片狀彈簧沖壓成形工藝與模具設(shè)計,片狀彈簧沖壓成形工藝與模具設(shè)計,片狀,彈簧,沖壓,成形,工藝,模具設(shè)計 中期檢查表 學生姓名 學 號 指導教師 選題情況 課題名稱 片狀彈簧沖壓成形工藝與模具設(shè)計 難易程度 偏難 適中 偏易 工作量 較大 合理 較小 符合規(guī)范化的要求 任務(wù)書 有 無 開題報告 有 無 外文翻譯質(zhì)量 優(yōu) 良 中 差 學習態(tài)度、出勤情況 好 一般 差 工作進度 快 按計劃進行 慢 中期工作匯報及解答問題情況 優(yōu) 良 中 差 中期成績評定： 所在專業(yè)意見： 負責人： 年 月 日 任務(wù)書 系 部： 專 業(yè)： 學生姓名: 學 號: 設(shè)計題目： 片狀彈簧沖壓成形工藝與模具設(shè)計 起迄日期: 指 導 教 師: 2013年11月 2 日 畢 業(yè) 設(shè) 計（論 文）任 務(wù) 書 1．本畢業(yè)設(shè)計（論文）課題來源及應(yīng)達到的目的： 本題目是來源與生產(chǎn)實際，通過該題目的畢業(yè)設(shè)計，將使學生達到理論知識與模具設(shè)計和制造的實踐相結(jié)合，提高學生對所學專業(yè)知識的掌握和綜合應(yīng)用能力。培養(yǎng)學生綜合分析和解決實際問題的能力，強調(diào)專業(yè)知識的綜合應(yīng)用。 2．本畢業(yè)設(shè)計（論文）課題任務(wù)的內(nèi)容和要求（包括原始數(shù)據(jù)、技術(shù)要求、工作要求等）： 工作要求： （1）完成模具的設(shè)計，編寫設(shè)計說明書一份 （2）繪制模具裝配圖以及全套的模具零件圖 (3) 編寫主要零件的加工工藝卡 所在專業(yè)審查意見： 負責人： 年 月 日 系部意見： 系領(lǐng)導： 年 月 日 工 藝 過 程 卡 片 產(chǎn) 品 代 號 材 料 Cr12 毛 坯 種 類 鍛坯 凸模 工序序號 工序 名稱 工 序 內(nèi) 容 設(shè) 備 夾 輔 具 名 稱 1 下料 45mmx18mmx45的坯料 鋸床 2 鍛造 45mmx18mmx45尺寸公差均為±2 空氣錘C41-250 3 退火 加熱爐 4 檢驗 5 刨 粗，半精加工上下面和側(cè)面，單面余量為0.8-1.2mm 銑床或刨床 虎鉗 6 磨 磨上,下平面,兩基準面至圖樣尺寸 磨床M7120A 7 熱處理 按熱處理工藝進行保證滲碳深度0.8mm到1.2mm檢驗硬度為60-64HRC 加熱爐,油槽 8 磨 精磨上,下面,表面粗糙度達圖紙規(guī)定要求 M1720A 9 劃線 劃彎曲外形輪廓 劃線平臺 10 電加工 線切割加工彎曲外形 電火花線切割機床HCKX250 11 研磨 研磨線切割加工外形使四壁粗糙度達到標準要求 虎鉗 12 修整 修整外形 H78-1電動拋光機 工 藝 過 程 卡 片 產(chǎn) 品 代 號 材 料 Cr12 毛 坯 種 類 鍛坯 凹模 工序序號 工序 名稱 工 序 內(nèi) 容 設(shè) 備 夾 輔 具 名 稱 1 下料 26mmx15mmx25的坯料 鋸床 2 鍛造 26mmx15mmx25尺寸公差均為±2 空氣錘C41-250 3 退火 加熱爐 4 檢驗 5 刨 粗，半精加工上下面和側(cè)面，單面余量為0.8-1.2mm 銑床或刨床 虎鉗 6 磨 磨上,下平面,兩基準面至圖樣尺寸 磨床M7120A 7 劃線 劃中心線,各螺孔,銷孔, 劃線平臺 8 加工各孔 各螺釘,銷釘孔與下模座配鉆配鉸 立鉆Z525 平行夾頭 9 熱處理 按熱處理工藝進行保證滲碳深度0.8mm到1.2mm檢驗硬度為60-64HRC 加熱爐,油槽 10 磨 精磨上,下面,表面粗糙度達圖紙規(guī)定要求 M1720A 11 劃線 劃型孔輪廓線 劃線平臺 12 電加工 線切割穿孔加工彎曲型孔 電火花線切割機床HCKX250 13 研磨 研磨線切割加工型孔使孔壁粗糙度達到標準要求 虎鉗 14 修整 修整型腔 H78-1電動拋光機 說明書 畢業(yè)設(shè)計題目：片狀彈簧沖壓成形工藝與模具設(shè)計 系 部 專 業(yè) 班 級 學生姓名 學 號 指導教師 2014年 4 月 15 日 1 緒論 近年來，沖壓成形工藝有很多新的進展，特別是精密沖裁、精密成形、精密剪切、復合材料成形、超塑性成形、軟模成形以及電磁成形等新工藝日新月異，沖壓件的精度日趨精確，生產(chǎn)率也有極大提高，正在把沖壓加工提高到高品質(zhì)的、新的發(fā)展水平。