啟動器端口沖壓成形工藝與模具設計【落料拉深復合?!?/h1>
啟動器端口沖壓成形工藝與模具設計【落料拉深復合模】,落料拉深復合模,啟動器端口沖壓成形工藝與模具設計【落料拉深復合?!?啟動器,端口,沖壓,成形,工藝,模具設計,落料拉深,復合
中期檢查表學生姓名學 號指導教師選題情況課題名稱啟動器端口沖壓成形工藝與模具設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 日設計任務書系 部: 專 業(yè): 學生姓名: 學 號: 設計題目:啟動器端蓋沖壓成形工藝及模具設計 起 迄 日 期: 指 導 教 師: 20013年 11月 2日畢 業(yè) 設 計 任 務 書1本畢業(yè)設計課題來源及應達到的目的:本題目是指導老師根據(jù)學校培養(yǎng)該學生的目標和該學生自身的特點以及當前的教育狀況來設計的。過該題目的畢業(yè)設計,將使學生達到理論知識與模具設計和制造的實踐相結(jié)合,提高學生對所學專業(yè)知識的掌握和綜合和應用能力。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)知識的綜合應用。2本畢業(yè)設計課題任務的內(nèi)容和要求(包括原始數(shù)據(jù)、技術要求、工作要求等):本畢業(yè)設計課題任務的題目是啟動器端蓋,材料為08鋼,料厚1 mm, 屬于大批量生產(chǎn)。其具體形狀與尺寸如下圖:所在專業(yè)審查意見:負責人: 年 月 日系部意見:系領導: 年 月 日設計說明書畢業(yè)設計題目:啟動器端蓋沖壓成形工藝與模具設計系 部 專 業(yè) 班 級 學生姓名 學 號 指導教師 2014年4月22日目 錄1 緒論12 啟動器端蓋落料拉深模設計82.1工藝分析82.2工藝方案的確定8 2.2.1拉深件毛坯尺寸的計算8 2.2.2拉深系數(shù)與拉深次數(shù)的確定9 3必要的工藝計算103.1排樣的計算 103.2拉深凸、凹模工作部分尺寸的設計計算123.3落料凸、凹模工作部分尺寸的設計計算133.4拉深凸、凹模圓角半徑的計算133.5凸、凹模間隙的計算143.6拉深力的計算及初選壓力機 144 模具總體設計164.1主要零部件的設計174.2拉深凸、凹模結(jié)構設計174.3壓邊裝置的設計184.4彈簧的設計184.5推桿的設計204.6凸模固板204.7墊板204.8模架的選用214.9聯(lián)接件的選用與標準化22 5 模具總裝圖22 6 加工工藝卡246.1拉深凹模的工藝卡片246.2拉深凸模的工藝過程卡25結(jié)束語26致謝28參考文獻29設計評語學生姓名: 班級: 學號:題 目: 啟動器端口沖壓成型工藝與模具設計 綜合成績: 指導者評語: 指導者(簽字): 年月日畢業(yè)設計評語 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): 年月日啟動器端蓋沖壓成形工藝與模具設計啟動器端蓋沖壓成形工藝及模具設計摘要:本設計題目為落料拉深復合模,體現(xiàn)了典型沖壓復合模的設計要求、內(nèi)容及方向,有一定的設計意義。通過對該模具的設計,加強了設計者對沖壓復合模設計基礎知識的理解和運用,為設計更復雜的沖裁模具做好了鋪墊。本設計運用沖裁工藝及模具設計的基礎知識,首先分析了板材的性能要求,為選取模具的類型做好了準備;然后計算了沖裁件的沖裁力,便于選取壓力機噸位及確定壓力機型號;最后分析了沖壓件的特征,便于確定模具的設計參數(shù)、設計模具結(jié)構零件及定位,卸件裝置。本設計采用了落料拉深復合模成形導向板。成形原理可劃分為三個個階段:凸模,凸凹模和落料凹模同時作用落料,彎曲成型。關鍵詞:復合模 落料 拉深 壓力機噸位 Trolleys axis bowl stamping process and die design Abstract:The topic for the design is compound blank and draw die design,It has manifested the typical blanking dies design request, the content and the direction, has certain design significance.Through the design of the component