三孔矩形垫板的落料冲孔倒装复合模具设计-冲压模含11张CAD图.zip
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中期汇报表学生姓名XX专 业XX学 号XX设计（论文）题目落料冲孔倒装复合模的设计毕业设计（论文）前期工作小结本文设计了落料冲孔倒装复合模，这属于冲压工艺的模具设计的一种。通过对工件结构的分析，确定落料和冲压工序的先后。随后在设计了三种设计方案，在经过对比的情况下，选择了落料冲孔倒装复合模。在确定了模具的设计方案之后，经过分析，确定模具的各个装置结构。在选用了合适的排样方法后，通过计算，算出模具的压力中心与凸凹模的刃口尺寸。利用计算的数值来选用适当的压力机及相应的模架，以及选用合适的装配方案。在研究过程中出现的问题：1、在设计过程中找合适的零件和，经常遇到找不到合适的参考文献；2、由于长期没有使用CAD等画图软件，操作起来十分生疏。已完成的工作及进展：1、学会透过校园网站检索课题相关的文章，查找并阅读相关文献，了解课题的研究背景与好处；2、制定出了可行的设计方案；3、对部分关键零件进行了计算。指导教师意见该生毕业设计进度符合毕业任务书要求，应能按时按量完成毕业设计。签名： 2018 年 4 月 21 日中期情况检查表 学院名称： 机电工程学院 检查日期： 2018 年 4 月 23 日学生姓名XX专 业XX指导教师XX设计（论文）题目落料冲孔倒装复合模的设计工作进度情况通过对工件结构的分析，确定落料和冲压工序的先后。随后在设计了三种设计方案，在经过对比的情况下，选择了落料冲孔倒装复合模。在确定了模具的设计方案之后，经过分析，确定模具的各个装置结构。在选用了合适的排样方法后，通过计算，算出模具的压力中心与凸凹模的刃口尺寸。利用计算的数值来选用适当的压力机及相应的模架，以及选用合适的装配方案。 是否符合任务书要求进度是 能否按期完成任务能 工作态度情况(态度、纪律、出勤、主动接受指导等)态度认真，按时出勤，能够积极主动的自主设计，不明白的也会主动询问老师。质量评价(针对已完成的部分)计算部分符合设计要求，图纸基本可以表达结构特点。 存在问题和解决办法说明书语言不够严谨，图纸图线标注部分略有不标准的地方，后期根据毕业设计要求进行改正。 检查人签名 教学院长签名 论文答辩 Themolddesignoftheblankingandback upcompositedie姓名XXX班级XXX学号XXX指导老师XX 徐州工程学院 落料冲孔倒装复合模的设计 背景和意义 模具在发展国民经济中起着重要的作用 研究和发展模具技术 对于促进国民经济的发展具有特别重要的意义 模具技术已成为衡量一个国家产品制造技术的重要标志之一 随着工业生产的迅速发展 模具工业在国民经济中的地位日益提高 并在国民经济发展过程中发挥越来越大的作用 设计方案的确定在比对了级进模 倒装复合模和正装复合模三种方案的情况下 选择了落料冲孔倒装复合模 模具装置通过分析确定模具的定位装置 推出件装置 卸出料装置 排样方式在考虑到实际工况及成本问题后选取合适的排样方式 01 02 03 研究内容 主体部分的计算通过计算得出模具的冲裁力 卸料力 再通过计算分析 确定模具的压力中心 冲压工艺计算通过分析计算得出凹凸模的具体尺寸及各个重要零部件的尺寸 计算闭合高度等 模具的装配与调试在完成设计后对模具进行装配及调试 04 05 06 研究内容 模具设计方案的分析 结构尺寸精度合理性材料材质 级进模倒装复合模正装复合模 1 工艺性分析 2 设计方案的选择 模具设计方案的分析 结构尺寸精度合理性材料材质 级进模倒装复合模正装复合模 1 工艺性分析 2 设计方案的选择 冲压工艺的计算 小凸模的大小计算 凹模的大小计算 结论1 设计方案选为落料冲孔倒装复合模 2 模具主要由小凸模 凹模 上下固定板 模架等组成 3 选用J21 200压力机 致谢在本次论文设计过程中 感谢田晶老师从选题 构思到最后定稿的各个环节给予细心指引与教导 使我能够最终完成这次的毕业设计 在大学四年的时间里 还得到了其他众多老师的支持和帮忙 在此 谨向老师们致以衷心的感谢和崇高的敬意 最后 我要向百忙之中抽时间对本文进行审阅 评判和参与本人论文答辩的各位老师表示由衷的感谢 THANKYOU 课题申报表指导教师XX职称XX教研室XX申报课题名称落料冲孔倒装复合模的设计课题类型工程设计类课题来源B.社会生产实践课题简介冲压模具是冲压生产必不可少的工艺装备，是技术密集型产品。冲压件的质量、生产效率以及生产成本等，与模具设计和制造有直接关系。模具设计与制造技术水平的高低，是衡量一个国家产品制造水平高低的重要标志之一。根据精度要求、生产批量、冲裁工艺等要求，采用落料冲孔倒装复合模进行加工，且一次冲压成型。课题要求（包括所具备的条件）计算排样、冲压力，确定模具压力中心，并计算凹凸模刃口尺寸；凹模与凸模的结构设计；模具总体设计与部分零件设计；用AutoCAD软件绘制落料冲孔倒装复合模的装配图和零件图，要求视图完整。参考文献至少15篇，其中有2篇以上外文文献。课题工作量要求进行加工工件的工艺计算和凹凸模的结构设计；完成落料冲孔倒装复合模的装配图与零件图，其中装配图1张，零件图若干，图纸满足本科毕业设计要求。完成1.5万字的毕业论文及4000汉字的英译汉。教研室审定意见 同意教研室主任签字：学 院审定意见同意 教学院长签字： 任 务 书 1毕业设计的背景：冲压模具是冲压生产必不可少的工艺装备，是技术密集型产品。冲压件的质量、生产效率以及生产成本等，与模具设计和制造有直接关系。模具设计与制造技术水平的高低，是衡量一个国家产品制造水平高低的重要标志之一，在很大程度上决定着产品的质量、效益和新产品的开发能力。根据精度要求、生产批量、冲裁工艺等要求，采用落料冲孔复合模进行加工，且一次冲压成型。落料冲孔复合模因其在生产过程中操作简单并可有效节约材料而普遍应用于冲压生产中，所以对落料冲压复合模的设计对生产实际有较大的影响。2毕业设计(论文)的内容和要求：计算排样、冲压力，确定模具压力中心，并计算凹凸模刃口尺寸。凹模与凸模的结构设计，以及模具总体设计与部分零件设计。完成落料冲孔复合模的装配图与零件图。用计算机画图，要求视图完整，其中装配图一张，零件图若干，符合本科毕业设计要求。参考文献至少15篇以上，另外有2篇以上外文文献。完成至少1万5千字的论文，并完成至少4000汉字的英文翻译。3主要参考文献：1傅建等.模具制造工艺学M.北京:机械工业出版社,2004.2高为国.模具材料M.北京:机械工业出版社,2004. 3黄志明.冲压模具设计的重点分析J.现代工业经济和信息化. 2015(15)4吴宗泽.机械设计实用手册M. 北京:机械工业出版社,2002.5冲模设计手册编写组.冲模设计手册M.北京:机械工业出版社,19996郑玲.板料冲压成形仿真技术的应用研究J.机电信息. 2013(09)7刘航.模具技术经济分析M. 北京:机械工业出版社,2002.89-100.8王孝培.冲压手册第三版M.北京:机械工业出版社,20129王伯平,互换性与测量技术基础第二版M.北京:机械工程出版社,200910邢邦圣.机械制图与计算机绘图M.北京:化学工业出版社, 2011.11叶玉驹,焦永和,张彤.机械制图手册5版M.北京；机械工业出版社,2012.6（2015.11重印）12成大先.机械设计手册J.第5卷.北京:化学工业民出版社,2008,3.13苏芳,黄清海.融合新技术的冲压模具设计与制造课程教学创新研究J.模具工业. 2017(01)14 Ral Palma,Oscar Corcho,Asuncin Gmez-Prez,Peter Haase. A holistic approach to collaborative ontology development based on change managementJ . Web Semantics: Science, Services and Agents on the World Wide Web . 2011 (3)15A.B.Shapiro.Using LS-DYNA for Hot StampingJ. 7thEuropean LS-DYNAConference . 20094毕业设计(论文)进度计划(以周为单位)：18年第1、2周 毕业实习，学生提交实习报告、开题报告18年第3、4周 与指导老师进行讨论，确定最终设计方案18年第5、6周 计算排样、冲压力，确定模具压力中心，并计算凹凸模刃口尺寸；18年第7、8周 凹模与凸模的结构设计,模具总体设计与部分零件设计18年第911周 绘制装配图和主要零件图，完成毕业设计论文。18年第12周 提交毕业设计材料18年第13周 答辩教研室审查意见：同意教研室主任签名： 年 月 日学院审查意见： 同意教学院长签名： 年 月 日开题报告课题名称落料冲孔倒装复合模的设计课题来源B.