托板沖壓模具設(shè)計【沖孔落料級進?！俊菊f明書+CAD】,沖孔落料級進模,說明書+CAD,托板沖壓模具設(shè)計【沖孔落料級進模】【說明書+CAD】,沖壓,模具設(shè)計,沖孔,落料級進模,說明書,仿單,cad 目錄 緒論………………………………………………………………………………… 沖裁模設(shè)計題目………………………………………………………………… （一）沖裁件工藝分析………………………………………………….…… （二） 確定工藝方案及模具結(jié)構(gòu)形式……………….……………… （三） 模具設(shè)計計算………………………………………….……..…… 1．排樣 計算條料寬度及確定步距………………………….……..…. 2利用率計算…………………………………………………….…..…… 3．計算總沖壓力……………………………………….. …….. ……….. 4．確定壓力中心……………………………………….. ………. …….. 5．沖模刃口尺寸及公差的計算……………………. .. ………. ……... 6. 確定各主要零件結(jié)構(gòu)尺寸……………….............. .. ………… …….. （1）凹模外形尺寸的確定……………………….. .. …….. ……….. （2）凸模長度L1的確定……………………………….. ………….. （3）設(shè)計并繪制總圖、選取標準件…………….. .... .. ……………. （五）繪制非標準零件圖………………………………... .. ..……….. (六) 模具主要零件加工工藝規(guī)程的制……………………………... 總裝工藝………………………………………………. ………. ….…... 墊板的加工工藝…………………………………………. ……. ….…... 凸模固定板的加工工藝………………………………. …. ………. .... 落料凸模的加工工藝………………………………….. …. ……….. ... 導(dǎo)正銷的加工工藝……………………………………. …. ……….. ... 沖孔凸模的加工工藝………………………………. …. …. ………. .... 卸料板加工工藝……………………………………. …. ….……….. ... 凹模加工工藝…………………………………………. …. ……….. ... 導(dǎo)料板加工工藝…………………………………... …. …. …….…. ... 始沖擋料銷的加工工藝…………………………. …. …. …….….. ... 體會…. …. ………. ... …. …. ……. ………. ... …. …. ………. …………... 參考文獻. …. ………. ... …. …. ……. ………. ... …. …. ……….……. ... 附圖紙. …. ………. ... …. …. ……. ………. ... …. …. ……….……. ....... 緒論 一：沖壓的概念，特點與發(fā)展 沖壓是利用安裝在沖壓設(shè)備（主要是壓力機）上的模具對材料施加壓力，使其產(chǎn)生分離或塑性變形，從而獲得所需零件（俗稱沖壓或沖壓件）的一種壓力加工方法。沖壓通常是在常溫下對材料進行冷變形加工，且主要采用板料來加工成所需零件，所以也叫冷沖壓或板料沖壓。沖壓是材料壓力加工或塑性加工的主要方法之一，隸屬于材料成型工程術(shù)。 沖壓所使用的模具稱為沖壓模具，簡稱沖模。沖模是將材料（金屬或非金屬）批量加工成所需沖件的專用工具。沖模在沖壓中至關(guān)重要，沒有符合要求的沖模，批量沖壓生產(chǎn)就難以進行；沒有先進的沖模，先進的沖壓工藝就無法實現(xiàn)。沖壓工藝與模具、沖壓設(shè)備和沖壓材料構(gòu)成沖壓加工的三要素，只有它們相互結(jié)合才能得出沖壓件。 與機械加工及塑性加工的其它方法相比，沖壓加工無論在技術(shù)方面還是經(jīng)濟方面都具有許多獨特的優(yōu)點。主要表現(xiàn)如下。 (1) 沖壓加工的生產(chǎn)效率高，且操作方便，易于實現(xiàn)機械化與自動化。