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附件4-4：任务书 任 务 书 兹发给 专业 班学生 设计（论文）任务书，内容如下：1 1.毕业设计（论文）题目：异形垫片零件冲压成形工艺及其落料冲孔级进模具设计2.应完成的项目： （1）完成开题报告。要求完成10篇以上相关文章的阅读量，撰写字数不少于2500字，内容包括工作任务分析、调研报告、方案拟定与分析、论文框架结构、实施计划、文献综述内容等；撰写格式参照附件4-5； （2）完成英文翻译。要求阅读3万印刷符以上的外文参考资料。提交3000汉字（或1.2万印刷符）以上的外文翻译。翻译外文内容必须与毕业设计（论文）有紧密联系，并说明出处；翻译格式参照附件4-6； （3）完成冲压工艺设计和模具结构设计，具体工作包括： 1）零件的冲压工艺方案和模具结构方案的分析和制定； 2）各冲压工序的冲压工艺计算； 3）凸模、凹模的外形结构和固定方式设计； 4）卸料机构、定位机构、导向机构、连接固定机构等选用和设计； （4）绘制图纸。模具总装图绘制,模具零部件设计和零件图绘制；（图纸总量不少于3张A0图纸；要求图面整洁，布局合理，线条粗细均匀，圆弧连接光滑，尺寸标注规范符合机械工程制图要求。） （5）编写设计说明书。说明书内容要求重点突出、观点鲜明、论据充分、分析透彻、条理清晰、图文并茂。字数不少于1.5万字(20页左右)；说明书的内容、书写规范和打印格式请严格按照2014届本科生毕业设计工作指南文件中第3.2、第3.3、第3.4、第3.5的要求规定，具体格式请参照附件4-1. 3.参考资料以及说明：（1） 刘建超、张宝忠 主编. 冲压模具设计与制造. 北京：高等教育出版社，2010 （2）吴诗惇，李淼泉. 冲压工艺及模具设计.西安：西北工业大学出版社，2002 （3）冲模设计手册编写组.冲模设计手册.机械工业出版社，1999.6 （4）王孝培主编. 冲压设计资料 . 北京：机械工业出版社，1983 （5）李天佑主编. 冲模图册. 北京：机械工业出版社，1990 4.本毕业设计（论文）任务书于2013年12月23日发出，应于2014年 5月 16日前完成，然后提交毕业设计（论文）答辩委员会进行答辩。 指导教师（导师组负责人） 签发，2013年12月23日教研室负责人 审核，2013年12月23日XXXX 学 院毕 业 设 计（论 文）说 明 书题 目 异形垫片冲压模具设计 学 生 系 别 机 电 工 程 系 专 业 班 级 学 号 指 导 教 师 摘要毕业设计是在模具专业理论教学之后进行的实践性教学环节。是对所学知识的一次总检验，是走向工作岗位前的一次实战演习。其目的是，综合运用所学课程的理论和实践知识,设计一副完整的模具训练、培养和提高自己的工作能力。巩固和扩充模具专业课程所学内容，掌握模具设计与制造的方法、步骤和相关技术规范。熟练查阅相关技术资料。掌握模具设计与制造的基本技能，如制件工艺性分析、模具工艺方案论证、工艺计算、加工设备选定、制造工艺、收集和查阅设计资料，绘图及编写设计技术文件等。本设计主要对异形垫片冲压模具进行设计。结合公司实际生产要求和产品的特点，在厂原有的设计上，对模具进行了改进设计。本设计对弯曲件加工工艺进行了分析，得出了最佳加工方案，在充分保证零件质量与精度的前提下，选择高生产率的加工工艺，降低生产成本，从而有效地节约了材料。本设计中使用计算机软件进行了辅助设计，在保证高精度的同时简化了传统的繁琐计算过程，使设计更为便捷。随着模具的迅速发展，在现代工业生产中，模具已经成为生产各种工业产品不可缺少的重要工艺设备。这次毕业设计是在学习完所有机械课程的基础上进行的，是对我综合能力的考核，是对我所学知识的综合运用，也是对我所学知识的回顾与检查。本次设计是在指导老师认真、耐心的指导下，对模具的经济性、模具的寿命、生产周期、及生产成本等指标下进行全面、仔细的分析下而进行设计的。在此, 我表示衷心的感谢他们对我的教诲.冲模是模具设计与制造专业的主要专业课程之一。它具有很强的实践性和综合性，通过学习这门课程，使我对冲压模具有了新的认识，从中也学到了不少知识，激发了我对冲压模具的爱好。但因本人经验有限，因此很难避免的存在一些不合理之处，望各位老师批评和指正，以使我的毕业设计做到合理，同时也为我走出校门步入社会打下坚实的基础。关键词冲压模具；弯曲模；辅助设计；模具结构目 录摘要2第一章、绪论51.1.冲压的概念、特点及应用51.2.冲压的基本工序及模具6第二章、零件的工艺性分析.82.1.零件的工艺性分析82.2.冲裁件的精度与粗糙度82.3.冲裁件的材料82.4.确定工艺方案.9第三章、冲压模具总体结构设计103.1.模具类型103.2.操作与定位方式103.3.卸料与出件方式103.4.模架类型及精度10第四章、冲压模具工艺与设计计算114.1.排样设计与计算114.2.设计冲压力与压力中心,初选压力机.124.2.1.冲裁力124.2.2.压力机的选择124.2.3.压力中心134.2.4.计算凸凹模刃口尺寸及公差14第无章、模具的总张图与零件图165.1.模具结构165.2.冲压模具的零件图175.2.1.凹模设计175.2.2.凸模设计185.2.3.选择坚固件及定位零件205.2.4.设计和选用卸料与出件零件215.2.5.选择模架及其它模具零件225.3.压力机的校核245.3.1.公称压力245.3.2.滑块行程245.3.3.行程次数245.3.4.工作台面的尺寸255.3.5.闭合高度25第六章、冲压模具零件加工工艺的编制266.1.凹模加工工艺过程266.2.凸模加工工艺过程266.3.卸料板加工工艺过程286.4.凸模固定板加工工艺过程286.5.上模座加工工艺过程296.6.下模座加工工艺过程29设计小结30致 谢31参考文献32第一章、绪论1.1.冲压的概念、特点及应用模具主要类型有：冲模，锻摸，塑料模，压铸模，粉末冶金模，玻璃模，橡胶模，陶瓷模等。除部分冲模以外的的上述各种模具都属于腔型模，因为他们一般都是依靠三维的模具形腔是材料成型。模具所涉及的工艺繁多，包括机械设计制造，塑料，橡胶加工，金属材料，铸造（凝固理论），塑性加工，玻璃等诸多学科和行业，是一个多学科的综合，其复杂程度显而易见。随着经济的发展，冲压技术应用范围越来越广泛，在国民经济各部门中，几乎都有冲压加工生产，它不仅与整个机械行业密切相关，而且与人们的生活紧密相连。冲压是利用安装在冲压设备（主要是压力机）上的模具对材料施加压力，使其产生分离或塑性变形，从而获得所需零件（俗称冲压或冲压件）的一种压力加工方法。冲压通常是在常温下对材料进行冷变形加工，且主要采用板料来加工成所需零件，所以也叫冷冲压或板料冲压。冲压是材料压力加工或塑性加工的主要方法之一，隶属于材料成型工程术。冲压所使用的模具称为冲压模具，简称冲模。冲模是将材料（金属或非金属）批量加工成所需冲件的专用工具。冲模在冲压中至关重要，没有符合要求的冲模，批量冲压生产就难以进行；没有先进的冲模，先进的冲压工艺就无法实现。冲压工艺与模具、冲压设备和冲压材料构成冲压加工的三要素，只有它们相互结合才能得出冲压件。与机械加工及塑性加工的其它方法相比，冲压加工无论在技术方面还是经济方面都具有许多独特的优点。主要表现如下。(1) 冲压加工的生产效率高，且操作方便，易于实现机械化与自动化。这是因为冲压是依靠冲模和冲压设备来完成加工，普通压力机的行程次数为每分钟可达几十次，高速压力要每分钟可达数百次甚至千次以上，而且每次冲压行程就可能得到一个冲件。（2）冲压时由于模具保证了冲压件的尺寸与形状精度，且一般不破坏冲压件的表面质量,而模具的寿命一般较长,所以冲压的质量稳定,互换性好,具有“一模一样”的特征。（3）冲压可加工出尺寸范围较大、形状较复杂的零件，如小到钟表的秒表，大到汽车纵梁、覆盖件等，加上冲压时材料的冷变形硬化效应，冲压的强度和刚度均较高。（4）冲压一般没有切屑碎料生成，材料的消耗较少，且不需其它加热设备，因而是一种省料，节能的加工方法，冲压件的成本较低。但是，冲压加工所使用的模具一般具有专用性，有时一个复杂零件需要数套模具才能加工成形，且模具 制造的精度高，技术要求高，是技术密集形产品。所以，只有在冲压件生产批量较大的情况下，冲压加工的优点才能充分体现，从而获得较好的经济效益。1.2.冲压的基本工序及模具由于冲压加工的零件种类繁多，各类零件的形状、尺寸和精度要求又各不相同，因而生产中采用的冲压工艺方法也是多种多样的。概括起来，可分为分离工序和成形工序两大类；分离工序是指使坯料沿一定的轮廓线分离而获得一定形状、尺寸和断面质量的冲压（俗称冲裁件）的工序；成形工序是指使坯料在不破裂的条件下产生塑性变形而获得一定形状和尺寸的冲压件的工序。上述两类工序，按基本变形方式不同又可分为冲裁、弯曲、拉深和成形四种基本工序，每种基本工序还包含有多种单一工序。在实际生产中，当冲压件的生产批量较大、尺寸较少而公差要求较小时，若用分散的单一工序来冲压是不经济甚至难于达到要求。这时在工艺上多采用集中的方案，即把两种或两种以上的单一工序集中在一副模具内完成，称为组合的方法不同，又可将其分为复合-级进和复合-级进三种组合方式。冲模的结构类型也很多。通常按工序性质可分为冲裁模、弯曲模、拉深模和成形模等；按工序的组合方式可分为单工序模、复合模和级进模等。但不论何种类型的冲模，都可看成是由上模和下模两部分组成，上模被固定在压力机工作台或垫板上，是冲模的固定部分。工作时，坯料在下模面上通过定位零件定位，压力机滑块带动上模下压，在模具工作零件（即凸模、凹模）的作用下坯料便产生分离或塑性变形，从而获得所需形状与尺寸的冲件。上模回升时，模具的卸料与出件装置将冲件或废料从凸、凹模上卸下或推、顶出来，以便进行下一次冲压循环。冲压件图如下图所示:冲压技术要求:1. 材料:10F2. 材料厚度:3.0mm3. 生产批量:中批量4. 