark of Mold-Masters Limited.Figure 19. Hot Runner System using valve gateThe gate diameter of a valve gate should be approximately 0.030” to 0.125”, depending on the size and thickness of the part. Valve gates do not require the material in the part to freeze before the valve is closed and hold pressure is released. Therefore, the screw recovery for the next cycle can start earlier and the total cycle time may be decreased. For very thick wall parts with the potential for sinks or shrink voids, valve gates can be held open for an extended time to supply make-up material and eliminate voids and sinks.Valve gate elements need to be insulated from the mold plates to maintain proper temperature control. Only valve gates can be used for multi-cavity foam molding or cascade molding to fill long thin flows without knit lines. Due to the low viscosity of some GLS grades, properly maintained tight valve gates are required to prevent leakage or hair flash. Valve gates may be pneumatically or hydraulically activated. Individual heater controls at each gate will allow fine control of the melt viscosity and filling.Hot Tip GatesHot tip gates are suitable for SBC compounds but will leave some gate vestige (which can be as high as 50% to 75% of the gate diameter). Vestige can be minimized by slightly recessing the gate below the part surface. The land length of the hot tip should be less than the diameter of the gate. The elements of the hot tip should be properly insulated from the mold plates and cavity. In order to achieve this, the land length of the gate may need to be lengthened and a portion of the land should be part of the cavity. All passages within the tip should be 20 highly polished and streamlined to minimize stagnation and degradation zones. The efficiency of the design may be verified by recording the time it takes to make a complete color change while producing parts. This demonstrates whether there is any residual dead zone material that continues to enter the melt stream.For hot tip gate systems, there should be a delay long enough for the part to set up completely before mastication is initiated for the next cycle. Without a delay, the parts may become over packed. This is particularly important for low hardness, high flow materials. To reduce over packing for thick-walled parts with large gates, use minimal back pressure during mastication.Since TPE compounds are slightly compressible in the molten state, larger runner volumes can cause hot tip gates to drool after the mold is opened. To prevent drool, the runner system should be minimized and the melt decompressed before the mold opens.Hot tips may be used to fill a secondary cold runner to supply material to multiple parts. Each hot tip gate should use an individual temperature controller. If the hot tip manufacturer selected does not have prior SBC compound experience, it may be necessary to experimentally determine the best gate type and geometry through prototyping.OVERMOLDINGOne of the largest areas of growth for TPEs is overmolding. Many product designers are utilizing TPEs to add a “soft touch” to a rigid material. GLS compounds can be overmolded onto many different substrates to alter the surface feel, improve aesthetics, and cushion against vibration the possibilities are limitless.Most Dynaflex and Kraton compounds (and Versalloy TPV Alloys) are suitable for two-shot or insert molding onto a PP (and in some cases, PE) substrate. The Versaflex OM grades have been specially formulated to bond PC, ABS, nylon 6/6, PC/ABS, and PPO. The new Versollan OM series, based on BASF high performance polyurethane (TPU), are TPU alloys specifically designed for thin-wall overmolding (both insert and two-shot molding) o nto PC, ABS, and PC/ABS substrates. With new innovative technologies, GLS continues to develop TPEs that bond to a variety of substrates. For additional information about the standard Versaflex OM series and the development of new TPEs that bond to unusual substrates, please contact your GLS Representative.For more information about overmolding part design, mold design and processing, please refer to the GLS publication “Overmolding Guide”, available at or by contacting your GLS representative.MACHINE SELECTIONMachine TypesReciprocating screw machines are recommended. However, ram or plunger equipment has been used to produce SBS parts. Newer machines with a computer interface offer improved process control and are preferred for multi-cavity tools and high production applications. Machines with the capability of programmable injection rates and pressures can produce better quality parts. Molding machi nes that control the shot size by position are preferable to machines that can only control by pressure and/or time. A vertical press with a rotary or shuttle table works well for insert molding. Multi-station rotary presses allow more cooling time for molding foamed parts.Clamp CapacityThe clamp capacity necessary for GLS styrenic compounds is lower than most TPEs. Clamp capacity can be calculated by the following equation:C=（1.53）A tA clamp capacity example calculation is shown in Figure 20.Figure 20. Estimating Machine Clamp CapacityBarrel CapacityIf possible, use a machine that utilizes 25% to 75% of the barrel shot size capacity. This allows for optimum temperature control of the material and minimizes material residence time at high temperatures. The material residence time for SEBS compounds should be no more than 10 minutes. The material residence time for SBS compounds should be no more than 8 minutes maximum. If a high level of regrind is utilized, the barrel capacity should be reduced.Nozzle SelectionSmaller nozzle diameters are recommended because they promote shear heating during injection and