mold, strengthens the designers understand and utilize to the blanking die design basical knowledge,has prepareed for designing more complex blanking die.The design has utilize blanking craft and the basical knowledge of the mold design, has first analyzed the property requirement of the plate , has prepared for selecting the mold type;then has calculated the blanking strength,has advantaged to select the press tonnage and determine press model; Finally has analyzed the characteristic of the products, has advantaged to finite the mold design variable,the design main point and shedder. This design used piercing and blanking progressive die to form the products.Three methods are generally used to reduce smooth the shock impact,piercing die,bending dies.Key word: compound die blanking drawing press tonnage1 緒 論 目前,我國沖壓技術與工業(yè)發(fā)達國家相比還相當?shù)穆浜?,主要原因是我國在沖壓基礎理論及成形工藝、模具標準化、模具設計、模具制造工藝及設備等方面與工業(yè)發(fā)達的國家尚有相當大的差距,導致我國模具在壽命、效率、加工精度、生產(chǎn)周期等方面與工業(yè)發(fā)達國家的模具相比差距相當大。我國模具近年來發(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)。近年來,模具行業(yè)結(jié)構調(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市場經(jīng)濟,再加上國內(nèi)模具工業(yè)基礎薄弱,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1520萬美元,有的高達2530萬美元,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,特別是設備數(shù)控化率和CAD/CAM應用覆蓋率要比國外企業(yè)低得多。由于體制和資金等原因,引進設備不配套,設備與附配件不配套現(xiàn)象十分普遍,設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。 第四,專業(yè)化、標準化、商品化的程度低、協(xié)作差 由于長期以來受“大而全”“小而全”影響,許多模具企業(yè)觀念落后,模具企業(yè)專業(yè)化生產(chǎn)水平低,專業(yè)化分工不細,商品化程度也低。目前國內(nèi)每年生產(chǎn)的模具,商品模具只占45%左右,其馀為自產(chǎn)自用。模具企業(yè)之間協(xié)作不好,難以完成較大規(guī)模的模具成套任務,與國際水平相比要落后許多。模具標準化水平低,標準件使用覆蓋率低也對模具質(zhì)量、成本有較大影響,對模具制造周期影響尤甚。 第五,模具材料及模具相關技術落后模具材料性能、質(zhì)量和品種往往會影響模具質(zhì)量、壽命及成本,國產(chǎn)模具鋼與國外進口鋼相比,無論是質(zhì)量還是品種規(guī)格,都有較大差距。塑料、板材、設備等性能差,也直接影響模具水平的提高。 