未注公差:按IT10确定.第二章、零件的工艺性分析.2.1.零件的工艺性分析该零件材料为10F钢，结构简单,形状复杂,产品宽度B=70+95+20=1851.2t(t为材料厚度) ,冲孔时有尺寸为20，45，60，根据冲压模具设计手册知冲孔时,因受凸模强度的限制,孔的尺寸不应太小.冲孔的最小尺寸取决于材料性能,凸模的强度和模具结构等.根据表3-3可查得圆形孔最小值得d=0.9t=0.9X3.0=2.7mm(1.52)t所以由冲件图可知C1=35.141X3.0=3, 由以上可知孔与孔之间距离C1满足工艺性要求, 由以上分析可得,冲件的尺寸很小,如图21所示。在模具结构上需要多考虑，确定后,我们才能继续做下一步的设计。2.2.冲裁件的精度与粗糙度冲裁件的经济公差等级不高于IT12级,一般落料公差等级最好低于IT10级,冲孔件公差等级最好低于IT9级,由工件图尺寸可查得落料公差,冲孔公差分别为0.40,0.08.而冲件落料公差,最高精度冲孔公差分别为0.5,0.15，孔中心距公差 0.15而冲件孔中心距最高精度公差为0.25,因此可用于一般精度的冲裁,普通冲裁可以达到要求10级。由于冲裁件没有断面粗糙度的要求,我们不必考虑.2.3.冲裁件的材料由材料方面的资料得,10F是优质碳素结构钢。其力学性能： 抗拉强度 b (MPa)：300-360 抗剪强度，=220-310Mpa，伸长率 ()：32%此材料具有良好的塑性级较高的弹性,冲裁性较好,可以冲裁加工.2.4.确定工艺方案.该冲裁件包括落料和冲孔两个基本工序,可采用的冲裁方案有单工序冲裁,复合冲裁和级进冲裁三种.零件属于中批量生产,因此采用单工序须要模具数量较多,生产率低,所用费用也高,不合理;若采用复合冲,可以得出冲件的精度和平直度较好,生产率较高,但因零件的孔边距太小,模具强度不能保证;用用级进模冲裁时,生产率高,操作方便,通过合理设计可以达到较好的零件质量和避免模具强度不够的问题,根据以上分析,该零件采用级进冲裁工艺方案.第三章、冲压模具总体结构设计3.1.模具类型根据零件的冲裁工艺方案,采用级进冲裁模.3.2.操作与定位方式零件中批量生产,安排生产可采用手工送料方式能够达到批量生产,且能降低模具成本,因此采用手工送料方式.零件尺寸较小，厚度较小，保证孔的精度及较好的定位，宜采用导料板导向，定位销导正。3.3.卸料与出件方式考虑零件尺寸较大，厚度较厚，采用弹压卸料方式，为了便于操作，提高生产率，冲件和废料采用凸模直接从凹模洞口推下的下出件方式。3.4.模架类型及精度由于零件材料较厚，模具间隙比较大，又是级进模因此采用导向平稳的四导柱模架，由于模具比较大，买标准件模价，从经济学角度出发，不实惠，不合理，因此，可以考虑自己制造的四导柱钢板非标准模架。第四章、冲压模具工艺与设计计算4.1.排样设计与计算该冲裁件材料厚度较薄，尺寸小，因此可采用以下排样比较合理,如图4-11所示。图4-1搭边值要合理确定，值过大，材料利用率低；值过小，搭边的强度与刚度不够，冲裁时容易翘曲或被拉断，不仅会增大冲裁件毛刺，有时甚至单边拉入模具间隙，造成冲裁力不均，损坏模具刃口。因此，搭边的最小宽度大于塑性变形区的宽度，一般可取等于材料的厚度。搭边值的大小还与材料的力学性能、厚度、零件的形状与尺寸、排样的形式、送料及挡料方式、卸料方式等因素有关。搭边值一般由经验确定，根据所给材料厚度=3.0mm，确定搭边工作间a1为3.0mm, a为3.0mm。因此根据式3-13，条料的宽度为B=（Dmax+2a+z）=220+23+23=232mm进距为:s=45+a1=185+3.0=188mm根据3-14，导板间距为：B0=B+Z=Dmax+2a+2z=232+0.5=232.5mm由零件图在CAD用计算机算得一个零件的面积为26347.74mm一个进距内的坯料面积:BXS=232X188=43616mm,因此材料利用率为:=(A/BS)X100%=(26347.74/43616)X100%=60.41%4.2.设计冲压力与压力中心,初选压力机.4.2.1.冲裁力 根据零件图,用CAD可计算出冲一次零件内外周边之和L=686.22mm(首次冲裁除外),又因为=310Mpa,t=3.0mm,取K=1.3,则根据式3-18,F=KLt=1.3686.223.0310=829.64KN，冲孔力的大小：F=KLt=1.3（3.1420+3.1445+3.1465）3.0310=493.51KN，切侧刃力的大小：F=nKLt=21.33883.0310=938.18KN，总的力为829.64+493.15+938.18=2260.97卸料力:,取Kx=0.06,则Fx=KxF=0.062260.97=135.66KN推件力:根据材料厚度取凹模刃口直壁高度h3mm,为了修模时能保证模具仍具有足够的强度,所以直壁高度取h=3mm,4.2.2.压力机的选择由式3-23应选取的压力机公称压力为:P0(1.11.2)F=(1.11.2)X（2260.97+135.66）=2636.293KN因此可选压力机型号为J21-350.型号为J21350压力机的基本参数如：（表一）公称压力/KN3500垫板尺寸/mm滑块行程/mm200厚度80滑块行程次数/（次/min）50模柄孔尺寸/mm最小封闭高度/mm120滑块底面积尺寸/mm封闭高度调节量80滑块中心线至床身距离/mm床身最大可倾角30工作台尺寸/mm前后880左右15504.2.3.压力中心根据排样,我们可以在CAD里使用查询便能得出冲孔的压力中心,F1冲侧刃力 F1=Ltb ，得F1=469.09KNF2冲侧刃力 F2=Ltb ，得F2=469.09KNF3冲孔力65 F3=Ltb ，得F3=246.76KNF4冲孔力20 F4=Ltb , 得F4=76KNF5冲孔力45 F5= Ltb , 得F5=170.83KNF6落料力 F6= Ltb , 得F6=829.64KNY1F1到X轴的力臂 Y1=116X1F1到Y轴的力臂 X1=282Y2F2到X轴的力臂 Y2=-116X2F2到Y轴的力臂 X2=282Y3F3到X轴的力臂 Y3=15X3F3到Y轴的力臂 X3=93Y4F4到X轴的力臂 Y4=90X4F4到Y轴的力臂 X4=0Y5F5到X轴的力臂 Y5=-70X5F5到Y轴的力臂 X5=-65Y6F6到X轴的力臂 Y6=15X6F6到Y轴的力臂 X6=-260.5根据合力距定理：YG = （Y1F1+ Y2F2+ Y3F3）/（F1+ F2+ F3）XG = （X1F1+ X2F2+ X3F3）/（F1+ F2+ F3）XGF冲压力到X轴的力臂；XG=1.08YGF冲压力到Y轴的力臂；YG=4.877所以由以上可以算得压力中心为G(1.08,4.877)4.2.4.计算凸凹模刃口尺寸及公差由于材料厚度中等，模具间隙较小,模具的间隙由配作保证,工艺比较简单,并且还可以放大基准件的制造公差,(一般可取冲件公差的1/4),使制造容易,因此采用配作加工为宜.由落料尺寸得,凹模会变小,所以得以凹模为基准,配作凸模.由冲孔尺寸得,凸模尺寸变小,所以以凸模为基准,配作凹模.由材料厚度可得Zmin=0.08mm, Zmax=0.12mm.由落料,凹模磨损后变大,磨损系数X1=0.50,X2=0.20所以:Ad1=(A1max-x)=(70-0.20X0.14) =69.98Ad2=(A2max-x)=(40-0.20X0.14) =39.98Ad3=(A3max-x)=(30-0.20X0.14) =29.98Ad4=(A4max-x)=(20-0.20X0.14) =19.98由于Ad1,为落料尺寸,故以凹模为基准,配作凸模，所以落料凸模刃口尺寸按凹模实际尺寸配作，保证双面间隙值为0.180.22mm。取0.20。落料凸模尺寸：Ah1=(Ad1-Z)+ =60-0.10=59.9+0.02; Ah2=(Aj2-Z)+ =40-0.10=39.9+0.02; Ah3=(Aj3-Z)+ =30-0.10=30.1+0.02; Ah4=(Aj4-Z)+ =20-0.04=19.96+0.02; 由冲孔尺寸凸模磨损后变小有:b1=20, b2=45, b3=65,磨损系数X1=X20.5,故bp6不需采用刃口尺寸公式计算,而直接取bp6=2bp5.所以:bp1=(b1min+X11)=(20+0.5X0.04)=20.02bp2=(b2min+X22)=(45+0.5X0.04)=45.02bp3=(b3min+X33)=(65X0.04)=65.02 凸,凹模磨损后不变的尺寸Cp1=85，Cp1=95， Cp1=106， 未注公差为IT10,所以20的公差为0.04, 35的公差为0.06,60的公差为0.06,得:Cp=(Cmin+0.5),所以:Cp1=(Cmin+0.5)=850.01Cp2=(Cmin+0.5)=950.01Cp3=(Cmin+0.5)=1060.01第五章、模具的总张图与零件图5.1.模具结构根据前面的设计与分析,我们可以得出如级进模具的总张图如图5-1所示:图5-1 级进模总装图1.下模板；2.导柱；3.凹模；4.落料凸模；5.卸料板；6.树脂；7.导套；8.冲头固定板；9.上垫板；10.上模板；11.内六角螺钉；12.导正销；13.中间孔冲头；14.切侧刃凸模；15.圆柱销；16.内六角螺钉；17.卸料螺钉；18.中间大孔冲头；19.中间孔冲头；20.导料板；21.内六角螺钉；22.圆柱销；23.内六角螺钉。5.2.冲压模具的零件图5.2.1.凹模设计凹模采用矩形板状结构和直接通过螺钉,圆柱销与下模座固定的固定方式.考虑凹模的磨损和保证冲件的质量根据表3-28,凹模刃口采用直筒形刃口壁结构,刃口高度根据前面“4.2”计算冲裁力时所取h=3mm,漏料部分刃口轮廓适当扩大，可以扩大0.51mm,取1mm,(为便于加工,落料凹模漏料孔可设计成近似于刃口轮廓的简化形状,如图所示),凹模轮廓尺寸计算如下:凹模轮廓尺寸的确定，凹模轮廓轮廓尺寸包括凹模板的平面尺寸LXB(长X宽)及厚度尺寸H.