這是因為沖壓是依靠沖模和沖壓設(shè)備來完成加工，普通壓力機的行程次數(shù)為每分鐘可達幾十次，高速壓力要每分鐘可達數(shù)百次甚至千次以上，而且每次沖壓行程就可能得到一個沖件。 （2）沖壓時由于模具保證了沖壓件的尺寸與形狀精度，且一般不破壞沖壓件的表面質(zhì)量,而模具的壽命一般較長,所以沖壓的質(zhì)量穩(wěn)定,互換性好,具有“一模一樣”的特征。 （3）沖壓可加工出尺寸范圍較大、形狀較復(fù)雜的零件，如小到鐘表的秒表，大到汽車縱梁、覆蓋件等，加上沖壓時材料的冷變形硬化效應(yīng)，沖壓的強度和剛度均較高。 （4）沖壓一般沒有切屑碎料生成，材料的消耗較少，且不需其它加熱設(shè)備，因而是一種省料，節(jié)能的加工方法，沖壓件的成本較低。 但是，沖壓加工所使用的模具一般具有專用性，有時一個復(fù)雜零件需要數(shù)套模具才能加工成形，且模具 制造的精度高，技術(shù)要求高，是技術(shù)密集形產(chǎn)品。所以，只有在沖壓件生產(chǎn)批量較大的情況下，沖壓加工的優(yōu)點才能充分體現(xiàn)，從而獲得較好的經(jīng)濟效益。 沖壓地、在現(xiàn)代工業(yè)生產(chǎn)中，尤其是大批量生產(chǎn)中應(yīng)用十分廣泛。相當(dāng)多的工業(yè)部門越來越多地采用沖壓法加工產(chǎn)品零部件，如汽車、農(nóng)機、儀器、儀表、電子、航空、航天、家電及輕工等行業(yè)。在這些工業(yè)部門中，沖壓件所占的比重都相當(dāng)?shù)拇?，少則60%以上，多則90%以上。不少過去用鍛造=鑄造和切削加工方法制造的零件，現(xiàn)在大多數(shù)也被質(zhì)量輕、剛度好的沖壓件所代替。因此可以說，如果生產(chǎn)中不諒采用沖壓工藝，許多工業(yè)部門要提高生產(chǎn)效率和產(chǎn)品質(zhì)量、降低生產(chǎn)成本、快速進行產(chǎn)品更新?lián)Q代等都是難以實現(xiàn) 的。 1.2 沖壓的基本工序及模具 由于沖壓加工的零件種類繁多，各類零件的形狀、尺寸和精度要求又各不相同，因而生產(chǎn)中采用的沖壓工藝方法也是多種多樣的。概括起來，可分為分離工序和成形工序兩大類；分離工序是指使坯料沿一定的輪廓線分離而獲得一定形狀、尺寸和斷面質(zhì)量的沖壓（俗稱沖裁件）的工序；成形工序是指使坯料在不破裂的條件下產(chǎn)生塑性變形而獲得一定形狀和尺寸的沖壓件的工序。 上述兩類工序，按基本變形方式不同又可分為沖裁、彎曲、拉深和成形四種基本工序，每種基本工序還包含有多種單一工序。 在實際生產(chǎn)中，當(dāng)沖壓件的生產(chǎn)批量較大、尺寸較少而公差要求較小時，若用分散的單一工序來沖壓是不經(jīng)濟甚至難于達到要求。這時在工藝上多采用集中的方案，即把兩種或兩種以上的單一工序集中在一副模具內(nèi)完成，稱為組合的方法不同，又可將其分為復(fù)合-級進和復(fù)合-級進三種組合方式。 復(fù)合沖壓——在壓力機的一次工作行程中，在模具的同一工位上同時完成兩種或兩種以上不同單一工序的一種組合方法式。 級進沖壓——在壓力機上的一次工作行程中，按照一定的順序在同一模具的不同工位上完面兩種或兩種以上不同單一工序的一種組合方式。 復(fù)合-級進——在一副沖模上包含復(fù)合和級進兩種方式的組合工序。 沖模的結(jié)構(gòu)類型也很多。通常按工序性質(zhì)可分為沖裁模、彎曲模、拉深模和成形模等；按工序的組合方式可分為單工序模、復(fù)合模和級進模等。但不論何種類型的沖模，都可看成是由上模和下模兩部分 組成，上模被固定在壓力機工作臺或墊板上，是沖模的固定部分。工作時，坯料在下模面上通過定位零件定位，壓力機滑塊帶動上模下壓，在模具工作零件（即凸模、凹模）的作用下坯料便產(chǎn)生分離或塑性變形，從而獲得所需形狀與尺寸的沖件。上?；厣龝r，模具的卸料與出件裝置將沖件或廢料從凸、凹模上卸下或推、頂出來，以便進行下一次沖壓循環(huán)。 1.3 沖壓技術(shù)的現(xiàn)狀及發(fā)展方向 隨著科學(xué)技術(shù)的不斷進步和工業(yè)生產(chǎn)的迅速發(fā)展，許多新技術(shù)、新工藝、新設(shè)備、新材料不斷涌現(xiàn)，因而促進了沖壓技術(shù)的不斷革新和發(fā)展。