上銷回轉(zhuǎn)架（二）沖壓工藝及模具設(shè)計【上銷是粗細紗機加壓裝置中的重要專件】【沖孔落料復(fù)合模】【折彎?！俊?套】

上銷回轉(zhuǎn)架（二）沖壓工藝及模具設(shè)計【上銷是粗細紗機加壓裝置中的重要專件】【沖孔落料復(fù)合模】【折彎?！俊?套】,上銷是粗細紗機加壓裝置中的重要專件,沖孔落料復(fù)合模,折彎模,2套,上銷回轉(zhuǎn)架（二）沖壓工藝及模具設(shè)計【上銷是粗細紗機加壓裝置中的重要專件】【沖孔落料復(fù)合?！俊菊蹚澞！俊?套】,回轉(zhuǎn),沖壓,工藝,模具設(shè)計 任務(wù)書畢業(yè)設(shè)計題目上銷回轉(zhuǎn)架（二）沖壓工藝及模具設(shè)計學(xué)生姓名專業(yè)班級學(xué) 號指導(dǎo)教師教 研 室機械設(shè)計教研室起止時間 畢業(yè)設(shè)計的目的： 上銷是粗細紗機加壓裝置中的重要專件。上銷、中鐵輥和上膠圈組成了牽伸控制裝置并通過上銷連接到搖架形成了粗細紗機牽伸機構(gòu)，其性能好壞對成紗質(zhì)量有很大影響。本設(shè)計中的上銷回轉(zhuǎn)架是麻紡粗紗上銷中的一個基礎(chǔ)定位零件，該零件與上銷鉗口板焊接連接構(gòu)成麻紡粗紗上銷。畢業(yè)設(shè)計是整個教學(xué)過程中極為重要的環(huán)節(jié)，通過本課題的完成，全面復(fù)習(xí)、鞏固大學(xué)四年所學(xué)的專業(yè)課程的基本理論，特別是沖壓工藝和模具設(shè)計方面的基礎(chǔ)知識，提高分析問題和解決問題的能力，培養(yǎng)事實求是的科學(xué)態(tài)度和認真細致的工作作風(fēng)。通過文獻檢索、英文翻譯、CAD輔助設(shè)計，提高計算機應(yīng)用水平及英文閱讀翻譯的能力。畢業(yè)設(shè)計的主要任務(wù)和要求：1了解上銷的工作原理，了解回轉(zhuǎn)架的結(jié)構(gòu)原理及在上銷中的作用。2查閱與課題相關(guān)的資料10篇以上。翻譯本專業(yè)外文資料一篇，不少于1.5萬個外文字符。3寫出開題報告，不少于1500個字符。4繪制上銷回轉(zhuǎn)架零件圖。5寫出工藝卡，畫出工藝展開圖。6設(shè)計沖孔落料模一副、壓彎模一副，沖四方孔模一副，繪制模具裝配圖和主要零件圖。7撰寫設(shè)計說明書一份，要求不少于1.5萬個字符，并有中英文摘要及關(guān)鍵詞。8圖紙工作量不少于3張A0。主要參考文獻與資料： 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 許發(fā)樾 . 實用模具設(shè)計與制造手冊M . 北京：機械工業(yè)出版社，2001 3 馬正元，韓啟 . 冷沖壓工藝及模具設(shè)計M . 北京：機械工業(yè)出版社，2000 4 陳劍鶴 . 冷沖壓工藝與模具設(shè)計M . 北京：機械工業(yè)出版社，2004 5 黃費哲，曾經(jīng)梁 . 冷沖壓工藝及模具設(shè)計指導(dǎo)M . 常德：湖南文理學(xué)院，2002 6 馮柄堯 . 模具設(shè)計與制造手冊M . 上海：上?？茖W(xué)技術(shù)出版社，1998 7 方昆凡 . 公差與配合技術(shù)手冊M . 北京：北京出版社，1998 8 肖景容 . 沖壓工藝學(xué)M . 北京：北京出版社，2000 9 李云程 . 沖壓工藝學(xué)M . 北京：機械工業(yè)出版社，2000 10 沖模設(shè)計手冊編寫組 . 沖模設(shè)計手冊M . 北京：機械工業(yè)出版社，1998 畢業(yè)設(shè)計進度安排： 12013.11.512.6 查閱文獻，收集資料。 22013.12.712.9 寫出開題報告 32013.12.102014.2.23 課題調(diào)研 42014.2.245.15 完成方案設(shè)計，進行設(shè)計計算，繪制裝配圖和零件圖，整理設(shè)計資料，編寫設(shè)計說明書。 