从凹模外边缘的最短距离称为凹模壁厚C.对于简单对称形状刃口凹模,由于压力中心即对称中心,所以凹模和平面尺寸即可沿刃口型孔向四周扩大一个凹模壁厚来确定,所以:L=l+2C=220+2X62=344 B=840C值可根据资料查得.整体式凹模板的厚度可按如下经验公式估算:H=K1K2=35mm, K1取1,K2根据资料取2.5.由以上算得凹模轮廓尺寸LBH=84035041,查有关国家标准,并无厚度合适,因此我选LB为标准尺寸,得LBH=84035040。凹模材料的选用:材料选用Cr12MoV，孔与孔的校核:校核最小A值为20,以上都能达到要求,因此得以校核.凹模刃口尺寸及其它具体见零件图5-21。后面所附的零件图。设计中,因为压力中心与凹模板的几何中心相差不太,压力中心仍在模柄投影面积,可设他们在同轴线上.图5-2 凹模5.2.2.凸模设计落料凸模刃口部分为异形,又在它里面开孔,装配导正销,为便于凸模和固定板的加工,可通这设计成铆接方式与固定板固定.冲孔凸模采用阶梯结构,设计成铆接方式.凸模的尺寸根据导料板尺寸、卸料板尺寸和安装固定要求尺寸h，取h1520，因为这里的凹模刃口尺寸为4 mm,在范围之内取18mm所以凸模的尺寸为L=18+20+25+2=65mm.凸模材料：参照冲压模具设计与制造选用Cr12MoV.考虑冲孔凸模的直径很小，故需对最小凸模20进行强度和钢度校核：根据表3-26可得：L90d/=(90X20X20)/=50.6mm.L为凸模的允许最大工作尺寸，而设计中，凸模的工作尺寸为6550.6,所以钢度不需要校核。具体零件图如后面所附零件图为准， 5.2.3.选择坚固件及定位零件螺钉规格的选用: 由凹模板的厚度可选用M10,在根据实际要求,查标准选用GB 70-85 M10X60,这里要8个,卸料板的螺钉选用GB 70-85 M8X60,这里要4个。销钉规格的选用: 销钉的公称直径可取与螺钉大径相同或小一个规格,因此根据标准选用GB 119-86 10X60, 选取材料为45钢.根据定位方式及坯料的形状与尺寸,选用合适的标准定位零件.导料板: 根据凹模LXB=840X350,查标准GB2865.5-81,选规格为:长度L=840,宽度B=350,厚度H=12,材料为45#的导料板,即导料板:270X62X12 如图5-10所示:5.2.4.设计和选用卸料与出件零件卸料以卸料板卸料,出件是以凸模往下冲即可,因此不用设计出件零件.固定卸料板的平面外形尺寸一般与凹模板相同,其厚度可取凹模厚度的0.51倍,所以卸料板的LBH=84035040/0.545=84013522.5，本设计中取25厚，卸料板在此仅起卸料作用,凸模与卸料板间的双边间隙一般取0.050.1mm,这里取0.1mm,材料为45#.由以上根据凸模和凹模可设计出卸料板如图5-.选择模架及其它模具零件选择模架:根据GB/T 2851.5-90,由凹模周界840350,及安装要求,选取凹模周界:LB=840350,闭合高度:H=170219,上模座:100042040，下模座:100042045,导柱:38170,导套:5570.由以上可得模架及其零件如图5-14所示.垫板: 垫板的作用是承受并扩散凸模传递的压力,以防止模座被挤压损伤,因此在与模座接触面之间加上一块淬硬磨平的垫板.垫板的外形尺寸与凸模固定板相同,厚度可取310mm,这里设计时,由于压力较大,根据GB2865.2-81选取规格为LXBXH=840X350X10.凸模固定板: 凸模固定板的外形尺寸与凹模的外形尺寸一致,厚度为凹模的0.40.6h,h为凹模的厚度,这里取0.4h,即0.4X45=18mm,根据核准选取板的规格为LXBXH=840X35X18;凸模与凸模固定板的配合为H7/n6,装配可通过2个销钉定位,8个螺钉与上模座连接固定,各形孔的位置尺寸与凹模的保持一致,顶部与凸模铆接,因此必须倒角,由以上可得凸模固定板的零件图如图5-16所示:5.3.压力机的校核5.3.1.公称压力根据公称压力的选取压力机型号为J21-350,它的压力为35002636.293,所以压力不需要校核;5.3.2.滑块行程滑块行程应保证坯料能顺利地放入模具和冲压能顺利地从模具中取出.这里只是材料的厚度t=3.0,导料板的厚度H=12及凸模冲入凹模的最大深度2,即S1=3+12+2=17S=130,所以不需要校核.5.3.3.行程次数行程次数为80/min.因为生产批量为中批量,又是手工送料,不能太快。5.3.4.工作台面的尺寸根据下模座LB=1000X420,且每边留出60100,即L1B1=1200X620,而压力机的工作台面L2B2=1550X880,冲压件和废料从下模漏出。故符合要求;5.3.5.闭合高度 由压力机型号知Hmax=380 M=90 H1=120Hmin=HmaxM=380-90=290(M为闭合高度调节量/mm,H1为垫板厚度/mm)由式(1-24):( HmaxH1)-5H( HminH1)+10,得(380120)-5194(290120)+10即 275194180 ,所以所选压力机合适.第六章、冲压模具零件加工工艺的编制6.1.凹模加工工艺过程表6-1 凹模加工工艺过程工序号工序名称工序内容设备1备料将毛坯锻成850mm360mm45mm2热处理退火3铣铣六面,厚度留单边磨量0.20.3mm铣床4平磨磨厚度到上限尺寸,磨侧基面保证互相垂直平面磨床5钳工划各型孔,螺孔,销孔位置划漏孔轮廓线6钳工加工好凸模,配作冲孔凹模达要求7铣铣漏料孔达要求铣床8钳工钻铰410,钻攻8XM10钻床9热处理淬火,回火,保证HRC606210平磨磨厚度及基面达到要求平面磨床11线切割按图切割各型孔,留0.0050.01单边研量线切割机床12钳工研光各型孔达要求13检验6.2.凸模加工工艺过程 表6-2-1 落料凸模加工工艺过程工序号工序名称工序内容设备1备料将毛坯锻成195mm230mm65mm2热处理退火3铣铣六面,厚度留单边磨量0.20.3mm铣床4平磨磨厚度到上限尺寸,磨侧基面保证互相垂直平面磨床5钳工划刃口轮廓尺寸及螺钉孔位置尺寸6钳工加工好凹模,配作落料凸模达要求7钳工钻孔攻丝钻床8热处理淬火,回火,保证HRC60649线切割按图切割外形,留0.0050.01单边研量线切割机床10钳工磨各配合面达要求11检验表6-2-2 冲孔凸模20加工工艺过程工序号工序名称工序内容设备1备料备料30mm70mm2热处理退火3车外圆车外圆达配合尺寸车床4车工作尺寸车工作尺寸达要求车床5倒角倒角达要求车床6钳工抛光达表面要求7热处理淬火,回火,保证HRC58628钳工磨平上下表面达要求9检验表6-2-3 冲孔凸模45加工工艺过程工序号工序名称工序内容设备1备料备料55mm70mm2热处理退火3车外圆车外圆达配合尺寸车床4车工作尺寸车工作尺寸达要求车床5倒角倒角达要求车床6钳工抛光达表面要求7热处理淬火,回火,保证HRC58628钳工磨平上下表面达要求9检验6.3.卸料板加工工艺过程 表6-3 卸料板加工工艺过程工序号工序名称工序内容设备1备料将毛坯锻成850mm360mm30mm2热处理退火3铣铣六面,厚度留单边磨量0.20.3mm，铣台阶铣床4平磨磨厚度到上限尺寸,磨侧基面保证互相垂直平面磨床5钳工划各型孔,螺孔,销孔位置划漏孔轮廓线6线切割按图切割各型孔,保证双面间隙0.5mm线切割机床7钳工钻沉，攻丝，6-M8钻床8平磨磨厚度及基面见光平面磨床9钳工研光各型孔达要求10检验6.4.凸模固定板加工工艺过程表6-4 凸模固定板加工工艺过程工序号工序名称工序内容设备1备料将毛坯锻成850mm360mm20mm2热处理退火3铣铣六面,厚度留单边磨量0.20.3mm铣床4平磨磨厚度到上限尺寸,磨侧基面保证互相垂直平面磨床5钳工划各型孔,螺孔,销孔位置划漏孔轮廓线6线切割按图切割各型孔,保证配合尺寸线切割机床7钳工钻铰410,钻攻8M10钻床8钳工铆接处倒角9平磨磨厚度及基面见光平面磨床10钳工研光各型孔达要求11检验6.5.上模座加工工艺过程 表6-5 上模座加工工艺过程工序号工序名称工序内容设备1备料取标准上模座2热处理退火4平磨平磨上下平面达要求平面磨床5钳工划螺孔,销孔位置划模柄孔轮廓线6线切割按图切割各型孔,保证配合尺寸线切割机床7钳工钻铰410,钻孔及沉孔,钻床8钳工去毛刺9检验6.6.下模座加工工艺过程表6-6 下模座加工工艺过程工序号工序名称工序内容设备1备料取标准上模座2热处理退火4平磨平磨上下平面达要求平面磨床5钳工划螺孔,销孔位置划线6线切割按图切割各型孔 线切割机床7钳工钻铰410,钻沉孔钻床8钳工去毛刺9检验设计小结此次毕业设计是在学完冲压工艺与模具设计，模具制造工艺和大部分专业课并进行了生产实习的基础上进行的，这次设计使我能够综合运用冲压工艺与模具设计中的基本理论，结合生产中所学的新知识、独立分析和解决工艺问题，初步具备了设计一个中等复杂程度的冷冲压模具的能力。通过分析，拟定设计方案，完成模具结构设计等一系列复杂工作，最终完成此次的设计任务。通过这次设计使我初步具备了设计一个中等复杂程度的冲压模具的工艺规程和掌握运用模具设计的基本原理和方法，同时也学会了熟练运用有关参考资料，图表等基本技能，增强了自我的读图和绘图能力，从而使我在能力方面又提高了一个台阶，为今后从事的工作打下了良好的基础。致 谢 对三年来辛勤教导我的老师和学校致以最崇高的敬意！ 对本次毕业设计指导我和给予我最多的老师表示我最衷心的感谢!毕业设计开始以来，有幸多次聆听老师的教诲。老师以他宽广的知识、高瞻远瞩的学识、在实际生产中所积累的经验。拓宽了我的视野和思维，更为重要的是老师以他对事业孜孜不倦的追求和待人接物谦逊的态度和豁达的胸襟，时刻都在潜移默化地影响着我，这将使我终生受益。参考文献1朱光力主编. 