其主要表現(xiàn)和發(fā)展方向如下。 (1).沖壓成形理論及沖壓工藝方面 沖壓成形理論的研究是提高沖壓技術(shù)的基礎(chǔ)。目前，國內(nèi)外對沖壓成形理論的研究非常重視，在材料沖壓性能研究、沖壓成形過程應(yīng)力應(yīng)變分析、板料變形規(guī)律研究及坯料與模具之間的相互作用研究等方面均取得了較大的進展。特別是隨著計算機技術(shù)的飛躍發(fā)展和塑性變形理論的進一步完善，近年來國內(nèi)外已開始應(yīng)用塑性成形過程的計算機模擬技術(shù)，即利用有限元（FEM）等有值分析方法模擬金屬的塑性成形過程，根據(jù)分析結(jié)果，設(shè)計人員可預(yù)測某一工藝方案成形的可行性及可能出現(xiàn)的質(zhì)量問題，并通過在計算機上選擇修改相關(guān)參數(shù)，可實現(xiàn)工藝及模具的優(yōu)化設(shè)計。這樣既節(jié)省了昂貴的試模費用，也縮短了制模具周期。 研究推廣能提高生產(chǎn)率及產(chǎn)品質(zhì)量、降低成本和擴大沖壓工藝應(yīng)用范圍的各種壓新工藝，也是沖壓技術(shù)的發(fā)展方向之一。目前，國內(nèi)外相繼涌現(xiàn)出精密沖壓工藝、軟模成形工藝、高能高速成形工藝及無模多點成形工藝等精密、高效、經(jīng)濟的沖壓新工藝。其中，精密沖裁是提高沖裁件質(zhì)量的有效方法，它擴大了沖壓加工范圍，目前精密沖裁加工零件的厚度可達25mm，精度可達IT16~17級；用液體、橡膠、聚氨酯等作柔性凸?；虬寄５能浤３尚喂に?，能加工出用普通加工方法難以加工的材料和復(fù)雜形狀的零件，在特定生產(chǎn)條件下具有明顯的經(jīng)濟效果；采用爆炸等高能效成形方法對于加工各種尺寸在、形狀復(fù)雜、批量小、強度高和精度要求較高的板料零件，具有很重要的實用意義；利用金屬材料的超塑性進行超塑成形，可以用一次成形代替多道普通的沖壓成形工序，這對于加工形狀復(fù)雜和大型板料零件具有突出的優(yōu)越性；無模多點成形工序是用高度可調(diào)的凸模群體代替?zhèn)鹘y(tǒng)模具進行板料曲面成形的一種先進技術(shù)，我國已自主設(shè)計制造了具有國際領(lǐng)先水平的無模多點成形設(shè)備，解決了多點壓機成形法，從而可隨意改變變形路徑與受力狀態(tài)，提高了材料的成形極限，同時利用反復(fù)成形技術(shù)可消除材料內(nèi)殘余應(yīng)力，實現(xiàn)無回彈成形。無模多點成形系統(tǒng)以CAD/CAM/CAE技術(shù)為主要手段，能快速經(jīng)濟地實現(xiàn)三維曲面的自動化成形。 (2.)沖模是實現(xiàn)沖壓生產(chǎn)的基本條件.在沖模的設(shè)計制造上,目前正朝著以下兩方面發(fā)展:一方面,為了適應(yīng)高速、自動、精密、安全等大批量現(xiàn)代生產(chǎn)的需要，沖模正向高效率、高精度、高壽命及多工位、多功能方向發(fā)展，與此相比適應(yīng)的新型模具材料及其熱處理技術(shù)，各種高效、精密、數(shù)控自動化的模具加工機床和檢測設(shè)備以及模具CAD/CAM技術(shù)也在迅速發(fā)展；另一方面，為了適應(yīng)產(chǎn)品更新?lián)Q代和試制或小批量生產(chǎn)的需要，鋅基合金沖模、聚氨酯橡膠沖模、薄板沖模、鋼帶沖模、組合沖模等各種簡易沖模及其制造技術(shù)也得到了迅速發(fā)展。 精密、高效的多工位及多功能級進模和大型復(fù)雜的汽車覆蓋件沖模代表了現(xiàn)代沖模的技術(shù)水平。目前，50個工位以上的級進模進距精度可達到2微米，多功能級進模不僅可以完成沖壓全過程，還可完成焊接、裝配等工序。我國已能自行設(shè)計制造出達到國際水平的精度達2?~5微米，進距精度2~3微米，總壽命達1億次。