托板冲压模具设计【冲孔落料级进模】【说明书+CAD】
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目录绪论冲裁模设计题目(一)冲裁件工艺分析.(二) 确定工艺方案及模具结构形式.(三) 模具设计计算.1排样 计算条料宽度及确定步距.2利用率计算.3计算总冲压力. . .4确定压力中心. . .5冲模刃口尺寸及公差的计算. . . .6. 确定各主要零件结构尺寸. . .(1)凹模外形尺寸的确定. . . .(2)凸模长度L1的确定. .(3)设计并绘制总图、选取标准件. . . .(五)绘制非标准零件图. . .(六) 模具主要零件加工工艺规程的制.总装工艺. . .垫板的加工工艺. . .凸模固定板的加工工艺. . . .落料凸模的加工工艺. . . .导正销的加工工艺. . . .冲孔凸模的加工工艺. . . . .卸料板加工工艺. . . .凹模加工工艺. . . .导料板加工工艺. . . . .始冲挡料销的加工工艺. . . . .体会. . . . . . . . . . . . .参考文献. . . . . . . . . . . . .附图纸. . . . . . . . . . . . .绪论一:冲压的概念,特点与发展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。 冲压地、在现代工业生产中,尤其是大批量生产中应用十分广泛。相当多的工业部门越来越多地采用冲压法加工产品零部件,如汽车、农机、仪器、仪表、电子、航空、航天、家电及轻工等行业。在这些工业部门中,冲压件所占的比重都相当的大,少则60%以上,多则90%以上。不少过去用锻造=铸造和切削加工方法制造的零件,现在大多数也被质量轻、刚度好的冲压件所代替。因此可以说,如果生产中不谅采用冲压工艺,许多工业部门要提高生产效率和产品质量、降低生产成本、快速进行产品更新换代等都是难以实现 的。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。 复合冲压在压力机的一次工作行程中,在模具的同一工位上同时完成两种或两种以上不同单一工序的一种组合方法式。 级进冲压在压力机上的一次工作行程中,按照一定的顺序在同一模具的不同工位上完面两种或两种以上不同单一工序的一种组合方式。 复合-级进在一副冲模上包含复合和级进两种方式的组合工序。 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。1.3 冲压技术的现状及发展方向 随着科学技术的不断进步和工业生产的迅速发展,许多新技术、新工艺、新设备、新材料不断涌现,因而促进了冲压技术的不断革新和发展。其主要表现和发展方向如下。(1).冲压成形理论及冲压工艺方面 冲压成形理论的研究是提高冲压技术的基础。目前,国内外对冲压成形理论的研究非常重视,在材料冲压性能研究、冲压成形过程应力应变分析、板料变形规律研究及坯料与模具之间的相互作用研究等方面均取得了较大的进展。特别是随着计算机技术的飞跃发展和塑性变形理论的进一步完善,近年来国内外已开始应用塑性成形过程的计算机模拟技术,即利用有限元(FEM)等有值分析方法模拟金属的塑性成形过程,根据分析结果,设计人员可预测某一工艺方案成形的可行性及可能出现的质量问题,并通过在计算机上选择修改相关参数,可实现工艺及模具的优化设计。这样既节省了昂贵的试模费用,也缩短了制模具周期。 研究推广能提高生产率及产品质量、降低成本和扩大冲压工艺应用范围的各种压新工艺,也是冲压技术的发展方向之一。目前,国内外相继涌现出精密冲压工艺、软模成形工艺、高能高速成形工艺及无模多点成形工艺等精密、高效、经济的冲压新工艺。其中,精密冲裁是提高冲裁件质量的有效方法,它扩大了冲压加工范围,目前精密冲裁加工零件的厚度可达25mm,精度可达IT1617级;用液体、橡胶、聚氨酯等作柔性凸模或凹模的软模成形工艺,能加工出用普通加工方法难以加工的材料和复杂形状的零件,在特定生产条件下具有明显的经济效果;采用爆炸等高能效成形方法对于加工各种尺寸在、形状复杂、批量小、强度高和精度要求较高的板料零件,具有很重要的实用意义;利用金属材料的超塑性进行超塑成形,可以用一次成形代替多道普通的冲压成形工序,这对于加工形状复杂和大型板料零件具有突出的优越性;无模多点成形工序是用高度可调的凸模群体代替传统模具进行板料曲面成形的一种先进技术,我国已自主设计制造了具有国际领先水平的无模多点成形设备,解决了多点压机成形法,从而可随意改变变形路径与受力状态,提高了材料的成形极限,同时利用反复成形技术可消除材料内残余应力,实现无回弹成形。无模多点成形系统以CAD/CAM/CAE技术为主要手段,能快速经济地实现三维曲面的自动化成形。(2.)冲模是实现冲压生产的基本条件.在冲模的设计制造上,目前正朝着以下两方面发展:一方面,为了适应高速、自动、精密、安全等大批量现代生产的需要,冲模正向高效率、高精度、高寿命及多工位、多功能方向发展,与此相比适应的新型模具材料及其热处理技术,各种高效、精密、数控自动化的模具加工机床和检测设备以及模具CAD/CAM技术也在迅速发展;另一方面,为了适应产品更新换代和试制或小批量生产的需要,锌基合金冲模、聚氨酯橡胶冲模、薄板冲模、钢带冲模、组合冲模等各种简易冲模及其制造技术也得到了迅速发展。 精密、高效的多工位及多功能级进模和大型复杂的汽车覆盖件冲模代表了现代冲模的技术水平。目前,50个工位以上的级进模进距精度可达到2微米,多功能级进模不仅可以完成冲压全过程,还可完成焊接、装配等工序。我国已能自行设计制造出达到国际水平的精度达25微米,进距精度23微米,总寿命达1亿次。我国主要汽车模具企业,已能生产成套轿车覆盖件模具,在设计制造方法、手段方面已基本达到了国际水平,但在制造方法手段方面已基本达到了国际水平,模具结构、功能方面也接近国际水平,但在制造质量、精度、制造周期和成本方面与国外相比还存在一定差距。 模具制造技术现代化是模具工业发展的基础。计算机技术、信息技术、自动化技术等先进技术正在不断向传统制造技术渗透、交叉、融合形成了现代模具制造技术。其中高速铣削加工、电火花铣削加工、慢走丝切割加工、精密磨削及抛光技术、数控测量等代表了现代冲模制造的技术水平。高速铣削加工不但具有加工速度高以及良好的加工精度和表面质量(主轴转速一般为1500040000r/min),加工精度一般可达10微米,最好的表面粗糙度Ra1微米),而且与传统切削加工相比具有温升低(工件只升高3摄氏度)、切削力小,因而可加工热敏材料和刚性差的零件,合理选择刀具和切削用量还可实现硬材料(60HRC)加工;电火花铣削加工(又称电火花创成加工)是以高速旋转的简单管状电极作三维或二维轮廓加工(像数控铣一样),因此不再需要制造昂贵的成形电极,如日本三菱公司生产的EDSCAN8E电火花铣削加工机床,配置有电极损耗自动补偿系统、CAD/CAM集成系统、在线自动测量系统和动态仿真系统,体现了当今电火花加工机床的技术水平;慢走丝线切割技术的发展水平已相当高,功能也相当完善,自动化程度已达到无人看管运行的程度,目前切割速度已达到300mm/min,加工精度可达1.5微米,表面粗糙度达Ra=010.2微米;精度磨削及抛光已开始使用数控成形磨床、数控光学曲线磨床、数控连续轨迹坐标磨床及自动抛光等先进设备和技术;模具加工过程中的检测技术也取得了很大的发展,现在三坐标测量机除了能高精度地测量复杂曲面的数据外,其良好的温度补偿装置、可靠的抗振保护能力、严密的除尘措施及简单操作步骤,使得现场自动化检测成为可能。此外,激光快速成形技术(RPM)与树脂浇注技术在快速经济制模技术中得到了成功的应用。利用RPM技术快速成形三维原型后,通过陶瓷精铸、电弧涂喷、消失模、熔模等技术可快速制造各种成形模。如清华大学开发研制的“M-RPMS-型多功能快速原型制造系统”是我国自主知识产权的世界惟一拥有两种快速成形工艺(分层实体制造SSM和熔融挤压成形MEM)的系统,它基于“模块化技术集成”之概念而设计和制造,具有较好的价格性能比。一汽模具制造公司在以CAD/CAM加工的主模型为基础,采用瑞士汽巴精化的高强度树脂浇注成形的树脂冲模应用在国产轿车试制和小批量生产开辟了新的途径。