模具设计与制造实训.第1版. 北京：高等教育出版社. 2002. 1341562温松明主编. 互换性与测量技术基础. 第2版. 长沙：湖南大学出版社. 1998. 453冯炳尧 韩泰荣 殷振海 蒋文森编. 模具设计与制造简明手册. 第1版.上海：上海科学技术出版社. 1985. 1 804刘朝儒 彭福荫 高政一主编. 机械制图. 第3版. 北京：高等教育出版社.20015张代东主编. 机械工程材料应用基础. 第1版.北京：机械工业出版社.2001.851036王卫卫主编. 材料成型设备. 第1版.北京：机械工业出版.2004. 47487傅建军主编. 模具制造工艺. 第1版.北京：机械工业出版社.2005. 24258王新华 袁联富主编.冲模结构图册. 第1版. 北京：机械工业出版社. 2003.9中国模具设计大典编委会.中国模具设计大典第2卷.南昌:江西科学技术出版社,2003.10傅建军. 模具制造工艺M.北京:机械工业出版社,2004.11单岩，王蓓，王刚.Moldflow模具分析技术基础.北京：清华大学出版社，2004.9 12王卫卫. 弯曲与塑料成型设备M. 北京:机械工业出版社,2004.13冯开平，左宗义主编.画法几何与机械制图.广州：华南理工大学出版社，2001.9.14R. A. Harris, H. A. Newlyn, R. J. M. Hague and P. M. Dickens, The future direction of stamping dies , Volume 43, Issue 9, July 2003, Pages 879-88715王昆，何小柏，汪信远主编.机械设计、机械设计基础课程设计.北京：高等教育出版社，1996.16开思论坛 17F. Chan, C. K. Law and K. K. Chan, Technical summary sheet metal stamping dies18姜奎华.冲压工艺及模具设计M.北京:机械工业出版社,1998.万战胜.冲压工艺及模具设计M.北京:中国铁道出版社,1995.19陈文亮. 板料成形CAE分析教程.北京:机械工业出版社，2005.20中国机械工程学会塑性工程学会.锻模手册.北京:机械工业出版社，2008. 21自编. 冲模设计课程设计指导书. 广东工业大学，2008. 22自编. 冲模图册. 广东工业大学，2008 23罗益旋主编. 最新冲压新工艺新技术及模具设计实用手册M. 长春: 吉林出版发行集团, 2004年. Int J Adv Manuf Technol (2002) 19:253259 2002 Springer-Verlag London LimitedAn Analysis of Draw-Wall Wrinkling in a Stamping Die DesignF.-K. Chen and Y.-C. LiaoDepartment of Mechanical Engineering, National Taiwan University, Taipei, TaiwanWrinkling that occurs in the stamping of tapered square cupsand stepped rectangular cups is investigated. A commoncharacteristic of these two types of wrinkling is that thewrinkles are found at the draw wall that is relatively unsup-ported. In the stamping of a tapered square cup, the effect ofprocess parameters, such as the die gap and blank-holderforce, on the occurrence of wrinkling is examined using finite-element simulations. The simulation results show that the largerthe die gap, the more severe is the wrinkling, and suchwrinkling cannot be suppressed by increasing the blank-holderforce. In the analysis of wrinkling that occurred in the stampingof a stepped rectangular cup, an actual production part thathas a similar type of geometry was examined. The wrinklesfound at the draw wall are attributed to the unbalancedstretching of the sheet metal between the punch head and thestep edge. An optimum die design for the purpose of eliminatingthe wrinkles is determined using finite-element analysis. Thegood agreement between the simulation results and thoseobserved in the wrinkle-free production part validates theaccuracy of the finite-element analysis, and demonstrates theadvantage of using finite-element analysis for stamping diedesign.Keywords: Draw-wall wrinkle; Stamping die; Stepped rec-tangular cup; Tapered square cups1.IntroductionWrinkling is one of the major defects that occur in the sheetmetal forming process. For both functional and visual reasons,wrinkles are usually not acceptable in a finished part. Thereare three types of wrinkle which frequently occur in the sheetmetal forming process: flange wrinkling, wall wrinkling, andelastic buckling of the undeformed area owing to residualelastic compressive stresses. In the forming operation of stamp-ing a complex shape, draw-wall wrinkling means the occurrenceCorrespondence and offprint requests to: Professor F.-K. Chen, Depart-ment of Mechanical Engineering, National Taiwan University, No. 1Roosevelt Road, Sec. 4, Taipei, Taiwan 10617. E-mail: fkchen?.twof wrinkles in the die cavity. Since the sheet metal in the wallarea is relatively unsupported by the tool, the elimination ofwall wrinkles is more difficult than the suppression of flangewrinkles. It is well known that additional stretching of thematerial in the unsupported wall area may prevent wrinkling,and this can be achieved in practice by increasing the blank-holder force; but the application of excessive tensile stressesleads to failure by tearing. Hence, the blank-holder force mustlie within a narrow range, above that necessary to suppresswrinkles on the one hand, and below that which producesfracture on the other. This narrow range of blank-holder forceis difficult to determine. For wrinkles occurring in the centralarea of a stamped part with a complex shape, a workablerange of blank-holder force does not