端蓋沖壓成形工藝及模具設(shè)計【落料拉深復(fù)合?！?/h1>

端蓋沖壓成形工藝及模具設(shè)計【落料拉深復(fù)合模】,落料拉深復(fù)合模,端蓋沖壓成形工藝及模具設(shè)計【落料拉深復(fù)合?！?沖壓,成形,工藝,模具設(shè)計,落料拉深,復(fù)合 機 械 加 工 工 藝 過 程 卡 零件號零 件 名 稱00-03上墊板工序號工 序 名 稱設(shè) 備夾 具刀 具量 具工 時名 稱型 號名 稱規(guī) 格名 稱規(guī) 格名 稱規(guī) 格01下料(110mm90mm15mm)鋸床直尺02粗銑六面(104mm84mm12mm)銑床虎鉗標(biāo)準(zhǔn)面銑刀游標(biāo)卡尺03磨削(101mm81mm11mm）磨床磁力夾具、虎鉗砂輪游標(biāo)卡尺04鉗工（鉆孔）鉆床虎鉗鉆頭、鉸刀高度尺、游標(biāo)卡尺05熱處理（淬火、回火36-42HRC）電熱爐火鉗06磨削(100.05mmx80.05mmx10.05mm)磨床磁力夾具、虎鉗砂輪游標(biāo)卡尺07鉗工（研磨）研磨工具游標(biāo)卡尺 編制 校對 審核 批準(zhǔn) 設(shè)計中期檢查表學(xué)生姓名學(xué) 號指導(dǎo)教師選題情況課題名稱端蓋沖壓成形工藝及模具設(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(xué)習(xí)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(fù)責(zé)人： 2009年4 月 10日 端蓋沖壓成形工藝及模具設(shè)計 摘 要：本設(shè)計課題介紹了盒形蓋體落料拉伸復(fù)合模的結(jié)構(gòu)設(shè)計及工作過程。針對零件落料后口部呈尖銳刃口狀現(xiàn)象，改進了模具結(jié)構(gòu)，消除部分加工缺陷，分體現(xiàn)了沖壓工藝先進性和高效性,有一定的設(shè)計意義。通過對工藝零件的工藝分析及模具結(jié)構(gòu)設(shè)計, 鞏固所學(xué)的知識、熟悉有關(guān)資料,樹立正確的設(shè)計思路,加強了對模具的整體認(rèn)識,提高自己的實際模具設(shè)計工作能力。本計運用了沖壓成形模具設(shè)計的基本知識，首先對整個零件的了解分析工藝參數(shù),沖壓工藝性能,然后確定沖壓模的結(jié)構(gòu)形式，工零部件的設(shè)計與計算，落料和拉深在一個工序上完成，本副模具優(yōu)點結(jié)構(gòu)簡單緊湊，易于加工維修，。關(guān)鍵詞：工藝分析, 拉深成形,落料 Cover Tensile Trimming Composite Modulus Design Abstract：The design issues on the box-shaped body covered crowded tensile shear modulus of the composite structure design and working process. Against cutting crowded parts after mouth was sharp blade-like phenomenon, improve the structure of the mold and eliminate some processing defects, embodies the Analysis and Die of the composite structure Design ,consolidate the knowledge acquired and are familiar with relevant information, establish the process advanced and efficient.So this design has a certain of significance. Through of the parts of the process design ideas, the right to strengthen the overall mold and enhance awareness of their actual ability to mold design.Total use of the stamping die design of the basic knowledge, the first part of the whole understanding、analysis of process parameters, stamping process performance, and then determine the structure of stamping die form, the design and calculation of the components, Drawing and trimming processes in a complete, the vice die advantages of simple structure compact and easy maintenance processing, shortcomings pick-up may not be convenient. Keywords : Process Analysis，Drawing molding， Trimming設(shè)計任務(wù)書系 部: 專 業(yè): 學(xué)生姓名: 學(xué) 號: 設(shè)計題目: 端蓋沖壓成形工藝及模具設(shè)計 起 迄 日 期: 指 導(dǎo) 教 師: 2013年 11月 2日畢 業(yè) 設(shè) 計任 務(wù) 書1本畢業(yè)設(shè)計課題來源及應(yīng)達到的目的：該課題來源于工廠實際生產(chǎn)。在完成該課題之后，應(yīng)對沖裁工藝生產(chǎn)較為熟悉，能熟練掌握相關(guān)設(shè)計手冊的使用，能獨立完成一套模具的設(shè)計及模具工作零件加工工藝的編制，能夠運用模具設(shè)計軟件完成模具裝配圖及零件圖的繪制。2本畢業(yè)設(shè)計課題任務(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）：（1）了解目前國內(nèi)外沖裁模具的發(fā)展現(xiàn)狀；（2）沖壓件的結(jié)構(gòu)工藝分析；（3）板體沖孔落料模設(shè)計，并編寫設(shè)計說明書一份；（4）繪制模具總裝圖一張，并畫出非標(biāo)準(zhǔn)零件的零件圖；（5）編制主要零件加工工藝過程卡。零件名稱：端蓋材料：LY12厚度：0.6mm生產(chǎn)批量：大批量所在專業(yè)審查意見：負(fù)責(zé)人： 年 月 日系部意見：系領(lǐng)導(dǎo)： 年 月 日設(shè)計說明書畢業(yè)設(shè)計題目：端蓋沖壓成形工藝及模具設(shè)計系 部 專 業(yè)班 級 學(xué)生姓名 學(xué) 號 指導(dǎo)教師 2014年 4 月 16日 機 械 加 工 工 藝 過 程 卡 零件號零 件 名 稱00-06落料凹模工序號工 序 名 稱設(shè) 備夾 具刀 具量 具工 時名 稱型 號名 稱規(guī) 格名 稱規(guī) 格名 稱規(guī) 格01下料(110mm90mm12mm)鋸床直尺02粗銑六面(104mm84mm10mm)銑床虎鉗標(biāo)準(zhǔn)面銑刀游標(biāo)卡尺03磨削(101mm81mm9mm）磨床磁力夾具、虎鉗砂輪游標(biāo)卡尺04鉗工（鉆孔，攻絲）鉆床虎鉗鉆頭、鉸刀、攻絲刀高度尺、游標(biāo)卡尺05熱處理（淬火、回火60-62HRC）電熱爐火鉗06磨削(100.05mmx80.05mmx8.05mm)磨床磁力夾具、虎鉗砂輪游標(biāo)卡尺07鉗工（研磨）研磨工具游標(biāo)卡尺 編制 校對 審核 批準(zhǔn) 目 錄1緒論11.1 國內(nèi)模具的現(xiàn)狀和發(fā)展趨勢11.1.1國內(nèi)模具的現(xiàn)狀11.1.2國內(nèi)模具的發(fā)展趨勢31.1.3國外模具的現(xiàn)狀和發(fā)展趨勢31.2 拉深件模具設(shè)計與制造方面41.2.1 端蓋拉深模具設(shè)計的設(shè)計思路52 沖壓件的工藝分析72.1 引言72.2拉深件工藝分析73 確定工藝方案84 主要工藝參數(shù)的計算94. 1 拉深毛坯尺寸94.2 確定拉深次數(shù)104.3確定是否用壓邊圈及類型114.4排樣方式的確定115 沖壓力計算及壓力機的選用125.1落料力的計算125.2拉深力的計算135.3 壓邊力的計算135.4 壓力機的選用146 模具的結(jié)構(gòu)設(shè)計及計算156.1 模具工作部分的工藝計算156.1.1 凸凹模的設(shè)計與計算156.1.2卸料橡膠的設(shè)計與計算166.1.3選用模架、確定閉合高度及總體尺寸186.2 模具零件的結(jié)構(gòu)設(shè)計196.2.1 拉深凸模196.2.2 凸凹模206.2.3上墊板206.2.4 導(dǎo)柱、導(dǎo)套216.2.5 其他零件216.3 模具總裝圖237 總結(jié)25致 謝26參考文獻27端蓋沖壓成形工藝及其模具設(shè)計 1緒論隨著我國改革開放步伐的進一步加快，中國正逐步成為全球制造業(yè)的基地，特別是加入WTO后，作為制造業(yè)基礎(chǔ)的模具行業(yè)近年來得到了迅速發(fā)展。模具是工業(yè)生產(chǎn)的基礎(chǔ)工藝裝備，在電子、汽車、電機、電器、儀表、家電和通信等產(chǎn)品中，60%80%的零部件都依靠模具成型。