上销回转架(二)冲压工艺及模具设计【上销是粗细纱机加压装置中的重要专件】【冲孔落料复合模】【折弯模】【2套】
上销回转架(二)冲压工艺及模具设计【上销是粗细纱机加压装置中的重要专件】【冲孔落料复合模】【折弯模】【2套】,上销是粗细纱机加压装置中的重要专件,冲孔落料复合模,折弯模,2套,上销回转架(二)冲压工艺及模具设计【上销是粗细纱机加压装置中的重要专件】【冲孔落料复合模】【折弯模】【2套】,回转,冲压,工艺,模具设计
任务书毕业设计题目上销回转架(二)冲压工艺及模具设计学生姓名专业班级学 号指导教师教 研 室机械设计教研室起止时间 毕业设计的目的: 上销是粗细纱机加压装置中的重要专件。上销、中铁辊和上胶圈组成了牵伸控制装置并通过上销连接到摇架形成了粗细纱机牵伸机构,其性能好坏对成纱质量有很大影响。本设计中的上销回转架是麻纺粗纱上销中的一个基础定位零件,该零件与上销钳口板焊接连接构成麻纺粗纱上销。毕业设计是整个教学过程中极为重要的环节,通过本课题的完成,全面复习、巩固大学四年所学的专业课程的基本理论,特别是冲压工艺和模具设计方面的基础知识,提高分析问题和解决问题的能力,培养事实求是的科学态度和认真细致的工作作风。通过文献检索、英文翻译、CAD辅助设计,提高计算机应用水平及英文阅读翻译的能力。毕业设计的主要任务和要求:1了解上销的工作原理,了解回转架的结构原理及在上销中的作用。2查阅与课题相关的资料10篇以上。翻译本专业外文资料一篇,不少于1.5万个外文字符。3写出开题报告,不少于1500个字符。4绘制上销回转架零件图。5写出工艺卡,画出工艺展开图。6设计冲孔落料模一副、压弯模一副,冲四方孔模一副,绘制模具装配图和主要零件图。7撰写设计说明书一份,要求不少于1.5万个字符,并有中英文摘要及关键词。8图纸工作量不少于3张A0。主要参考文献与资料: 1 Constantin Ispas, Miron Zapciu, Cristina Mohora, Dorel Anania. Basic Machining Operations and Cutting Technology J. Journal of Materials Processing Technology,1999(01):Page17-30. 2 许发樾 . 实用模具设计与制造手册M . 北京:机械工业出版社,2001 3 马正元,韩启 . 冷冲压工艺及模具设计M . 北京:机械工业出版社,2000 4 陈剑鹤 . 冷冲压工艺与模具设计M . 北京:机械工业出版社,2004 5 黄费哲,曾经梁 . 冷冲压工艺及模具设计指导M . 常德:湖南文理学院,2002 6 冯柄尧 . 模具设计与制造手册M . 上海:上海科学技术出版社,1998 7 方昆凡 . 公差与配合技术手册M . 北京:北京出版社,1998 8 肖景容 . 冲压工艺学M . 北京:北京出版社,2000 9 李云程 . 冲压工艺学M . 北京:机械工业出版社,2000 10 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,1998 毕业设计进度安排: 12013.11.512.6 查阅文献,收集资料。 22013.12.712.9 写出开题报告 32013.12.102014.2.23 课题调研 42014.2.245.15 完成方案设计,进行设计计算,绘制装配图和零件图,整理设计资料,编写设计说明书。 