前幾年的精密沖壓主要市是指對平板零件進行精密沖裁，而現(xiàn)在，除了精密沖裁外還可兼有精密彎曲、拉深、壓印等，可以進行復雜零件的立體精密成形。過去的精密沖裁只能對厚度為5~8mm以下的中板或薄板進行加工，而現(xiàn)在可以對厚度達25mm 的厚板實現(xiàn)精密沖裁，并可對σb >900MPa的高強度合金材料進行精沖。 由于引入了CAE，沖壓成形已從原來的對應(yīng)力應(yīng)變進行有限元等分析而逐步發(fā)展到采用計算機進行工藝過程的模擬與分析，以實現(xiàn)沖壓過程的優(yōu)化設(shè)計。在沖壓毛坯設(shè)計方面也開展了計算機輔助設(shè)計，可以對排樣或拉深毛坯進行優(yōu)化設(shè)計。 當前，我國工業(yè)生產(chǎn)的特點是產(chǎn)品品種多、更新快和市場競爭激烈。在這種情況下， 用戶對模具制造的要求是交貨期短、精度高、質(zhì)理好、價格低。因此，模具工業(yè)的發(fā)展的趨勢是非常明顯的。 我國模具工業(yè)近年來發(fā)展很快，據(jù)不完全統(tǒng)計，2003年我國模具生產(chǎn)廠點約有２萬多家，從業(yè)人員約50多萬人，2004年模具行業(yè)的發(fā)展保持良好勢頭，模具企業(yè)總體上訂單充足，任務(wù)飽滿，2004年模具產(chǎn)值530億元。進口模具18.13億 美元，出口模具4.91億美元，分別比2003年增長18%、32.4%和45.9%。進出口之比2004年為3.69:1，進出口相抵后的進凈口達13.2億美元，為凈進口量較大的國家。 在２萬多家生產(chǎn)廠點中，有一半以上是自產(chǎn)自用的。在模具企業(yè)中，產(chǎn)值過億元的模具企業(yè)只有20多家，中型企業(yè)幾十家，其余都是小型企業(yè)，多數(shù)只有幾十名職工，百十萬產(chǎn)值，自有資金有限，靠自我發(fā)展很困難。近年來，模具行業(yè)結(jié)構(gòu)調(diào)整和體制改革步伐加快，主要表現(xiàn)為：大型、精密、復雜、長壽命中高檔模具及模具標準件發(fā)展速度快于一般模具產(chǎn)品；塑料模和壓鑄模比例增大；專業(yè)模具廠數(shù)量增加，能力提高較快；"三資"及私營企業(yè)發(fā)展迅速；國企股份制改造步伐加快等。 2004年模具行業(yè)還顯現(xiàn)另外兩個特點，一是各地政府對模具工業(yè)的發(fā)展進一步關(guān)注。許多地方政府進一步認識到模具工業(yè)對發(fā)展制造業(yè)的重要意義，因此加強了模具工業(yè)園區(qū)的建設(shè)。已有的園區(qū)進一步擴大，如寧波余姚、寧海和蘇州昆山等模具園區(qū)都有所擴大；新的模具工業(yè)園區(qū)正在加緊建設(shè)，如重慶、大連、深圳市等已建立模具園區(qū)；另外沈陽、西安、成都、上海、寧波北侖、浙江黃巖等地都在積極籌備建立模具園區(qū)，以利帶動地區(qū)模具及相關(guān)產(chǎn)業(yè)鏈乃至制造業(yè)的發(fā)展，有些高科園內(nèi)模具企業(yè)已占有相當?shù)姆萘?，像天津高新區(qū)就有40多家模具企業(yè)。 二是外資及社會投資模具產(chǎn)業(yè)增長顯著。許多地方加強了吸引外資及合資投入模具工業(yè)的工作，特別是在高新技術(shù)園區(qū)和工業(yè)園區(qū)，外資、合資模具企業(yè)進一步增加，如蘇州昆山模具園區(qū)，60%以上是外資企業(yè)。大連模具園區(qū)到日本、韓國招商。而有些地區(qū)高科技園內(nèi)模具企業(yè)已占有相當?shù)姆萘?，像天津高新區(qū)有40多家模具企業(yè)。由于汽車產(chǎn)業(yè)發(fā)展的拉動，社會投資模具產(chǎn)業(yè)有所加強，如五糧液集團投資5億元建立汽車模具生產(chǎn)廠，比亞迪公司投資2億元建立了北京汽車模具公司，等等。 