52014.5.165.17 準備畢業(yè)設(shè)計答辯課題申報與審查指導(dǎo)教師（簽名）： 年 月 日教研室主任（簽名）： 年 月 日學(xué)院教學(xué)院長（簽名）： 年 月 日畢業(yè)設(shè)計說明書題 目： 上銷回轉(zhuǎn)架的沖壓工藝及 模具設(shè)計院 （部）： 專 業(yè)： 班 級：姓 名： 學(xué) 號： 指導(dǎo)教師： 完成日期：目 錄摘 要IUABSTRACTU前 言11.1 模具加工及金屬薄板沖壓加工的特點及優(yōu)勢11.2 課題討論及難點分析21.3 課題總體設(shè)計思路32工藝分析及工藝方案確定52.1工件的零件圖52.2工藝分析52.2.1彎曲部分工藝分析62.2工藝方案的確定63落料沖孔模的設(shè)計93.1毛坯尺寸計算93.2 排樣93.3 確定模具壓力中心103.4 沖壓力的計算103.4.1 落料力103.4.2沖孔力113.4.3卸料力113.4.4推件力113.4.5總沖壓力113.5沖壓設(shè)備的選擇113.6工作部分尺寸計算123.6.1落料凸、凹模刃口的尺寸計算123.6.2沖孔凸、凹模的刃口尺寸133.7沖孔落料復(fù)合模的設(shè)計143.7.1落料沖孔復(fù)合模結(jié)構(gòu)的設(shè)計143.7.2 落料沖孔復(fù)合模主要零件的設(shè)計154彎曲模的設(shè)計304.1確定模具壓力中心304.2彎曲力的計算304.3沖壓設(shè)備的選擇304.4翻邊模刃口尺寸計算304.5彎曲模的設(shè)計314.5.1彎曲模結(jié)構(gòu)的設(shè)計314.5.2彎曲模主要零件的設(shè)計325結(jié) 論36謝 辭37參考文獻38摘 要本課題所設(shè)計的零件是較為典型的U型彎曲件。工件一側(cè)有一個腰圓孔。通過對零件各部分進行計算分析后最終確定加工工序。經(jīng)計算得翻邊可以一次成型，工件整個成型過程所涉及的工序有：落料、沖孔、彎曲三步。在對零件進行工藝分析后，確定最終工藝方案為：落料沖孔復(fù)合，彎曲順次進行。在確定工藝方案的基礎(chǔ)上對主要模具進行設(shè)計，分析工件成型過程，并畫出模具裝配圖及零件圖。在本次設(shè)計中主要對落料復(fù)合模以及、彎曲模進行設(shè)計。關(guān)鍵詞：落料沖孔；沖小孔；翻邊；彎曲 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畢業(yè)設(shè)計說明書前 言1.1 模具加工及金屬薄板沖壓加工的特點及優(yōu)勢隨著汽車工業(yè)的快速發(fā)展，服務(wù)于汽車生產(chǎn)的模具近年來也快速發(fā)展1。服務(wù)于汽車生產(chǎn)的模具和塑料模具使用量最大的兩大類。此外，還有鑄造模具、鍛造模具、橡膠模具、粉末冶金模具及拉絲模具和無機材料成型模具等。在汽車工業(yè)十分發(fā)達的國家，為汽車服務(wù)的模具往往要占到全部模具生產(chǎn)量的40%以上。經(jīng)過多年發(fā)展，我國目前為汽車服務(wù)的模具約已占到了全部模具產(chǎn)量的1/3左右2。在這些模具中，沖壓模具在模具行業(yè)和汽車覆蓋件模具，直接關(guān)系到汽車車型，因此其地位尤為重要。要生產(chǎn)出大量的各式各樣的汽車，先進技術(shù)裝備必不可少，而模具就是汽車先進技術(shù)裝備中的重要裝備。“現(xiàn)代工業(yè)，模具先行”、“沒有高水平的模具，就沒有高水平的產(chǎn)品”，這已成為人們的共識。不管是汽車還是模具，雖然近年來發(fā)展迅速，我國已成為生產(chǎn)大國，但離生產(chǎn)強國的距離還很遠。然而，要成為制造業(yè)強國，要成為汽車、模具等的制造強國是我們的目標。為了向汽車行業(yè)提供更為先進的技術(shù)裝備，必須不斷提高汽車沖壓模具的沖壓模具的水平與能力。金屬薄板沖壓成形是現(xiàn)代工業(yè)生產(chǎn)中一種非常重要的制造技術(shù)3，金屬薄板及其制品在沖壓成形過程中所表現(xiàn)出的成形性能或成形性，是橫跨薄板冶金制造和沖壓成形生產(chǎn)兩大行業(yè)之間的交叉性工程技術(shù) ，即沖壓成形性能及其應(yīng)用。