國民經(jīng)濟的五大支柱產(chǎn)業(yè)，即機械、電子、汽車、石化、建筑，都要求模具工業(yè)的發(fā)展與之相適應(yīng)。模具生產(chǎn)水平的高低，己成為衡量一個國家產(chǎn)品制造水平高低的重要標(biāo)志，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。因此，我國要從一個制造業(yè)大國發(fā)展成為一個制造業(yè)強國，必須要振興和發(fā)展我國的模具工業(yè)，提高模具工業(yè)的整體技術(shù)水平。目前，我國沖壓技術(shù)與工業(yè)發(fā)達國家相比還相當(dāng)?shù)穆浜?，主要原因是我國在沖壓基礎(chǔ)理論及成形工藝、模具標(biāo)準(zhǔn)化、模具設(shè)計、模具制造工藝及設(shè)備等方面與工業(yè)發(fā)達的國家尚有相當(dāng)大的差距，導(dǎo)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(dāng)大。1.1 國內(nèi)模具的現(xiàn)狀和發(fā)展趨勢1.1.1國內(nèi)模具的現(xiàn)狀我國模具近年來發(fā)展很快，目前，我國制造業(yè)的資源已突破了企業(yè)社會國家的界線，制造業(yè)的國際化已是一個客觀事實。據(jù)不完全統(tǒng)計，2010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，2011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，2011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2010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(gòu)調(diào)整和體制改革步伐加快，主要表現(xiàn)為：1大型、精密、復(fù)雜、長壽命中高檔模具及模具標(biāo)準(zhǔn)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(yuǎn)遠(yuǎn)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1520萬美元，有的高達2530萬美元，與之相對的是我國相當(dāng)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。 第四，專業(yè)化、標(biāo)準(zhǔn)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(xì)，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(wù)，與國際水平相比要落后許多。模具標(biāo)準(zhǔn)化水平低，標(biāo)準(zhǔn)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(guān)技術(shù)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1論是質(zhì)量還是品種規(guī)格，都有較大差距。塑料、板材、設(shè)備等性能差，也直接影響模具水平的提高。1.1.2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)； （5）提高模具標(biāo)準(zhǔn)化水平和模具標(biāo)準(zhǔn)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(shù)；（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(yīng)用模具的高速測量技術(shù)與逆向工程； （10）開發(fā)新的成形工藝和模具。 1.1.3國外模具的現(xiàn)狀和發(fā)展趨勢用模具生產(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。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(fù)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。2011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。2010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(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1520萬美元，有的達到 2530萬美元。 國外先進國模具標(biāo)準(zhǔn)件使用覆蓋率達70%以上，而我國才達到451.2 拉深件模具設(shè)計與制造方面拉深是沖壓基本工序之一，它是利用拉深模在壓力機作用下，將平板坯料或空心工序件制成開口空心零件的加工方法。拉深不僅可以加工旋轉(zhuǎn)體零件，還可以加工盒形零件及其他形狀復(fù)雜的薄壁零件，但是，加工出來的制件的精度都很底。一般情況下，拉深件的尺寸精度應(yīng)在IT13級以下，不宜高于IT11級。本設(shè)計為簡單的拉深件，形狀比較規(guī)則，但底部圓角存在較高的工藝性問題，直邊區(qū)的變形不是簡單的彎曲, 應(yīng)力分布不均,可以利用塑性加工理論進行定性分析。因此，只有加強拉深變形基礎(chǔ)理論的研究，才能提供更加準(zhǔn)確、實用、方便的計算方法，才能正確地確定拉深工藝參數(shù)和模具工作部分的幾何形狀與尺寸，解決拉深變形中出現(xiàn)的各種實際問題，從而，進一步提高制件質(zhì)量。其工作過程較簡單就一個低方形拉深和下部的低桶形件拉深，根據(jù)工藝分析及計算確定它能一次拉深成功。根據(jù)計算的結(jié)果和選用的標(biāo)準(zhǔn)模架。為了保證制件的尺寸精度，設(shè)計時可能高度出現(xiàn)誤差，應(yīng)當(dāng)邊試沖邊修改高度。其上部方行件是最典型的盒形拉深件，根據(jù)盒形件能否一次拉深成形將其分兩類：低盒形件與高盒形件。盒形件在拉深時由于其幾何形狀的非回轉(zhuǎn)特性，變形沿變形區(qū)周邊的分布是不均的，直邊區(qū)變形小，圓角區(qū)變形大，而且變形是非常的復(fù)雜的。通過網(wǎng)格實驗的分析得出拉深方形的一些變形特點：1.直邊區(qū)的變形不是簡單的彎曲，橫向受壓縮，縱向受拉深，越靠近圓角區(qū)變形越大，另外橫向壓縮變形要比相應(yīng)圓筒形件小。2.應(yīng)力分布不均，特別是徑向拉應(yīng)力的分布很不均勻，中間最大，向兩側(cè)直邊區(qū)減小。方形件拉深時同樣存在起皺和裂問題，且發(fā)生在圓角區(qū)。在直邊區(qū)還有一個特殊的工藝問題，即所謂“直邊緩松”現(xiàn)象，這是由于拉深過程中圓角區(qū)材料從橫向擠向徑向直邊，使直邊區(qū)材料沿橫向顯得偏多，造成工件的剛性不好，嚴(yán)重時可造成工件的形狀不規(guī)則，出現(xiàn)扭曲現(xiàn)象。這是方形件拉深的特殊質(zhì)量問題，應(yīng)該引起注意的。1.2.1 端蓋拉深模具設(shè)計的設(shè)計思路1、明確設(shè)計任務(wù)書，收集有關(guān)資料在指導(dǎo)老師的指導(dǎo)下，擬定設(shè)計任務(wù)方形件拉深以及設(shè)計進度計劃，并仔細(xì)閱讀沖壓工藝與模具設(shè)計教材，了解本設(shè)計的目的、內(nèi)容、要求和步驟，以及查閱有關(guān)模具圖冊、設(shè)計手冊等資料；了解本設(shè)計零件的用途、結(jié)構(gòu)、性能，在整個產(chǎn)品中的裝配關(guān)系、技術(shù)要求、生產(chǎn)批量，采用的沖壓設(shè)備型號和規(guī)格，模具零件的制造加工工藝及標(biāo)準(zhǔn)化等情況。2、工藝分析及工藝方案的制定經(jīng)分析制件的技術(shù)要求，結(jié)構(gòu)工藝性及經(jīng)濟性都符合工藝要求，確定總體工藝方案，填寫工藝卡。3、工藝計算及設(shè)計（1）排樣及材料利用率計算 （2）刃口尺寸的計算（3）沖壓的計算，壓力中心的確定，沖壓設(shè)備的初選，根據(jù)排樣圖和所選的模具結(jié)構(gòu)形式，可以方便計算出所需總壓力。待模具總設(shè)計好后，校核設(shè)備裝模尺寸，最終確定設(shè)備型號及工藝參數(shù)。4、模具結(jié)構(gòu)設(shè)計 (1)確定凹模尺寸 先計算出凹模的厚度，再根據(jù)厚度確定凹模周界尺寸，在此需要考慮的三個問題：第一，要考慮凹模上的螺孔、銷孔的布置；第二，壓力中心一般與凹模的幾何中心重合；第三，凹模外形尺寸盡量按國家標(biāo)準(zhǔn)選取。（2）選擇模架并確定其他沖模零件的主要參數(shù) 根據(jù)凹模周界尺寸大小，從冷沖模國家標(biāo)準(zhǔn)中確定模架規(guī)格及主要沖模零件的規(guī)格參數(shù)。（3）畫沖模裝配圖 裝配圖上零件較多、結(jié)構(gòu)復(fù)雜，為準(zhǔn)確、迅速地完成畫圖工作，必須掌握正確的畫法。（4）畫沖模零件圖（5）編寫技術(shù)文件 技術(shù)文件包括：說明書、沖壓工藝卡和機械加工工藝過程卡。2 沖壓件的工藝分析2.1 引言設(shè)計的目的是在于鞏固所學(xué)的理論知識，熟悉了解有關(guān)資料，樹立正確的設(shè)計思想，掌握設(shè)計方法，培養(yǎng)實際工作能力，通過沖模結(jié)構(gòu)設(shè)計，在沖壓工藝性分析，沖壓工藝方案論證，沖壓工藝計算，沖模零件結(jié)構(gòu)設(shè)計，編寫技術(shù)文件和查閱技術(shù)文獻等方面受到依次綜合訓(xùn)練。