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)在模具設計制造中廣泛應用CAD/CAE/CAM技術;3)模具掃描及數(shù)字化系統(tǒng);4)在塑料模具中推廣應用熱流道技術、氣輔注射成型和高壓注射成型技術;5)提高模具標準化水平和模具標準件的使用率;6)發(fā)展優(yōu)質(zhì)模具材料和先進的表面處理技術;7)模具的精度將越來越高;8)模具研磨拋光將自動化、智能化;9)研究和應用模具的高速測量技術與逆向工程;10)開發(fā)新的成形工藝和模具。模具是工業(yè)生產(chǎn)關鍵的工藝裝備,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,6080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)供不應求的局面,世界模具市場年交易總額為600650億美元左右。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。國外模具總量中,大型、精密、復雜、長壽命模具的比例占到50%以上;國外模具企業(yè)的組織形式是大而專、大而精。2004年中國模協(xié)在德國訪問時,從德國工、模具行業(yè)組織-德國機械制造商聯(lián)合會(VDMA)工模具協(xié)會了解到,德國有模具企業(yè)約5000家。2003年德國模具產(chǎn)值達48億歐元。其中(VDMA)會員模具企業(yè)有90家,這90家骨干模具企業(yè)的產(chǎn)值就占德國模具產(chǎn)值的90%,可見其規(guī)模效益。 隨著時代的進步和技術的發(fā)展,國外的一些掌握和能運用新技術的人才如模具結(jié)構設計、模具工藝設計、高級鉗工及企業(yè)管理人才,他們的技術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1520萬美元,有的達到 2530萬美元。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%。所以我們這一代青年學子一定要奮發(fā)向上,為祖國的未來增添一份絢麗的光彩!大學三年的學習即將結(jié)束,畢業(yè)設計是大學三年教學環(huán)節(jié)中的最后一個實踐環(huán)節(jié),是對大學三年所學的知識及所掌握的技能的綜合運用和檢驗。在學校的近三年學習中,已完成了模具專業(yè)教學計劃中所要求的理論課程及相關的實踐環(huán)節(jié)。在畢業(yè)前夕,通過畢業(yè)設計的實踐環(huán)節(jié),進行對所學知識的全面總結(jié)整合和應用,使其系統(tǒng)化,提高綜合運用能力及擴大模具領域的新視野。畢業(yè)設計其目的在于鞏固所學知識,熟悉相關資料的查閱,樹立正確的設計思想,掌握設計方法,培養(yǎng)實際工作能力。通過設計,使我在工藝性分析、工藝方案論證、工藝計算、零件結(jié)構設計、編寫技術文件和閱讀技術文獻等方面受到一次綜合訓練,使自己的認識增長了許多。畢業(yè)設計要達到的具體要求是:1.系統(tǒng)總結(jié),鞏固過去所學的基礎知識和專業(yè)課知識。2. 運用所學知識解決模具技術領域內(nèi)的實際工程問題,以此進行綜合知識的訓練。3.通過某項具體工程設計和實驗研究,達到多種綜合能力的培養(yǎng),掌握設計和科研的基本過程和基本方法。4.提高和運用與工程技術有關的人文科學,價值工程和技術經(jīng)濟的綜合知識。此次我做的是冷沖壓模具設計,為一副簡單的落料拉深復合模具,冷沖壓是利用安裝在壓力機上的沖模對材料施加壓力,使其產(chǎn)生分離或塑性變形,從而獲得需要零件(俗稱沖壓件或沖件)的一種壓力加工方法。因為它通常是在室溫下進行加工,所以稱為冷沖壓。冷沖壓與其他加工方法相比,具有獨到的特點,所以在工業(yè)生產(chǎn)中,尤其在大批量生產(chǎn)中應用十分廣泛。相當多的工業(yè)部門越來越多地采用冷沖壓加工產(chǎn)品零部件,如汽車、拖拉機、電器、儀表、電子、國防以及日用品等行業(yè)。在這些工業(yè)部門中,沖壓件所占的比重相當大。不少過去有鑄造、鍛造、切削加工方法制造的零件,現(xiàn)在已經(jīng)被質(zhì)量輕、剛度好的沖壓件所代替。通過沖壓加工制造,大大提高了生產(chǎn)效率,降低了成本。可以說如果在生產(chǎn)中不廣泛采用沖壓工藝,許多工業(yè)部門的產(chǎn)品要提高生產(chǎn)率,提高質(zhì)量,降低成本,進行產(chǎn)品的更新?lián)Q代是難以實現(xiàn)的。