沖壓加工是靠沖壓設(shè)備和模具實現(xiàn)對板料毛坯的塑性加工過程。沖壓加工具有許多十分明顯的優(yōu)點，它利用沖壓設(shè)備與沖模的簡單的運動完成相當復(fù)雜形狀零件的制造過程，而且并不需要操作工人的過多參與，所以沖壓加工的生產(chǎn)效率很高，產(chǎn)品質(zhì)量穩(wěn)定，一般情況下，沖壓加工的生產(chǎn)效率為每分鐘數(shù)十件。又由于沖壓加工的操作十分簡單，為操作過程的機械化與自動化提供了十分有利的條件。因此，對某些工藝成熟的沖壓件，生產(chǎn)效率可達每分鐘數(shù)百件，甚至超過一千件以上。 沖壓加工用的原材料多為冷軋板料和冷軋帶材4。原材料的良好表面質(zhì)量使用大量生產(chǎn)方式、高效而廉價的方法獲得的。在沖壓加工中這些良好的表面質(zhì)量又不容易遭到破壞，所以沖壓件的表面質(zhì)量又不致遭到破壞，所以沖壓件的表面質(zhì)量好，而成本都很低廉。這個特點，在汽車支撐件件的生產(chǎn)上表現(xiàn)得十分明顯5。 利用沖壓加工方法，可以制造形狀十分復(fù)雜的零件，能夠把強度好、剛度大、重量輕等相互矛盾的特點融為一體，形成十分合理的結(jié)構(gòu)形式。沖壓加工時，一般不需要對毛坯加熱，而且也不像切削加工那樣把一部分金屬切成切屑，造成原材料的損耗，所以它是一種節(jié)約能源和資源的具有環(huán)保意義的加工方法。沖壓產(chǎn)品的質(zhì)量與尺寸精度都是由沖模保證的6，基本上不受操作人員的素質(zhì)與其他偶然因素的影響，所以沖壓產(chǎn)品的質(zhì)量管理簡單，也容易實現(xiàn)自動化與智能化生產(chǎn)。沖壓件的尺寸精度與表面質(zhì)量好，通常都不需要后續(xù)的加工而直接裝配或作為成品零件直接使用。沖壓加工是一種高生產(chǎn)率的加工方法的，如汽車車身等大型零件每分鐘可生產(chǎn)幾件，而小零高速沖壓則每分鐘可生產(chǎn)千件以上。由于沖壓加工的毛坯是板材或卷材，一般又在冷狀態(tài)下加工，因此較易實現(xiàn)機械化和自動化，比較適合配置機器人而實現(xiàn)無人化生產(chǎn)7。沖壓加工的材料利用率較高，一般可達70%85%，沖壓加工的能耗也較低，由于沖壓生產(chǎn)具有節(jié)材、節(jié)能和高生產(chǎn)率等特點，所以沖壓件呈批量生產(chǎn)時，其成本比較低，經(jīng)濟效益高8。沖壓件與鑄件、鍛件相比，具有薄、勻、輕、強的特點。沖壓可制出其他方法難于制造的帶有加強筋、肋、起伏或翻邊的工件，以提高其剛性。由于采用精密模具，工件精度可達微米級，且重復(fù)精度高、規(guī)格一致，可以沖壓出孔窩、凸臺等。 冷沖壓件一般不再經(jīng)切削加工，或僅需要少量的切削加工。熱沖壓件精度和表面狀態(tài)低于冷沖壓件，但仍優(yōu)于鑄件、鍛件，切削加工量少。 沖壓是高效的生產(chǎn)方法9，采用復(fù)合模，尤其是多工位級進模，可在一臺壓力機上完成多道沖壓工序，實現(xiàn)由帶料開卷、矯平、沖裁到成形、精整的全自動生產(chǎn)。生產(chǎn)效率高，勞動條件好，生產(chǎn)成本低，一般每分鐘可生產(chǎn)數(shù)百件5。由于沖壓加工方法具有前述的許多優(yōu)點，現(xiàn)在他已經(jīng)成為金屬加工中的一種非常重要的制造方法。1.2 課題討論及難點分析本課題所要設(shè)計的上銷回轉(zhuǎn)架如圖1.1，它是凸包定位且焊接組合在車架的電氣元件支架類類零件，材料Q235，厚度為2mm，年生產(chǎn)量5萬件，首先它是薄板類零件，形狀較為復(fù)雜，零件又需要翻邊，且生產(chǎn)批量較大，這些都是用沖壓加工較容易實現(xiàn)而其他加工方法所不具備的，所以用沖壓方法來加工該零件是非常理想的。針對這個零件，分別要經(jīng)過落料、沖孔、沖小孔、U形彎曲等幾個工序才能完成。在設(shè)計每套模具的時候又有很多難點和需要注意的問題。