社会生产实践课题类型工程设计类1选题的背景及意义：进入新世纪以来，我国机械行业飞速发展。模具作为机械生产不可或缺的一部分，也得到了飞速的发展。研究与发展模具工艺，对于国家机械行业的发展具有重要意义。模具技术也已成为衡量一个国家工业水平的一个重要标志。随着模具工艺的飞速发展，我国的工业水平会不断提高，机械行业在国民经济中的地位越来越高，所发挥的作用也会越来越大。2研究内容拟解决的主要问题：（1） 冲裁工艺方案的确定，参考收集的资料，提出不同的方案，通过对单工序冲裁、复合冲擦、级进冲裁进行分析，选择比较优化的倒装复合冲裁；（2） 模具结构形式的选择，根据有冲裁工艺方案，采用倒装式复合模。（3） 通过对落料力、冲孔力、卸料力、推件力，得出冲床的总压力，初选压力机。（4）冲压工艺的计算：通过对落料力、冲孔力、卸料力、推件力，得出冲床的总压力，初选压力机。根据零件与冲压力查表计算出凹凸模的刃口尺寸。（5）通过对冲压工艺的计算与分析完成主要零部件的设计，选用模架及其他零部件。3研究方法技术路线： 主要研究方法：依据课题任务，进行相关资料收集、加工、整理和正确使用工具书，对冲压模具的结构特点和加工工艺进行研究，在此基础上，对零件工艺性进行分析，并确定工艺方案。进行零件工艺计算（排样计算、冲压力计算、模具压力中心的确定以及凹凸模刃口尺寸的计算）。对凹模、凸模以及凹凸模的结构进行设计，最后进行模具的总体设计和零部件的设计。4研究的总体安排和进度计划：第1、2周：毕业实习，提交实习报告、毕业设计开题报告第3、4周：确定模具的总体设计方案第5周：确定零件的加工方法第6周：数据计算第7周：外文文献的翻译第8、9周：绘制装配图、零件图第10、11周：完成毕业设计论文第12周：提交毕业材料 第13周：毕业答辩5主要参考文献： 1傅建等.模具制造工艺学M.北京:机械工业出版社,2004.2高为国.模具材料M.北京:机械工业出版社,2004. 3黄志明.冲压模具设计的重点分析J.现代工业经济和信息化. 2015(15)4吴宗泽.机械设计实用手册M. 北京:机械工业出版社,2002.5冲模设计手册编写组.冲模设计手册M.北京:机械工业出版社,19996郑玲.板料冲压成形仿真技术的应用研究J.机电信息. 2013(09)7刘航.模具技术经济分析M. 北京:机械工业出版社,2002.89-100.8王孝培.冲压手册第三版M.北京:机械工业出版社,20129王伯平,互换性与测量技术基础第二版M.北京:机械工程出版社,200910邢邦圣.机械制图与计算机绘图M.北京:化学工业出版社, 2011.11叶玉驹,焦永和,张彤.机械制图手册5版M.北京；机械工业出版社,2012.6（2015.11重印）12成大先.机械设计手册J.第5卷.北京:化学工业民出版社,2008,3.13苏芳,黄清海.融合新技术的冲压模具设计与制造课程教学创新研究J.模具工业. 2017(01)14 Ral Palma,Oscar Corcho,Asuncin Gmez-Prez,Peter Haase. A holistic approach to collaborative ontology development based on change managementJ . Web Semantics: Science, Services and Agents on the World Wide Web . 2011 (3)15A.B.Shapiro.Using LS-DYNA for Hot StampingJ. 7thEuropean LS-DYNAConference . 2009指导教师意见：该生拟进行落料冲孔倒装复合模的设计，前期对该领域的研究进展进行了较为详尽的了解。在此基础上，提出了该研究的主要问题，研究的技术路线可行。预期可按计划完成毕业设计的研究工作，同意选题。 指导教师签名： 年 月 日教研室意见：同意开题 教研室主任签名： 年 月 日学院意见： 同意开题教学院长签名： 年 月 日指导记录第一次指导记录： 第一次指导，田老师给我们的毕业设计整体的进度进行了细致的安排。给我点明了毕业设计的思路及设计方向。 指导地点 XX1 2018年3月5 日第二次指导记录： 对我个人的设计进行了细致的规划，并向我推荐了几篇参考文献。给我划分了各阶段的设计任务，指导我完成了开题报告。指导地点 XX1 2018年3月12日第三次指导记录： 老师对我摘要部分的英文翻译进行了检查，指出了其中的语法错误，并对我设计方案的选择提出了指导。 指导地点 XX1 2018年3月19日第四次指导记录： 田老师在审阅过我已经完成部分内容后，对我模具中重要结构部分进行了指导。向我解释了这些部件的具体作用及意义。 指导地点 XX1 2018年3月26日 第五次指导记录： 老师在检查过我的主体设计部分之后，对我刃口尺寸的计算部分进行了改正。并对我接下来的模具结构的选择提出了一些意见。 指导地点 XX1 2018年4月2日第六次指导记录： 在我完成毕业设计中装配部分之后，老师对我的装配部分进行了细微的修改。并向我推荐了几篇外文翻译让我进行选择。指导地点 XX1 2018年4月9日第七次指导记录： 设计说明书初稿完成，老师对我设计说明书进行第一次的通篇审阅，删除了不必要的部分。并对我说明书的格式提出了修改意见。指导地点 XX1 2018年4月16日第八次指导记录： 在我完成外文翻译之后，老师对我的翻译进行审阅，修改了其中语句或逻辑不通顺的语句。督促我开始进行图纸的绘制。 指导地点 XX1 2018年4月23日 第九次指导记录： 在我完成装配图的草图后，老师对我图纸上错误的部分进行了修改，并指导我进行细致的指导，指导我完成了装配图的绘制。 指导地点 XX1 2018年5月2日 第十次指导记录： 在我完成部分零件图的绘制后，老师对我图幅的选择及比例的选择提供了一些意见。指导我完成了中期汇报。 指导地点 XX1 2018年5月9日 第十一次指导记录： 在我完成了所有图纸的绘制之后，老师对我所有的图纸进行了审核，指出其中错误或者不合理的地方。 指导地点 XX1 2018年 5月14日 第十二次指导记录： 田老师对我的毕业设计进行了最后整体的检查，对毕业设计说明书、外文翻译、附件及图纸标注问题进行详细的批注。 指导地点 XX1 2018年5月21日 第十三次指导记录： 答辩前最后一次指导，田老师最后关于答辩的形式及答辩方法与技巧对我进行了指导，以便于我顺利通过毕业答辩。 指导地点 XX1 2018年5月27日 第十四次指导记录： 指导地点 年 月 日 第十五次指导记录： 指导地点 年 月 日 指导教师评阅表学院： 机电工程学院 专业： XX 学生： XX 学号：XX题目： 落料冲孔倒装复合模的设计 评价项目评价要素成绩评定优良中及格不及格工作态度工作态度认真，按时出勤能按规定进度完成设计任务选题质量选题方向和范围选题难易度选题理论意义和实际应用价值能力水平查阅和应用文献资料能力综合运用知识能力研究方法与手段实验技能和实践能力创新意识设计论文质量内容与写作结构与水平规范化程度成果与成效指导教师意见建议成绩80是否同意参加答辩同意评语： 该生进行了 落料冲孔倒装复合模的设计，并绘制了该模具的装配图和零件图。论文选题符合专业培养目标，题目有难度，工作量较大。选题具有较好的实践指导意义。该生查阅文献资料能力较强，能较好的收集关于课题的相关资料，设计过程中能综合运用所学知识进行设计分析，综合运用知识能力较强。文章篇幅符合规定，内容较为完整，层次结构安排科学，主要观点突出，设计图纸格式规范。设计工作量符合毕业设计要求。同意答辩。指导教师签名：2018年 5月 22日 评阅教师评阅表学院： 机电工程学院 专业： XX 学生： XX 学号： XX 题目： 落料冲孔倒装复合模的设计 评价项目评价要素成绩评定优良中及格不及格选题质量选题方向和范围选题难易度选题理论意义和实际应用价值能力水平查阅和应用文献资料能力综合运用知识能力研究方法与手段实验技能和实践能力创新意识设计论文质量内容与写作结构与水平规范化程度成果与成效评阅教师意见建议成绩80 是否同意参加答辩同意 评语：图纸、说明书工作量达到毕业设计要求，同意参加答辩！ 评阅教师签名：2018年 5 月 24 日 答辩及综合成绩评定表学 院 机电工程学院专 业XX 学生姓名XX 学 号 XX指导教师XX 设计论文题 目 XX答辩时间 2018年5月 28 日 16时 0分至 16 时15分答辩地点教3C501 答辩小组成 员姓名职称答辩记录提问人提问主要内容学生回答摘要 陈 韩 代 1.装配图上零件有两处零件解释他们的名称及作用。 2.模具设计注意事项，结合本设计说明。 3.凸模的公差要求，说明理由。 1.导柱与导套，组成导向装置，保证动定模对合。2.强制回位机构，推出件装置，卸料口。3.尽可能减少进模范围，标注危险范围充分安全保护装置。