在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、機械設計、機械原理等專業(yè)基礎課和專業(yè)課方面的知識,對機械制造、加工的工藝有了一個系統(tǒng)、全面的了解,達到了學習的目標,模具設計是一個實踐性非常強的教學環(huán)節(jié),我們進行的大量實習環(huán)節(jié)為其提供了一定的現(xiàn)場認知。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計步驟有了一個全新的認識,豐富了各種模具的結(jié)構和動作過程方面的知識,而對于模具的制造工藝更是有了零的突破。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手冊和書籍,設計中,充分利用和查閱各種資料,并與同學進行充分討論,盡了最大努力做畢業(yè)設計。在設計的過程中,雖然有一定的困難,但在指導老師的細心指導、同學間的討論和自己的努力下,完滿的完成畢業(yè)設計任務。由于水平有限,而且缺乏經(jīng)驗,設計中難免會出現(xiàn)疏漏和不妥之處,敬請各位老師指正。2 啟動器端蓋落料拉深模設計名稱:手推車軸碗材料:08鋼料厚:1 mm批量:大批量圖1 制件圖2.1工藝分析 制件為無凸緣筒形零件,要求外形尺寸,對厚度變化沒有要求。制件的形狀滿足拉深工藝要求。底部圓角半徑r=4mm,大于拉深凸模圓角半徑rr=(23)t=(23)1=23mm(t為板料厚度),滿足首次拉深對圓角半徑的要求,尺寸58按公差表查得IT14級,滿足拉深工序?qū)χ萍畹燃壍囊蟆?.2工藝方案確定2.2.1拉深件毛坯尺寸的計算在計算拉深毛坯尺寸時,首先確定修邊余量。并把修邊余量加到拉深件高度上,這時拉深件的高度(H)為原拉深高度(h)與修邊余量(h)之和,即拉深系數(shù)與拉深次數(shù)的確定H=h+h1.確定修邊余量h 該件h=16 mm,d=58-1=57 mm所示h= h/d=16/570.28因為h料厚t=1故該件在拉深時不需修邊余量。2.計算毛坯直徑 D= = 80mm式中 D拉深件毛坯尺寸,mm; r拉深件底部圓角半徑,mm。實際生產(chǎn)中針對無需修邊的拉深件,在毛坯尺寸確定的方法上,一般根據(jù)理論計算的結(jié)果,備制拉深件的毛坯,待拉深試模合格后,再制作拉深件的毛坯落料模。2.2.2拉深系數(shù)與拉深次數(shù)的確定工件總的拉深系數(shù)為:m總=d/D=57/800.71拉深次數(shù)的確定 毛坯相對厚度為t/D=1/80100%1.2457%查沖壓工藝與模具設計,首次拉伸的極限拉深系數(shù)為m1=0.6m總=0.710.6故工件可以一次拉深成形。該工件僅包含落料和拉深兩個基本工序,可以采用以下兩種工藝方案:方案一:落料拉深,采用單工序模生產(chǎn)。方案二:落料拉深,采用復合模生產(chǎn)。方案三:拉深級進沖壓,采用級進模生產(chǎn)。方案一:模具結(jié)構簡單,成本較低,但需要兩道工序兩副模具,由于兩次定位使得工件的形位誤差難以保證,制件的質(zhì)量較差,效率低,難以滿足大批量生產(chǎn)要求,故不宜采用。方案二:只需一副模具,由于一次成形,減少了多次定位出現(xiàn)的定位誤差,并且在模具結(jié)構中采用彈性壓料裝置,使其制件質(zhì)量較好,工件的精度及生產(chǎn)效率都較高。方案三:也只需一副模具,生產(chǎn)效率高,但模具結(jié)構比較復雜,送進操作不方便。通過對上述三種方案分析比較,雖然方案一和方案三也能滿足要求,但對工人要求較高并且經(jīng)濟效率沒有復合模高,故:綜合考慮采用第二種沖壓工藝方案進行為好。即采用復合模生產(chǎn)。2.3必要的工藝計算2.3.1排樣的計算單個步距內(nèi)的材料利用率:=式中:A一個步距內(nèi)沖裁件的實際面積; B條料寬度; S步距。由下表1得a1=0.8,a=1.0A=R2=3.14(16-4+4.53.14/2+29-1-4)2=5805.86mm2,B=86+21.0=88,S=86+0.8=86.8故= =76%表1材料厚度t工件間a1側(cè)面a0.25以下1.82.00.250.51.21.50.50.81.01.20.81.20.81.01.21.61.01.21.62.01.21.52.02.51.51.82.53.01.82.23.03.52.22.53.54.02.52.84.05.03.03.55.0120.6t0.7t排樣如圖2所示: 圖 22.3.2拉深凸、凹模工作部分尺寸的設計計算 對于制件一次拉成的拉深模及末次拉深模,其凸模和凹模的尺寸及公差應按制件的要求確定。 