我國主要汽車模具企業(yè)，已能生產(chǎn)成套轎車覆蓋件模具，在設(shè)計制造方法、手段方面已基本達到了國際水平，但在制造方法手段方面已基本達到了國際水平，模具結(jié)構(gòu)、功能方面也接近國際水平，但在制造質(zhì)量、精度、制造周期和成本方面與國外相比還存在一定差距。 模具制造技術(shù)現(xiàn)代化是模具工業(yè)發(fā)展的基礎(chǔ)。計算機技術(shù)、信息技術(shù)、自動化技術(shù)等先進技術(shù)正在不斷向傳統(tǒng)制造技術(shù)滲透、交叉、融合形成了現(xiàn)代模具制造技術(shù)。其中高速銑削加工、電火花銑削加工、慢走絲切割加工、精密磨削及拋光技術(shù)、數(shù)控測量等代表了現(xiàn)代沖模制造的技術(shù)水平。高速銑削加工不但具有加工速度高以及良好的加工精度和表面質(zhì)量（主軸轉(zhuǎn)速一般為15000~40000r/min）,加工精度一般可達10微米，最好的表面粗糙度Ra≤1微米），而且與傳統(tǒng)切削加工相比具有溫升低（工件只升高3攝氏度）、切削力小，因而可加工熱敏材料和剛性差的零件，合理選擇刀具和切削用量還可實現(xiàn)硬材料（60HRC）加工；電火花銑削加工（又稱電火花創(chuàng)成加工）是以高速旋轉(zhuǎn)的簡單管狀電極作三維或二維輪廓加工（像數(shù)控銑一樣），因此不再需要制造昂貴的成形電極，如日本三菱公司生產(chǎn)的EDSCAN8E電火花銑削加工機床，配置有電極損耗自動補償系統(tǒng)、CAD/CAM集成系統(tǒng)、在線自動測量系統(tǒng)和動態(tài)仿真系統(tǒng)，體現(xiàn)了當(dāng)今電火花加工機床的技術(shù)水平；慢走絲線切割技術(shù)的發(fā)展水平已相當(dāng)高，功能也相當(dāng)完善，自動化程度已達到無人看管運行的程度，目前切割速度已達到300mm/min,加工精度可達±1.5微米，表面粗糙度達Ra=01~0.2微米;精度磨削及拋光已開始使用數(shù)控成形磨床、數(shù)控光學(xué)曲線磨床、數(shù)控連續(xù)軌跡坐標磨床及自動拋光等先進設(shè)備和技術(shù);模具加工過程中的檢測技術(shù)也取得了很大的發(fā)展,現(xiàn)在三坐標測量機除了能高精度地測量復(fù)雜曲面的數(shù)據(jù)外,其良好的溫度補償裝置、可靠的抗振保護能力、嚴密的除塵措施及簡單操作步驟，使得現(xiàn)場自動化檢測成為可能。此外，激光快速成形技術(shù)（RPM）與樹脂澆注技術(shù)在快速經(jīng)濟制模技術(shù)中得到了成功的應(yīng)用。利用RPM技術(shù)快速成形三維原型后，通過陶瓷精鑄、電弧涂噴、消失模、熔模等技術(shù)可快速制造各種成形模。如清華大學(xué)開發(fā)研制的“M-RPMS-Ⅱ型多功能快速原型制造系統(tǒng)”是我國自主知識產(chǎn)權(quán)的世界惟一擁有兩種快速成形工藝（分層實體制造SSM和熔融擠壓成形MEM）的系統(tǒng)，它基于“模塊化技術(shù)集成”之概念而設(shè)計和制造，具有較好的價格性能比。一汽模具制造公司在以CAD/CAM加工的主模型為基礎(chǔ)，采用瑞士汽巴精化的高強度樹脂澆注成形的樹脂沖模應(yīng)用在國產(chǎn)轎車試制和小批量生產(chǎn)開辟了新的途徑。 (3) 沖壓設(shè)備和沖壓生產(chǎn)自動化方面 性能良好的沖壓設(shè)備是提高沖壓生產(chǎn)技術(shù)水平的基本條件，高精度、高壽命、高效率的沖模需要高精度、高自動化的沖壓設(shè)備相匹配。為了滿足大批量高速生產(chǎn)的需要，目前沖壓設(shè)備也由單工位、單功能、低速壓力機朝著多工位、多功能、高速和數(shù)控方向發(fā)展，加之機械乃至機器人的大量使用，使沖壓生產(chǎn)效率得到大幅度提高，各式各樣的沖壓自動線和高速自動壓力機紛紛投入使用。如在數(shù)控四邊折彎機中送入板料毛坯后，在計算機程序控制下便可依次完成四邊彎曲，從而大幅度提高精度和生產(chǎn)率；在高速自動壓力機上沖壓電機定轉(zhuǎn)子沖片時，一分鐘可沖幾百片，并能自動疊成定、轉(zhuǎn)子鐵芯，生產(chǎn)效率比普通壓力機提高幾十倍，材料利用率高達97%；公稱壓力為250KN的高速壓力機的滑塊行程次數(shù)已達2000次/min以上。