even exist.In order to examine the mechanics of the formation ofwrinkles, Yoshida et al. 1 developed a test in which a thinplate was non-uniformly stretched along one of its diagonals.They also proposed an approximate theoretical model in whichthe onset of wrinkling is due to elastic buckling resulting fromthe compressive lateral stresses developed in the non-uniformstress field. Yu et al. 2,3 investigated the wrinkling problemboth experimentally and analytically. They found that wrinklingcould occur having two circumferential waves according totheir theoretical analysis, whereas the experimental results indi-cated four to six wrinkles. Narayanasamy and Sowerby 4examined the wrinkling of sheet metal when drawing it througha conical die using flat-bottomed and hemispherical-endedpunches. They also attempted to rank the properties thatappeared to suppress wrinkling.These efforts are focused on the wrinkling problems associa-ted with the forming operations of simple shapes only, suchas a circular cup. In the early 1990s, the successful applicationof the 3D dynamic/explicit finite-element method to the sheet-metal forming process made it possible to analyse the wrinklingproblem involved in stamping complex shapes. In the presentstudy, the 3D finite-element method was employed to analysethe effects of the process parameters on the metal flow causingwrinkles at the draw wall in the stamping of a tapered squarecup, and of a stepped rectangular part.A tapered square cup, as shown in Fig. 1(a), has an inclineddraw wall on each side of the cup, similar to that existing ina conical cup. During the stamping process, the sheet metalon the draw wall is relatively unsupported, and is therefore254F.-K. Chen and Y.-C. LiaoFig. 1. Sketches of (a) a tapered square cup and (b) a steppedrectangular ne to wrinkling. In the present study, the effect of variousprocess parameters on the wrinkling was investigated. In thecase of a stepped rectangular part, as shown in Fig. 1(b),another type of wrinkling is observed. In order to estimate theeffectiveness of the analysis, an actual production part withstepped geometry was examined in the present study. Thecause of the wrinkling was determined using finite-elementanalysis, and an optimum die design was proposed to eliminatethe wrinkles. The die design obtained from finite-element analy-sis was validated by observations on an actual production part.2.Finite-Element ModelThe tooling geometry, including the punch, die and blank-holder,weredesignedusingtheCADprogramPRO/ENGINEER. Both the 3-node and 4-node shell elements wereadopted to generate the mesh systems for the above toolingusing the same CAD program. For the finite-element simul-ation, the tooling is considered to be rigid, and the correspond-ing meshes are used only to define the tooling geometry andFig. 2. Finite-element mesh.are not for stress analysis. The same CAD program using 4-node shell elements was employed to construct the meshsystem for the sheet blank. Figure 2 shows the mesh systemfor the complete set of tooling and the sheet-blank used in thestamping of a tapered square cup. Owing to the symmetricconditions, only a quarter of the square cup is analysed. Inthe simulation, the sheet blank is put on the blank-holder andthe die is moved down to clamp the sheet blank against theblank-holder. The punch is then moved up to draw the sheetmetal into the die cavity.In order to perform an accurate finite-element analysis, theactual stressstrain relationship of the sheet metal is requiredas part of the input data. In the present study, sheet metalwith deep-drawing quality is used in the simulations. A tensiletest has been conducted for the specimens cut along planescoinciding with the rolling direction (0) and at angles of 45and 90 to the rolling direction. The average flow stress ?,calculated from the equation ? ? (?0? 2?45? ?90)/4, for eachmeasured true strain, as shown in Fig. 3, is used for thesimulations for the stampings of the tapered square cup andalso for the stepped rectangular cup.All the simulations performed in the present study were runon an SGI Indigo 2 workstation using the finite-element pro-gram PAMFSTAMP. To complete the set of input data requiredFig. 