從地區(qū)分布來說，以珠江三角洲和長江三角洲為中心的東南沿海地區(qū)（模具產(chǎn)值已占全國總量的70%左右）發(fā)展快于中西部地區(qū)，南方的發(fā)展快于北方。目前發(fā)展最快、模具生產(chǎn)較為集中的省份是廣東和浙江。我國模具總量雖然已位居日、美、德之后，但設(shè)計制造水平在總體上要比德、美、日、法、意等發(fā)達國家落后許多，也要比英國、加拿大、西班牙、葡萄牙、韓國、新加坡等有差距在2萬多家生產(chǎn)廠點中，有一半以上是自產(chǎn)自用的。在模具企業(yè)中，產(chǎn)值過億元的模具企業(yè)只有20多家，中型企業(yè)幾十家，其余都是小型企業(yè)。?近年來，?模具行業(yè)結(jié)構(gòu)調(diào)整和體制改革步伐加快，主要表現(xiàn)為：大型、精密、復雜、長壽命中高檔模具及模具標準件發(fā)展速度快于一般模具產(chǎn)品；專業(yè)模具廠數(shù)量增加，能力提高較快；"三資"及私營企業(yè)發(fā)展迅速；國企股份制改造步伐加快等。 雖然說我國模具業(yè)發(fā)展迅速，但遠遠不能適應(yīng)國民經(jīng)濟發(fā)展的需要。我國尚存在以下幾方面的不足: 第一，體制不順，基礎(chǔ)薄弱。 “三資”企業(yè)雖然已經(jīng)對中國模具工業(yè)的發(fā)展起了積極的推動作用，私營企業(yè)近年來發(fā)展較快，國企改革也在進行之中，但總體來看，體制和機制尚不適應(yīng)市場經(jīng)濟，再加上國內(nèi)模具工業(yè)基礎(chǔ)薄弱，因此，行業(yè)發(fā)展還不盡如人意，特別是總體水平和高新技術(shù)方面。 第二，開發(fā)能力較差，經(jīng)濟效益欠佳.我國模具企業(yè)技術(shù)人員比例低，水平較低，且不重視產(chǎn)品開發(fā)，在市場中經(jīng)常處于被動地位。我國每個模具職工平均年創(chuàng)造產(chǎn)值約合1萬美元，國外模具工業(yè)發(fā)達國家大多是15～20萬美元，有的高達25～30萬美元，與之相對的是我國相當一部分模具企業(yè)還沿用過去作坊式管理，真正實現(xiàn)現(xiàn)代化企業(yè)管理的企業(yè)較少。 第三，工藝裝備水平低，且配套性不好，利用率低．雖然國內(nèi)許多企業(yè)采用了先進的加工設(shè)備，但總的來看裝備水平仍比國外企業(yè)落后許多，特別是設(shè)備數(shù)控化率和CAD/CAM應(yīng)用覆蓋率要比國外企業(yè)低得多。由于體制和資金等原因，引進設(shè)備不配套，設(shè)備與附配件不配套現(xiàn)象十分普遍，設(shè)備利用率低的問題長期得不到較好解決。裝備水平低，帶來中國模具企業(yè)鉗工比例過高等問題。 國內(nèi)模具的發(fā)展趨勢 巨大的市場需求將推動中國模具的工業(yè)調(diào)整發(fā)展。雖然我國的模具工業(yè)和技術(shù)在過去的十多年得到了快速發(fā)展，但與國外工業(yè)發(fā)達國家相比仍存在較大差距，尚不能完全滿足國民經(jīng)濟高速發(fā)展的需求。未來的十年，中國模具工業(yè)和技術(shù)的主要發(fā)展方向包括以下幾方面:???? 1） 模具日趨大型化；??? ? 2）在模具設(shè)計制造中廣泛應(yīng)用CAD/CAE/CAM技術(shù)；?? 3）模具掃描及數(shù)字化系統(tǒng)；??? ? 4）在塑料模具中推廣應(yīng)用熱流道技術(shù)、氣輔注射成型和高壓注射成型技術(shù)；? 國外模具的現(xiàn)狀和發(fā)展趨勢 模具是工業(yè)生產(chǎn)關(guān)鍵的工藝裝備，在電子、建材、汽車、電機、電器、儀器儀表、家電和通訊器材等產(chǎn)品中，60％－80％的零部件都要依靠模具成型。用模具生產(chǎn)制作表現(xiàn)出的高效率、低成本、高精度、高一致性和清潔環(huán)保的特性，是其他加工制造方法所無法替代的。模具生產(chǎn)技術(shù)水平的高低，已成為衡量一個國家制造業(yè)水平高低的重要標志，并在很大程度上決定著產(chǎn)品的質(zhì)量、效益和新產(chǎn)品的開發(fā)能力。