答辩记录人签名：答辩小组意见答辩评语：该同学答辩时，自述思路清晰，语言流利。设计方案合理、论文结构正确、图面质量好、实验数据和结论可靠。能提出正确合理的设计依据，能熟练应用所学基础理论和基本技能，回答主要问题准确、深入。基本概念清晰、基础理论掌握牢固，掌握知识全面。 答辩成绩：88 答辩小组组长签名：综合成绩评定指导教师评定成绩评阅教师评定成绩答辩成绩综合评定成绩80808883.2答辩委员会主任签名： 年 月 日 15ELSEVIER Journal of Materials Processing Technology 55 (1995) 408-416 Materials Processing Technology Analysis of die designs for the stamping of an automobile rear floor panel Fuh-Kuo Chen*, Jia-Hong Liu Department of Mechanical Engineering, National Taiwan Universi, Taipei, Taiwan, ROC Received 10 October 1994 Industrial summary The stamping process of manufacturing a one-piece rear floor panel of a passenger car has been investigated in the present study. An analysis of the original die design, in which a split defect occurred at the drawn-cup wall, was performed using circle-grid analysis as well as the 3-D finite-element method. The split defect is due to the large area of sheet metal under the blank-holder that limits the flow of the metal towards the cup area. An optimum die design, which consists of a separate die face and a wedge mechanism mounted in the lower die frame, was proposed to provide additional metal for the cup area and to eliminate the split defect without adding an extra operation. This optimum die design was validated by the results of circle-grid analysis performed for the first and second draw operations and also by the good-quality panels produced. Keywords: Stamping dies; Rear floor panel; Splits; Circle-grid analysis. 1. Introduction Splits are amongst the major defects occurring com- monly in the stamping process. A lot of research effort has been made to investigate the causes of and solutions to the split problem during the last few decades 1-4, the methods used including forming-limit analysis and the finite-element method. Since Keeler and Backofen 5- first introduced the concept of forming-limit diagrams (FLDs) in 1963, they have been used widely in the ana- lysis of sheet metal forming in press shops. The FLDs indicate the strains which lead to failure and thus provide a useful tool to determine if the forming process is likely to be prone to splitting, whilst the finite-element method can calculate the strain distributions in the stamped parts accurately and thus predict if the split defect is likely to occur. In general, the solution to problems of splitting is to provide more metal to the critical area before the major drawing process starts. This can be achieved either by decreasing the blank-holder pressure or improving the lubrication conditions, but the most straight-forward method is to add an extra operation solely for the pur- pose of feeding more metal into the critical area. * Corresponding author. 0924-0136/96/$15.00 1996 Elsevier Science S.A. All rights reserved SSDI 0924-0136(95)02038-N However, the extra operation increases the production cost by adding one more set of dies and additional man-power; and hence in reality, it should be avoided. In the present study, an optimum die design in which a separate die face and a wedge mechanism mounted in the lower die frame is proposed to eliminate the occur- rence of a split-defect in the stamping process for a one- piece floor panel of a passenger car. The special die face and wedge mechanism were designed to provide addi- tional metal for the critical area where the split defect occurred, without adding an extra operation. Both circle- grid analysis and 3-D finite-element simulations were performed to analyze this split defect. 