3. The stressstrain relationship for the sheet metal.Draw-Wall Wrinkling in a Stamping Die Design255for the simulations, the punch speed is set to 10 m s?1and acoefficient of Coulomb friction equal to 0.1 is assumed.3.Wrinkling in a Tapered Square CupA sketch indicating some relevant dimensions of the taperedsquare cup is shown in Fig. 1(a). As seen in Fig. 1(a), thelength of each side of the square punch head (2Wp), the diecavity opening (2Wd), and the drawing height (H) are con-sidered as the crucial dimensions that affect the wrinkling.Half of the difference between the dimensions of the die cavityopening and the punch head is termed the die gap (G) in thepresent study, i.e. G ? Wd? Wp. The extent of the relativelyunsupported sheet metal at the draw wall is presumably dueto the die gap, and the wrinkles are supposed to be suppressedby increasing the blank-holder force. The effects of both thedie gap and the blank-holder force in relation to the occurrenceof wrinkling in the stamping of a tapered square cup areinvestigated in the following sections.3.1Effect of Die GapIn order to examine the effect of die gap on the wrinkling,the stamping of a tapered square cup with three different diegaps of 20 mm, 30 mm, and 50 mm was simulated. In eachsimulation, the die cavity opening is fixed at 200 mm, and thecup is drawn to the same height of 100 mm. The sheet metalused in all three simulations is a 380 mm ? 380 mm squaresheet with thickness of 0.7 mm, the stressstrain curve for thematerial is shown in Fig. 3.The simulation results show that wrinkling occurred in allthree tapered square cups, and the simulated shape of thedrawn cup for a die gap of 50 mm is shown in Fig. 4. It isseen in Fig. 4 that the wrinkling is distributed on the drawwall and is particularly obvious at the corner between adjacentwalls. It is suggested that the wrinkling is due to the largeunsupported area at the draw wall during the stamping process,also, the side length of the punch head and the die cavityFig. 4. Wrinkling in a tapered square cup (G ? 50 mm).opening are different owing to the die gap. The sheet metalstretched between the punch head and the die cavity shoulderbecomes unstable owing to the presence of compressive trans-verse stresses. The unconstrained stretching of the sheet metalunder compression seems to be the main cause for the wrink-ling at the draw wall. In order to compare the results for thethree different die gaps, the ratio ? of the two principal strainsis introduced, ? being ?min/?max, where ?maxand ?minare themajor and the minor principal strains, respectively. Hosfordand Caddell 5 have shown that if the absolute value of ? isgreater than a critical value, wrinkling is supposed to occur,and the larger the absolute value of ?, the greater is thepossibility of wrinkling.The ? values along the cross-section MN at the samedrawing height for the three simulated shapes with differentdie gaps, as marked in Fig. 4, are plotted in Fig. 5. It is notedfrom Fig. 5 that severe wrinkles are located close to the cornerand fewer wrinkles occur in the middle of the draw wall forall three different die gaps. It is also noted that the bigger thedie gap, the larger is the absolute value of ?. Consequently,increasing the die gap will increase the possibility of wrinklingoccurring at the draw wall of the tapered square cup.3.2Effect of the Blank-Holder ForceIt is well known that increasing the blank-holder force canhelp to eliminate wrinkling in the stamping process. In orderto study the effectiveness of increased blank-holder force, thestamping of a tapered square cup with die gap of 50 mm,which is associated with severe wrinkling as stated above, wassimulated with different values of blank-holder force. Theblank-holder force was increased from 100 kN to 600 kN,which yielded a blank-holder pressure of 0.33 MPa and 1.98MPa, respectively. The remaining simulation conditions aremaintained the same as those specified in the previous section.An intermediate blank-holder force of 300 kN was also usedin the simulation.The simulation results show that an increase in the blank-holder force does not help to eliminate the wrinkling thatoccurs at the draw wall. The ? values along the cross-sectionFig. 