近幾年，全球模具市場呈現(xiàn)供不應(yīng)求的局面，世界模具市場年交易總額為600～650億美元左右。美國、日本、法國、瑞士等國家年出口模具量約占本國模具年總產(chǎn)值的三分之一。? 隨著時代的進步和技術(shù)的發(fā)展，國外的一些掌握和能運用新技術(shù)的人才如模具結(jié)構(gòu)設(shè)計、模具工藝設(shè)計、高級鉗工及企業(yè)管理人才，他們的技術(shù)水平比較高．故人均產(chǎn)值也較高．我國每個職工平均每年創(chuàng)造模具產(chǎn)值約合1萬美元左右，而國外模具工業(yè)發(fā)達國家大多15～20萬美元，有的達到 25～30萬美元。國外先進國家模具標準件使用覆蓋率達70%以上，而我國才達到45％． 模具技術(shù)的發(fā)展應(yīng)該為適應(yīng)模具產(chǎn)品“交貨期短”、“精度高”、“質(zhì)量好”、“價格低”的要求服務(wù)。達到這一要求急需發(fā)展如下幾項：? (1)全面推廣CAD/CAM/CAE技術(shù) 模具CAD/CAM/CAE技術(shù)是模具設(shè)計制造的發(fā)展方向。隨著微機軟件的發(fā)展和進步，普及CAD/CAM/CAE技術(shù)的條件已基本成熟，各企業(yè)將加大CAD/CAM 技術(shù)培訓和技術(shù)服務(wù)的力度；進一步擴大CAE技術(shù)的應(yīng)用范圍。計算機和網(wǎng)絡(luò)的發(fā)展正使CAD/CAM/CAE技術(shù)跨地區(qū)、跨企業(yè)、跨院所地在整個行業(yè)中推廣成為可能，實現(xiàn)技術(shù)資源的重新整合，使虛擬制造成為可能。? (2)高速銑削加工? 國外近年來發(fā)展的高速銑削加工，大幅度提高了加工效率，并可獲得極高的表面光潔度。另外，還可加工高硬度模塊，還具有溫升低、熱變形小等優(yōu)點。高速銑削加工技術(shù)的發(fā)展，對汽車、家電行業(yè)中大型型腔模具制造注入了新的活力。目前它已向更高的敏捷化、智能化、集成化方向發(fā)展。?? (3)模具掃描及數(shù)字化系統(tǒng) 高速掃描機和模具掃描系統(tǒng)提供了從模型或?qū)嵨飹呙璧郊庸こ銎谕哪Ｐ退璧闹T多功能，大大縮短了模具的在研制制造周期。有些快速掃描系統(tǒng)，可快速安裝在已有的數(shù)控銑床及加工中心上，實現(xiàn)快速數(shù)據(jù)采集、自動生成各種不同數(shù)控系統(tǒng)的加工程序、不同格式的CAD數(shù)據(jù)，用于模具制造業(yè)的“逆向工程”。模具掃描系統(tǒng)已在汽車、摩托車、家電等行業(yè)得到成功應(yīng)用，相信在“十五”期間將發(fā)揮更大的作用。? (4)電火花銑削加工?? ??? 電火花銑削加工技術(shù)也稱為電火花創(chuàng)成加工技術(shù)，這是一種替代傳統(tǒng)的用成型電極加工型腔的新技術(shù)，它是有高速旋轉(zhuǎn)的簡單的管狀電極作三維或二維輪廓加工(像數(shù)控銑一樣)，因此不再需要制造復雜的成型電極，這顯然是電火花成形加工領(lǐng)域的重大發(fā)展。國外已有使用這種技術(shù)的機床在模具加工中應(yīng)用。預計這一技術(shù)將得到發(fā)展。? 如今，我國模具成型工業(yè)已形成了相當規(guī)模的完整體系，越來越多的新技術(shù)，新工藝，新材料誕生，并將應(yīng)用在模具產(chǎn)業(yè)中，這將促使我國模具工業(yè)的飛躍發(fā)展。同時，我國模具工業(yè)的總體水平與世界先進國家相比還有一定差距，還要大 力推進模具產(chǎn)業(yè)的科技進步，開展新技術(shù)，新材料研究開發(fā)，并進一步加強對模具工業(yè)專業(yè)技術(shù)人才的培養(yǎng)，使之可持續(xù)發(fā)展，為我國模具成型加工技術(shù)超趕世界先進水平作出貢獻。 大學三年的學習即將結(jié)束，畢業(yè)設(shè)計是其中最后一個實踐環(huán)節(jié)，是對以前所學的知識及所掌握的技能的綜合運用和檢驗。隨著我國經(jīng)濟的迅速發(fā)展，采用模具的生產(chǎn)技術(shù)得到愈來愈廣泛的應(yīng)用。