此工件要求的是外形尺寸,設計凸,凹模時,應以凹模尺寸為基準進行計算,即 凹模尺寸 Da=(D1-0.75)+0/4 =(58-0.750.5)+00.5/4 =57.625+00.125 mm式中 D1拉深件的基本尺寸,mm; 拉深件的尺寸公差,mm。間隙取在凸模上,則凸模尺寸可標注凹模基本尺寸,不標注公差,但在技術中要注明按單面拉深間隙配作。注:拉深凸,凹模采用分別加工時,要嚴格控制凸,凹模的制造公差,保證拉伸間隙在允許的范圍內(nèi)。2.3.3落料凸、凹模工作部分尺寸的設計計算結(jié)合工件外形并考慮加工,將落料凸、凹模設計成直通式,4個M10的螺釘固定在墊板上,與凹模固定板配合按H6/m5。安排凸、凹模在模架的位置時,根據(jù)壓力中心的數(shù)據(jù),將壓力中心和模柄中心重合,其落料凸、凹模的長度根據(jù)拉深凸模的長度進行設計,取L=40mm根據(jù)前面凸模的設計時的尺寸計算可以得出,下面對其輪廓尺寸進行計算:凹模的厚度 H=KB 由表2 查得K=0.3表2S材料厚度t1133650501001002002000.300.400.200.300.150.200.100.150.350.500.220.350.180.220.120.180.450.600.300.450.220.300.150.22則H=0.358=17.4mm此為最小值,應取大點值H=40mm寬度L1 =100mm凸、凹模的長度 取L2=142mm即凸、凹模的輪廓尺寸為142mm100mm40mm2.3.4拉深凸、凹模圓角半徑的計算1.凹模的圓角半徑ra 一般來說,大的ra可以降低拉深系數(shù),還可以提高拉深件的質(zhì)量,所以應盡量取大些。但ra太大,拉深時板料將過早失去壓邊,有可能出現(xiàn)拉深后期起皺。故凹模的圓角半徑的合理值應當不小于4 t (t為料厚)。拉深凹模圓角半徑取ra=5 mm。2.凸模的圓角半徑r t r t對拉深變形的影響,不象ra那樣影響拉深的全過程,但r t過大或過小同樣對防止起皺和拉裂及降低極限拉深系數(shù)不利。故r t的合理取值應不小于(23)t只有變形程度較小時,才允許取(23) r t=2 t。設計制件可以一次拉成的拉深模或多次拉深的末次拉深模,r t應取制件底部圓角相等數(shù)值,如果拉深件零件圖上所標注的圓角半徑小于r t的合理值,拉深模的r t仍需取合理值。代拉深后再用整形方法使圓角半徑達到圖樣要求。此件需一次拉深成形,所以r t值取與制件底部圓角相同的R值,即r t=3mm r t(23)t2.3.5凸、凹模間隙的計算 拉深間隙是指單邊間隙,即Z=(da-dt)/2.間隙過小會增加摩擦力,使拉深件容易拉裂,且易擦傷制件表面,降低模具壽命.間隙過大則對坯料的校直作用小,影響制件的尺寸精度.因此,確定間隙的原則是,既要考慮料厚的公差,又要考慮筒形件口部的增厚現(xiàn)象,根據(jù)拉深時是否采用壓邊圈和制件的尺寸精度、表面粗糙度要求合理確定。此件拉深模采用壓邊裝置,經(jīng)工藝計算一次就能拉深成形,故間隙為Z=1.1t=1.1mm2.3.6拉深力的計算及初選壓力機由表3確定壓邊力的計算公式 表3 壓邊力的計算公式拉深情況公式拉深任何形狀的工件FQ=Ap圓筒件第一次拉深FQ=/4D2-(d1+2r凹)2p圓筒件以后各次拉深FQ=/4 (dn-1- dn)2p即 FQ=式中 r凹=4mm,D=80mm,d1=57mm,由表4查得q=2.5 Mpa;表4材料名稱單位壓力p/MPa材料名稱單位壓力p/MPa鋁0.81.208鋼,20鋼鍍錫鋼板2.53.0紫銅,硬鋁1.21.8軟化狀態(tài)的耐熱鋼2.83.5黃銅1.52.0高合金鋼高錳鋼不銹鋼3.04.5壓軋青銅2.02.5把以上數(shù)據(jù)代入上式,得壓邊力為:FQ = = 4268(N)計算拉深力 F =3.14 d tKb已知m=0.60 mm,由表5查得k=0.86,08鋼的強度極限b=440 Mpa表5M10.550.570.600.620.650.670.700.720.750.770.80K11.000.930.860.790.720.660.600.550.500.450.40M20.700.720.750.770.800.850.900.95K21.000.950.900.850.800.700.600.50將d=57mm,k=0.86,t=1mm,6=440 Mpa代入上式,即: F=3.145714400.86 =67726.032 67726(N)按式4-37,壓力機的工稱壓力為拉深所需的壓力: F壓1.8(F+FQ)=1.8(4268+67726)=1.871994=129589.2(N)130(kN)故壓力機的公稱壓力要大于130kN,取160kN。