本設(shè)計題目為低上盒下圓形件拉深模,但對做畢業(yè)設(shè)計的畢業(yè)生有一定的設(shè)計意義，它概括了拉深零件的設(shè)計要求、內(nèi)容及方向。通過對該零件模具的設(shè)計，進一步加強了設(shè)計者沖壓模設(shè)計的基礎(chǔ)，為設(shè)計更復(fù)雜的沖壓模具做好了鋪墊和吸取了更深刻的經(jīng)驗。拉深件的工藝性是指從沖壓工藝方面來衡量其設(shè)計是否合理，一般地講，在滿足工件的使用要求條件下，能以最簡單的最經(jīng)濟的方法將工件沖制出來。2.2拉深件工藝分析原始資料：如圖1所示材 料：LY12厚 度： 0.6mm圖1 制件圖由零件結(jié)構(gòu)可知：此工件為無凸緣上方下圓形工件，沒有厚度不變的要求。此工件的形狀滿足拉深的工藝要求，可采用拉深工序加工。工件底部圓角半徑r=3mm,大于三倍的壁厚尺寸，滿足首次拉深工藝要求，因此不需在拉深工序（拉深工序底部圓角半徑r=0.5mm）后須增加一道整形工序以滿足制件尺寸上質(zhì)量要求。內(nèi)形尺寸為32mm的公差等級為IT13級，滿足拉深工序?qū)ぜ畹燃壍囊?。用于拉深的材料的一般具有較好的塑性、低的屈強比、大的板厚方向性系數(shù)和小的板平面方向性。LY12是較普遍的材料，價格便宜，資源豐富，厚度為0.6mm。3 確定工藝方案 由制件工藝性分析可知,制件上部為一個方形拉深件下部為一個筒形件。經(jīng)制件的工藝性分析，由沖裁工藝可知，該制件可能包括落料、拉深工序，可以有以下二種工藝方案： 方案一：先落料，再拉深。采用單工序模生產(chǎn)。 方案二：落料和拉深復(fù)合沖壓。采用復(fù)合模生產(chǎn)。方案一、雖然模具結(jié)構(gòu)簡單，但需兩道工序兩副模具，制件要多次定位，比較麻煩，而且加工尺寸積累誤差較大，模具制造成本偏高生產(chǎn)率低，不能滿足大批量生產(chǎn)要求。方案二、只需一副模具，工件的精度及生產(chǎn)效率都較高，工件平整,對稱度及位置誤差小,不會有累計誤差，模具制造成本低且能滿足大批量生產(chǎn)要求。綜合以上考慮方案二為最佳。4 主要工藝參數(shù)的計算 拉深件的工藝計算是拉深工藝設(shè)計中的一個環(huán)節(jié)，其主要的內(nèi)容包括計算毛坯、決定拉深次數(shù)及確定壓邊裝置等。4. 1 拉深毛坯尺寸根據(jù)表面積相等原則，用解析法求該零件的毛坯。1.確定修邊余量在拉深的過程中，由于各種因素會使拉深的口部不齊。為了確保制件高度方向的尺寸精度，須進行修邊，計算毛坯尺寸時須計入修邊余量。2.計算拉深毛坯尺寸因為板厚t小于1mm，故可直接用工件圖所注尺寸計算。 （1）計算下部筒形部分毛坯由沖壓工藝與模具設(shè)計一書中式4.5計算可得， （2）盒形彎曲部分的展開長度L由r角/B=3/32=0.094，工件的相對高度H/r=2.2/3=0.73，由式3.2 計算展開長度為式中， H拉深件高度（mm）， R底底部圓角半徑（mm），r角轉(zhuǎn)角圓角半徑（mm）.即 L=2.2+0.570.5=2.485mm（3）圓角部分展開的圓弧半徑R由式 = =4.57mm圓角與直邊部分以圓弧過渡。由以上的計算可推算出整體毛坯為方形邊長取38mm。4.2 確定拉深次數(shù)利用筒形件相對高度進行判斷, h/d=5.2/26=0.20.6和盒形件H/B=2.2/32=0.0690.3B可知工件可一次拉成4.3確定是否用壓邊圈及類型在拉深過程中工件易發(fā)生起皺現(xiàn)象，制件在成形過程中，凸緣的起皺現(xiàn)象主要取決于毛坯的相對厚度、變形程度和凹模的幾何形狀等。為了解決這個問題，生產(chǎn)實際中主要方法是在模具結(jié)構(gòu)上采用壓料裝置。常用的壓料裝置有剛性壓料裝置和彈性壓料裝置兩種。是否采用壓料裝置主要看拉深過程中是否可能發(fā)生起皺現(xiàn)象，可根據(jù)坯料相對厚度來確定，相對厚度t/D100=0.6/38100=1.58，查表得，當(dāng)1.5t/D1002時可用壓邊圈，拉深時一般采用平面壓邊裝置,其結(jié)構(gòu)如下圖所示: 圖2 壓邊圈采用形式4.4排樣方式的確定設(shè)計復(fù)合模先設(shè)計條料排樣圖。該工件的毛坯是近方形，采用有廢料直排的排樣方式。查表2.9工件間搭邊值取1.5mm，側(cè)搭邊值取1.8mm。 拍樣圖如下： 圖3 排樣圖5 沖壓力計算及壓力機的選用5.1落料力的計算 式中各含義： F-落料力（KN）， L-落料周邊長度（mm）， _材料抗剪強度 t-制件的材料厚度（mm）,查手冊得LY12的 =252MPa即 F=1.3（432+233.14）2520.6 =28.86KN5.2拉深力的計算拉深力的計算公式以生產(chǎn)中常用的經(jīng)驗公式計算： 式中各含義5： F拉-拉深力（KN）， b-材料的抗拉強度（N/mm）, K-系數(shù),一般取0.8 查手冊得LY12的b =200N/mm 即拉深力 F拉=（426+233.14）0.62000.8 =11.79KN 5.3 壓邊力的計算壓邊圈產(chǎn)生的壓邊力F壓大小應(yīng)適當(dāng)，F(xiàn)壓太小，防皺效果不好；F壓太大，則會增大傳力區(qū)危險斷面上的拉應(yīng)力，從而引起材料嚴(yán)重變薄甚至拉裂。因此，實際應(yīng)用中，在保證變形區(qū)不起皺的前提下，盡量選小的壓邊力。其計算公式可按下式計算：壓邊力 式中各含義見4 A壓邊圈的面積（mm）; p單位壓邊力（Mpa）;查表1-56壓床上拉深時單位壓邊力的數(shù)值可知LY12的單位壓邊力p=1.6 Mpa，即壓邊力 F壓（41.62-322）1.6 1.13KN總拉深力 F總F+F拉+F壓28.86+11.79+1.13 41.78KN 5.4 壓力機的選用 壓力機額定壓力的選擇，必須使壓力機額定壓力大于拉深力，為了使拉深的工藝力的曲線處于壓力機壓力曲線之內(nèi)，在選用壓力機的額定壓力時，可按下列淺拉深件經(jīng)驗公式選用： =1.840.65 =73.17KN 壓力機的工作行程需要考慮工件的成形和方便取件，因此，工作行程根據(jù)拉深力的計算結(jié)果和工件的高度，開式雙柱可傾壓力機部分參數(shù)初步可選J23-10A： 型號：J23-10A 公稱壓力/KN：100 滑塊行程/mm：75 滑塊行程次數(shù)/min：135 最大閉合高度/mm：180閉合高度調(diào)節(jié)量/mm：50滑塊中心線至車身距離/mm：130工作臺尺寸/mm，前后： 240左右：360墊塊厚度/mm：50模柄孔尺寸/mm，直徑：30 深度：506 模具的結(jié)構(gòu)設(shè)計及計算6.1 模具工作部分的工藝計算6.1.1 凸凹模的設(shè)計與計算1、凸凹模間隙拉深模的凸凹模之間的間隙對拉深過程有較大的影響。它不僅影響拉深件的質(zhì)量與尺寸精度，而且影響拉深模的壽命以及拉深是否能夠順利進行。間隙過大，制件有錐度，易起皺，精度差；間隙過小，則直壁變薄嚴(yán)重，甚至拉裂，同時降低模具壽命。因此，應(yīng)該綜合考慮各種影響因素，選取適當(dāng)?shù)睦铋g隙值，既可保證工件的要求，又能使拉深順利進行。直邊部分的單邊間隙按式，由表3-5-29選取為 Z/2=1.05t=0.63mm故直邊部分間隙為1.26mm。圓角部分的單邊間隙比直邊部分大0.1t，即圓角部分間隙為1.38mm。2、拉深模的圓角半徑 凸模、凹模的選用在制件拉深過程中有著很大的作用。凸模圓角半徑的選用可以大些，這樣會減低板料繞凸模的彎曲拉應(yīng)力，工件不易被拉裂，極限拉深因數(shù)會變小些；凹模的圓角半徑也可以選大些，這樣沿凹模圓角部分的流動阻力就會小些，拉深力也會減小，極限拉深因數(shù)也會相應(yīng)減小。但是凸、凹模的圓角半徑也不易過大，過大的圓角半徑，就會減少板料與凸模和凹模端面的接觸面積及壓邊圈的壓料面積，板料懸空面積增大，容易產(chǎn)生失穩(wěn)起皺。 拉深凹模的圓角半徑由表3-5-30選取r凹=2t，既r凹=20.6=1.2mm，拉深凸模的圓角半徑等于工件的圓角半徑，即r凸=r=0.5mm.3、拉深凸凹模工作部分的尺寸和公差制件的尺寸要求內(nèi)形尺寸，拉深以凸模為基準(zhǔn)，考慮到凸模越磨越小，按式凸模尺寸：凹模尺寸：式中 dmin工件的內(nèi)形公稱尺寸 工件的公差d凸、d凸、凹模的制造公差工件的公差為IT13級，凸凹模的制造公差取IT8級。查表3-5-32 d凸=0.020mm, d=0.020mm, 核對Zmax-Zmin=0.04將=0.34mm，Z=1.26mm代入上式，則凸、凹模的尺寸分別為dp =（32+0.340.4）=32.14mmdd =（32+0.40.34+1.26）=33.40mm筒形部分凸凹模計算步驟類似上部，可得：d凸=26 d凹=27.266.1.2卸料橡膠的設(shè)計與計算1.卸料板工作行程h工 h工=h1+h2+t =1mm+5.2mm+0.6mm =6.8mm h1凸模凹進壓料板的高度 h2凸模沖裁后進入凹模的深度 取5.2mm2.橡膠工作行程H工H工=h工+h修 =6.8mm+2mm =8.8mm h修凸模修模量 取2mm 3.橡膠自由高度H自由 取H工為橡膠自由高度的25 H自由=48.8mm =35.2mm 4.橡膠的預(yù)壓縮量H預(yù) 一般H預(yù)為（0.10.15）H自由 取： H預(yù)=0.15 H自由 =0.1535.2mm =5.28mm5.每個橡膠承受的載荷F1 選用兩個圓筒形橡膠；F1=F壓/2 =11302N =565N6.橡膠的外徑D D= = =39mm7.校核橡膠自由高度H自由 0.5H自由/D=0.901.5滿足要求 8.