2. Problem description The common design for a rear floor panel of a passen- ger car is usually a two-piece type, namely, welding two stamped pieces together, as shown in Fig. 1. The two- piece type design is chosen mainly due to the difficulty encountered in stamping a one-piece rear floor panel, in which a split tends to take place at the wall of the deeply drawn cup used for storing the spare tire, as shown in Fig. 2. The occurrence of the split is attributed to the substantial distance between the cup wall and one side of the blank-holder, as shown by line A-B in Fig. 3, that F.-K. Chen, J.-H. Liu / Journal of Materials Processing Technology 55 (1995) 408 416 409 ) Fig. 1. A two-piece rear floor panel. split Fig. 2. A split occurring at the cup wall. Fig. 3. The location of the drawn cup in the sheet-blank. restricts the metal under the blank-holder from flowing into the cup area. Whilst in the two-piece design this distance is much shorter and sufficient metal can flow easily into the cup to prevent the edge of the cup from splitting, due to cost-effective considerations, a one-piece rear floor panel is always desired, so that the split prob- lem must therefore be overcome. The original procedure in the press shop for the pro- duction of the one-piece rear floor panel consists of four operations: first draw, second draw, trimming, and flang- ing. The first-draw operation was designed only to pro- duce a cup shape, as shown in Fig. 3. As tor the ribs around the cup, these were formed in the second-draw operation. Like most stamping processes, the main defor- mation of the rear floor panel is completed in the first- draw operation. The conventional draw process allows the punch to pull more metal into the die cavity from the blank-holder. To facilitate metal-flow, no draw beads were employed on the blank-holder surface. However, due to the large draw depth and the geometric difficulty mentioned above, a split was still found at the cup wall near the bottom after the first-draw operation, as shown in Fig. 2. The location of the split defect indicates that the considerable distance between one side of the cup wall and the blank-holder does prevent the metal from flow- ing towards the cup. Some efforts have been made to help the metal to flow toward the cup area. The, attempt of decreasing the blank-holder pressure led to more wrinkles at the root of the cup area but without eliminat- ing the split. Improvement of the sheet metal quality was also proven to be in vain. Extreme care taken with the lubrication conditions can ease the split problem: how- ever, this is not cost-effective for the process of mass production. Also the large quantity of lubrication oil used in the stamping process may pollute the shop floor. Hence, the most efficient way left to solve this problem is to provide more metal for the cup area before the punch starts to form the cup. To achieve this end, modification of the blank-holder surface to form a better binder-wrap shape which provides more metal around the cup area was considered. The binder-wrap is the deformed shape of the sheet-blank at the closure of the blank-holders. However, due to the same geometrical reason, i.e. the considerable distance between the cup and one side of the blank-holder, the optimum blank-holder surface is not easy to obtain. Finally, a separate die face designed for the first-draw operation aided by a special wedge mechanism mounted in the lower die frame provided more metal for the cup area and enabled the production of sound prod- ucts without split defects. 3. Analysis of the original design The problem of splitting is usually related to the strain distribution in the critical area. The strain distribution in any cross section of the formed part is determined by two factors: one is the amount of metal-flow resulting from draw-in over the blank-holder; the other is the amount of stretch created by the contacts between the punch and the die 6. To quantify the effect of the tooling geometry on the metal flow, the original design was analyzed by circle-grid analysis (CGA) and the finite-element method (FEM). 