generate less cold slug material. Suggested starting diameters are 0.0625” - 0.1875” (1.59 mm - 4.76 mm). Static mixing nozzles have been used to improve color dispersion for concentrates with a high letdown ratio. Extended nozzles have also been used to decrease the length of the sprue (resulting in less scrap). If a foaming agent is required (to produce foamed parts), a mechanical shut-off nozzle must be used to control foaming activity and to prevent drooling.Screw SelectionGeneral-purpose screws are suitable for styrenic TPEs. Compression ratios of 2:1 to 3:1 are commonly used for both SEBS and SBS compounds.MATERIAL HANDLING AND PREPARATIONDryingDrying is not typically required for GLS styrenic TPE compounds. Certain specialty products, such as the Versaflex and Versollan overmolding grades, are hygroscopic; thus they need to be dried prior to molding. A desiccant dryer with a 40F dewpoint is strongly recommended for drying hygroscopic materials. Specific drying temperatures and times can be found on the Technical Datasheets for each individual product.ColoringSBC compounds have inherently superior color than most other TPEs. Therefore, they require less color concentrate to achieve a particular color and the colors produced are cleaner (less yellow) than other TPEs. Generally, the color concentrate should be lower in viscosity (have higher melt index) than the base compound. This will promote ease of dispersion. Styrenic color carriers are recommended for the SBS compounds. Polypropylene (PP) carriers are recommended for the harder SEBS compounds. For soft SEBS compounds low-density polyethylene (LDPE) or ethylene vinyl acetate copolymer (EVA) have been used. PP carrier is not recommended for softer grades, as the compound hardness will be affected.Liquid colors can be used but the carrier should be a paraffin type mineral. Poly vinyl chloride (PVC) plasticizers, such as dioctyl phthalate (DOP), should not be used as carriers. Dry colors have also been used but may require more material and time to perform color changes.The use of a polyethylene (PE) carrier may adversely effect adhesion to the substrate for some overmolding applications. If using a specialty overmolding grade, follow the coloring recommendations given on the individual product Technical Data Sheets. Detailed coloring recommendations are summarized in TPE Tip # 3.Gloss and ClarityGLS compounds are available in opaque, translucent and water-clear grades. The Versaflex CL series is formulated for high clarity. Clear grades can produce the best metallic or pearlescent colors. High gloss clear grades have higher COFs and more intimate mold contact and therefore are more difficult to eject. Filled opaque compounds are more difficult to color in deep intense colors, but will produce good pastel colors.RegrindUp to 80% regrind may be used for SEBS compounds. High levels of regrind are better tolerated in black materials. Natural, light-colored or clear compounds will more easily show contamination or discoloration. Organic pigments used to produce yellow, red, blue and green colors are more likely to change color after prolonged residence time or high regrind levels. For SBS compounds, the regrind should be kept below 25%.Dynaflex compounds have high elongation and good tear strength and therefore require the use of a high quality grinder with sharp kni ves. For lower durometer styrenic compounds the clearances should be set to 0.003” maximum. Only grinders with high quality support bearings and a rigid frame can maintain the tolerances necessary to achieve the necessary rotor knife to bed knife clearances. The use of a small amount of a dusting agent such as talc or calcium carbonate can minimize agglomeration during the grinding process. Feed small amounts of parts into the grinder at one time to minimize heat buildup, which can lead to agglomeration.To allow the best incorporation of the regrind into the virgin material, the screen size should be chosen to yield particles that are roughly the same size as virgin pellets.PurgingIf the press is down for more than 10 minutes, purge before restarting production. To prevent flashing, restart the machine using a reduced shot size and gradually increase it back to the original shot size. This will help to prevent flashing from occurring behind slides or inserts. For SBS compounds - if a machine is to be left at temperature longer than one hour, purge with LDPE or polystyrene before shut down. For SEBS compounds - if the machine is down over the weekend, purge with a high molecular weight (low or fractional melt flow) LDPE at low temperatures before shut down. On start up, retract the extruder and air purge it well before attempting to fill the mold.PROCESSING CONDITIONSIntroductionThis section describes general processing guidelines for styrenic TPEs. The specific starting conditions for each individual product are located in the Product Technical Datasheet.Setting Barrel TemperaturesFigure 21 shows typical starting barrel temperatures. Barrel temperatures should be set progressively. The feed zone temperatures should be set fairly low typically 250F - 300F (120C -150C) to avoid feed-throat bridging and allow entrapped air to escape. Lower temperatures in the transition zone allow proper compression and shearing of the compound before it fully melts. To improve mixing when using color concentrates, set the transition zone temperatures above the melt temperature of the concentrate. The zone nearest to the nozzle should be set close to the desired melt temperature.After the process has stabilized, the actual barrel temperatures should be compared to the set points. If the actual temperature exceeds the set temperature, then shear heating has caused the material to