在完成大學三年的課程學習和課程、生產(chǎn)實習，我熟練地掌握了機械制圖、機械設(shè)計、機械原理等專業(yè)基礎(chǔ)課和專業(yè)課方面的知識，對機械制造、加工的工藝有了一個系統(tǒng)、全面的理解，達到了學習的目的。對于模具設(shè)計這個實踐性非常強的設(shè)計課題，我們進行了大量的實習。經(jīng)過在新飛電器有限公司、洛陽中國一拖的生產(chǎn)實習，我對于模具特別是沖壓模具的設(shè)計步驟有了一個全新的認識，豐富了各種模具的結(jié)構(gòu)和動作過程方面的知識，而對于模具的制造工藝更是實現(xiàn)了零的突破。在指導老師的協(xié)助下和在工廠師傅的講解下，同時在現(xiàn)場查閱了很多相關(guān)資料并親手拆裝了一些典型的模具實體，明確了模具的一般工作原理、制造、加工工藝。并在圖書館借閱了許多相關(guān)手冊和書籍，設(shè)計中，將充分利用和查閱各種資料，并與同學進行充分討論，盡最大努力搞好本次畢業(yè)設(shè)計。 在設(shè)計的過程中，將有一定的困難，但有指導老師的悉心指導和自己的努力，相信會完滿的完成畢業(yè)設(shè)計任務(wù)。由于學生水平有限，而且缺乏經(jīng)驗，設(shè)計中不妥之處在所難免，肯請各位老師指正。 。 23 河南機電高等?？茖W校畢業(yè)設(shè)計說明書 2 彎曲工藝性分析 沖壓零件如圖1-1。材料H68，工件厚度：1 mm，板寬8.5mm。模具精度：普通的。該零件是彎曲件,沖壓加工經(jīng)濟性良好。 圖 1-1 工件圖 從零件圖分析，該沖壓件采用1mm的H68沖壓而成，可保證足夠的剛度與強度。零件外形尺寸注有公差要求，壁部圓角半徑r=2mm，可以彎曲成型。 從零件尺寸標注可以看出模具精度為普通，形狀簡單，而且尺寸要求相對較高，主要分析其彎曲成型問題，通過綜合分析決定采用單工序彎曲成形生產(chǎn)。 3 工藝與設(shè)計計算 2.1彎曲工件的毛坯展開尺寸計算 彎曲邊的展開尺寸可按式（1-1）計算。即 圖 1-2 毛坯分析圖 上式中，圓角半徑r=2mm；板料厚度t=1mm；t為中性層系數(shù)，查的k=0.37；l1為工件的豎直邊的長（除去圓角部分），有圖1-2可知L1=2.58，l2為水平邊的長度（除去圓角部分），L2=6.92。將這些數(shù)值代入，可得到L=41.8mm，取41.8。 最后得出如圖2.1所示的毛坯的形狀和尺寸。 圖2.1 毛坯展開圖 2.2壓力中心 為了設(shè)計方便，壓力中心選擇工件原圓孔的中心。 2.3彎曲力計算 （1）自由彎曲力計算，計算公式如下： 式中 —自由彎曲在沖壓行程結(jié)束時的彎曲力，N； B—彎曲件的寬度，； —彎曲件的內(nèi)彎曲半徑，； —彎曲件的材料厚度，； —材料的抗拉強度，MPa； —安全系數(shù)，一般取=1.3。 該零件取σb=400，t=1mm，B=8.5mm，r=2mm，代入公式中可得出： F1=884N （2）校正彎曲力計算 板料經(jīng)自由彎曲階段后，開始與凸、凹模表面全面接觸 ，此時，如果凸模繼續(xù)下行，零件受到模具擠壓繼續(xù)彎曲，彎曲力急劇增大，稱為校正彎曲。校正彎曲的目的，在于減少回彈，提高彎曲質(zhì)量。校正彎曲力可按下列式近似計算： F2=qA 式中 F2—校正彎曲力，N； A—彎曲件的校正部分的投影面積，355.3mm2； P—單位校正力，取40MPA。 代入上式中得，F(xiàn)2=355.3×40=14212KN 2.5壓力機初選 有彎曲工藝可知，彎曲時的校正彎曲力、自由彎曲力不是同時發(fā)生的，而且校正力比其它力大的多。因此可以按校正力F2=14.2KN選擇沖壓設(shè)備，同時由于彎曲模的閉合高度相對較高，實際選用100KN的壓力機，型號為J23-10。 參照設(shè)計手冊選取公稱壓力為的壓力機，壓力機型號為J23-10。 河南機電高等?？茖W校畢業(yè)設(shè)計說明書 4 模具總體結(jié)構(gòu)的確定 3.1 模具類型的選擇 由以上沖壓工藝分析可知，采用彎曲模沖壓。 3.2 送料方式的選擇 由于零件的毛坯為單工序模，所以采用人工手動送料。 3.3 定位方式的選擇 坯料采用定位銷和導料銷完成定位。 