410 F.-K. Chen, J.-H. Liu / Journal of Materials Processing Technology 55 (1995) 408-416 0.5 0.4 0.3 0.2 0.1 TRUE STRESS(GPa) 0 0.1 0.2 0.3 TRUE STRAIN 0.4 0.5 Fig. 4. The stress-strain curve for the sheet-blank. 3.1. Circle-grid analysis Circle grid analysis has been used widely in the press shop to measure the strain distributions and thus to enable an analysis of the formability of the sheet metal by plotting the measured strains on the forming-limit dia- gram. The circle grids have a major advantage over the other types of grid, such as square grids, since they do not have any preferred orientations. This advantage lies in that the deformation of the circles will result in ellipses, the two principal directions being displayed clearly by the major and minor axes. The magnitudes of the princi- pal strains can then be calculated from the measurements of the lengths of the major and minor axes. By plotting these measured major and minor strains on the forming limit diagram, the severity of areas of a formed part can be evaluated. In the present study, a production floor-panel made using the original die design was first analyzed with circle-grid analysis. The steel sheet used for production is 0.7 mm thick and of DDQ quality, with material proper- ties as shown in Fig. 4. The corresponding forming-limit diagram for this material provided by the steel supplier is shown by the solid curve in Fig. 5. Any area of a formed part which is deformed with the strains located on or close to this curve will tend to split. In practice, the forming-limit curve shifted down by 10%, as shown by the dashed line in Fig. 5, is used as the design curve. The area above the forming limit curve is called the failure zone; the area between the forming-limit curve and the design curve is termed the marginal zone; and the area below the design curve is named the safe zone. In general, the strain distributions in any area of a formed part should fall in the safe zone to make the stamping process stable, a stamping process being said to be stable if it is less sensitive to process variations. Before being stamped, the critical area of the sheet- blank was imprinted with 5-mm diameter circles with 6-mm spacing between their centres. To imprint the circles the critical area of the sheet-blank was first cleaned using a special cleaner, then a stencil with the correct grid pattern was placed in position on the part. Using the electrolyte as conductor, the area covered by the stencil was marked with the grid pattern by an etching process. To prevent the marked area from rust- ing, a piece of cloth saturated with cleaner was used to wipe off excess electrolyte and residual oxides in the marks. After being stamped, a split was found on the cup wall near to the top, as shown in Fig. 2. The major and minor strains of the deformed circles around the split, as shown in Fig. 6, were measured and plotted on the forming limit diagram, as shown in Fig. 7. As can be seen in this figure, the measured strains are either above or close to the F.-K. Chen, J.-H. Liu /Journal of Materials Processing Technology. 55 (1995) 408-416 411 90 85 80 75 70 65 55 # 50 45 _ 40 0 35 0 3r 30 25 Failure zone fe zone 20 15 10 5 -30-25-20-15-10-5 0 5 10 15 20 25 30 35 40 Minor Strain (%) Fig. 5. The forming-limit diagram for 0.7 mm DDQ steel sheet. 90 85 80 75 70 65 6o 55 r- _ 5O -,- 45 40 . 