例如在沖2X5的小孔時，凸模的強度是否可以達到要求，是不是需要安裝一個凸模保護套，還有在翻邊的過程中邊緣是否會發(fā)生破裂，再比如若翻邊完成后，彎曲時如何固定板料。這些都是在設(shè)計時急需解決的問題。圖1.1上銷回轉(zhuǎn)架示意圖1.3 課題總體設(shè)計思路 （1）分析沖壓件的工藝性根據(jù)設(shè)計題目的要求，分析沖壓件成型的結(jié)構(gòu)工藝性，分析沖壓件的形狀特點、尺寸、大小、精度要求及所用材料是否符合沖壓工藝要求。（2）制定沖壓件工藝方案在分析了沖壓件的工藝性后，通?？梢粤谐鰩追N不同的沖壓工藝方案（包括工序性質(zhì)、工序數(shù)目、工序順序及組合方式），從產(chǎn)品質(zhì)量、生產(chǎn)效率、設(shè)備占用情況、模具制造難易程度和模具壽命高低、工藝成本、操作方便和安全程度等方面，進行綜合分析、比較，然后確定適合于具體生產(chǎn)條件的最經(jīng)濟合理的工藝方案。（3）確定毛坯形狀、尺寸和下料方式在最經(jīng)濟的原則下，決定毛坯的形狀、尺寸和下料方式，確定材料的消耗量。（4）確定沖模類型及結(jié)構(gòu)形式根據(jù)所確定的工藝方案和沖壓件的形狀特點、精度要求、生產(chǎn)批量、模具制造條件、操作方便及安全的要求，以及利用現(xiàn)有通用機械化、自動化裝置的可能，選定沖模類型及結(jié)構(gòu)形式，繪制模具結(jié)構(gòu)草圖。（5）進行必要的工藝計算計算毛坯尺寸，以便在最經(jīng)濟的原則下進行排樣和合理使用材料。計算沖壓力（沖裁力、彎曲力、卸料力、推件力等）以便選擇壓力機。計算模具壓力中心，防止模具因受偏心負荷作用影響模具壽命和精度。計算模具各主要零件（凹模、凸模、凸模固定板、墊板）的外形尺寸，以及卸料彈簧的自由高度等。確定凸、凹模的間隙，計算凸、凹模工作部分尺寸9。（6）選擇壓力機壓力機的選擇是模具設(shè)計的一項重要內(nèi)容，設(shè)計模具時必須把所選的壓力機的類型、型號、規(guī)格確定下來。壓力機的確定主要取決于沖壓工藝的要求和沖模結(jié)構(gòu)情況。（7）繪制模具總圖和非標準零件圖2工藝分析及工藝方案確定2.1工件的零件圖上銷回轉(zhuǎn)架的零件圖如圖2.2圖2.2上銷回轉(zhuǎn)架零件圖2.2工藝分析本課題所要設(shè)計的上銷回轉(zhuǎn)架，是凸包定位且焊接組合在車架的電氣元件支架類類零件，該零件屬隱蔽件，外觀上要求不高，只需平整。材料Q235，厚度為2mm，年生產(chǎn)量5萬件。此零件屬于較為典型的U型彎曲件，其中一側(cè)有一個腰圓孔。根據(jù)零件的形狀，需要分別經(jīng)過落料、沖孔、U形彎曲等幾個工序才能完成。現(xiàn)首先對翻邊部分進行計算，確定能否一次成形。另外，零件圖中的尺寸公差為未注公差，在處理這類零件時按IT14級要求10。2.2.1彎曲部分工藝分析本零件是典型的U型彎曲件，在彎曲過程中會可能出現(xiàn)回彈，但其對外性要求不高，可以忽略不計。彎曲圓角半徑為0.5大于最小彎曲半徑（rmin=0.4t=0.41=0.6mm），故此零件形狀、尺寸均滿足彎曲工藝的要求，可以彎曲工序進行加工。2.1工藝方案的確定通過工藝性分析，可得到以下幾種方案：（1）單工序落料、沖孔、彎曲，采用單工序模具。每道工序分別設(shè)計一套模具，加工過程中按照工序一步步完成。優(yōu)點：設(shè)計簡單明了，設(shè)備沖裁力不必很大就可完成工作。缺點：每道工序都要制作一套模具。模具費用昂貴，這就增加了生產(chǎn)成本； 生產(chǎn)過程中，坯料要經(jīng)過至少3道工序，工序繁雜，生產(chǎn)效率低； 坯料每經(jīng)過一道工序就要重新定位以便于加工，這就增加了尺寸誤差，使產(chǎn)品精度下降； 占用車間工位和設(shè)備，不方便操作12。（2）采用復(fù)合模進行加工，即落料沖孔復(fù)合，彎曲順次進行。優(yōu)點：在完成這些工序過程中，沖壓坯料無需進給移動。生產(chǎn)效率高，結(jié)構(gòu)簡單，節(jié)省制造費用，且定位準確，生產(chǎn)精度高。