橡膠的安裝高度H安 H安=H自由-H預(yù) =35.2mm-5.28mm =29.92mm 取安裝高度30mm6.1.3選用模架、確定閉合高度及總體尺寸由于拉深凹模外形尺寸較小，為了工作過程穩(wěn)定，選用中間導(dǎo)柱模架。再按其標(biāo)準(zhǔn)選擇具體結(jié)構(gòu)尺寸見表6-1。表6-1 模架規(guī)格選用名稱尺寸材料熱處理上模座1008025HT200下模座1008030HT200導(dǎo)柱20100、2210020滲碳5862導(dǎo)套206523、22652320滲碳5862Hmin=130mm,Hmax=150mm 模具的閉合高度H=上模座厚+墊板厚+支撐板厚+凸凹模厚+下模座厚=25+10+32+48+30=145mm因為模具的封閉高度H應(yīng)該介于壓力機的最大封閉高度Hmax和最小封閉高度Hmin之間，一般?。篐max-5mmHHmin+10mm由此可以看出，要想讓制件順利加工和從模具上取出，只有使模具有足夠的封閉高度： HmaxH+5mm=145+5=150mm HminH-10mm=145-10=135mm6.2 模具零件的結(jié)構(gòu)設(shè)計6.2.1 拉深凸模拉深凸模的外形尺寸，即工作尺寸由前面的計算確定。其結(jié)構(gòu)見下圖： 圖 4 拉深凸模 6.2.2 凸凹模 內(nèi)、外形尺寸已由前面的計算確定，經(jīng)查閱有關(guān)資料并根據(jù)模具結(jié)構(gòu)要求，初步確定拉深凹模它需要兩個銷釘定位和四個的螺釘，以便與下模座固定。其結(jié)構(gòu)見下圖：圖5凸凹模6.2.3上墊板上墊板的尺寸已確定，經(jīng)查閱有關(guān)資料并根據(jù)模具結(jié)構(gòu)要求，初步確定上墊板它需要兩個銷釘定位和四個的螺釘，以便與上模座固定。其結(jié)構(gòu)見下圖：圖6上墊板6.2.4 導(dǎo)柱、導(dǎo)套對于生產(chǎn)批量大、要求模具壽命高的模具，一般采用導(dǎo)柱、導(dǎo)套來保證上、下模的導(dǎo)向精度。導(dǎo)柱、導(dǎo)套在模具中主要起導(dǎo)向作用。導(dǎo)柱與導(dǎo)套之間采用間隙配合。根據(jù)沖壓工序性質(zhì)、沖壓的精度及材料厚度等的不同，其配合間隙也稍微不同。因為本制件的厚度為0.6mm，所以采用H7/h6。6.2.5 其他零件模具其他零件的選用見表6-2表6-2 模具其他零件的選用序號名稱數(shù)量材料規(guī)格/ mm標(biāo)準(zhǔn)熱處理1上模座1HT2001008025GB/T28559-902模柄1Q235GB/T2862.1-813止轉(zhuǎn)銷145M612GB/T7653-944螺釘245860GB/T7653-944045HRC5拉深凹模模1Cr1210080456062HRC6卸料板14510080104348HRC7橡膠聚胺脂8卸料螺釘245M865GB/T2867.6-923035HRC9固定銷2456354045HRC10下模座1HT2001008030GB/T2855.10-9411螺釘245640GB/T7653-944045HRC12擋料銷245A48GB/T119.1-20004045HRC13導(dǎo)柱22020（22）100GB/T2862.1-94滲碳5862HRC14導(dǎo)套22020（22）63100GB/T2862.6-94滲碳5862HRC15固定銷220860GB/T2855.1-904045HRC6.3 模具總裝圖由以上設(shè)計，可得到模具的總裝圖，見下圖： 圖 7 模具總體結(jié)構(gòu)1上模座 2模柄 3止轉(zhuǎn)銷 4緊固螺釘 5上墊板 6拉深凸模 7支撐板 8落料凹模 9 卸料板 10橡膠 11連接螺釘 12凸凹模 13固定銷 14下模座 15緊固螺釘 16導(dǎo)柱 17導(dǎo)套 18固定銷 其工作過程是：條料沿兩個導(dǎo)料銷由前向后送進，在導(dǎo)料銷與擋料銷共同作用下定位，上模下行，導(dǎo)柱、導(dǎo)套對上下模的運動起可靠的導(dǎo)向。落料凹模8與凸凹模12共同作用落料。上模繼續(xù)下行拉深凸模6與凸凹模12進行拉深。落料拉深完畢，上模上行，卡在凸凹模外的條料搭邊廢料由卸料板卸下，工件卡在上模，隨上模一起回程，由彈性卸料裝置卸下推出模外。7 總結(jié)此工件件屬于簡單拉深件，但拉深工藝相對復(fù)雜。由于在零件制造前進行了預(yù)測，分析了制件在生產(chǎn)過程中可能出現(xiàn)的缺陷，采取了相應(yīng)的工藝措施。因此，模具在生產(chǎn)零件的時候才可以減少廢品的產(chǎn)生。 低盒形件的形狀結(jié)構(gòu)較為簡單，但是高度不大，不適合將拉深毛坯的加工工序與拉深工序在一副模具上生產(chǎn)。要保證零件的順利加工和取件及生產(chǎn)的經(jīng)濟性，本模具采用落料拉深復(fù)合模，能較好地實現(xiàn)拉深，模具設(shè)計制造簡便易行，能極大地提高生產(chǎn)效率，但落料拉深模設(shè)計較為重要，設(shè)計中應(yīng)充分考慮其拉深?？谛螤睿駝t易影響制件形狀。本次的畢業(yè)設(shè)計，是理論知識與實踐有機的結(jié)合，更加系統(tǒng)地對理論知識做了更深切貼實的闡述。通過設(shè)計的這一環(huán)節(jié)使我更深刻地認(rèn)識到，設(shè)計的好壞直接影響到制件質(zhì)量和勞動強度以及生產(chǎn)成本。所以設(shè)計者應(yīng)該具備淵博的知識和大量的實踐經(jīng)驗作為基礎(chǔ)，應(yīng)該懂得生產(chǎn)的環(huán)節(jié)。這樣才能設(shè)計出好的實用的模具來。同時也使我意識到要想做為一名合理的模具設(shè)計人員，必須要有扎實的專業(yè)基礎(chǔ)，并不斷學(xué)習(xí)新知識新技術(shù)，樹立終身學(xué)習(xí)的觀念，把理論知識應(yīng)用到實踐中去，并堅持科學(xué)、嚴(yán)謹(jǐn)、求實的精神。雖然我傾注了大量的勞動和汗水在這個設(shè)計，由于缺乏經(jīng)驗與實踐。設(shè)計的十分艱辛，雖然借鑒了許多，還是有好多不明白之處。希望在老師的指導(dǎo)和今后自己的工作中不斷充實自我的能力。致 謝本設(shè)計是在韓艷艷老師精心指導(dǎo)和大力支持下完成的。韓老師以其嚴(yán)謹(jǐn)求實的治學(xué)態(tài)度、高度的敬業(yè)精神、兢兢業(yè)業(yè)、孜孜以求的工作作風(fēng)和大膽創(chuàng)新的進取精神對我產(chǎn)生重要影響。他淵博的知識、開闊的視野和敏銳的思維給了我深深的啟迪。感謝母校河南機電高等?？茖W(xué)校的辛勤培育之恩！感謝材料工程系給我提供的良好學(xué)習(xí)及實踐環(huán)境，使我學(xué)到了許多新的知識，掌握了一定的操作技能。同時，在此次畢業(yè)設(shè)計過程中我也學(xué)到了許多了關(guān)模具設(shè)計方面的知識再次對關(guān)心幫助我的老師和同學(xué)表示衷心地感謝。參考文獻1陳錫棟、周小玉主編.實用模具技術(shù)手冊M.北京：機械工業(yè)出版社，20012李紹林、馬長福主編.實用模具技術(shù)手冊M.上?？茖W(xué)技術(shù)出版社，19983許發(fā)樾主編.實用模具設(shè)計與制造手冊M.北京：機械工業(yè)出版社，20004楊玉英主編.實用沖壓工藝及模具設(shè)計手冊M. 北京：機械工業(yè)出版社，20045模具實用技術(shù)叢書編委會.沖壓設(shè)計應(yīng)用實例M.北京：機械工業(yè)出版社.19996翟德梅、段維峰主編.模具制造技術(shù)M.北京：化學(xué)工業(yè)出版社20057原紅玲主編.沖壓工藝與模具設(shè)計M. 北京：機械工業(yè)出版社，20088任嘉卉主編.公差與配合手冊M. 北京：機械工業(yè)出版社，20009李易、于成功、聞小芝主編.現(xiàn)代模具設(shè)計、制造、調(diào)試與維修實用手冊M.北京：金版電子出版公司，200325Int J Adv Manuf Technol (2002) 19:253259 2002 Springer-Verlag London Limited An Analysis of Draw-Wall Wrinkling in a Stamping Die Design F.-K. Chen and Y.