3.4 卸料、出件方式的選擇 剛性卸料是采用固定卸料板結(jié)構(gòu)，常用于較硬、較厚且精度要求不高的工件沖裁后卸料。 彈性卸料具有卸料與壓料的雙重作用，主要用在沖料厚在2mm及以下厚度的板料，由于有壓料作用，沖裁件比較平整。彈壓卸料板與彈性元件、卸料螺釘組成彈壓裝置。 因為工件料厚為1mm，由于需要保證工件的平整性，所以采用彈性卸料裝置。 3.5 導向方式的選擇 方案一：采用對角導柱模架。由于導柱安裝在模具壓力中心對稱的對角線上，所以上模座在導柱上滑動平穩(wěn)。常用于橫向送料級進?；蚩v向送料的落料模、復合模。 方案二：采用后側(cè)導柱模架。由于前面和左、右不受限制，送料和操作比較方便。因為導柱安裝在后側(cè)，操作者可以看見條料在模具中的送進動作。但是不能使用浮動模柄。 方案三：采用四導柱模架。具有導向平穩(wěn)、導向準確可靠、剛性好等優(yōu)點。常用于沖壓件尺寸較大或精度要求較高的沖壓零件及大量生產(chǎn)用的自動沖壓模架。 方案四：采用中間導柱模架。導柱安裝在模具的對稱線上，導向平穩(wěn)、準確。 只能一個方向送料。 河南機電高等?？茖W校畢業(yè)設(shè)計 （a） （b） （c） （d） 圖4-1 導柱模架 （a）下模座 （b）導柱 （c）導套 （d）上模座 根據(jù)以上方案比較并結(jié)合模具結(jié)構(gòu)形式和送料方式，為提高模具壽命和工件質(zhì)量，采用后側(cè)導柱模架，操作者可以看見條料在模具中的送進動作。由于前面和左、右不受限制，能滿足工件成型的要求。即方案二最佳。 河南機電高等?？茖W校畢業(yè)設(shè)計說明書 5 模具零件的設(shè)計 4.1工作零件的結(jié)構(gòu)設(shè)計 凸、凹模刃口尺寸計算 彎曲時，U形件的彎曲，必須選擇適當?shù)拈g隙，間隙的大小對于工件質(zhì)量和彎曲力的大小有很大的影響。間隙越小，彎曲力越大。間隙過小，會使工件壁變薄，并降低凸模壽命。間隙過大，則回彈較大，還會降低工件的精度。 彎曲時，間隙值利用公式計算。 （4-1） 式中 ——彎曲凸、凹模的單面間隙； t——材料的公稱厚度； n——因數(shù)，與工件的彎曲高度和彎曲線長度有關(guān)，查表，取0.05。 代入公式可得：。 彎曲件標注的為外形公差，應(yīng)計算模具的凹模尺寸，凸模根據(jù)單面間隙配作。 彎曲凸、凹模的制造公差查表得： 彎曲凸模的尺寸計算： R2mmmm 為彎曲件的外形尺寸 彎曲件標注的為內(nèi)形公差，應(yīng)計算模具的凸模尺寸，凹模根據(jù)單面間隙配作。 （4-2） 代入數(shù)據(jù)： 凸、凹模的圓角設(shè)計 1 凸模圓角半徑 一般情況下，凸模圓角角半徑等于或略小于工件內(nèi)側(cè)的圓角半徑，對于工件圓角半徑較大(R/t＞10)，而且精度要求較高時，應(yīng)考慮回彈的影響，將凸模圓角半徑根據(jù)回彈角的大小作相應(yīng)的調(diào)整，以補償彎曲的回彈量。 2 凹模圓角半徑 工件在壓彎過程中，凸模將工件壓入凹模而成形，凹?？诓康膱A角半徑對于彎曲力和零件質(zhì)量都有明顯的影響。凹模圓角半徑尺寸的大小與材料進入凹模的深度、彎邊高度和材料厚度有關(guān)。在一般情況下，可用式(3-3)確定。 （4-3） 取凹模半徑為4mm。 凸模的結(jié)構(gòu)設(shè)計 如圖3-1所示，安裝時將其通過凸模固定板固定在上模座上；凹模直利用螺釘直接固定在系模座上，凹模結(jié)構(gòu)和尺寸如圖3-2所示。 圖3-1 凸模 河南機電高等專科學校畢業(yè)設(shè)計說明書 圖3-2 凹模 4.2閉合高度的確定 當模具的閉合高度大于壓力機的最大閉合高度時，模具無法在壓力機上安裝，沖模不能在該機床上使用，必須選取其他壓力機。當模具的閉合高度小于壓力機 的最小閉合高度時，可以在壓力機的墊板上再加墊板來使用。 本次設(shè)計中各零件厚度如下 (1)下模座厚度為40mm； (2)上模座厚度為30mm； (3)墊板厚度為8mm； (4)凸模高度為41mm； (5)彎曲凹模厚度為20mm； 該模具的閉合高度為：H=133mm。 另外，模具的其他結(jié)構(gòu)尺寸也必須與壓力機配合。 