(3) 冲压设备和冲压生产自动化方面 性能良好的冲压设备是提高冲压生产技术水平的基本条件,高精度、高寿命、高效率的冲模需要高精度、高自动化的冲压设备相匹配。为了满足大批量高速生产的需要,目前冲压设备也由单工位、单功能、低速压力机朝着多工位、多功能、高速和数控方向发展,加之机械乃至机器人的大量使用,使冲压生产效率得到大幅度提高,各式各样的冲压自动线和高速自动压力机纷纷投入使用。如在数控四边折弯机中送入板料毛坯后,在计算机程序控制下便可依次完成四边弯曲,从而大幅度提高精度和生产率;在高速自动压力机上冲压电机定转子冲片时,一分钟可冲几百片,并能自动叠成定、转子铁芯,生产效率比普通压力机提高几十倍,材料利用率高达97%;公称压力为250KN的高速压力机的滑块行程次数已达2000次/min以上。在多功能压力机方面,日本田公司生产的2000KN“冲压中心”采用CNC控制,只需5min时间就可完成自动换模、换料和调整工艺参数等工作;美国惠特尼公司生产的CNC金属板材加工中心,在相同的时间内,加工冲压件的数量为普通压力机的410倍,并能进行冲孔、分段冲裁、弯曲和拉深等多种作业。 近年来,为了适应市场的激烈竞争,对产品质量的要求越来越高,且其更新换代的周期大为缩短。冲压生产为适应这一新的要求,开发了多种适合不同批量生产的工艺、设备和模具。其中,无需设计专用模具、性能先进的转塔数控多工位压力机、激光切割和成形机、CNC万能折弯机等新设备已投入使用。特别是近几年来在国外已经发展起来、国内亦开始使用的冲压柔性制造单元(FMC)和冲压柔性制造系统(FMS)代表了冲压生产新的发展趋势。FMS系统以数控冲压设备为主体,包括板料、模具、冲压件分类存放系统、自动上料与下料系统,生产过程完全由计算机控制,车间实现24小时无人控制生产。同时,根据不同使用要求,可以完成各种冲压工序,甚至焊接、装配等工序,更换新产品方便迅速,冲压件精度也高。(4)冲压标准化及专业化生产方面 模具的标准化及专业化生产,已得到模具行业和广泛重视。因为冲模属单件小批量生产,冲模零件既具的一定的复杂性和精密性,又具有一定的结构典型性。因此,只有实现了冲模的标准化,才能使冲模和冲模零件的生产实现专业化、商品化,从而降低模具的成本,提高模具的质量和缩短制造周期。目前,国外先进工业国家模具标准化生产程度已达70%80%,模具厂只需设计制造工作零件,大部分模具零件均从标准件厂购买,使生产率大幅度提高。模具制造厂专业化程度越不定期越高,分工越来越细,如目前有模架厂、顶杆厂、热处理厂等,甚至某些模具厂仅专业化制造某类产品的冲裁模或弯曲模,这样更有利于制造水平的提高和制造周期的缩短。我国冲模标准化与专业化生产近年来也有较大发展,除反映在标准件专业化生产厂家有较多增加外,标准件品种也有扩展,精度亦有提高。但总体情况还满足不了模具工业发展的要求,主要体现在标准化程度还不高(一般在40%以下),标准件的品种和规格较少,大多数标准件厂家未形成规模化生产,标准件质量也还存在较多问题。另外,标准件生产的销售、供货、服务等都还有待于进一步提高。冲裁模设计题目如图1所示零件:托扳生产批量:大批量材料:08F t=2mm设计该零件的冲压工艺与模具 图1 托板零件图(一)冲裁件工艺分析1. 材料:08F钢板是优质碳素结构钢,具有良好的可冲压性能。2. 工件结构形状:冲裁件内、外形应尽量避免有尖锐清角,为提高模具寿命,建议将所有90清角改为R1的圆角。3凸模最小尺寸校核 :查冷冲压技术表3-9无导向凸模冲孔的 最小尺寸;d=0.9t =0.9*2 =1.8小于3.5可以冲裁4. 尺寸精度:零件图上所有尺寸均未标注公差,属自由尺寸,可按IT14级确定工件尺寸的公差。经查公差配合与技术测量表2-4得,各尺寸公差为:54-0.74、34-0.62、30-0.52、16-0.44、170.22、3.5+0.3结论:可以冲裁(二) 确定工艺方案及模具结构形式经分析,工件尺寸精度要求不高,形状不大,但工件产量较大,根据材料较厚(2mm)的特点,为保证孔位精度,冲模有较高的生产率,通过比较,决定实行工序集中的工艺方案,采取利用导正钉进行定位、刚性卸料装置、自然漏料方式的连续冲裁模结构形式。(三) 模具设计计算1排样 计算条料宽度及确定步距首先查冷冲压技术表确定搭边值。根据零件形状,两工件间按矩形取搭边值b=2,侧边按圆形取搭边值a=2。连续模进料步距为32mm。条料宽度按相应的公式计算:查冷冲压技术公式3-21B=(D+2a)- 查表3.15得条料宽度误差 =0.6B=(54+22)-0.6=58-0.6画出排样图,图2 2利用率计算;查冷冲压技术公式3-19得n=A/SB*100% =34*30+4*30+200.96-21/58*32 =71.1% 所以用剪扳机剪取58*1000的条料 图2 排样图2计算总冲压力由于冲模采用刚性卸装置和自然漏料方式,故总的冲压力为:由冷冲压技术公式3-35得P0=P+PtP=P1+P2而式中 P1-落料时的冲裁力P2-冲孔时的冲裁力按推料力公式计算冲裁力:查冷冲压技术得公式P1=KLt 查冷冲压技术表2-23得抗剪强度=300MPa=1.32(58-16)+2(30-16)+16+2*4*2*300/10000=12.03 (t)P2=1.3*4*3.5*2*300/10000 =3.4(t)按推料力公式计算推料力Pt:查冷冲压技术公式3-31得Pt=nKtP 取n=h/t=6/2=3, 查表3-19得,Kt=0.055Pt=3*0.055*(12.6+3.4)=2.541(t) 计算总冲压力PZ:PZ=P1+P2+Pt =12.03+3.4+2.541 =17.941(t)3确定压力中心:根据图3分析,因为工件图形对称,故落料时P1的压力中心在O1上;冲孔时P2的压力中心在O2上。设冲模压力中心离O1点的距离为X,根据力矩平衡原理得:P1X=(32-X)P 图3 压力中心 由此算得X=7m4冲模刃口尺寸及公差的计算刃口尺寸计算方法及演算过程不再赘述,仅将计算结果列于表1 中。在冲模刃尺寸计算时需要注意:在计算工件外形落料时,应以凹模为基准,凸模尺寸按相应的凹模实际尺寸配制,保证双面间隙为0.250.36mm。为了保证R8与尺寸为16的轮廓线相切,R8的凹模尺寸,取16的凹模尺寸的一半,公差也取一半。在计算冲孔模刃口尺寸时,应以凸模为基准,凹模尺寸按凸模实际尺寸配制,查公差配合与技术测量表3-5得保证双面间隙为0.250.36mm。表1 冲模刃口尺寸*X在从冷冲压技术中查表3-7得冲裁性质工作尺寸计算公式凹模尺寸注法凸模尺寸注法落料58-0.7438-0.6230-0.5216-0.44R8磨损后变大的 公式;Amax- x)+从冷冲压技术中公式得57.6+0.1837.7+0.1629.7+0.1316.8+0.11R7.9+0.06凸模尺寸按实际尺寸配置,保证双边间隙 0.250.36mm冲孔3.5+0.3磨损后变小的公式;(bmin+x)-/4从冷冲压技术得公式3-14凹模尺寸按凹模实际尺寸配置,保证双边间隙0.250.36mm3.65-0.08在计算模具中心距尺寸时,制造偏差值取工件公差的1/8。据此,冲孔凹模和凸模固定板孔中心距的制造尺寸为:L17=170.44/8=170.0555. 确定各主要零件结构尺寸(1)凹模外形尺寸的确定凹模厚度H的确定:根据经验公式得: H= P取总压力=17941NH=26mm凹模长度L的确定; W1=2.1H=31;工件b=58 L=b+2W1=58+2*31=120mm凹模宽度B的确定; B= 步距+工件宽+2W2取:步距=32;工件=30;W2=1.5HB2=32+30+2*39 =140mm根据上述数据查模具设计与制造简明手册表1-282选用标准凹摸板160*125*28(2)凸模长度L1的确定凸模长度计算为:L1=h1+h2+h3+Y其中 导料板厚h1=8;卸料板厚h2=12;凸模固定板厚h3=18; 凸模修磨量Y=18则L1=8+12+18+18=56m选用冲床的公称压力,应大于计算出的总压力P0=17.941t;最大闭合高度应大于冲模闭合高度+5mm;工作台台面尺寸应能满足模具的正确安装。按上述要求,查模具设计与制造简明手册表1-82得,可选用J23-25开式双柱可倾压力机。