5. ?-value along the cross-section MN for different die gaps.256F.-K. Chen and Y.-C. LiaoMN, as marked in Fig. 4, are compared with one another forthe stamping processes with blank-holder force of 100 kN and600 kN. The simulation results indicate that the ? values alongthe cross-section MN are almost identical in both cases. Inorder to examine the difference of the wrinkle shape for thetwo different blank-holder forces, five cross-sections of thedraw wall at different heights from the bottom to the line MN, as marked in Fig. 4, are plotted in Fig. 6 for both cases.It is noted from Fig. 6 that the waviness of the cross-sectionsfor both cases is similar. This indicates that the blank-holderforce does not affect the occurrence of wrinkling in the stamp-ing of a tapered square cup, because the formation of wrinklesis mainly due to the large unsupported area at the draw wallwhere large compressive transverse stresses exist. The blank-holder force has no influence on the instability mode of thematerial between the punch head and the die cavity shoulder.4.Stepped Rectangular CupIn the stamping of a stepped rectangular cup, wrinkling occursat the draw wall even though the die gaps are not so significant.Figure 1(b) shows a sketch of a punch shape used for stampinga stepped rectangular cup in which the draw wall C is followedby a step DE. An actual production part that has this typeof geometry was examined in the present study. The materialused for this production part was 0.7 mm thick, and the stressstrain relation obtained from tensile tests is shown in Fig. 3.The procedure in the press shop for the production of thisstamping part consists of deep drawing followed by trimming.In the deep drawing process, no draw bead is employed onthe die surface to facilitate the metal flow. However, owingto the small punch corner radius and complex geometry, asplit occurred at the top edge of the punch and wrinkles werefound to occur at the draw wall of the actual production part,as shown in Fig. 7. It is seen from Fig. 7 that wrinkles aredistributed on the draw wall, but are more severe at the corneredges of the step, as marked by AD and BE in Fig. 1(b).The metal is torn apart along the whole top edge of the punch,as shown in Fig. 7, to form a split.In order to provide a further understanding of the defor-mation of the sheet-blank during the stamping process, a finite-element analysis was conducted. The finite-element simulationwas first performed for the original design. The simulatedshape of the part is shown from Fig. 8. It is noted from Fig.8 that the mesh at the top edge of the part is stretchedFig. 6. Cross-section lines at different heights of the draw wall fordifferent blank-holder forces. (a) 100 kN. (b) 600 kN.Fig. 7. Split and wrinkles in the production part.Fig. 8. Simulated shape for the production part with split and wrinkles.significantly, and that wrinkles are distributed at the draw wall,similar to those observed in the actual part.The small punch radius, such as the radius along the edgeAB, and the radius of the punch corner A, as marked in Fig.1(b), are considered to be the major reasons for the wallbreakage. However, according to the results of the finite-element analysis, splitting can be avoided by increasing theabove-mentioned radii. This concept was validated by theactual production part manufactured with larger corner radii.Several attempts were also made to eliminate the wrinkling.First, the blank-holder force was increased to twice the originalvalue. However, just as for the results obtained in the previoussection for the drawing of tapered square cup, the effect ofblank-holder force on the elimination of wrinkling was notfound to be significant. The same results are also obtained byincreasing the friction or increasing the blank size. We concludethat this kind of wrinkling cannot be suppressed by increasingthe stretching force.Since wrinkles are formed because of excessive metal flowin certain regions, where the sheet is subjected to large com-pressive stresses, a straightforward method of eliminating thewrinkles