52014.5.165.17 准备毕业设计答辩课题申报与审查指导教师(签名): 年 月 日教研室主任(签名): 年 月 日学院教学院长(签名): 年 月 日毕业设计说明书题 目: 上销回转架的冲压工艺及 模具设计院 (部): 专 业: 班 级:姓 名: 学 号: 指导教师: 完成日期:目 录摘 要IUABSTRACTU前 言11.1 模具加工及金属薄板冲压加工的特点及优势11.2 课题讨论及难点分析21.3 课题总体设计思路32工艺分析及工艺方案确定52.1工件的零件图52.2工艺分析52.2.1弯曲部分工艺分析62.2工艺方案的确定63落料冲孔模的设计93.1毛坯尺寸计算93.2 排样93.3 确定模具压力中心103.4 冲压力的计算103.4.1 落料力103.4.2冲孔力113.4.3卸料力113.4.4推件力113.4.5总冲压力113.5冲压设备的选择113.6工作部分尺寸计算123.6.1落料凸、凹模刃口的尺寸计算123.6.2冲孔凸、凹模的刃口尺寸133.7冲孔落料复合模的设计143.7.1落料冲孔复合模结构的设计143.7.2 落料冲孔复合模主要零件的设计154弯曲模的设计304.1确定模具压力中心304.2弯曲力的计算304.3冲压设备的选择304.4翻边模刃口尺寸计算304.5弯曲模的设计314.5.1弯曲模结构的设计314.5.2弯曲模主要零件的设计325结 论36谢 辞37参考文献38摘 要本课题所设计的零件是较为典型的U型弯曲件。工件一侧有一个腰圆孔。通过对零件各部分进行计算分析后最终确定加工工序。经计算得翻边可以一次成型,工件整个成型过程所涉及的工序有:落料、冲孔、弯曲三步。在对零件进行工艺分析后,确定最终工艺方案为:落料冲孔复合,弯曲顺次进行。在确定工艺方案的基础上对主要模具进行设计,分析工件成型过程,并画出模具装配图及零件图。在本次设计中主要对落料复合模以及、弯曲模进行设计。关键词:落料冲孔;冲小孔;翻边;弯曲 Punching Process Analyzed and Die Design of the U Shape GrooUeABSTRACTTypical bended workpiece of U shape with three folds was designed in this graduation project. Two hoes are flanged on one side with a 1.8 mm hole. There are three holes on the other side. The process was determined by calculating and analyzing. Flanging can be shaped by one step after calculating. FiUe steps as blanking, punching, punching a small hole, flanging and bending were included. Analyzed the technics of parts, the final process was determined as four steps: blanking-punching compound, punching a small hole, flanging and bending. Besides, the main dies were designed, the process was analyzed, and the die assembly and workpiece pictures were drawed. In this graduation project, blanking-punching compound die, punching a small hole die, flanging die and flanging die were designed. Key words: blanking-punching compound; punching a small hole; flanging; bending毕业设计说明书前 言1.1 模具加工及金属薄板冲压加工的特点及优势随着汽车工业的快速发展,服务于汽车生产的模具近年来也快速发展1。服务于汽车生产的模具和塑料模具使用量最大的两大类。