缺點：需要的沖裁力較大，模具制作復(fù)雜，生產(chǎn)過程中容易磨損。（3）級進模：沖孔、落料、彎曲遞進完成。優(yōu)點：生產(chǎn)效率高且操作安全。缺點：模具結(jié)構(gòu)復(fù)雜，制造周期長，生產(chǎn)成本高，因此只有在特大量生產(chǎn)中才比較適宜。定位不準確，尤其是在沖小孔時無法保證尺寸精度。 綜合考慮成本、效率生產(chǎn)批量和要生產(chǎn)的實際工件等方面因素，采用復(fù)合模加工比較合理。經(jīng)落料沖孔后的坯料圖分別如圖2.3所示。圖2.3 落料沖孔后的零件圖3落料沖孔模的設(shè)計3.1毛坯尺寸計算毛坯寬度計算：因為r/t=0.5/1=0.5，參照中國模具設(shè)計大典12表19.3-1，得x=0.25查表19.3-6得l彎=1.46mml=115.6mmX69.05mm則毛坯的外形尺寸為長L為115.6mm,寬為69.05mm的長方形板料。3.2 排樣工件排樣根據(jù)落料工序設(shè)計，考慮操作方便及模具結(jié)構(gòu)簡單，由于件展開尺寸大于65mm，因此采用單行排列，查表2-1613得 搭邊值a1=1.5mm,a=1.5mm,條料的排樣圖如圖3.1所示，則：條料寬：b=115.6+4=119.6mm條料的進距為：h=69.05+a1=71.55mm 條料的利用率：=s/（hb）100 （3.2a）=5092/（124.464.5）100=63.5圖3.1 條料排樣圖3.3 確定模具壓力中心 由于零件形狀左右對稱，上下不對稱，故x0=31.5mmy0=liyi/li （3.3a）=47464.55/2381.27=19.93mm3.4 沖壓力的計算3.4.1 落料力F落=KLt （3.4a） =1.34342400 451.4KN3.4.2沖孔力 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總沖壓力 F總 = F落F孔F卸F推 （3.4e）=557.71KN3.5沖壓設(shè)備的選擇 為了保證安全，防止設(shè)備的過載，可按公稱壓力F壓(1.61.8)F總的原則選取壓力機13。參照沖壓工藝與模具設(shè)計14，落料沖孔工步可選取公稱壓力350KN的J23-35型開式雙柱可傾壓力機，該壓力機與模具設(shè)計的有關(guān)參數(shù)為；公稱壓力：650KN；滑塊行程：70mm；最大閉合高度：220mm；封閉高度調(diào)節(jié)量：60mm ；工作臺尺寸：550mm400mm；模柄孔尺寸：50mm50mm。3.6工作部分尺寸計算3.6.1落料凸、凹模刃口的尺寸計算落料時應(yīng)先確定凹模的尺寸。由于工件尺寸屬于未注公差尺寸，在計算凸模與凹模尺寸時，沖壓件公差尺寸的極限偏差數(shù)值通常按GB1800-79IT14級。凸模尺寸按照凹模尺寸配做，保證其最小間隙值為零。該零件材料為Q235，料厚2mm，由沖壓工藝與模具設(shè)計，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)由實用沖壓工藝與模具設(shè)計15表3-13可查得：落料凹模長： x=0.370落料凹模寬： x=0.310落料凹模長： Ad1=(D1-x) (3.6c) =(115.6-0.370)mm =115.23mm式中：零件的制造偏差，x系數(shù)落料凹模寬： Ad2=(D2-x) (3.6c) =(69.05-0.300)mm =68.75mm落料凸模長： Ap1=( Ad1- Zmin) (3.6d) =(115.23-0.13) =115.1mm落料凸模寬： A p2=( Ad2- Zmin) (3.6d) =(68.75-0.14) =68.61mm3.6.2沖孔凸、凹模的刃口尺寸沖孔時應(yīng)先確定凸模的尺寸。由于工件尺寸屬于未注公差尺寸，在計算凸模與凹模尺寸時，沖壓件公差尺寸的極限偏差數(shù)值通常按GB1800-79IT14級15。凹模尺寸按照凸模尺寸配做，保證其最小間隙值為零。