并需在工作台面上配备垫块,垫块实际尺寸可配制。其基本参数如下:最大闭合高度 270闭合高度调节量 55工作台尺寸 前后370 左右560工作台孔尺寸 前后200 左右290垫板尺寸 50模柄尺寸 直径40 深度60倾角 30(3)设计并绘制总图、选取标准件 模板 卸料板 导料板 垫板 导柱 导套模架 模柄都是从模具设计与制造简明手册有的是把标准件买回来加工,螺钉 销 在机械制图中选用标准件 ,模架选用标准中间导柱模架 标准是 GB/T2851.3-90 根据 模具技术标准应用参数如下:周界是 160*125最大闭合高度 190最小闭合高度 160上模座厚度 35下模座厚度 40模具的闭合高度校核:40+35+28+56+10=170该模具符合要求按已确定的模具形式及参数绘制模具总装图。如图4,单排冲孔落料连续模。图四总装图技术要求1采用标准模架后侧导柱模架,标准是GB/T2851.1-902冲模零件不 允许有裂痕,工作表面不允许有划痕,机械损伤,锈蚀等表面缺陷,3冲模凹模工作孔不允许有 倒锥度4冲裁的凸凹模刃口及侧刃等必须锋利不允许有崩刃和机械损伤,5零件图上未标明的倒角尺寸,除刃口外所有的锐边都倒角1X45度或道圆角,表2 零件明细表(五)绘制非标准零件图,(略) 看零件图 (六) 模具主要零件加工工艺规程的编制总装工艺1备料2将模柄装入9上模座后磨平,然后用手枪钻直径6mm的齐缝销孔配铰大 入12销3将13导正销装入14落料凸模中,把再把落料凸模组和7冲孔凸模装入到6凸模固定板中然后铆紧磨平4用等高块把9上模座支起,将8垫板,6固定板,调整后用4螺钉固定,配铰直径8mm的孔,大入10销5把9上模座放下到一定高度,保证模架的 移动平稳,灵活,无泻止现象,让凸模刃口在凹模刃口下,调整间隙,保证图纸设计要求,用螺钉紧固,15卸料板,16导料板,19始冲档料销及17凹模。再用3螺钉紧固17凹模和1下模座然后配饺销孔大入销,6试模7调整到合格8入库垫板的加工工艺1备料(外购标准模块160x125x10)2按图纸要求画线,3在钻洗床上加工4检验5入库凸模固定板的加工工艺1备料(外购标准模块160x125x18)2按图纸要求画线,3在钻洗床上加工四个凸模孔和两个销孔四个螺钉通孔4攻4*M8螺纹孔5在电火花满走丝上加工落料凸模孔6检验7入库落料凸模的加工工艺1备料2锻造成62*35*60的模块3在刨床上先刨一平面4以该面为基准按图纸要求画线5在数控铣床上铣出图纸上的外形6在钻铣床上钻出导正销的孔7按图纸要求做热处理8检验9入库导正销的加工工艺1备料2锻造成直径8*60的胚料3在数控车床上加工零件按图纸要求4按图纸要求热处理5检验6入库冲孔凸模的加工工艺1备料2锻造成直径为14*60的胚料3在数控车床上加工零件按图纸要求4按图纸要求热处理5检验6入库卸料板加工工艺1备料(外购标准模块100x125x12)2按图纸要求画线,3在钻洗床上加工四螺钉通孔和两个销孔及四个通过凸模的孔4在铣床上加工剩余的部分5检验6入库凹模加工工艺1备料(外购标准模块160x125x28)2按图纸要求画线,3在钻洗床上加工两销孔和四螺纹孔4攻丝5用点火花加工工作刃口6按图纸要求做热处理7检验8入库导料板加工工艺1备料(外购标准模块120x125x8)在 标准模块上切割成两块120*35*82按图纸要求画线,3在刨床上把不平整的边刨床平及始冲挡料销的槽,在插床上加工始冲挡料销的剩余部分4在钻铣床上加工两销孔和四个螺纹通孔5攻螺纹丝4*M86检验7入库始冲挡料销的加工工艺1备料2锻造成55*5*10的胚料3在刨床上先刨一平面做基准4在基准上划线5在铣床上加工出零件图的样子6按图纸要求做相应的热处理7检验8入库体会俗话说“凡事必亲躬”,唯有自己亲自去做的事,才懂得其过程的艰辛。通过做这次大作业,我着实遇到了不少的困难,构思、定数据、画图、写论文等都得自己去做。每天泡在图书馆,找例证、查资料,个中自有不少困难,而这些难题都是课本中所不曾提到过的。开始时,由于书本上没有任何提示,我甚至不知道从何入手,只能与同学们相互切磋,这样我慢慢地入了门,进而也可以自己搞定了。这其中有一个习惯问题最需要克服。众所周知,课堂、书本给我们的都是一种确切的数据,但实际上你去做的时候就会发现它们都是经验性的,也就是说需要你根据从资料上查得的范围靠经验自己去定,这就给习惯于接受确切数字的我带来了很大的挑战。幸而,最终我还是学会了怎样去查找自己想要的资料,这应该是这次作业的一大收获吧。第二大收获就是学会了做一次设计项目的具体流程。从策划构思、总体设计到各个模块的的具体设计及其组合,再到编写需要提交的论文,这一切如今仍历历在目。我想,这种对整体设计流程的把握应该是以后走上工作岗位所必需的技能,而这种技能却只能通过自己的亲身实践才能获得。这也是为什么我认为机械设计大作业这种教学实践模式值得推广的原因。毕业设计是我在大学生涯完成的最后一项内容,此时此刻,我感觉自己有很多想要说的话,有很多需要感谢的人。首先感谢指导老师给予的支持与指导,但由于工作的原因和条件的限制,我在外面所做的毕业设计并不完善。自从回校之后,向老师们请教和指导,他们都在百忙之中给予了我悉心的指导和帮助。师生之情无法言表,在此,谨向恩师们深表谢意!也许,我的学生生涯从此就会结束,但是学习的道路却还将持续下去,未来的人生路途中难免会遇到各种各样的困难和挫折,使我始终能够勇敢的迎接新的挑战。参考文献1;冷冲压技术 翁其金主编 北京机械工业出版社 2000.11 2;公差配合与技术测量 薛彦成主编 北京机械工业出版社1999.103;机械制图 李澄 闻百桥 吴天生主编 北京高等教育出版社2003.84;模具设计与制造简明手册 冯炳尧 韩泰来 蒋文森 主编 上海科学技术出版社 1998(第二版)5;模具技术标准应用 全国模具标准技术委员会秘书处四川省模具工业协会印 1992.821Int J Adv Manuf Technol (2002) 19:253259 2002 Springer-Verlag London Limited An Analysis of Draw-Wall Wrinkling in a Stamping Die Design F.-K. Chen and Y.-C. Liao Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan Wrinkling that occurs in the stamping of tapered square cups and stepped rectangular cups is investigated. A common characteristic of these two types of wrinkling is that the wrinkles are found at the draw wall that is relatively unsup- ported. In the stamping of a tapered square cup, the effect of process parameters, such as the die gap and blank-holder force, on the occurrence of wrinkling is examined using finite- element simulations. The simulation results show that the larger the die gap, the more severe is the wrinkling, and such wrinkling cannot be suppressed by increasing the blank-holder force. In the analysis of wrinkling that occurred in the stamping of a stepped rectangular cup, an actual production part that has a similar type of geometry was examined. The wrinkles found at the