is to add drawbars in the wrinkled area to absorb theredundant material. The drawbars should be added parallel tothe direction of the wrinkles so that the redundant metal canbe absorbed effectively. Based on this concept, two drawbarsare added to the adjacent walls, as shown in Fig. 9, to absorbthe excessive material. The simulation results show that theDraw-Wall Wrinkling in a Stamping Die Design257Fig. 9. Drawbars added to the draw walls.wrinkles at the corner of the step are absorbed by the drawbarsas expected, however some wrinkles still appear at the remain-ing wall. This indicates the need to put more drawbars at thedraw wall to absorb all the excess material. This is, however,not permissible from considerations of the part design.One of the advantages of using finite-element analysis forthe stamping process is that the deformed shape of the sheetblank can be monitored throughout the stamping process, whichis not possible in the actual production process. A close lookat the metal flow during the stamping process reveals that thesheet blank is first drawn into the die cavity by the punchhead and the wrinkles are not formed until the sheet blanktouches the step edge DE marked in Fig. 1(b). The wrinkledshape is shown in Fig. 10. This provides valuable informationfor a possible modification of die design.An initial surmise for the cause of the occurrence of wrink-ling is the uneven stretch of the sheet metal between the punchcorner radius A and the step corner radius D, as indicated inFig. 1(b). Therefore a modification of die design was carriedout in which the step corner was cut off, as shown in Fig.11, so that the stretch condition is changed favourably, whichallows more stretch to be applied by increasing the step edges.However, wrinkles were still found at the draw wall of thecup. This result implies that wrinkles are introduced becauseof the uneven stretch between the whole punch head edge andthe whole step edge, not merely between the punch corner andFig. 10. Wrinkle formed when the sheet blank touches the steppededge.Fig. 11. Cut-off of the stepped corner.the step corner. In order to verify this idea, two modificationsof the die design were suggested: one is to cut the whole stepoff, and the other is to add one more drawing operation, thatis, to draw the desired shape using two drawing operations.The simulated shape for the former method is shown in Fig.12. Since the lower step is cut off, the drawing process isquite similar to that of a rectangular cup drawing, as shown inFig. 12. It is seen in Fig. 12 that the wrinkles were eliminated.In the two-operation drawing process, the sheet blank wasfirst drawn to the deeper step, as shown in Fig. 13(a). Sub-sequently, the lower step was formed in the second drawingoperation, and the desired shape was then obtained, as shownin Fig. 13(b). It is seen clearly in Fig. 13(b) that the steppedrectangular cup can be manufactured without wrinkling, by atwo-operation drawing process. It should also be noted that inthe two-operation drawing process, if an opposite sequence isapplied, that is, the lower step is formed first and is followedby the drawing of the deeper step, the edge of the deeper step,as shown by AB in Fig. 1(b), is prone to tearing because themetal cannot easily flow over the lower step into the die cavity.The finite-element simulations have indicated that the diedesign for stamping the desired stepped rectangular cup usingone single draw operation is barely achieved. However, themanufacturing cost is expected to be much higher for the two-operation drawing process owing to the additional die cost andoperation cost. In order to maintain a lower manufacturingcost, the part design engineer made suitable shape changes,and modified the die design according to the finite-elementFig. 12. Simulated shape for the modified die design.258F.-K. Chen and Y.-C. LiaoFig. 13. (a) First operation and (b) second operation in the two-operation drawing process.simulation result to cut off the lower step, as shown in Fig.12. With the modified die design, the actual stamping die forproduction was manufactured and the production part wasfound to be free from wrinkles, a