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)對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對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沖孔落料復(fù)合模的設(shè)計3.7.1落料沖孔復(fù)合模結(jié)構(gòu)的設(shè)計(1) 模具總體設(shè)計在確定采用復(fù)合模后，便要考慮采用正裝式還是倒裝式復(fù)合模。采用倒裝式復(fù)合模，拉深后工件嵌在上模部分的落料凹模內(nèi)，由推件裝置推出，再由壓力機上附加的接件裝置接走，條料由下模的卸料裝置脫出。這樣操作方便而且安全，能保證較高的生產(chǎn)率。而正裝式復(fù)合模，工件則由下模的推件裝置向上推出，條料由上模卸料裝置脫出，二者混雜在一起，如果萬一來不及排除廢料或工件而進行下一次沖壓，就容易崩裂模具刃口。因此，這副落料沖孔復(fù)合模采用倒裝結(jié)構(gòu)。(2) 推件裝置在倒裝式復(fù)合模中，沖裁后工件嵌在上模部分的落料凹模內(nèi)，需由剛性或彈性推件裝置推出。剛性推件裝置推件可靠，可以將工件穩(wěn)當?shù)赝瞥霭寄?，但在沖裁時，剛性推件裝置對工件不起壓平作用，故工件平整度和尺寸精度比用彈性推件裝置時要低些。根據(jù)生產(chǎn)實際經(jīng)驗，用剛性推件裝置已能保證零件所有尺寸精度，故這副模具采用剛性推件塊。(3) 卸料裝置復(fù)合模沖裁時，條料將卡在凸凹模外緣，因此需要在下模裝卸料裝置。卸料裝置有二種形式：一種是將卸料零件，裝在卸料板與凸凹模固定板之間；另一種是將卸料零件裝設(shè)在下模板下面。由于零件的條料卸料力大，故采用前一種結(jié)構(gòu)復(fù)雜，彈性卸料裝置。 (4) 導(dǎo)向裝置15由于工件為彎曲件精度要求不高，而且材料不是很薄，模具間隙一般 ，故采用中間導(dǎo)柱模架。(5) 工作過程本沖模在一次行程中完成落料、沖孔兩個工序，生產(chǎn)效率高。沖壓時，條料從5-活動導(dǎo)料銷中通過，由3凸凹模和18落料凹模進行落料。11頂板繼續(xù)下行，7活動擋料銷擋住板料，3凸凹模和12、13凸模完成工件沖孔工序。沖孔后，嵌在3凸凹模內(nèi)的工件由9推件器推出，廢料由4卸料板卸下，整個過程完成。落料沖孔復(fù)合模裝配圖如圖3.2所示：3.1.2 落料沖孔復(fù)合模主要零件的設(shè)計對于復(fù)合模來說，工作部分包括凸凹模、凸模和凹模三個零件?，F(xiàn)在這副模具的凸凹模用電火花線切割一次割出，所以要將凸凹模的刃口尺寸全部算出，其外形按落料凹模計算，內(nèi)孔按沖孔凸模計算。凸模按凸凹模內(nèi)孔線切割，也需標出刃口尺寸16。凹模也用線切割加工，無論是光電跟蹤還是程序控制的線切割，在制作光電跟蹤圖或者計算輸入方程時，均以凹模刃口工作部分尺寸作為依據(jù)，故凹模刃口尺寸也需計算。 圖3.2 落料沖孔復(fù)合模裝配圖 由于，凸凹模、凸模和凹模三個零件都需要進行線切割 ，而且三個之間的尺寸有一定的聯(lián)系，所以可以連續(xù)加工。首先，加工一塊凹模外形尺寸的模具板材，確定壓力中心，在板材上線切割出凹模的刃口，調(diào)節(jié)線切割設(shè)備選用合適的鉬絲使切割量小于凸、凹模間隙，在切下的廢料上切割出拉深凹模刃口，接下來在切下的廢料上切割出拉深凸模，然后在數(shù)控銑上銑出頭部曲面，完成模具工作零件的加工17。（1）落料凹模的設(shè)計17材料：Cr12MoU；外形尺寸：27020025；由于大批量生產(chǎn)，對刃口強度要求較高，所以刃口采用直刃式，磨損后刃口尺寸變化小，凹模刃口厚度為5mm；加工后進行熱處理：5860HRC；凹模采用M10銷釘定位，通過4個M10內(nèi)六角螺釘經(jīng)過凸模固定板與墊板緊固在上模座上，表面粗糙度為1.6。如圖2.4所示。（2）凸凹模的設(shè)計材料：Cr12MoU；外形尺寸：如圖2.4所示加工后進行熱處理：58-60 HRC；凸凹模通過鉚接固定在下固定板上，表面粗糙度為1.6。