在多功能壓力機方面，日本田公司生產(chǎn)的2000KN“沖壓中心”采用CNC控制，只需5min時間就可完成自動換模、換料和調(diào)整工藝參數(shù)等工作；美國惠特尼公司生產(chǎn)的CNC金屬板材加工中心，在相同的時間內(nèi)，加工沖壓件的數(shù)量為普通壓力機的4~10倍，并能進行沖孔、分段沖裁、彎曲和拉深等多種作業(yè)。 近年來，為了適應(yīng)市場的激烈競爭，對產(chǎn)品質(zhì)量的要求越來越高，且其更新?lián)Q代的周期大為縮短。沖壓生產(chǎn)為適應(yīng)這一新的要求，開發(fā)了多種適合不同批量生產(chǎn)的工藝、設(shè)備和模具。其中，無需設(shè)計專用模具、性能先進的轉(zhuǎn)塔數(shù)控多工位壓力機、激光切割和成形機、CNC萬能折彎機等新設(shè)備已投入使用。特別是近幾年來在國外已經(jīng)發(fā)展起來、國內(nèi)亦開始使用的沖壓柔性制造單元（FMC）和沖壓柔性制造系統(tǒng)（FMS）代表了沖壓生產(chǎn)新的發(fā)展趨勢。FMS系統(tǒng)以數(shù)控沖壓設(shè)備為主體，包括板料、模具、沖壓件分類存放系統(tǒng)、自動上料與下料系統(tǒng)，生產(chǎn)過程完全由計算機控制，車間實現(xiàn)24小時無人控制生產(chǎn)。同時，根據(jù)不同使用要求，可以完成各種沖壓工序，甚至焊接、裝配等工序，更換新產(chǎn)品方便迅速，沖壓件精度也高。 (4)沖壓標準化及專業(yè)化生產(chǎn)方面 模具的標準化及專業(yè)化生產(chǎn)，已得到模具行業(yè)和廣泛重視。因為沖模屬單件小批量生產(chǎn)，沖模零件既具的一定的復(fù)雜性和精密性，又具有一定的結(jié)構(gòu)典型性。因此，只有實現(xiàn)了沖模的標準化，才能使沖模和沖模零件的生產(chǎn)實現(xiàn)專業(yè)化、商品化，從而降低模具的成本，提高模具的質(zhì)量和縮短制造周期。目前，國外先進工業(yè)國家模具標準化生產(chǎn)程度已達70%~80%，模具廠只需設(shè)計制造工作零件，大部分模具零件均從標準件廠購買，使生產(chǎn)率大幅度提高。模具制造廠專業(yè)化程度越不定期越高，分工越來越細，如目前有模架廠、頂桿廠、熱處理廠等，甚至某些模具廠僅專業(yè)化制造某類產(chǎn)品的沖裁模或彎曲模，這樣更有利于制造水平的提高和制造周期的縮短。我國沖模標準化與專業(yè)化生產(chǎn)近年來也有較大發(fā)展，除反映在標準件專業(yè)化生產(chǎn)廠家有較多增加外，標準件品種也有擴展，精度亦有提高。但總體情況還滿足不了模具工業(yè)發(fā)展的要求，主要體現(xiàn)在標準化程度還不高（一般在40%以下），標準件的品種和規(guī)格較少，大多數(shù)標準件廠家未形成規(guī)?；a(chǎn)，標準件質(zhì)量也還存在較多問題。另外，標準件生產(chǎn)的銷售、供貨、服務(wù)等都還有待于進一步提高。 沖裁模設(shè)計題目 如圖1所示零件：托扳 生產(chǎn)批量：大批量 材料：08F t=2mm 設(shè)計該零件的沖壓工藝與模具 圖1 托板零件圖 （一）沖裁件工藝分析 1. 材料：08F鋼板是優(yōu)質(zhì)碳素結(jié)構(gòu)鋼，具有良好的可沖壓性能。 2. 工件結(jié)構(gòu)形狀：沖裁件內(nèi)、外形應(yīng)盡量避免有尖銳清角，為提高模具壽命，建議將所有90°清角改為R1的圓角。 3凸模最小尺寸校核 ：查〈〈冷沖壓技術(shù)〉〉表3-9無導(dǎo)向凸模沖孔的 最小尺寸；d=0.9t =0.9*2 =1.8 小于3.5可以沖裁 4. 尺寸精度：零件圖上所有尺寸均未標注公差，屬自由尺寸，可按IT14級確定工件尺寸的公差。