4.3定位零件的設(shè)計 定位零件采用擋料銷和定位銷進行定位，擋料銷材料為45鋼，直徑為6mm，高度為2mm。 4.4模架的設(shè)計 1）模架的選擇 該模具的設(shè)計采用中間導柱模架（GB/T2855），兩導柱，導套分別裝在上、下模座中間位置，凹模面積是導套中間的有效區(qū)域?？捎糜跊_壓較寬條料。主要適用于一般精度要求的沖模，適用于中型模具。其凹模周界范圍100mm×100mm。上、下模座尺寸為100mm×100mm×40mm、100mm×100mm×30mm。 2）導套、導柱的選擇 由于選擇了標準模架，導套和導柱的基本尺寸也就決定了，又由于閉合高度為305mm，所以導套和導柱的基本尺寸也就決定了，導柱d/mm×L/mm分別為φ20×100；導套d/mm×L/mm×D/mm分別為φ20×70×32。 4.5其他零部件設(shè)計 模柄 模柄作用：將上模固定在壓力機的滑塊上。 要求：模具的壓力中心與模柄中心線重合。 應(yīng)用：常用于1000KN以下的中小型模具上。 類型及應(yīng)用場合： 旋入式：下圖a）所示，通過螺紋與上模座連接，為防止松動，常用防轉(zhuǎn)螺釘緊固。這種模柄裝拆方便，但模柄軸線與上模座的垂直度較差，多用于有導柱的小型沖模。 壓入式：下圖b）所示，它與模座孔采用過渡配合H7/m6，并加銷釘防轉(zhuǎn)。這種模柄可較好保證軸線與上模座的垂直度。適用于各種中、小型沖模，生產(chǎn)中最 圖5-6槽型模柄和通用模柄 凸緣式：下圖c）所示，用3~ 4個螺釘固定在上模座的窩孔內(nèi)，模柄的凸緣與上模座的窩孔采用H7/js6過渡配合。多用于較大型的模具。槽型模柄和通用模柄：下圖d）、e）所示，均用于直接固定凸模，也稱為帶模座的模柄，它更換凸模方便，主要用于簡單模。 模柄的選用：首先應(yīng)根據(jù)模具的大小及零件精度等方面的要求，確定模柄的類型，然后根據(jù)所選壓力機的模柄孔尺寸確定模柄的規(guī)格。選擇模柄時應(yīng)注意模柄安裝直徑d和長度L應(yīng)與滑塊模柄孔尺寸相適應(yīng)。模柄直徑可取與模柄孔相等，采用間隙配合H11/dll，模柄長度應(yīng)小于模柄孔深度5~l0mm。本設(shè)計中利用壓入式模柄，直徑為40mm，材料為Q235。 螺釘與銷釘 沖模上的緊固件包括連接螺釘和定位銷釘。受力較大的連接螺釘一般都采用內(nèi)六角螺釘，其特點是用45號鋼制造，并淬火達43～48HRC，因此可承受較大的拉應(yīng)力。受力不大的小螺釘可以采用普通圓柱頭螺釘，但一般不用半球頭螺釘或沉頭螺釘。前者一字槽容易擰環(huán)，后者裝配時不便調(diào)整。 定位銷釘采用普通圓柱銷，可以承受一定的切應(yīng)力。該模具中的標準件為： 螺釘?????????????GB70—2000 圓柱銷????????????GB119—2000 河南機電高等?？茖W校畢業(yè)設(shè)計說明書 6 模具圖紙繪制 5.1模具裝配圖的設(shè)計繪制 5.2模具零件圖的設(shè)計繪制 見附圖 片狀彈簧沖壓成形工藝與模具設(shè)計 7 沖壓設(shè)備的選定 表5-1[4] 型 號 J23-10 公稱壓力/kN 100 滑塊行程/mm 45 滑塊行程次數(shù)/（次/mm） 145 最大閉合高度/mm 220 閉合高度調(diào)節(jié)量/mm 35 墊板尺寸（厚度mm×孔徑mm） 350×220 模柄孔尺寸（直徑mm×深度mm） Φ30×55 工作臺尺寸 前后 240 左右 370 河南機電高等專科學校畢業(yè)設(shè)計說明書 8 模具的裝配 根據(jù)模具裝配要點，選凹模作為裝配基準件，先裝下模，再裝上模，并調(diào)整間隙、試沖、返修，具體裝配見表7.1。 表7.1 模具的裝配表 序號 工序 工藝說明 1 凸、凹模預配 （1）裝配前仔細檢查各凸模形狀以及凹模形孔，是否符合圖紙要求尺寸精度、形狀。 （2）將各凸模分別與相應(yīng)的凹?？紫嗯?，檢查其間隙是否加工均勻。不合適則應(yīng)重新修磨或更換。 2 裝配下模 （1） 在下模座上劃中心線，按中心預裝凹模； （2） 在下模座，用已加工好的凹模分別確定其螺孔位置，并分別鉆孔，攻絲 （3） 將下模座、凹模裝在一起，并用螺釘緊固，打入銷釘 3 裝配上模 （1） 在已裝好的下模上放等高墊鐵，再在凹模中放入0.12mm片； （2） 預裝上模座，劃出與凸模相應(yīng)螺孔。