（3）沖孔凸模的設(shè)計18材料：Cr12MoU；凸模圓角半徑為5mm；加工后進行熱處理：58-60HRC；凸模通過與固定板一起磨平后卡在一起；表面粗糙度為1.6。圖2.3 落料凹模圖2.4 凸凹模 （4）卸料板的設(shè)計卸料裝置的形式比較多，它包括固定卸料板、活動卸料板、彈壓卸料板和廢料切刀等幾種。本制件較薄且要求平整，而且卸料板是用在復(fù)合模中，所以選用彈壓卸料板如圖2.9所示。圖2.9 卸料板（5）模柄的選擇16中小型沖模通過模柄將上模固定在壓力機的滑塊上。通過對制件的分析，決定采用適合于較大模具上的凸緣模柄，如圖2.10所示。 （6）固定板與墊板的設(shè)計 固定板選用矩形，厚度是22mm，固定板選用規(guī)格是27020020。 墊板不需經(jīng)淬硬磨平，厚度取10mm，墊板選用規(guī)格是27020010。圖2.10 凸緣模柄4彎曲模的設(shè)計4.1確定模具壓力中心 由于零件形狀左右對稱，上下不對稱，故x0=31.5mmy0=liyi/li （6.1a） =47373.17/2378.72=19.92mm4.2彎曲力的計算彎曲力： F彎= 0.7KBt2b/（rt） （6.2a） =0.71.31022215/（0.50.9） =0.11KN壓料力： F壓=F頂=0.8 F彎=0.2KN F總= F彎F壓F頂 = 0.31KN 4.3沖壓設(shè)備的選擇 為了保證安全，防止設(shè)備的過載，可按公稱壓力F壓(1.61.8)F總的原則選取壓力機。參照沖壓工藝與模具設(shè)計，落料沖孔工步可選取公稱壓力100KN的J23-10型開式雙柱可傾壓力機，該壓力機與模具設(shè)計的有關(guān)參數(shù)為；公稱壓力：100KN；滑塊行程：50mm；最大閉合高度：210mm；封閉高度調(diào)節(jié)量：50mm ；工作臺尺寸：360mm240mm；模柄孔尺寸：40mm50mm。4.44.4彎曲模的設(shè)計4.4.1彎曲模結(jié)構(gòu)的設(shè)計（1）模具總體設(shè)計模具采用中間導(dǎo)柱標準模架，模具上模部分主要由上模架、墊板、凸模固定板組成，卸料方式為彈性卸料，以彈簧為彈性元件。下模部分由下模座、凹模、凹模墊板、頂件塊、定位板等組成。其裝配圖如圖6.1所示。（2）模具的特點該模具結(jié)構(gòu)簡單，在壓力機上安裝，調(diào)節(jié)方便。定件板在彎曲時與凸模將板料壓緊，并且背壓力可以根據(jù)需要調(diào)節(jié)大小，始終能對工件底部施加較大的反頂件力，能使工件底部保持平整，能有效地防止彎曲件的滑移，由于彎曲結(jié)束時制件能得到可靠的校正，因而大大降低了制件的回彈量17。（3）模具工作過程工作中，先將板料放在固定板中，上模下行，凸模與頂件板將板料夾緊，凸模與凹模對板料進行彎曲直至頂件板與凹模墊板接觸，并將凸模和頂件板進行特殊加工，使其在彎曲的過程中可以使坯料彎出褶邊，彎曲結(jié)束后頂件板可以通過頂桿和彈簧將彎曲件頂出凹模。 圖6.1 彎曲模裝配圖4.4.2彎曲模主要零件的設(shè)計（1）凹模的設(shè)計17材料：Cr12MoU；外形尺寸：270020035；由于大批量生產(chǎn)，對刃口強度要求較高，所以刃口采用直刃式。加工后進行熱處理：5860HRC；凹模通過通過四個M10螺釘和兩個圓柱銷與凹模墊板一塊固定在下模座上，表面粗糙度為1.6。如圖6.2所示。圖6.2 彎曲凹模圖6.3 彎曲凸模（3）頂件塊的設(shè)計材料：45；外形尺寸：7310.215；加工后進行熱處理：5860HRC；其置于凹模之間，工作時被壓下并與凹模墊板緊密接觸，工作完畢后由卸料螺釘通過彈簧將其頂出，如圖6.4所示。圖6.4 頂件板（4）定位板的設(shè)計材料：45鋼；外形尺寸：1401402mm；加工后熱處理：4650 HRC；將坯料放在定位板中，使其不能滑動7結(jié) 論 （1）為U型支架類零件設(shè)計模具時，首先要計算毛坯直徑，通過計算分析加工工序，確定工藝方案的可行性。 （2）落料、沖孔工序采用倒裝式復(fù)合模，工件由上面的凹模帶上后，由推件裝置推出，再由壓力機上附加的接件裝置接走，條料由下模的卸料裝置脫出。