經(jīng)查〈〈公差配合與技術(shù)測量〉〉表2-4得，各尺寸公差為： 54-0.74、34-0.62、30-0.52、16-0.44、17±0.22、Ф3.5+0.3 結(jié)論：可以沖裁 （二） 確定工藝方案及模具結(jié)構(gòu)形式 經(jīng)分析，工件尺寸精度要求不高，形狀不大，但工件產(chǎn)量較大，根據(jù)材料較厚（2mm）的特點，為保證孔位精度，沖模有較高的生產(chǎn)率，通過比較，決定實行工序集中的工藝方案，采取利用導(dǎo)正釘進行定位、剛性卸料裝置、自然漏料方式的連續(xù)沖裁模結(jié)構(gòu)形式。 （三） 模具設(shè)計計算 1．排樣 計算條料寬度及確定步距 首先查〈〈冷沖壓技術(shù)〉表確定搭邊值。根據(jù)零件形狀，兩工件間按矩形取搭邊值b=2,側(cè)邊按圓形取搭邊值a=2。 連續(xù)模進料步距為32mm。 條料寬度按相應(yīng)的公式計算：查〈〈冷沖壓技術(shù)〉公式3-21 B=(D+2a)-⊿ 查表3.15得條料寬度誤差 ⊿=0.6 B=(54+2×2)-0.6 =58-0.6 畫出排樣圖，圖2 2利用率計算； 查〈〈冷沖壓技術(shù)〉公式3-19得 n=A/SB*100% =34*30+4*30+200.96-21/58*32 =71.1% 所以用剪扳機剪取58*1000的條料 圖2 排樣圖 2．計算總沖壓力 由于沖模采用剛性卸裝置和自然漏料方式，故總的沖壓力為：由〈〈冷沖壓技術(shù)〉公式3-35得 P0=P+Pt P=P1+P2 而式中 P1--------落料時的沖裁力 P2--------沖孔時的沖裁力 按推料力公式計算沖裁力： 查〈〈冷沖壓技術(shù)〉得公式 P1=KLtτ 查〈〈冷沖壓技術(shù)〉表2-23得抗剪強度τ=300MPa =1.3[2（58-16）+2（30-16）+16π+2*4]*2*300/10000 =12.03 (t) P2=1.3*4π*3.5*2*300/10000 =3.4(t) 按推料力公式計算推料力Pt：查〈〈冷沖壓技術(shù)〉公式3-31得 Pt=nKtP 取n=h/t=6/2=3， 查表3-19得，Kt=0.055 Pt=3*0.055*(12.6+3.4)=2.541(t) 計算總沖壓力PZ： PZ=P1+P2+Pt =12.03+3.4+2.541 =17.941(t) 3．確定壓力中心： 根據(jù)圖3分析，因為工件圖形對稱，故落料時P1的壓力中心在O1上；沖孔時P2的壓力中心在O2上。 設(shè)沖模壓力中心離O1點的距離為X，根據(jù)力矩平衡原理得： P1X=(32-X)P 圖3 壓力中心 由此算得X=7m 4．沖模刃口尺寸及公差的計算 刃口尺寸計算方法及演算過程不再贅述，僅將計算結(jié)果列于表1 中。 在沖模刃尺寸計算時需要注意：在計算工件外形落料時，應(yīng)以凹模為基準，凸模尺寸按相應(yīng)的凹模實際尺寸配制，保證雙面間隙為0.25~0.36mm。為了保證R8與尺寸為16的輪廓線相切，R8的凹模尺寸，取16的凹模尺寸的一半，公差也取一半。 在計算沖孔模刃口尺寸時，應(yīng)以凸模為基準，凹模尺寸按凸模實際尺寸配制，查〈〈公差配合與技術(shù)測量〉〉表3-5得保證雙面間隙為0.25~0.36mm。 表1 沖模刃口尺寸 *X在〈〈從冷沖壓技術(shù)〉〉中查表3-7得 沖裁性質(zhì) 工作尺寸 計算公式 凹模尺寸注法 凸模尺寸注法 落料 58-0.74 38-0.62 30-0.52 16-0.44 R8 磨損后變大的 公式； Amax- x⊿）+⊿ 《〈從冷沖壓技術(shù)〉》中公式得 57.6+0.18 37.7+0.16 29.7+0.13 16.8+0.11 R7.9+0.06 凸模尺寸按實際尺寸配置，保證雙邊間隙 0.25~0.36mm 沖孔 φ3.5+0.3 磨損后變小的公式； （bmin+x⊿）-⊿/4 〈〈從冷沖壓技術(shù)〉〉得公式3-14 凹模尺寸按凹模實際尺寸配置，保證雙邊間隙0.25~0.36mm 3.65-0.08 在計算模具中心距尺寸時，制造偏差值取工件公差的1/8。據(jù)此，沖孔凹模和凸模固定板孔中心距的制造尺寸為： L17=17±0.44/8=17±0.055 5. 