35 30 25 20 15 10 5 J -30-25-20-15-10 -5 0 J I I ! I I 5 10 15 20 25 30 35 40 Minor Strain (%) Fig. 7. Measured strains around the split. Fig. 6. Deformed circles on the sheet-blank. forming-limit curve, and the failure is obviously due to stretching, since both the major and minor strains are positive. It is also noted that the strains are very close to the plane-strain failure mode, i.e., close to the axis on which the minor strain is zero. The results of the circle-grid analysis indicate that the original design is very unstable. The FLD also indicates that the major strain is too large: this is consistent with the present authors opinion that the considerable dis- tance between the cup and one side of the blank-holder limits the flow of metal towards the cup area, resulting in the large strains. As discussed in the previous sections, the most effective method of decreasing the major strain is to provide more metal for the cup area. 3.2. Finite element analysis To help further understanding of the deformation of the sheet-blank during the stamping process, a 3-D finite- element analysis was performed for the first-draw opera- tion of the original design. The explicit finite-element code PAM-STAMP, which is capable of handling any arbitrary 3-D die shapes, was used to conduct the simula- tions. Since the 3-D die geometries, including the punch, the die cavity, the blank-holder and the draw beads, are not simplified, the finite-element program is able to simu- late the actual production processes more accurately. In order to describe the geometry of the die compo- nents, a commercial CAD program was used to construct the surface models for these components. The mesh sys- tems required by PAM-STAMP as the input data for the die geometries were then generated by the same commer- cial CAD program, as shown in Fig. 8. In earlier periods, it was very difficult, if not impossible, to generate the mesh system for a complicate 3-D die shape, such as the stamping dies. However, as CAD systems are being used with increasing popularity in the die and mould industry, the above procedures to generate the mesh systems for the die geometries become trivial. Since the PAM- STAMP code treats the die components as rigid bodies, the mesh systems are used only to describe the geometries 412 F.-K. Chen, J.-H. Liu / Journal of Materials Processing Technology 55 (1995) 408-416 blank holder sheet-blank punch Fig. 8. Mesh system for the original die design. of these components and not for stress analysis. In the present investigation, a mixture of 3-node triangular and 4-node rectangular elements is used to construct the mesh systems. The mesh system for the sheet-blank is also shown in Fig. 8. As seen in this figure, the mesh density is much higher in the cup area than elsewhere, since the cup area is the location where splitting occurs. The numbers of elements used in the analysis are sum- marized as follows: die: 9,910; punch: 5,499; blank-holder: 4,411; sheet: 4,891; total: 24,711. The material properties used for the finite-element analysis are the same as those given in the previous section, the other operational conditions being: blank- holder pressure: 57 kPa; punch velocity: 10 m/s; punch stroke: 895 mm; and coefficient of friction: 0.12. The CPU time spent on an HP735 work-station to run a single job is about 11 100 s, the simulation results being displayed on an SGI work-station. One of the advantages of using finite-element analysis for stamping process is that the deformed shape of the sheet-blank can be monitored throughout the stamping process, which is not possible in the real production process. Amongst the deformed shapes, the binder-wrap is the most interesting to the die designer, since it can be used to determine if the blank-holder surface has been designed properly. In the present study, the main purpose of the finite-element analysis is to investigate the defor- mation of the sheet-blank and the location where the split is most likely to occur. Hence, the deformed shape and the thickness