所以初選壓力機型號為JA21-35。2.4模具總體設計(1) 拉深模結(jié)構簡圖的畫法如圖3所示: 圖3 拉深模簡圖1上模座 2凹模固定板 3推件板 4凹模 5壓邊圈 6凸模 7凸模固定板 8下模座(2) 采用的結(jié)構形式 拉深模結(jié)構采用帶壓邊圈的倒裝式結(jié)構,采用這種結(jié)構的優(yōu)勢在于可采用通用的彈頂裝置。2.5主要零部件的設計2.5.1拉深凸、凹模結(jié)構設計由以上對拉深凸、凹模尺寸的計算,可對其結(jié)構作如下設計,如圖4和圖5所示: 圖3 凹模 圖4 凸模2.5.2壓邊裝置的設計 該拉深模選在單動壓力機上進行拉深加工,所以必須借助彈性元件在受壓時所產(chǎn)生的壓力提供壓邊力。故選用具有通用性的彈性壓邊裝置作為彈性元件,這樣可避免每副模具都設計一套專用的彈性壓邊裝置。模具只需配備壓邊圈和頂桿,并采用倒裝式結(jié)構。壓邊裝置如圖6所示:圖6 壓邊裝置2.5.3彈簧的設計 由以上計算可知落料時壓邊力和拉深力分別為FQ=4268N,F=6776N,這個力相對不太大,采用彈簧卸料裝置較為合適。1)所選彈簧必須滿足預壓力的要求: FOFx/n式中:FO 彈簧預壓狀態(tài)的壓力(N); Fx卸料力(N); n彈簧數(shù)量即FOFx/n=1000/3 =333.3(N)2) 所選彈簧必須滿足最大許可壓縮量的要求: 即 H2 HH=H0+H3+H1式中:H2彈簧最大許可壓縮量();H彈簧實際總壓縮量();H0彈簧預壓縮量();H1卸料板的工作行程(),一般取H1=t+1,t為板料厚度;H3凸模刃磨量和調(diào)整量,一般取510。計算:H0=Fo/F2H2=(250/533)/14.7=6.9校核:設H1=2,H3=5 H=H0+H1+H3 =(6.9+2+5) =13.9由于14.713.9,即H2H。3) 根據(jù)F預的大小,從表中初選彈簧規(guī)格,使所選彈簧的工作極限負荷 Fj大于F預。4) 根據(jù)所選彈簧的工作極限負荷Fj和hj 工作極限負荷下的總變形量 ,作出該序號彈簧的特性曲線。 5) 檢查彈簧最大允許壓縮量,如滿足下列條件,則彈簧選得合適。 hjh預+h工+h修磨式中 h預 彈簧預壓縮量; h工 卸料板工作行程,一般取料厚加1 h修磨 凸,凹模修模量,取6mm 如果hj h預+h工+h修磨 .則必須重新選擇彈簧。 分別把FQ和F代入上公式中,計算并查表得所用的彈簧分別為:31575 GB2089-80 和 11020GB2089-80 . 2.5.4推件板的設計 推件板的作用就是協(xié)助推桿推出制件,完成拉深的最后一道工序。所以它不需要過多要求。由于拉深凹模的尺寸是14214265,故根據(jù)推件板與它的配合取推件板的尺寸為6161302.5.5凸模固定板的設計 因為凸模固定板是固定凸模的,對它的要求應優(yōu)先考慮凸模是否適合,經(jīng)查11確定凸模固定板的尺寸為14214230,如圖7所示: 圖72.5.6墊板的設計 墊板是配合凹模工作的,材料選擇Q235,外形銳角應倒鈍,整體尺寸為14214225,如8圖所示:圖 82.5.7模架的選用該模具采用中后側(cè)導柱模架,這種模架的導柱在模具后側(cè)位置,模具較敞開。以凹模周界尺寸為依據(jù),選擇模架規(guī)格。根據(jù)模具周界的具體尺寸,查2選選后側(cè)導柱模架最合適的規(guī)格是:上模座39020045 GB/T2855.5下模座39020045 GB/T2855.681的標準模架,材料為Q235。拉深模閉合高度H:H=Hs+Hag+Ha+Hy+Htg+Hx+s+t=45+45+25+60+30+30+(3045)+1=266281(mm) 取274 mm式中 Hs上模座厚度,mm; Hx下模座厚度,mm; Hag凹模固定板厚度,mm; Ha凹模厚度,mm; Hy壓邊圈厚度,mm; Htg凸模固定板厚度,mm; s安全距離,mm,一般取3045 mm; t拉深件厚度,mm,一般取1 mm。