overheat. If good parts are being produced, the temperature settings should be reset to be the same as the actual temperatures.The heaters should demand power 25% to 50% of the time. If the heaters are on continuously, there is not enough heat being produced from shear. To increase shear heating, increase the screw rpm and back pressure.Figure 21. Suggested Initial Start-Up Conditions for Injection Molding.Setting Mold TemperaturesMold temperatures should be set above the dew point temperature in the molding area. This prevents sweating of the mold and possible water contamination in the cavity. Water contamination usually appears as streaks in the parts. Mold temperatures may be raised if there are long or thin sections of the part that have proven to be difficult to fill. Higher mold temperatures usually result in higher cycle times but may improve weld line integrity and part appearance.Table 6. Product Family and TemperaturesProductFamilyMoldMeltNozzleZone 3Zone 2Zone 1FeedSBSCompounds75-90F(25-32C)370-390F(190-200C)370-390F(190-200C)360-380F(185-195C)340-360F(170-182C)300-330F(150-165C)100-150F （40-65C)SEBSCompounds110-130F(43-55C)370-430F(190-220C)390-430F(200-220C)390-430F(200-220C)370-390F(190-200C)350-370F(175-190C)100-170F (40-75C)SupersoftCompounds110-130F(43-55C)340-390F(170-200C)360-390F(180-200C)360-390F(180-200C)335-375F(170-190C)300-330F(150-165C)100-120F (40-50C)Setting Shot SizeWhen starting up a new mold, begin with short-shots, then gradually increase the shot size until all part cavities are 80-90% filled. This procedure can minimize the potential for over packing and prevent flash in vents. The screw position should be noted and used to set the transfer point. Monitor the cushion to insure that it is maintained during the pack and hold phase. If there is no cushion, the pack pressure cannot be maintained and there is no control of part densification. After the gate freezes, any additional material volume or pressure will just pack the sprue and runner system, which can cause difficulties with sprue removal during part ejection.Screw rpm, Back Pressure and Screw Delay TimeThe screw rpm should be set so that the screw is fully recovered for the next shot, typically 2 to 3 seconds before the mold opens. Typical screw speeds range from 50 rpm to 150 rpm. If the screw recovers too fast, and the machine is equipped with a screw delay timer, set the delay time so that there is minimal delay after the screw is fully recovered and the mold opens. This will reduce material residence time at temperature and dead time in the barrel.Increasing the back pressure increases shear heating of the material. Normal settings for back pressure are 50-150 psi. When mixing color concentrates, higher back pressure is preferred to achieve optimum dispersion.Injection SpeedIf possible, profile the injection speed to fill the runner system rapidly and then slow down after the material starts flowing through the gate and into the cavity. Maintain this speed until the part is 90% full and then reduce it further to completely fill the cavity without flashing the part. As stated earlier, GLS compounds are shear responsive. If a part has difficulty filling, increase the injection speeds before increasing temperature. The injection time to fill the part should be between one and two seconds. Slower fill rates may be required if surface flow defects occur.Injection and Transfer pressuresIf the machine is not capable of being controlled by fill speed, set the injection pressure high enough to fill the runner system and cavity in about 1 to 5 seconds. Adjus t the initial transfer pressure to approximately 50% of the injection pressure required to fill the part cavity. This helps to minimize the pressure during the pack and hold phase of injection. When setting the shot size, monitor the cushion to insure it is maintained during the pack and hold phases.Transfer From Boost to Pack to HoldNewer molding equipment provides additional options for transferring from injection boost (first-stage Injection) to the pack and hold phase. The most accurate method to transfer from boost to pack pressure is by screw position. Using screw position allows the processor to consistently inject a specific volume of material to the cavity. It also provides accurate control of part packing and densification, which can help prevent sinks and voids in the part. Time is another method for controlling transfer but is not recommended. Transfer using cavity pressure is expensive because it involves installing pressure transducers in the part cavity. This process is used when highly accurate molding tolerances are required. Reducing the transfer pressure from boost to pack and hold will help to control drool at the bushing tip. If the injection unit is equipped with a profiled pack and hold phase, it can be used to reduce the velocity and pressure to the runner.Injection TimeThe optimum time to fill the runner system is approximately 0.5 - 1.5 seconds. It should take another 1 - 5 seconds to fill the cavities. If possible, it is better to control the fill time by controlling the injection speed.Hold TimeThe hold time should be set to achieve gate freeze. Usually, the gate size is the determining factor for hold time. The larger the gate the longer the hold time required to achieve gate freeze.Cooling TimeThe cooling time is principally dependent on the temperature of the melt, the wall thickness of the part and cooling efficiency. In addition, the material hardness is a factor. Harder grades (50 Shore A) will set up faster in the mold compared to very soft grades (20 Shore A). For an average part and medium hardness SEBS compound the cooling time will be approx
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