contour obtained from the finite-ele- ment simulations were investigated. The deformed mesh is shown in Fig. 9. As seen in this figure, the cup is formed without causing any wrinkling. As for the thickness contour shown in Fig. 10, the darker area represented the thinner portion of the steel sheet. It can be seen from this figure that the thinnest portion is at the cup wall near to the bottom: this location agrees with that found in the production panel. In addition, the distribution of the major and minor principal strains around the thinnest portion obtained from the finite-element simulation, as shown in Fig. 11, is very consistent with that found in the real production panel, as shown in Fig. 7. Hence, the finite-element simulation confirms the previous circle-grid analysis and is validated by the production process. With the validated process parameters, the finite-element analysis F.-K. Chen, J.-H. Liu / Journal of Materials Processing Technology 55 (1995) 408-416 413 Fig. 9. Deformed shape for the original die design. can be used for the analysis of any modified die design to substitute for the real die try-out. Compared with the real die try-out, the finite-element simulation is not only cost-effective but also time-saving, the example given in the following section demonstrating this advant- age. 4. A modified die design Since the split-defect is due to the lack of metal around the cup, one possible modification is to open the blank-holder at one side of the cup, as shown in Fig. 12, which may cause more metal to flow into the cup. The geometries of the die and the sheet-blank remain the same as in the original design and, hence, are not shown in Fig. 12. In order to validate this modification, a 3-D finite-element simulation was performed instead of re-vamping the real die. The simulation conditions were the same as those for the original design, except that the geometries of the punch and the blank-holder were changed, as shown in Fig. 12. The distribution of the major and minor strains of the whole panel obtained from the finite-element simulation THICKNESS _ 1 CONTOUR VALUES = 4.1E-O 1 = 4.6E-0 = 52E-0 i = 5.718E-0 I = 6227E-0 = 6.737E-0 = 7.2,I6E-O = 7.756E-0 = 82E- MIN = 3.680E- IN ELEM. 102 MAX = 8.775E. IN ELEM. 103 Fig. 10. Thickness contour obtained from finite-element simulation for the original die design. 414 F.-K. Chen, J.-H. Liu / Journal of Materials Processing Technology 55 (1995) 408-416 8O 6o ,- 40 o 20 -3( I I I I I I I -20 -10 0 1.0 20 30 Minor Strain (%) Fig. 11. The strain distribution obtained from finite-element simulation for the original die design. 80 6o 40 20 | 4 I I | i | -30 -20 -10 0 10 20 30 Minor Strain (%) Fig. 13. The strain distribution for the modified die design. punch /III/:/I/ /h.:.:. tgggtg !ft/ Illlllllllllllllllll IIIIIIIIIIIIIIll I/l/Ill/lilt/Ill ffffff Ih . , : blank-holder Fig. 12. The modified die design. Fig. 14. The deformed shape for the modified die design. for the modified die design is shown in Fig. 13. As seen in this figure, due to a lot of material being drawn into the cup from the unconstrained area, the strain distribution moves down a little bit but is still in the marginal area. Fig. 14 shows the deformed shape, in which serious wrinkles are observed in the unconstrained area. Al- though the split problem might be avoided in this modi- fied design, the serious wrinkles are unacceptable. As a result, the modified design was not feasible according to the 3-D finite-element simulation, and the re-vamping of the real die was avoided. F.