draw wall are attributed to the unbalanced stretching of the sheet metal between the punch head and the step edge. An optimum die design for the purpose of eliminating the wrinkles is determined using finite-element analysis. The good agreement between the simulation results and those observed in the wrinkle-free production part validates the accuracy of the finite-element analysis, and demonstrates the advantage of using finite-element analysis for stamping die design. Keywords: Draw-wall wrinkle; Stamping die; Stepped rec- tangular cup; Tapered square cups 1. Introduction Wrinkling is one of the major defects that occur in the sheet metal forming process. For both functional and visual reasons, wrinkles are usually not acceptable in a finished part. There are three types of wrinkle which frequently occur in the sheet metal forming process: flange wrinkling, wall wrinkling, and elastic buckling of the undeformed area owing to residual elastic compressive stresses. In the forming operation of stamp- ing a complex shape, draw-wall wrinkling means the occurrence Correspondence and offprint requests to: Professor F.-K. Chen, Depart- ment of Mechanical Engineering, National Taiwan University, No. 1 Roosevelt Road, Sec. 4, Taipei, Taiwan 10617. E-mail: fkchenL50560 w3.me.ntu.edu.tw of wrinkles in the die cavity. Since the sheet metal in the wall area is relatively unsupported by the tool, the elimination of wall wrinkles is more difficult than the suppression of flange wrinkles. It is well known that additional stretching of the material 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 stresses leads to failure by tearing. Hence, the blank-holder force must lie within a narrow range, above that necessary to suppress wrinkles on the one hand, and below that which produces fracture on the other. This narrow range of blank-holder force is difficult to determine. For wrinkles occurring in the central area of a stamped part with a complex shape, a workable range of blank-holder force does not even exist. In order to examine the mechanics of the formation of wrinkles, Yoshida et al. 1 developed a test in which a thin plate was non-uniformly stretched along one of its diagonals. They also proposed an approximate theoretical model in which the onset of wrinkling is due to elastic buckling resulting from the compressive lateral stresses developed in the non-uniform stress field. Yu et al. 2,3 investigated the wrinkling problem both experimentally and analytically. They found that wrinkling could occur having two circumferential waves according to their theoretical analysis, whereas the experimental results indi- cated four to six wrinkles. Narayanasamy and Sowerby 4 examined the wrinkling of sheet metal when drawing it through a conical die using flat-bottomed and hemispherical-ended punches. They also attempted to rank the properties that appeared to suppress wrinkling. These efforts are focused on the wrinkling problems associa- ted with the forming operations of simple shapes only, such as a circular cup. In the early 1990s, the successful application of the 3D dynamic/explicit finite-element method to the sheet- metal forming process made it possible to analyse the wrinkling problem involved in stamping complex shapes. In the present study, the 3D finite-element method was employed to analyse the effects of the process parameters on the metal flow causing wrinkles at the draw wall in the stamping of a tapered square cup, and of a stepped rectangular part. A tapered square cup, as shown in Fig. 1(a), has an inclined draw wall on each side of the cup, similar to that existing in a conical cup. During the stamping process, the sheet metal on the draw wall is relatively unsupported, and is therefore 254 F.