此外,还有铸造模具、锻造模具、橡胶模具、粉末冶金模具及拉丝模具和无机材料成型模具等。在汽车工业十分发达的国家,为汽车服务的模具往往要占到全部模具生产量的40%以上。经过多年发展,我国目前为汽车服务的模具约已占到了全部模具产量的1/3左右2。在这些模具中,冲压模具在模具行业和汽车覆盖件模具,直接关系到汽车车型,因此其地位尤为重要。要生产出大量的各式各样的汽车,先进技术装备必不可少,而模具就是汽车先进技术装备中的重要装备。“现代工业,模具先行”、“没有高水平的模具,就没有高水平的产品”,这已成为人们的共识。不管是汽车还是模具,虽然近年来发展迅速,我国已成为生产大国,但离生产强国的距离还很远。然而,要成为制造业强国,要成为汽车、模具等的制造强国是我们的目标。为了向汽车行业提供更为先进的技术装备,必须不断提高汽车冲压模具的冲压模具的水平与能力。金属薄板冲压成形是现代工业生产中一种非常重要的制造技术3,金属薄板及其制品在冲压成形过程中所表现出的成形性能或成形性,是横跨薄板冶金制造和冲压成形生产两大行业之间的交叉性工程技术 ,即冲压成形性能及其应用。冲压加工是靠冲压设备和模具实现对板料毛坯的塑性加工过程。冲压加工具有许多十分明显的优点,它利用冲压设备与冲模的简单的运动完成相当复杂形状零件的制造过程,而且并不需要操作工人的过多参与,所以冲压加工的生产效率很高,产品质量稳定,一般情况下,冲压加工的生产效率为每分钟数十件。又由于冲压加工的操作十分简单,为操作过程的机械化与自动化提供了十分有利的条件。因此,对某些工艺成熟的冲压件,生产效率可达每分钟数百件,甚至超过一千件以上。 冲压加工用的原材料多为冷轧板料和冷轧带材4。原材料的良好表面质量使用大量生产方式、高效而廉价的方法获得的。在冲压加工中这些良好的表面质量又不容易遭到破坏,所以冲压件的表面质量又不致遭到破坏,所以冲压件的表面质量好,而成本都很低廉。这个特点,在汽车支撑件件的生产上表现得十分明显5。 利用冲压加工方法,可以制造形状十分复杂的零件,能够把强度好、刚度大、重量轻等相互矛盾的特点融为一体,形成十分合理的结构形式。冲压加工时,一般不需要对毛坯加热,而且也不像切削加工那样把一部分金属切成切屑,造成原材料的损耗,所以它是一种节约能源和资源的具有环保意义的加工方法。冲压产品的质量与尺寸精度都是由冲模保证的6,基本上不受操作人员的素质与其他偶然因素的影响,所以冲压产品的质量管理简单,也容易实现自动化与智能化生产。冲压件的尺寸精度与表面质量好,通常都不需要后续的加工而直接装配或作为成品零件直接使用。冲压加工是一种高生产率的加工方法的,如汽车车身等大型零件每分钟可生产几件,而小零高速冲压则每分钟可生产千件以上。由于冲压加工的毛坯是板材或卷材,一般又在冷状态下加工,因此较易实现机械化和自动化,比较适合配置机器人而实现无人化生产7。冲压加工的材料利用率较高,一般可达70%85%,冲压加工的能耗也较低,由于冲压生产具有节材、节能和高生产率等特点,所以冲压件呈批量生产时,其成本比较低,经济效益高8。冲压件与铸件、锻件相比,具有薄、匀、轻、强的特点。冲压可制出其他方法难于制造的带有加强筋、肋、起伏或翻边的工件,以提高其刚性。由于采用精密模具,工件精度可达微米级,且重复精度高、规格一致,可以冲压出孔窝、凸台等。 冷冲压件一般不再经切削加工,或仅需要少量的切削加工。热冲压件精度和表面状态低于冷冲压件,但仍优于铸件、锻件,切削加工量少。 冲压是高效的生产方法9,采用复合模,尤其是多工位级进模,可在一台压力机上完成多道冲压工序,实现由带料开卷、矫平、冲裁到成形、精整的全自动生产。生产效率高,劳动条件好,生产成本低,一般每分钟可生产数百件5。由于冲压加工方法具有前述的许多优点,现在他已经成为金属加工中的一种非常重要的制造方法。