-K. Chen, J,-H. Liu / Journal of Materials Processing Technology 55 (1995) 408 416 415 5. The optimum die design As discussed in the previous sections, the most effective method to eliminate the split-defect from the production panel is to provide more metal for the cup area. Several attempts have been made to achieve this end but only the die design depicted below has been found to be feasible and efficient. In the press shop, the rear floor panel was stamped by a single-action press with two nitrogen cylinders sup- plying power to the blank-holder. In order to provide more metal for the cup area without adding an extra operation, the lower die shape was divided into two portions, as shown in Fig. 15. The middle portion of the die shape was driven by a wedge mechanism and can move up and down relative to the rest of the lower die, which remains stationary. Since the modified die shape was designed to eliminate the split-defect, the location of the movable portion was chosen at the cup area. The movable portion was driven upwards through the wedge mechanism as the blank-holder closed. At the closure of the blank-holder, the movable portion lifted the sheet- blank to a particular height, providing the cup area with more metal than that in the original design. The movable portion was then forced to move downwards when it was contacted by the top die during the die-closing process. At die closure, the movable portion was retrieved to its position and a sound part was formed. It is obvious that the mechanism for the movable portion of the lower die provides a better binder-wrap in the cup area before the punch moves down. However, the optimum amount of additional metal provided is yet to be determined. The optimum amount of metal is defined as that with which the split defect can be eliminated without causing unacceptable wrinkles. In the present study, a simple calculation which limited the average elongation of cross-sections at the cup area to a max- imum value of 20% was performed to determine this amount. According to the calculation, the movable por- tion of the lower die should raise 300 mm at the closure of blank-holder to provide the proper amount of metal for the cup area. _ separate die face f. lJ -,1 I , , ! | I i wedge j Fig. 15. The separate die face and the wedge mechanism. v t- O 90 85 80 75 70 65 60 55 50 /.5 40 35 30 25 20 15 10 5 I j / f -30-25-20-15-10-5 0 5 10 15 20 25 30 35 40 Minor Strain (%) Fig. 16. Measured strains for the first draw of the optimum die design. 6. Results and discussion A modified lower die frame corresponding to the above calculation was manufactured to validate the opti- mum die design. As a result, rear floor panels with good quality were obtained using the modified dies during the try-out period. To quantify the quality, circle-grid ana- lysis was conducted again for the formed part, the circles being scribed on the same area as they were in the original design. The major and minor strains around the cup wall where the split used to occur were measured and plotted in the forming-limit diagram, as shown in Fig. 16. As seen in this figure, all the measured strains were in the safe zone, which indicates that the first-draw operation with the modified dies is very stable and is not sensitive to process variation. In order to make the validation more complete, circle- grid analysis was performed for the second-draw opera- tion also. In addition to forming the ribs in the panels, as shown in Fig. 1, the second-draw operation also sharp- ened the corner radii at the root of the cup. Thus, the second draw would stretch the cup area a little. The major and minor strains measured in the first draw and the second draw at the cup area are shown in Fig. 17. It is 416 F.-K. Chert, J.-H. Liu / Journal of Materials Processing Technology 55 (1995) 408-416 90 85 -: first operation 8o -: second operation 75 70 G5 55
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