銷孔位置并鉆絞螺孔、銷孔； （3） 用螺釘將凸模、上模座連接在一起，但不要擰緊； （4） 將卸料板固定在凹模上， （5） 安裝導正銷、承料板； 總結(jié) 時光匆匆而逝，十多天的片狀彈簧沖壓工藝及模具設(shè)計畫上了圓滿的句號。在設(shè)計過程中，查閱有關(guān)模具設(shè)計手冊與冷模具設(shè)計的資料并繪制出成型的總裝配圖及各種無標準零件圖。本設(shè)計說明書詳細介紹了片狀彈簧沖壓模具設(shè)計過程，對各個工序的設(shè)計構(gòu)思及具體實施方案，主要有前言設(shè)計說明書，講述模具設(shè)計工藝方案及工藝過程等。 設(shè)計的要求是首先要保證產(chǎn)品質(zhì)量節(jié)約原材料，降低勞動強度，減低成本，提高勞動生產(chǎn)率原則，制圖符合國家標準，標注尺寸合理，圖面整潔，布局合理，說明書力求系統(tǒng)性強，易懂，便于查看。通過這次沖壓模的設(shè)計讓我知道;沖壓是建立在金屬塑性變形的基礎(chǔ)上，在常溫下利用安裝在壓力機上的模具對材料施加壓力，是其產(chǎn)生分離或塑性變形從而獲得一定形狀、吃春和性能的零件的一種壓力加工方法。并且通過這次沖壓模設(shè)計，使我重新溫習了以前學過的有關(guān)這些方面的知識，并且通過查閱資料了解了一些新的知識，使我對模具設(shè)計有了更進一步的了解 致謝 本課題在選題及研究過程中得到老師的悉心指導。老師多次詢問研究進程，并為我指點迷津，幫助我開拓研究思路，精心點撥、熱忱鼓勵。陳老師一絲不茍的作風，嚴謹求實的態(tài)度，踏踏實實的精神，不僅授我以文，而且教我做人。雖歷時才1個月，卻給我以終生受益無窮之道。對陳老師的感激之情是無法用言語表達的。 本課程設(shè)計是L形件的彎曲模設(shè)計，選題難，結(jié)構(gòu)比較復雜。選完課題我就開始盲目，實在是無從下手，關(guān)鍵時刻是我的指導老師指點我，先花二個周時間學習模具知識，經(jīng)過一個月的系統(tǒng)學習，對模具有了一定的了解，期間也收集了一些模具的相關(guān)資料，設(shè)計進入正式階段，設(shè)計方案的確定，設(shè)計過程中的一些細節(jié)問題一次又一次的把我難住，更由于沒見過實物，給我解決問題增加了難度。最后還是在老師的幫助下不斷的克服困難，完成了本次設(shè)計。 這次課程設(shè)計不僅僅讓我學到了沖壓模具的相關(guān)知識，對我畢業(yè)后工作更是起到了巨大的幫助。設(shè)計是科學的，設(shè)計是嚴謹?shù)?，來不得半點差錯，設(shè)計中的一丁點差錯，很可能在生產(chǎn)中帶來巨大的損失，因此對于設(shè)計中的沒一個細節(jié)都必須深思熟慮，設(shè)計中老師不光給我們指導專業(yè)知識，還教我們以后工作中應(yīng)該注意的問題,由于本人的水平有限，設(shè)計中結(jié)構(gòu)可能還存在一定問題。 感謝我的父母及親人多年來對我學業(yè)上默默地鼓勵和對我生活上無微不致地關(guān)懷，使我能夠順利地完成學業(yè)，在這里我衷心地祝愿他們身體健康，萬事如意！ 通過三年課程的認真學習，使我在此基礎(chǔ)上利用所學東西順利進行并完成了設(shè)計。 參考文獻 [1] 許發(fā)樾主編.實用模具設(shè)計與制造手冊.北京：機械工業(yè)出版社，2001 [2] 周開華主編.簡明精沖手冊.北京：國防工業(yè)出版社，1999 [3] 唐志玉.模具設(shè)計師指南.北京：國防工業(yè)出版社，1999 [4]《沖壓模具簡明設(shè)計手冊》表13.10，P389 評語 學生姓名： 班級: 學號： 題 目： 片狀彈簧沖壓成形工藝與模具設(shè)計 綜合成績： 指導者評語： 指導者(簽字)： 年 月 日 畢業(yè)設(shè)計（論文）評語 評閱者評語： 評閱者(簽字)： 年 月 日 答辯委員會（小組）評語： 答辯委員會（小組）負責人(簽字)： 年 月 日 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.