1.2 课题讨论及难点分析本课题所要设计的上销回转架如图1.1,它是凸包定位且焊接组合在车架的电气元件支架类类零件,材料Q235,厚度为2mm,年生产量5万件,首先它是薄板类零件,形状较为复杂,零件又需要翻边,且生产批量较大,这些都是用冲压加工较容易实现而其他加工方法所不具备的,所以用冲压方法来加工该零件是非常理想的。针对这个零件,分别要经过落料、冲孔、冲小孔、U形弯曲等几个工序才能完成。在设计每套模具的时候又有很多难点和需要注意的问题。例如在冲2X5的小孔时,凸模的强度是否可以达到要求,是不是需要安装一个凸模保护套,还有在翻边的过程中边缘是否会发生破裂,再比如若翻边完成后,弯曲时如何固定板料。这些都是在设计时急需解决的问题。图1.1上销回转架示意图1.3 课题总体设计思路 (1)分析冲压件的工艺性根据设计题目的要求,分析冲压件成型的结构工艺性,分析冲压件的形状特点、尺寸、大小、精度要求及所用材料是否符合冲压工艺要求。(2)制定冲压件工艺方案在分析了冲压件的工艺性后,通常可以列出几种不同的冲压工艺方案(包括工序性质、工序数目、工序顺序及组合方式),从产品质量、生产效率、设备占用情况、模具制造难易程度和模具寿命高低、工艺成本、操作方便和安全程度等方面,进行综合分析、比较,然后确定适合于具体生产条件的最经济合理的工艺方案。(3)确定毛坯形状、尺寸和下料方式在最经济的原则下,决定毛坯的形状、尺寸和下料方式,确定材料的消耗量。(4)确定冲模类型及结构形式根据所确定的工艺方案和冲压件的形状特点、精度要求、生产批量、模具制造条件、操作方便及安全的要求,以及利用现有通用机械化、自动化装置的可能,选定冲模类型及结构形式,绘制模具结构草图。(5)进行必要的工艺计算计算毛坯尺寸,以便在最经济的原则下进行排样和合理使用材料。计算冲压力(冲裁力、弯曲力、卸料力、推件力等)以便选择压力机。计算模具压力中心,防止模具因受偏心负荷作用影响模具寿命和精度。计算模具各主要零件(凹模、凸模、凸模固定板、垫板)的外形尺寸,以及卸料弹簧的自由高度等。确定凸、凹模的间隙,计算凸、凹模工作部分尺寸9。(6)选择压力机压力机的选择是模具设计的一项重要内容,设计模具时必须把所选的压力机的类型、型号、规格确定下来。压力机的确定主要取决于冲压工艺的要求和冲模结构情况。(7)绘制模具总图和非标准零件图2工艺分析及工艺方案确定2.1工件的零件图上销回转架的零件图如图2.2图2.2上销回转架零件图2.2工艺分析本课题所要设计的上销回转架,是凸包定位且焊接组合在车架的电气元件支架类类零件,该零件属隐蔽件,外观上要求不高,只需平整。材料Q235,厚度为2mm,年生产量5万件。此零件属于较为典型的U型弯曲件,其中一侧有一个腰圆孔。根据零件的形状,需要分别经过落料、冲孔、U形弯曲等几个工序才能完成。现首先对翻边部分进行计算,确定能否一次成形。另外,零件图中的尺寸公差为未注公差,在处理这类零件时按IT14级要求10。2.2.1弯曲部分工艺分析本零件是典型的U型弯曲件,在弯曲过程中会可能出现回弹,但其对外性要求不高,可以忽略不计。弯曲圆角半径为0.5大于最小弯曲半径(rmin=0.4t=0.41=0.6mm),故此零件形状、尺寸均满足弯曲工艺的要求,可以弯曲工序进行加工。2.1工艺方案的确定通过工艺性分析,可得到以下几种方案:(1)单工序落料、冲孔、弯曲,采用单工序模具。每道工序分别设计一套模具,加工过程中按照工序一步步完成。优点:设计简单明了,设备冲裁力不必很大就可完成工作。缺点:每道工序都要制作一套模具。模具费用昂贵,这就增加了生产成本; 生产过程中,坯料要经过至少3道工序,工序繁杂,生产效率低; 坯料每经过一道工序就要重新定位以便于加工,这就增加了尺寸误差,使产品精度下降; 占用车间工位和设备,不方便操作12。(2)采用复合模进行加工,即落料冲孔复合,弯曲顺次进行。优点:在完成这些工序过程中,冲压坯料无需进给移动。生产效率高,结构简单,节省制造费用,且定位准确,生产精度高。缺点:需要的冲裁力较大,模具制作复杂,生产过程中容易磨损。(3)级进模:冲孔、落料、弯曲递进完成。