-C. Liao Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan Wrinkling that occurs in the stamping of tapered square cups and stepped rectangular cups is investigated. A common characteristic of these two types of wrinkling is that the wrinkles are found at the draw wall that is relatively unsup- ported. In the stamping of a tapered square cup, the effect of process parameters, such as the die gap and blank-holder force, on the occurrence of wrinkling is examined using finite- element simulations. The simulation results show that the larger the die gap, the more severe is the wrinkling, and such wrinkling cannot be suppressed by increasing the blank-holder force. In the analysis of wrinkling that occurred in the stamping of a stepped rectangular cup, an actual production part that has a similar type of geometry was examined. The wrinkles found at the draw wall are attributed to the unbalanced stretching of the sheet metal between the punch head and the step edge. An optimum die design for the purpose of eliminating the wrinkles is determined using finite-element analysis. The good agreement between the simulation results and those observed in the wrinkle-free production part validates the accuracy of the finite-element analysis, and demonstrates the advantage of using finite-element analysis for stamping die design. Keywords: Draw-wall wrinkle; Stamping die; Stepped rec- tangular cup; Tapered square cups 1. Introduction Wrinkling is one of the major defects that occur in the sheet metal forming process. For both functional and visual reasons, wrinkles are usually not acceptable in a finished part. There are three types of wrinkle which frequently occur in the sheet metal forming process: flange wrinkling, wall wrinkling, and elastic buckling of the undeformed area owing to residual elastic compressive stresses. In the forming operation of stamp- ing a complex shape, draw-wall wrinkling means the occurrence Correspondence and offprint requests to: Professor F.-K. Chen, Depart- ment of Mechanical Engineering, National Taiwan University, No. 1 Roosevelt Road, Sec. 4, Taipei, Taiwan 10617. E-mail: fkchenL50560 w3.me.ntu.edu.tw of wrinkles in the die cavity. Since the sheet metal in the wall area is relatively unsupported by the tool, the elimination of wall wrinkles is more difficult than the suppression of flange wrinkles. It is well known that additional stretching of the material in the unsupported wall area may prevent wrinkling, and this can be achieved in practice by increasing the blank- holder force; but the application of excessive tensile stresses leads to failure by tearing. Hence, the blank-holder force must lie within a narrow range, above that necessary to suppress wrinkles on the one hand, and below that which produces fracture on the other. This narrow range of blank-holder force is difficult to determine. For wrinkles occurring in the central area of a stamped part with a complex shape, a workable range of blank-holder force does not even exist. In order to examine the mechanics of the formation of wrinkles, Yoshida et al. 1 developed a test in which a thin plate was non-uniformly stretched along one of its diagonals. They also proposed an approximate theoretical model in which the onset of wrinkling is due to elastic buckling resulting from the compressive lateral stresses developed in the non-uniform stress field. Yu et al. 2,3 investigated the wrinkling problem both experimentally and analytically. They found that wrinkling could occur having two circumferential waves according to their theoretical analysis, whereas the experimental results indi- cated four to six wrinkles. Narayanasamy and Sowerby 4 examined the wrinkling of sheet metal when drawing it through a conical die using flat-bottomed and hemispherical-ended punches. They also attempted to rank the properties that appeared to suppress wrinkling. These efforts are focused on the wrinkling problems associa- ted with the forming operations of simple shapes only, such as a circular cup. In the early 1990s, the successful application of the 3D dynamic/explicit finite-element method to the sheet- metal forming process made it possible to analyse the wrinkling problem involved in stamping complex shapes. In the present study, the 3D finite-element method was employed to analyse the effects of the process parameters on the metal flow causing wrinkles at the draw wall in the stamping of a tapered square cup, and of a stepped rectangular part. A tapered square cup, as shown in Fig. 1(a), has an inclined draw wall on each side of the cup, similar to that existing in a conical cup. During the stamping process, the sheet metal on the draw wall is relatively unsupported, and is therefore 254 F.-K. Chen and Y.