-K. Chen and Y.-C. Liao Fig. 1. Sketches of (a) a tapered square cup and (b) a stepped rectangular cup. prone to wrinkling. In the present study, the effect of various process parameters on the wrinkling was investigated. In the case of a stepped rectangular part, as shown in Fig. 1(b), another type of wrinkling is observed. In order to estimate the effectiveness of the analysis, an actual production part with stepped geometry was examined in the present study. The cause of the wrinkling was determined using finite-element analysis, and an optimum die design was proposed to eliminate the wrinkles. The die design obtained from finite-element analy- sis was validated by observations on an actual production part. 2. Finite-Element Model The tooling geometry, including the punch, die and blank- holder, were designed using the CAD program PRO/ ENGINEER. Both the 3-node and 4-node shell elements were adopted to generate the mesh systems for the above tooling using 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 and Fig. 2. Finite-element mesh. are not for stress analysis. The same CAD program using 4- node shell elements was employed to construct the mesh system for the sheet blank. Figure 2 shows the mesh system for the complete set of tooling and the sheet-blank used in the stamping of a tapered square cup. Owing to the symmetric conditions, only a quarter of the square cup is analysed. In the simulation, the sheet blank is put on the blank-holder and the die is moved down to clamp the sheet blank against the blank-holder. The punch is then moved up to draw the sheet metal into the die cavity. In order to perform an accurate finite-element analysis, the actual stressstrain relationship of the sheet metal is required as part of the input data. In the present study, sheet metal with deep-drawing quality is used in the simulations. A tensile test has been conducted for the specimens cut along planes coinciding with the rolling direction (0) and at angles of 45 and 90 to the rolling direction. The average flow stress H9268, calculated from the equation H9268H11005(H9268 0 H11001 2H9268 45 H11001H9268 90 )/4, for each measured true strain, as shown in Fig. 3, is used for the simulations for the stampings of the tapered square cup and also for the stepped rectangular cup. All the simulations performed in the present study were run on an SGI Indigo 2 workstation using the finite-element pro- gram PAMFSTAMP. To complete the set of input data required Fig. 3. The stressstrain relationship for the sheet metal. Draw-Wall Wrinkling in a Stamping Die Design 255 for the simulations, the punch speed is set to 10 m s H110021 and a coefficient of Coulomb friction equal to 0.1 is assumed. 3. Wrinkling in a Tapered Square Cup A sketch indicating some relevant dimensions of the tapered square cup is shown in Fig. 1(a). As seen in Fig. 1(a), the length of each side of the square punch head (2W p ), the die cavity opening (2W d ), 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 cavity opening and the punch head is termed the die gap (G) in the present study, i.e. G H11005 W d H11002 W p . The extent of the relatively unsupported sheet metal at the draw wall is presumably due to the die gap, and the wrinkles are supposed to be suppressed by increasing the blank-holder force. The effects of both the die gap and the blank-holder force in relation to the occurrence of wrinkling in the stamping of a tapered square cup are investigated in the following sections. 