优点:生产效率高且操作安全。缺点:模具结构复杂,制造周期长,生产成本高,因此只有在特大量生产中才比较适宜。定位不准确,尤其是在冲小孔时无法保证尺寸精度。 综合考虑成本、效率生产批量和要生产的实际工件等方面因素,采用复合模加工比较合理。经落料冲孔后的坯料图分别如图2.3所示。图2.3 落料冲孔后的零件图3落料冲孔模的设计3.1毛坯尺寸计算毛坯宽度计算:因为r/t=0.5/1=0.5,参照中国模具设计大典12表19.3-1,得x=0.25查表19.3-6得l弯=1.46mml=115.6mmX69.05mm则毛坯的外形尺寸为长L为115.6mm,宽为69.05mm的长方形板料。3.2 排样工件排样根据落料工序设计,考虑操作方便及模具结构简单,由于件展开尺寸大于65mm,因此采用单行排列,查表2-1613得 搭边值a1=1.5mm,a=1.5mm,条料的排样图如图3.1所示,则:条料宽:b=115.6+4=119.6mm条料的进距为:h=69.05+a1=71.55mm 条料的利用率:=s/(hb)100 (3.2a)=5092/(124.464.5)100=63.5图3.1 条料排样图3.3 确定模具压力中心 由于零件形状左右对称,上下不对称,故x0=31.5mmy0=liyi/li (3.3a)=47464.55/2381.27=19.93mm3.4 冲压力的计算3.4.1 落料力F落=KLt (3.4a) =1.34342400 451.4KN3.4.2冲孔力 F孔=KLt (3.4b) =1.369.32400 72.1KN3.4.3卸料力 F卸= K卸F落 (3.4c) =0.06451.4KN 27KN3.4.4推件力 F推= NK推F孔 (3.4d) =2X0.0572.1N 7.21KN3.4.5总冲压力 F总 = F落F孔F卸F推 (3.4e)=557.71KN3.5冲压设备的选择 为了保证安全,防止设备的过载,可按公称压力F压(1.61.8)F总的原则选取压力机13。参照冲压工艺与模具设计14,落料冲孔工步可选取公称压力350KN的J23-35型开式双柱可倾压力机,该压力机与模具设计的有关参数为;公称压力:650KN;滑块行程:70mm;最大闭合高度:220mm;封闭高度调节量:60mm ;工作台尺寸:550mm400mm;模柄孔尺寸:50mm50mm。3.6工作部分尺寸计算3.6.1落料凸、凹模刃口的尺寸计算落料时应先确定凹模的尺寸。由于工件尺寸属于未注公差尺寸,在计算凸模与凹模尺寸时,冲压件公差尺寸的极限偏差数值通常按GB1800-79IT14级。凸模尺寸按照凹模尺寸配做,保证其最小间隙值为零。该零件材料为Q235,料厚2mm,由冲压工艺与模具设计,表2-5可查得:Zmax=0.20 Zmin=0.14 Zmax- Zmin=0.200.14=0.06 (3.6a)由表2-10查得凸、凹模制造公差:落料部分: d=+0.03 p=0.02d +p=+0.03+0.02=0.05Zmax- Zmin=0.06 (3.6b)由实用冲压工艺与模具设计15表3-13可查得:落料凹模长: x=0.370落料凹模宽: x=0.310落料凹模长: Ad1=(D1-x) (3.6c) =(115.6-0.370)mm =115.23mm式中:零件的制造偏差,x系数落料凹模宽: Ad2=(D2-x) (3.6c) =(69.05-0.300)mm =68.75mm落料凸模长: Ap1=( Ad1- Zmin) (3.6d) =(115.23-0.13) =115.1mm落料凸模宽: A p2=( Ad2- Zmin) (3.6d) =(68.75-0.14) =68.61mm3.6.2冲孔凸、凹模的刃口尺寸冲孔时应先确定凸模的尺寸。由于工件尺寸属于未注公差尺寸,在计算凸模与凹模尺寸时,冲压件公差尺寸的极限偏差数值通常按GB1800-79IT14级15。凹模尺寸按照凸模尺寸配做,保证其最小间隙值为零。