-C. Liao Fig. 1. Sketches of (a) a tapered square cup and (b) a stepped rectangular cup. prone to wrinkling. In the present study, the effect of various process parameters on the wrinkling was investigated. In the case of a stepped rectangular part, as shown in Fig. 1(b), another type of wrinkling is observed. In order to estimate the effectiveness of the analysis, an actual production part with stepped geometry was examined in the present study. The cause of the wrinkling was determined using finite-element analysis, and an optimum die design was proposed to eliminate the wrinkles. The die design obtained from finite-element analy- sis was validated by observations on an actual production part. 2. Finite-Element Model The tooling geometry, including the punch, die and blank- holder, were designed using the CAD program PRO/ ENGINEER. Both the 3-node and 4-node shell elements were adopted to generate the mesh systems for the above tooling using the same CAD program. For the finite-element simul- ation, the tooling is considered to be rigid, and the correspond- ing meshes are used only to define the tooling geometry and Fig. 2. Finite-element mesh. are not for stress analysis. The same CAD program using 4- node shell elements was employed to construct the mesh system for the sheet blank. Figure 2 shows the mesh system for the complete set of tooling and the sheet-blank used in the stamping of a tapered square cup. Owing to the symmetric conditions, only a quarter of the square cup is analysed. In the simulation, the sheet blank is put on the blank-holder and the die is moved down to clamp the sheet blank against the blank-holder. The punch is then moved up to draw the sheet metal into the die cavity. In order to perform an accurate finite-element analysis, the actual stressstrain relationship of the sheet metal is required as part of the input data. In the present study, sheet metal with deep-drawing quality is used in the simulations. A tensile test has been conducted for the specimens cut along planes coinciding with the rolling direction (0) and at angles of 45 and 90 to the rolling direction. The average flow stress H9268, calculated from the equation H9268H11005(H9268 0 H11001 2H9268 45 H11001H9268 90 )/4, for each measured true strain, as shown in Fig. 3, is used for the simulations for the stampings of the tapered square cup and also for the stepped rectangular cup. All the simulations performed in the present study were run on an SGI Indigo 2 workstation using the finite-element pro- gram PAMFSTAMP. To complete the set of input data required Fig. 3. The stressstrain relationship for the sheet metal. Draw-Wall Wrinkling in a Stamping Die Design 255 for the simulations, the punch speed is set to 10 m s H110021 and a coefficient of Coulomb friction equal to 0.1 is assumed. 3. Wrinkling in a Tapered Square Cup A sketch indicating some relevant dimensions of the tapered square cup is shown in Fig. 1(a). As seen in Fig. 1(a), the length of each side of the square punch head (2W p ), the die cavity opening (2W d ), and the drawing height (H) are con- sidered as the crucial dimensions that affect the wrinkling. Half of the difference between the dimensions of the die cavity opening and the punch head is termed the die gap (G) in the present study, i.e. G H11005 W d H11002 W p . The extent of the relatively unsupported sheet metal at the draw wall is presumably due to the die gap, and the wrinkles are supposed to be suppressed by increasing the blank-holder force. The effects of both the die gap and the blank-holder force in relation to the occurrence of wrinkling in the stamping of a tapered square cup are investigated in the following sections. 3.1 Effect of Die Gap In order to examine the effect of die gap on the wrinkling, the stamping of a tapered square cup with three different die gaps of 20 mm, 30 mm, and 50 mm was simulated. In each simulation, the die cavity opening is fixed at 200 mm, and the cup is drawn to the same height of 100 mm. The sheet metal used in all three simulations is a 380 mm H11003 380 mm square sheet with thickness of 0.7 mm, the stressstrain curve for the material is shown in Fig. 3. The simulation results show that wrinkling occurred in all three tapered square cups, and the simulated shape of the drawn cup for a die gap of 50 mm is shown in Fig. 4. It is seen in Fig. 4 that the wrinkling