根據(jù)設計出來的最大閉合高度設計導柱和導套,有模座上的導柱和導套的尺寸確定選擇的尺寸查2得:導柱A22h5130 GB/T2861.181導套A22H68033 GB/T2861.681模柄的設計根據(jù)壓力的相關參數(shù),查3選擇模柄為壓入式模柄其參數(shù)為2580 ,JB/T7646.181Q235。模柄與上模座的聯(lián)接采用壓入。2.5.8聯(lián)接件的選用與標準化本模具采用螺釘固定,銷釘定位。具體講內(nèi)六角螺釘標記:45鋼M660 GB7085卸料螺釘標記:45鋼M880 GB2867.581螺釘標記:45鋼M650 GB6876圓柱銷釘標記:45鋼A660 GB 11986 2.6模具總裝圖裝配圖如圖9所示: 圖9 拉深模裝配圖1上模座 2導套 3導柱 4凹模墊板 5螺釘 6推件板 7模柄 8防轉(zhuǎn)銷 9推桿 10銷釘 11拉深凹模 12壓邊圈13卸料螺釘 14凸模固定板 15下模座 16限位柱 17定位銷 18拉深凸模 19彈簧 20銷釘 21螺塞這種拉深模結(jié)構簡單,使用方便,制造容易。工作時將毛坯放入壓邊圈5上面的定位銷或定位板內(nèi),上模下降,彈性壓邊圈先將毛坯壓住,然后凸模6對毛坯進行拉深。當拉深結(jié)束上?;厣龝r,包在凸模上的工件被壓邊圈頂出,并由推件板3把工件從凹模4內(nèi)推下。這里彈性壓邊圈不僅起壓邊作用,而且還起定位和卸件作用。凸模上需開設排氣孔,以防拉伸件緊吸于凸模上而造成卸件困難。采用倒裝式結(jié)構,方便在空間位置較大的下模部分安裝和調(diào)節(jié)壓邊裝置。2.7壓力機的選定根據(jù)已初選壓力機公稱壓力機公稱壓力值160kN,其最大閉合高度226 mm,不符合設計要求,應選壓力機型號為JA21-35(見表6),最大閉合高度為274 mm,滿足模具設計要求。表6 開式雙柱固定臺壓力機技術規(guī)格型 號JA21-35公稱壓力/kN350滑塊行程/ mm130滑塊行程次數(shù)/(次/min)50最大閉合高度/ mm280閉合高度調(diào)節(jié)量/ mm60滑快中心線至床身距離/ mm205立柱距離/ mm428工作臺尺寸/ mm前 后380左 右610工作臺孔尺寸/ mm前 后200左 右290直 徑260墊板尺寸/ mm厚 度60直 徑22.5模柄孔尺寸/ mm直 徑50深 度70滑塊底面尺寸/ mm前 后210左 右2702.8加工工藝卡2.8.1拉深凹模的工藝卡片工序號工序名稱工序內(nèi)容1下料將毛坯鍛造成筒形142mm142 mm65mm2粗車粗車外型3精車精車外型4劃線劃線加工安裝5熱處理淬火6磨平面修磨各平面及型孔或研磨各型孔7拋光使其達到圖紙要求8檢驗整體檢查有無不符之處2.8.2拉深凸模的工藝過程卡工序號工序名稱工序內(nèi)容 1下料將毛坯鍛造成筒形80mm120 mm80mm 2熱處理退火3粗車粗車各面及退刀槽,各留余量3 mm4精車精車各面,保證所要尺寸的前提下,留余量0.2 mm5熱處理淬火6磨平面磨裝配處成形面,修磨成形端面和圓角R7拋光按圖要求加工成所需尺寸8檢驗整體檢查有無不符之處結(jié) 束 語本課程設計是我們進行完了三年的模具設計與制造專業(yè)課程后進行的,它是對我們?nèi)陙硭鶎W課程的又一次深入、系統(tǒng)的綜合性的復習,也是一次理論聯(lián)系實踐的訓練。它在我們的學習中占有重要的地位。通過這次畢業(yè)設計使我從新系統(tǒng)的復習了所學專業(yè)知識同時也鞏固了先前學到了的知識,同時感觸最深刻的是:所學知識只有在應用中才能在更深刻理解和長時間記憶。對一些原來一知半解的理論也有了進一步的的認識。特別是原來所學的一些專業(yè)基礎課:如機械制圖、模具材料、公差配合與技術測量、冷沖模具設計與制造等有了更深刻的理解,使我進一步的了解了怎樣將這些知識運用到實際的設計中。同時還使我更清楚了模具設計過程中要考慮的問題,如怎樣使制造的模具既能滿足使用要求又不浪費材料,保證工件的經(jīng)濟性,加工工藝的合理性。在設計的過程中通過沖壓手冊、模具制造簡明手冊、模具標準應用手冊等隊要設計的問題進行查詢,我了解了通過更多的途徑去了解我要做的設計,使設計更具合理性。也使我學會了設計過程中對資料的查詢和運用。