由表2-10查得凸、凹模制造公差:d=+0.02 p=0.02d +p=+0.02+0.02=0.04Zmax- Zmin=0.06 (3.6a)对5孔: dp1=(d+x) (3.6b) = (5+0.50.2) mm =5.1 mm dd1=( dp1+ Zmin) (3.6c) = (5.10.14)mm =5.24 mm对2孔: dp2=(d+x) (3.6c) = (2+0.50.2) mm =2.1 mm dd2=( dp2+ Zmin) (3.6c) = (2.10.14) mm =2.24mm3.7冲孔落料复合模的设计3.7.1落料冲孔复合模结构的设计(1) 模具总体设计在确定采用复合模后,便要考虑采用正装式还是倒装式复合模。采用倒装式复合模,拉深后工件嵌在上模部分的落料凹模内,由推件装置推出,再由压力机上附加的接件装置接走,条料由下模的卸料装置脱出。这样操作方便而且安全,能保证较高的生产率。而正装式复合模,工件则由下模的推件装置向上推出,条料由上模卸料装置脱出,二者混杂在一起,如果万一来不及排除废料或工件而进行下一次冲压,就容易崩裂模具刃口。因此,这副落料冲孔复合模采用倒装结构。(2) 推件装置在倒装式复合模中,冲裁后工件嵌在上模部分的落料凹模内,需由刚性或弹性推件装置推出。刚性推件装置推件可靠,可以将工件稳当地推出凹模,但在冲裁时,刚性推件装置对工件不起压平作用,故工件平整度和尺寸精度比用弹性推件装置时要低些。根据生产实际经验,用刚性推件装置已能保证零件所有尺寸精度,故这副模具采用刚性推件块。(3) 卸料装置复合模冲裁时,条料将卡在凸凹模外缘,因此需要在下模装卸料装置。卸料装置有二种形式:一种是将卸料零件,装在卸料板与凸凹模固定板之间;另一种是将卸料零件装设在下模板下面。由于零件的条料卸料力大,故采用前一种结构复杂,弹性卸料装置。 (4) 导向装置15由于工件为弯曲件精度要求不高,而且材料不是很薄,模具间隙一般 ,故采用中间导柱模架。(5) 工作过程本冲模在一次行程中完成落料、冲孔两个工序,生产效率高。冲压时,条料从5-活动导料销中通过,由3凸凹模和18落料凹模进行落料。11顶板继续下行,7活动挡料销挡住板料,3凸凹模和12、13凸模完成工件冲孔工序。冲孔后,嵌在3凸凹模内的工件由9推件器推出,废料由4卸料板卸下,整个过程完成。落料冲孔复合模装配图如图3.2所示:3.1.2 落料冲孔复合模主要零件的设计对于复合模来说,工作部分包括凸凹模、凸模和凹模三个零件。现在这副模具的凸凹模用电火花线切割一次割出,所以要将凸凹模的刃口尺寸全部算出,其外形按落料凹模计算,内孔按冲孔凸模计算。凸模按凸凹模内孔线切割,也需标出刃口尺寸16。凹模也用线切割加工,无论是光电跟踪还是程序控制的线切割,在制作光电跟踪图或者计算输入方程时,均以凹模刃口工作部分尺寸作为依据,故凹模刃口尺寸也需计算。 图3.2 落料冲孔复合模装配图 由于,凸凹模、凸模和凹模三个零件都需要进行线切割 ,而且三个之间的尺寸有一定的联系,所以可以连续加工。首先,加工一块凹模外形尺寸的模具板材,确定压力中心,在板材上线切割出凹模的刃口,调节线切割设备选用合适的钼丝使切割量小于凸、凹模间隙,在切下的废料上切割出拉深凹模刃口,接下来在切下的废料上切割出拉深凸模,然后在数控铣上铣出头部曲面,完成模具工作零件的加工17。(1)落料凹模的设计17材料:Cr12MoU;外形尺寸:27020025;由于大批量生产,对刃口强度要求较高,所以刃口采用直刃式,磨损后刃口尺寸变化小,凹模刃口厚度为5mm;加工后进行热处理:5860HRC;凹模采用M10销钉定位,通过4个M10内六角螺钉经过凸模固定板与垫板紧固在上模座上,表面粗糙度为1.6。如图2.4所示。(2)凸凹模的设计材料:Cr12MoU;外形尺寸:如图2.4所示加工后进行热处理:58-60 HRC;凸凹模通过铆接固定在下固定板上,表面粗糙度为1.6。