確定各主要零件結(jié)構(gòu)尺寸 （1）凹模外形尺寸的確定 凹模厚度H的確定： 根據(jù)經(jīng)驗公式得： H= P取總壓力=17941N H==26mm 凹模長度L的確定； W1=2.1H=31； 工件b=58 L=b+2W1=58+2*31=120mm 凹模寬度B的確定； B= 步距+工件寬+2W2 取：步距=32；工件=30；W2=1.5H B2=32+30+2*39 =140mm 根據(jù)上述數(shù)據(jù)查《〈模具設(shè)計與制造簡明手冊〉》表1-282選用標準凹摸板160*125*28 （2）凸模長度L1的確定 凸模長度計算為： L1=h1+h2+h3+Y 其中 導(dǎo)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則 L1=8+12+18+18=56m 選用沖床的公稱壓力，應(yīng)大于計算出的總壓力P0=17.941t;最大閉合高度應(yīng)大于沖模閉合高度+5mm;工作臺臺面尺寸應(yīng)能滿足模具的正確安裝。按上述要求，查《〈模具設(shè)計與制造簡明手冊〉》表1-82得，可選用J23-25開式雙柱可傾壓力機。并需在工作臺面上配備墊塊，墊塊實際尺寸可配制。其基本參數(shù)如下： 最大閉合高度 270 閉合高度調(diào)節(jié)量 55 工作臺尺寸 前后370 左右560 工作臺孔尺寸 前后200 左右290 墊板尺寸 50 模柄尺寸 直徑40 深度60 傾角 30 （3）設(shè)計并繪制總圖、選取標準件 模板 卸料板 導(dǎo)料板 墊板 導(dǎo)柱 導(dǎo)套 模架 模柄都是從《〈模具設(shè)計與制造簡明手冊〉》有的是把標準件買回來加工，螺釘 銷 在《〈機械制圖〉》中選用標準件 ， 模架選用標準中間導(dǎo)柱模架 標準是 GB/T2851.3-90 根據(jù)《〈 模具技術(shù)標準應(yīng)用〉》 參數(shù)如下： 周界是 160*125 最大閉合高度 190 最小閉合高度 160 上模座厚度 35 下模座厚度 40 模具的閉合高度校核：40+35+28+56+10=170 該模具符合要求 按已確定的模具形式及參數(shù) 繪制模具總裝圖。 如圖4，單排沖孔落料連續(xù)模。 圖四總裝圖 技術(shù)要求 1采用標準模架后側(cè)導(dǎo)柱模架，標準是GB/T2851.1-90 2沖模零件不 允許有裂痕，工作表面不允許有劃痕，機械損傷，銹蝕等表面缺陷， 3沖模凹模工作孔不允許有 倒錐度 4沖裁的凸凹模刃口及側(cè)刃等必須鋒利不允許有崩刃和機械損傷， 5零件圖上未標明的倒角尺寸，除刃口外所有的銳邊都倒角1X45度或道圓角， 表2 零件明細表 （五）繪制非標準零件圖，（略） 看零件圖 (六) 模具主要零件加工工藝規(guī)程的編制 總裝工藝 1備料 2將模柄裝入9上模座后磨平，然后用手槍鉆直徑6mm的齊縫銷孔配鉸大 入12銷 3將13導(dǎo)正銷裝入14落料凸模中，把再把落料凸模組和7沖孔凸模裝入到6凸模固定板中然后鉚緊磨平 4用等高塊把9上模座支起，將8墊板，6固定板，調(diào)整后用4螺釘固定，配鉸直徑8mm的孔，大入10銷 5把9上模座放下到一定高度，保證模架的 移動平穩(wěn)，靈活，無瀉止現(xiàn)象，讓凸模刃口在凹模刃口下，調(diào)整間隙，保證圖紙設(shè)計要求，用螺釘緊固，15卸料板，16導(dǎo)料板，19始沖檔料銷及17凹模。再用3螺釘緊固17凹模和1下模座然后配餃銷孔大入銷， 6試模 7調(diào)整到合格 8入庫 墊板的加工工藝 1備料（外購標準模塊160x125x10） 2按圖紙要求畫線， 3在鉆洗床上加工 4檢驗 5入庫 凸模固定板的加工工藝 1備料（外購標準模塊160x125x18） 2按圖紙要求畫線， 3在鉆洗床上加工四個凸模孔和兩個銷孔四個螺釘通孔 4攻4*M8螺紋孔 5在電火花滿走絲上加工落料凸?？? 