3.1 Effect of Die Gap In order to examine the effect of die gap on the wrinkling, the stamping of a tapered square cup with three different die gaps of 20 mm, 30 mm, and 50 mm was simulated. In each simulation, the die cavity opening is fixed at 200 mm, and the cup is drawn to the same height of 100 mm. The sheet metal used in all three simulations is a 380 mm H11003 380 mm square sheet with thickness of 0.7 mm, the stressstrain curve for the material is shown in Fig. 3. The simulation results show that wrinkling occurred in all three tapered square cups, and the simulated shape of the drawn cup for a die gap of 50 mm is shown in Fig. 4. It is seen in Fig. 4 that the wrinkling is distributed on the draw wall and is particularly obvious at the corner between adjacent walls. It is suggested that the wrinkling is due to the large unsupported area at the draw wall during the stamping process, also, the side length of the punch head and the die cavity Fig. 4. Wrinkling in a tapered square cup (G H11005 50 mm). opening are different owing to the die gap. The sheet metal stretched between the punch head and the die cavity shoulder becomes unstable owing to the presence of compressive trans- verse stresses. The unconstrained stretching of the sheet metal under compression seems to be the main cause for the wrink- ling at the draw wall. In order to compare the results for the three different die gaps, the ratio H9252 of the two principal strains is introduced, H9252 being H9280 min /H9280 max , where H9280 max and H9280 min are the major and the minor principal strains, respectively. Hosford and Caddell 5 have shown that if the absolute value of H9252 is greater than a critical value, wrinkling is supposed to occur, and the larger the absolute value of H9252, the greater is the possibility of wrinkling. The H9252 values along the cross-section MN at the same drawing height for the three simulated shapes with different die gaps, as marked in Fig. 4, are plotted in Fig. 5. It is noted from Fig. 5 that severe wrinkles are located close to the corner and fewer wrinkles occur in the middle of the draw wall for all three different die gaps. It is also noted that the bigger the die gap, the larger is the absolute value of H9252. Consequently, increasing the die gap will increase the possibility of wrinkling occurring at the draw wall of the tapered square cup. 3.2 Effect of the Blank-Holder Force It is well known that increasing the blank-holder force can help to eliminate wrinkling in the stamping process. In order to study the effectiveness of increased blank-holder force, the stamping of a tapered square cup with die gap of 50 mm, which is associated with severe wrinkling as stated above, was simulated with different values of blank-holder force. The blank-holder force was increased from 100 kN to 600 kN, which yielded a blank-holder pressure of 0.33 MPa and 1.98 MPa, respectively. The remaining simulation conditions are maintained the same as those specified in the previous section. An intermediate blank-holder force of 300 kN was also used in the simulation. The simulation results show that an increase in the blank- holder force does not help to eliminate the wrinkling that occurs at the draw wall. The H9252 values along the cross-section Fig. 5. H9252-value along the cross-section MN for different die gaps. 256 F.