(3)冲孔凸模的设计18材料:Cr12MoU;凸模圆角半径为5mm;加工后进行热处理:58-60HRC;凸模通过与固定板一起磨平后卡在一起;表面粗糙度为1.6。图2.3 落料凹模图2.4 凸凹模 (4)卸料板的设计卸料装置的形式比较多,它包括固定卸料板、活动卸料板、弹压卸料板和废料切刀等几种。本制件较薄且要求平整,而且卸料板是用在复合模中,所以选用弹压卸料板如图2.9所示。图2.9 卸料板(5)模柄的选择16中小型冲模通过模柄将上模固定在压力机的滑块上。通过对制件的分析,决定采用适合于较大模具上的凸缘模柄,如图2.10所示。 (6)固定板与垫板的设计 固定板选用矩形,厚度是22mm,固定板选用规格是27020020。 垫板不需经淬硬磨平,厚度取10mm,垫板选用规格是27020010。图2.10 凸缘模柄4弯曲模的设计4.1确定模具压力中心 由于零件形状左右对称,上下不对称,故x0=31.5mmy0=liyi/li (6.1a) =47373.17/2378.72=19.92mm4.2弯曲力的计算弯曲力: F弯= 0.7KBt2b/(rt) (6.2a) =0.71.31022215/(0.50.9) =0.11KN压料力: F压=F顶=0.8 F弯=0.2KN F总= F弯F压F顶 = 0.31KN 4.3冲压设备的选择 为了保证安全,防止设备的过载,可按公称压力F压(1.61.8)F总的原则选取压力机。参照冲压工艺与模具设计,落料冲孔工步可选取公称压力100KN的J23-10型开式双柱可倾压力机,该压力机与模具设计的有关参数为;公称压力:100KN;滑块行程:50mm;最大闭合高度:210mm;封闭高度调节量:50mm ;工作台尺寸:360mm240mm;模柄孔尺寸:40mm50mm。4.44.4弯曲模的设计4.4.1弯曲模结构的设计(1)模具总体设计模具采用中间导柱标准模架,模具上模部分主要由上模架、垫板、凸模固定板组成,卸料方式为弹性卸料,以弹簧为弹性元件。下模部分由下模座、凹模、凹模垫板、顶件块、定位板等组成。其装配图如图6.1所示。(2)模具的特点该模具结构简单,在压力机上安装,调节方便。定件板在弯曲时与凸模将板料压紧,并且背压力可以根据需要调节大小,始终能对工件底部施加较大的反顶件力,能使工件底部保持平整,能有效地防止弯曲件的滑移,由于弯曲结束时制件能得到可靠的校正,因而大大降低了制件的回弹量17。(3)模具工作过程工作中,先将板料放在固定板中,上模下行,凸模与顶件板将板料夹紧,凸模与凹模对板料进行弯曲直至顶件板与凹模垫板接触,并将凸模和顶件板进行特殊加工,使其在弯曲的过程中可以使坯料弯出褶边,弯曲结束后顶件板可以通过顶杆和弹簧将弯曲件顶出凹模。 图6.1 弯曲模装配图4.4.2弯曲模主要零件的设计(1)凹模的设计17材料:Cr12MoU;外形尺寸:270020035;由于大批量生产,对刃口强度要求较高,所以刃口采用直刃式。加工后进行热处理:5860HRC;凹模通过通过四个M10螺钉和两个圆柱销与凹模垫板一块固定在下模座上,表面粗糙度为1.6。如图6.2所示。图6.2 弯曲凹模图6.3 弯曲凸模(3)顶件块的设计材料:45;外形尺寸:7310.215;加工后进行热处理:5860HRC;其置于凹模之间,工作时被压下并与凹模垫板紧密接触,工作完毕后由卸料螺钉通过弹簧将其顶出,如图6.4所示。图6.4 顶件板(4)定位板的设计材料:45钢;外形尺寸:1401402mm;加工后热处理:4650 HRC;将坯料放在定位板中,使其不能滑动7结 论 (1)为U型支架类零件设计模具时,首先要计算毛坯直径,通过计算分析加工工序,确定工艺方案的可行性。 (2)落料、冲孔工序采用倒装式复合模,工件由上面的凹模带上后,由推件装置推出,再由压力机上附加的接件装置接走,条料由下模的卸料装置脱出。这样操作方便而且安全,能保证较高的生产率。在倒装式复合模中,冲孔后工件嵌在上模部分的落料拉深凸凹模内,采用刚性推件装置推出。