is distributed on the draw wall and is particularly obvious at the corner between adjacent walls. It is suggested that the wrinkling is due to the large unsupported area at the draw wall during the stamping process, also, the side length of the punch head and the die cavity Fig. 4. Wrinkling in a tapered square cup (G H11005 50 mm). opening are different owing to the die gap. The sheet metal stretched between the punch head and the die cavity shoulder becomes unstable owing to the presence of compressive trans- verse stresses. The unconstrained stretching of the sheet metal under compression seems to be the main cause for the wrink- ling at the draw wall. In order to compare the results for the three different die gaps, the ratio H9252 of the two principal strains is introduced, H9252 being H9280 min /H9280 max , where H9280 max and H9280 min are the major and the minor principal strains, respectively. Hosford and Caddell 5 have shown that if the absolute value of H9252 is greater than a critical value, wrinkling is supposed to occur, and the larger the absolute value of H9252, the greater is the possibility of wrinkling. The H9252 values along the cross-section MN at the same drawing height for the three simulated shapes with different die gaps, as marked in Fig. 4, are plotted in Fig. 5. It is noted from Fig. 5 that severe wrinkles are located close to the corner and fewer wrinkles occur in the middle of the draw wall for all three different die gaps. It is also noted that the bigger the die gap, the larger is the absolute value of H9252. Consequently, increasing the die gap will increase the possibility of wrinkling occurring at the draw wall of the tapered square cup. 3.2 Effect of the Blank-Holder Force It is well known that increasing the blank-holder force can help to eliminate wrinkling in the stamping process. In order to study the effectiveness of increased blank-holder force, the stamping of a tapered square cup with die gap of 50 mm, which is associated with severe wrinkling as stated above, was simulated with different values of blank-holder force. The blank-holder force was increased from 100 kN to 600 kN, which yielded a blank-holder pressure of 0.33 MPa and 1.98 MPa, respectively. The remaining simulation conditions are maintained the same as those specified in the previous section. An intermediate blank-holder force of 300 kN was also used in the simulation. The simulation results show that an increase in the blank- holder force does not help to eliminate the wrinkling that occurs at the draw wall. The H9252 values along the cross-section Fig. 5. H9252-value along the cross-section MN for different die gaps. 256 F.-K. Chen and Y.-C. Liao MN, as marked in Fig. 4, are compared with one another for the stamping processes with blank-holder force of 100 kN and 600 kN. The simulation results indicate that the H9252 values along the cross-section MN are almost identical in both cases. In order to examine the difference of the wrinkle shape for the two different blank-holder forces, five cross-sections of the draw wall at different heights from the bottom to the line M N, as marked in Fig. 4, are plotted in Fig. 6 for both cases. It is noted from Fig. 6 that the waviness of the cross-sections for both cases is similar. This indicates that the blank-holder force does not affect the occurrence of wrinkling in the stamp- ing of a tapered square cup, because the formation of wrinkles is mainly due to the large unsupported area at the draw wall where large compressive transverse stresses exist. The blank- holder force has no influence on the instability mode of the material between the punch head and the die cavity shoulder. 