這樣操作方便而且安全，能保證較高的生產(chǎn)率。在倒裝式復(fù)合模中，沖孔后工件嵌在上模部分的落料拉深凸凹模內(nèi)，采用剛性推件裝置推出。復(fù)合模沖裁時，條料將卡在凹凸模外緣，因此下模采用彈性卸料裝置。由于工件為彎曲件精度要求不高，模具間隙一般，故采用中間導(dǎo)柱模架。（3）主要零件加工方案由于凸凹模、凸模和凹模三個零件都需要進行線切割 ，而且三個之間的尺寸有一定的聯(lián)系，所以可以連續(xù)加工。首先，加工一塊凹模外形尺寸的模具板材，確定壓力中心，在板材上線切割出凹模的刃口，調(diào)節(jié)線切割設(shè)備選擇合適的鉬絲使切割量小于凸、凹模間隙，在切下的廢料上切割出拉深凹模刃口，接下來在切下的廢料上切割出拉深凸模，然后在數(shù)控銑床上銑出頭部曲面。（4）在彎曲模具設(shè)計時，模具采用中間導(dǎo)柱標準模架，工作中，先將板料放在固定板中，上模下行，凸模與頂件板將板料夾緊，凸模與凹模對板料進行彎曲直至頂件板與凹模墊板接觸，并將凸模和頂件板進行特殊加工，使其在彎曲的過程中可以使坯料彎出褶邊，彎曲結(jié)束后頂件板可以通過頂桿和彈簧將彎曲件頂出凹模。謝 辭畢業(yè)設(shè)計得以完成，要感謝的人實在太多了，首先要感謝任國成老師，因為我的畢業(yè)設(shè)計的整個過程都是在任老師的悉心指導(dǎo)下完成的。老師淵博的專業(yè)知識，嚴謹?shù)闹螌W(xué)態(tài)度，精益求精的工作作風(fēng)，誨人不倦的高尚師德，嚴以律己、寬以待人的崇高風(fēng)范，樸實無華、平易近人的人格魅力對我影響深遠。本次畢業(yè)設(shè)計從選題到完成，每一步都是在老師的指導(dǎo)下完成的，傾注了老師大量的心血。再次我要對我們課題組的同學(xué)表示衷心的感謝，在平時的實驗過程中得到了他們很多的幫助。同時，畢業(yè)設(shè)計的順利完成，離不開其他各位老師的關(guān)心和幫助，感謝我們學(xué)院其他各位老師在大學(xué)期間給予我的教導(dǎo)與幫助。XXIII畢業(yè)設(shè)計說明書參考文獻1 徐義，李落星，李光耀，等型材彎曲工藝的現(xiàn)狀及發(fā)展前景J 塑形工程學(xué)報，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 姜奎華沖壓工藝與模具設(shè)計M. 機械工業(yè)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，姜奎華主編沖壓工藝與模具設(shè)計M. 機械工業(yè)出版社，北京：19997 周大雋沖模結(jié)構(gòu)設(shè)計M .機械工業(yè)出版社，北京：20068模具設(shè)計與制造技術(shù)教育叢書編委會編.模具結(jié)構(gòu)設(shè)計M. 機械工業(yè)出版社，北京2003.109 鄭家賢著.沖壓模具設(shè)計使用手冊M . 機械工業(yè)出版社，北京： 2007.910 阮雪榆.中國模具工業(yè)和技術(shù)的發(fā)展J.模具技術(shù)，2001（2）：727411 洪慎章.塑性成形技術(shù)的現(xiàn)狀及發(fā)展趨勢J.模具技術(shù)，2003（1）：545612 白容恩.典型零件復(fù)合模設(shè)計探討J.模具工業(yè)，1989（11）：5913金滌塵.現(xiàn)代模具制造技術(shù)M.北京：機械工業(yè)出版社，200314付宏生模具試圖與制圖M北京：化學(xué)工業(yè)出版社,200615王秀鳳，萬良輝.冷沖壓模具設(shè)計與制造M.北京：北京航空航天大學(xué)出版社，2005:2-316周大雋.沖模結(jié)構(gòu)設(shè)計要領(lǐng)與范例M.北京：機械工業(yè)出版社，2005:23-3517中國機械工程學(xué)會鍛壓學(xué)會.鍛壓手冊（第2卷）M.北京：機械工業(yè)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.