复合模冲裁时,条料将卡在凹凸模外缘,因此下模采用弹性卸料装置。由于工件为弯曲件精度要求不高,模具间隙一般,故采用中间导柱模架。(3)主要零件加工方案由于凸凹模、凸模和凹模三个零件都需要进行线切割 ,而且三个之间的尺寸有一定的联系,所以可以连续加工。首先,加工一块凹模外形尺寸的模具板材,确定压力中心,在板材上线切割出凹模的刃口,调节线切割设备选择合适的钼丝使切割量小于凸、凹模间隙,在切下的废料上切割出拉深凹模刃口,接下来在切下的废料上切割出拉深凸模,然后在数控铣床上铣出头部曲面。(4)在弯曲模具设计时,模具采用中间导柱标准模架,工作中,先将板料放在固定板中,上模下行,凸模与顶件板将板料夹紧,凸模与凹模对板料进行弯曲直至顶件板与凹模垫板接触,并将凸模和顶件板进行特殊加工,使其在弯曲的过程中可以使坯料弯出褶边,弯曲结束后顶件板可以通过顶杆和弹簧将弯曲件顶出凹模。谢 辞毕业设计得以完成,要感谢的人实在太多了,首先要感谢任国成老师,因为我的毕业设计的整个过程都是在任老师的悉心指导下完成的。老师渊博的专业知识,严谨的治学态度,精益求精的工作作风,诲人不倦的高尚师德,严以律己、宽以待人的崇高风范,朴实无华、平易近人的人格魅力对我影响深远。本次毕业设计从选题到完成,每一步都是在老师的指导下完成的,倾注了老师大量的心血。再次我要对我们课题组的同学表示衷心的感谢,在平时的实验过程中得到了他们很多的帮助。同时,毕业设计的顺利完成,离不开其他各位老师的关心和帮助,感谢我们学院其他各位老师在大学期间给予我的教导与帮助。XXIII毕业设计说明书参考文献1 徐义,李落星,李光耀,等型材弯曲工艺的现状及发展前景J 塑形工程学报,2005,(3):61-692 O.W.Salomons,F.J.A.M.Uan.Hooten,H.J.J.Kals,ReUiew of Research in Feature-Based Design,Journal of Manufacturing Systems,Uol.12,No.2,1992.3 Mantyla M.A Modleing system for top-down of assembled products IBM Jres&DeUelop, 1990, 34 (5): 636-659.4 姜奎华冲压工艺与模具设计M. 机械工业出版社,1998.55 Mantyla M.A Modleing system for top-down of assembled products IBM Jres&DeUelop, 1990, 34 (5): 636-6596 肖景容,姜奎华主编冲压工艺与模具设计M. 机械工业出版社,北京:19997 周大隽冲模结构设计M .机械工业出版社,北京:20068模具设计与制造技术教育丛书编委会编.模具结构设计M. 机械工业出版社,北京2003.109 郑家贤著.冲压模具设计使用手册M . 机械工业出版社,北京: 2007.910 阮雪榆.中国模具工业和技术的发展J.模具技术,2001(2):727411 洪慎章.塑性成形技术的现状及发展趋势J.模具技术,2003(1):545612 白容恩.典型零件复合模设计探讨J.模具工业,1989(11):5913金涤尘.现代模具制造技术M.北京:机械工业出版社,200314付宏生模具试图与制图M北京:化学工业出版社,200615王秀凤,万良辉.冷冲压模具设计与制造M.北京:北京航空航天大学出版社,2005:2-316周大隽.冲模结构设计要领与范例M.北京:机械工业出版社,2005:23-3517中国机械工程学会锻压学会.锻压手册(第2卷)M.北京:机械工业出版社,1993:56-642Int 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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