-K. Chen and Y.-C. Liao MN, as marked in Fig. 4, are compared with one another for the stamping processes with blank-holder force of 100 kN and 600 kN. The simulation results indicate that the H9252 values along the cross-section MN are almost identical in both cases. In order to examine the difference of the wrinkle shape for the two different blank-holder forces, five cross-sections of the draw wall at different heights from the bottom to the line M N, 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-sections for both cases is similar. This indicates that the blank-holder force does not affect the occurrence of wrinkling in the stamp- ing of a tapered square cup, because the formation of wrinkles is mainly due to the large unsupported area at the draw wall where large compressive transverse stresses exist. The blank- holder force has no influence on the instability mode of the material between the punch head and the die cavity shoulder. 4. Stepped Rectangular Cup In the stamping of a stepped rectangular cup, wrinkling occurs at the draw wall even though the die gaps are not so significant. Figure 1(b) shows a sketch of a punch shape used for stamping a stepped rectangular cup in which the draw wall C is followed by a step DE. An actual production part that has this type of geometry was examined in the present study. The material used for this production part was 0.7 mm thick, and the stress strain relation obtained from tensile tests is shown in Fig. 3. The procedure in the press shop for the production of this stamping part consists of deep drawing followed by trimming. In the deep drawing process, no draw bead is employed on the die surface to facilitate the metal flow. However, owing to the small punch corner radius and complex geometry, a split occurred at the top edge of the punch and wrinkles were found to occur at the draw wall of the actual production part, as shown in Fig. 7. It is seen from Fig. 7 that wrinkles are distributed on the draw wall, but are more severe at the corner edges 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 simulation was first performed for the original design. The simulated shape 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 stretched Fig. 6. Cross-section lines at different heights of the draw wall for different 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 edge AB, and the radius of the punch corner A, as marked in Fig. 1(b), are considered to be the major reasons for the wall breakage. However, according to the results of the finite- element analysis, splitting can be avoided by increasing the above-mentioned radii. This concept was validated by the actual 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 original value. However, just as for the results obtained in the previous section for the drawing of tapered square cup, the effect of blank-holder force on the elimination of wrinkling was not found to be significant. The same results are also obtained by increasing the friction or increasing the blank size. We conclude that this kind of wrinkling cannot be suppressed by increasing the stretching force. Since wrinkles are formed because of excessive metal flow in certain regions, where the sheet is subjected to large com- pressive stresses, a straightforward method of eliminating the wrinkles is to add drawbars in the wrinkled