6檢驗 7入庫 落料凸模的加工工藝 1備料 2鍛造成62*35*60的模塊 3在刨床上先刨一平面 4以該面為基準按圖紙要求畫線 5在數(shù)控銑床上銑出圖紙上的外形 6在鉆銑床上鉆出導(dǎo)正銷的孔 7按圖紙要求做熱處理 8檢驗 9入庫 導(dǎo)正銷的加工工藝 1備料 2鍛造成直徑8*60的胚料 3在數(shù)控車床上加工零件按圖紙要求 4按圖紙要求熱處理 5檢驗 6入庫 沖孔凸模的加工工藝 1備料 2鍛造成直徑為14*60的胚料 3在數(shù)控車床上加工零件按圖紙要求 4按圖紙要求熱處理 5檢驗 6入庫 卸料板加工工藝 1備料（外購標準模塊100x125x12） 2按圖紙要求畫線， 3在鉆洗床上加工四螺釘通孔和兩個銷孔及四個通過凸模的孔 4在銑床上加工剩余的部分 5檢驗 6入庫 凹模加工工藝 1備料（外購標準模塊160x125x28） 2按圖紙要求畫線， 3在鉆洗床上加工兩銷孔和四螺紋孔 4攻絲 5用點火花加工工作刃口 6按圖紙要求做熱處理 7檢驗 8入庫 導(dǎo)料板加工工藝 1備料（外購標準模塊120x125x8）在 標準模塊上切割成兩塊120*35*8 2按圖紙要求畫線， 3在刨床上把不平整的邊刨床平及始沖擋料銷的槽，在插床上加工始沖擋料銷的剩余部分 4在鉆銑床上加工兩銷孔和四個螺紋通孔 5攻螺紋絲4*M8 6檢驗 7入庫 始沖擋料銷的加工工藝 1備料 2鍛造成55*5*10的胚料 3在刨床上先刨一平面做基準 4在基準上劃線 5在銑床上加工出零件圖的樣子 6按圖紙要求做相應(yīng)的熱處理 7檢驗 8入庫 體會 俗話說“凡事必親躬”,唯有自己親自去做的事，才懂得其過程的艱辛。通過做這次大作業(yè)，我著實遇到了不少的困難，構(gòu)思、定數(shù)據(jù)、畫圖、寫論文等都得自己去做。每天泡在圖書館，找例證、查資料，個中自有不少困難，而這些難題都是課本中所不曾提到過的。開始時，由于書本上沒有任何提示，我甚至不知道從何入手，只能與同學(xué)們相互切磋，這樣我慢慢地入了門，進而也可以自己搞定了。這其中有一個習(xí)慣問題最需要克服。眾所周知，課堂、書本給我們的都是一種確切的數(shù)據(jù)，但實際上你去做的時候就會發(fā)現(xiàn)它們都是經(jīng)驗性的，也就是說需要你根據(jù)從資料上查得的范圍靠經(jīng)驗自己去定，這就給習(xí)慣于接受確切數(shù)字的我?guī)砹撕艽蟮奶魬?zhàn)。幸而，最終我還是學(xué)會了怎樣去查找自己想要的資料，這應(yīng)該是這次作業(yè)的一大收獲吧。 第二大收獲就是學(xué)會了做一次設(shè)計項目的具體流程。從策劃構(gòu)思、總體設(shè)計到各個模塊的的具體設(shè)計及其組合，再到編寫需要提交的論文，這一切如今仍歷歷在目。我想，這種對整體設(shè)計流程的把握應(yīng)該是以后走上工作崗位所必需的技能，而這種技能卻只能通過自己的親身實踐才能獲得。這也是為什么我認為機械設(shè)計大作業(yè)這種教學(xué)實踐模式值得推廣的原因。 畢業(yè)設(shè)計是我在大學(xué)生涯完成的最后一項內(nèi)容,此時此刻，我感覺自己有很多想要說的話，有很多需要感謝的人。首先感謝指導(dǎo)老師給予的支持與指導(dǎo),但由于工作的原因和條件的限制,我在外面所做的畢業(yè)設(shè)計并不完善。自從回校之后,向老師們請教和指導(dǎo),他們都在百忙之中給予了我悉心的指導(dǎo)和幫助。師生之情無法言表，在此，謹向恩師們深表謝意！ 也許，我的學(xué)生生涯從此就會結(jié)束，但是學(xué)習(xí)的道路卻還將持續(xù)下去，未來的人生路途中難免會遇到各種各樣的困難和挫折，使我始終能夠勇敢的迎接新的挑戰(zhàn)。 參考文獻 1；冷沖壓技術(shù) 翁其金主編 北京機械工業(yè)出版社 2000.11 2；公差配合與技術(shù)測量 薛彥成主編 北京機械工業(yè)出版社1999.10 3；機械制圖 李澄 聞百橋 吳天生主編 北京高等教育出版社2003..8 4；模具設(shè)計與制造簡明手冊 馮炳堯 韓泰來 蔣文森 主編 上海科學(xué)技術(shù)出版社 1998（第二版） 5；模具技術(shù)標準應(yīng)用 全國模具標準技術(shù)委員會秘書處四川省模具工業(yè)協(xié)會印 1992.8 21 Int 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.