通過這次設計,我更加深入地學習了冷沖壓技術工作設計的內(nèi)容。冷沖壓技術工作設計的內(nèi)容包括冷沖壓工藝設計、模具設計及沖模制造三方面內(nèi)容,盡管三者的工作內(nèi)容不同,但三者之間存在著相互滲透、相互補充、相互依存的關系。冷沖壓工藝設計是針對給定的產(chǎn)品圖樣,根據(jù)其生產(chǎn)批量的大小、沖壓設備的類型規(guī)格、模具制造能力及工人技術水平等具體生產(chǎn)條件,從對產(chǎn)品零件圖的沖壓工藝性分析入手經(jīng)過必要的工藝計算,制定出合理的工藝方案,最后編寫沖壓工藝卡的一個綜合分析、計算、設計過程。沖壓工藝方案的確定包括工序性質(zhì)、數(shù)量的確定,工序順序的安排,工序組合方式及工序定位方式的確定等內(nèi)容。沖壓模具設計則是依據(jù)制定的沖壓工藝規(guī)程,在認真考慮毛坯的定位、出件、廢料排出諸問題以及模具的制造維修方便、操作安全可靠等因素后,設計計算并構思出與沖壓設備相適應的模具總體結(jié)構,然后繪制出模具總裝圖和所有非標準零件圖的整個設計繪圖過程。歷經(jīng)近三個月的畢業(yè)設計即將結(jié)束,在這次畢業(yè)設計中通過參考、查閱各種有關模具方面的資料,請教各位老師有關模具方面的問題,并且和同學的探討,模具設計在實際中可能遇到的具體問題,使我在這短暫的時間里,對模具的認識有了一個質(zhì)的飛躍。從陌生到開始接觸,從了解到熟悉,這是每個人學習事物所必經(jīng)的一般過程對模具的認識過程亦是如此。經(jīng)過近三個月的努力,我相信這次畢業(yè)設計一定能為三年的大學生涯劃上一個圓滿的句號,為將來的事業(yè)奠定堅實的基礎。- 25 -致 謝通過設計實踐,我逐步樹立了正確的設計思想,增強了創(chuàng)新意識,熟悉掌握沖壓模具設計的一般規(guī)律,培養(yǎng)了分析問題和解決問題的能力;通過設計計算、繪圖以及運用技術標準、規(guī)范、設計手冊等有關設計資料,進行了全面的塑料模具設計基本技能的訓練。從陌生到開始接觸,從了解到熟悉,這是每個人學習事物所必經(jīng)的一般過程,我對模具的認識過程亦是如此。經(jīng)過近三個月的努力,我相信這次畢業(yè)設計一定能為三年的大學生涯劃上一個圓滿的句號,為將來的事業(yè)奠定堅實的基礎。在這次設計過程中得到了老師以及許多同學的幫助,特別是韓艷艷老師的悉心指導,使我受益匪淺。在此,對關心和指導過我各位老師和幫助過我的同學表示衷心的感謝! 感謝母校河南機電高等??茖W校的辛勤培育之恩!感謝材料工程系給我提供的良好學習及實踐環(huán)境,使我學到了許多新的知識,掌握了一定的操作技能。最后,我非常慶幸在三年的的學習、生活中認識了很多可敬的老師和可親的同學,并感激師友的教誨和幫助!畢業(yè)之后,我一定會努力工作的,不辜負各位老師對我們的深切期望,在這里也說一聲:老師,您辛苦了!祝各位老師:身體健康、萬事如意!參 考 文 獻1王孝培主編.沖壓手冊M.北京:機械工業(yè)出版社,19902李紹林主編.實用模具技術手冊M.上??茖W技術出版社,19983陳錫棟、主編.實用模具技術手冊M.北京:機械工業(yè)出版社,20014模具實用技術叢書編委會.沖壓設計應用實例M.北京:機械工業(yè)出版社,19995楊玉英主編.實用沖壓工藝及模具設計手冊M. 北京:機械工業(yè)出版社,20046許發(fā)樾主編.實用模具設計與制造手冊M.北京:機械工業(yè)出版社,20007王芳主編.冷沖壓模具設計指導M. 北京:機械工業(yè)出版社,19988李易、于成功、聞小芝主編.現(xiàn)代模具設計、制造、調(diào)試與維修實用手冊M.北京:金版電子出版公司,20039翟德梅主編.模具制造技術M.河南機電高等??茖W校10任嘉卉主編.公差與配合手冊M. 北京:機械工業(yè)出版社,200011劉建超主編.沖壓模具設計與制造 M. 北京:高等教育出版社,199612成虹主編.沖壓工藝與模具設計M.北京:電子科技大學出版社,200213駱志斌主編.模具工實用技術手冊M.南京:江蘇科學技術出版社,199914周玲主編.沖模設計實例講解M.北京:化學工業(yè)出版社,200715模具實用技術叢書編委會編M.北京:機械工業(yè)出版社,1999Int 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.