area to absorb the redundant material. The drawbars should be added parallel to the direction of the wrinkles so that the redundant metal can be absorbed effectively. Based on this concept, two drawbars are added to the adjacent walls, as shown in Fig. 9, to absorb the excessive material. The simulation results show that the Draw-Wall Wrinkling in a Stamping Die Design 257 Fig. 9. Drawbars added to the draw walls. wrinkles at the corner of the step are absorbed by the drawbars as expected, however some wrinkles still appear at the remain- ing wall. This indicates the need to put more drawbars at the draw 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 for the stamping process is that the deformed shape of the sheet blank can be monitored throughout the stamping process, which is not possible in the actual production process. A close look at the metal flow during the stamping process reveals that the sheet blank is first drawn into the die cavity by the punch head and the wrinkles are not formed until the sheet blank touches the step edge DE marked in Fig. 1(b). The wrinkled shape is shown in Fig. 10. This provides valuable information for 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 punch corner radius A and the step corner radius D, as indicated in Fig. 1(b). Therefore a modification of die design was carried out in which the step corner was cut off, as shown in Fig. 11, so that the stretch condition is changed favourably, which allows more stretch to be applied by increasing the step edges. However, wrinkles were still found at the draw wall of the cup. This result implies that wrinkles are introduced because of the uneven stretch between the whole punch head edge and the whole step edge, not merely between the punch corner and Fig. 10. Wrinkle formed when the sheet blank touches the stepped edge. Fig. 11. Cut-off of the stepped corner. the step corner. In order to verify this idea, two modifications of the die design were suggested: one is to cut the whole step off, and the other is to add one more drawing operation, that is, 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 is quite similar to that of a rectangular cup drawing, as shown in Fig. 12. It is seen in Fig. 12 that the wrinkles were eliminated. In the two-operation drawing process, the sheet blank was first drawn to the deeper step, as shown in Fig. 13(a). Sub- sequently, the lower step was formed in the second drawing operation, and the desired shape was then obtained, as shown in Fig. 13(b). It is seen clearly in Fig. 13(b) that the stepped rectangular cup can be manufactured without wrinkling, by a two-operation drawing process. It should also be noted that in the two-operation drawing process, if an opposite sequence is applied, that is, the lower step is formed first and is followed by 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 the metal cannot easily flow over the lower step into the die cavity. The finite-element simulations have indicated that the die design for stamping the desired stepped rectangular cup using one single draw operation is barely achieved. However, the manufacturing cost is expected to be much higher for the two- operation drawing process owing to the additional die cost and operation cost. In order to maintain a lower manufacturing cost, the part design engineer made suitable shape changes, and modified the die design according to the finite-element Fig. 12.
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