4. Stepped Rectangular Cup In the stamping of a stepped rectangular cup, wrinkling occurs at the draw wall even though the die gaps are not so significant. Figure 1(b) shows a sketch of a punch shape used for stamping a stepped rectangular cup in which the draw wall C is followed by a step DE. An actual production part that has this type of geometry was examined in the present study. The material used for this production part was 0.7 mm thick, and the stress strain relation obtained from tensile tests is shown in Fig. 3. The procedure in the press shop for the production of this stamping part consists of deep drawing followed by trimming. In the deep drawing process, no draw bead is employed on the die surface to facilitate the metal flow. However, owing to the small punch corner radius and complex geometry, a split occurred at the top edge of the punch and wrinkles were found to occur at the draw wall of the actual production part, as shown in Fig. 7. It is seen from Fig. 7 that wrinkles are distributed on the draw wall, but are more severe at the corner edges of the step, as marked by AD and BE in Fig. 1(b). The metal is torn apart along the whole top edge of the punch, as shown in Fig. 7, to form a split. In order to provide a further understanding of the defor- mation of the sheet-blank during the stamping process, a finite- element analysis was conducted. The finite-element simulation was first performed for the original design. The simulated shape of the part is shown from Fig. 8. It is noted from Fig. 8 that the mesh at the top edge of the part is stretched Fig. 6. Cross-section lines at different heights of the draw wall for different blank-holder forces. (a) 100 kN. (b) 600 kN. Fig. 7. Split and wrinkles in the production part. Fig. 8. Simulated shape for the production part with split and wrinkles. significantly, and that wrinkles are distributed at the draw wall, similar to those observed in the actual part. The small punch radius, such as the radius along the edge AB, and the radius of the punch corner A, as marked in Fig. 1(b), are considered to be the major reasons for the wall breakage. However, according to the results of the finite- element analysis, splitting can be avoided by increasing the above-mentioned radii. This concept was validated by the actual production part manufactured with larger corner radii. Several attempts were also made to eliminate the wrinkling. First, the blank-holder force was increased to twice the original value. However, just as for the results obtained in the previous section for the drawing of tapered square cup, the effect of blank-holder force on the elimination of wrinkling was not found to be significant. The same results are also obtained by increasing the friction or increasing the blank size. We conclude that this kind of wrinkling cannot be suppressed by increasing the stretching force. Since wrinkles are formed because of excessive metal flow in certain regions, where the sheet is subjected to large com- pressive stresses, a straightforward method of eliminating the wrinkles is to add drawbars in the wrinkled area to absorb the redundant material. The drawbars should be added parallel to the direction of the wrinkles so that the redundant metal can be absorbed effectively. Based on this concept, two drawbars are added to the adjacent walls, as shown in Fig. 9, to absorb the excessive material. The simulation results show that the Draw-Wall Wrinkling in a Stamping Die Design 257 Fig. 9. Drawbars added to the draw walls. wrinkles at the corner of the step are absorbed by the drawbars as expected, however some wrinkles still appear at the remain- ing wall. This indicates the need to put more drawbars at the draw wall to absorb all the excess material. This is, however, not permissible from considerations of the part design. One of the advantages of using finite-element analysis for the stamping process is that the deformed shape of the sheet blank can be monitored throughout the stamping process, which is not possible in the actual production process. A close look at the metal flow during the stamping process reveals that the sheet blank is first drawn into the die cavity by the punch head and the wrinkles are not formed until the sheet blank touches the step edge DE marked in Fig. 1(b). The wrinkled shape is shown in Fig. 10. This provides valuable information for a possible modification of die design. An initial surmise for the cause of the occurrence of wrink- ling is the uneven stretch of the sheet metal between the punch corner radius A and the step corner radius D, as indicated in Fig. 1(b). Therefore a modification of die design was carried out in which the step corner was cut off, as shown in Fig. 11, so that the stretch condition is changed favourably, which allows more stretch to be applied by increasing the step edges. However, wrinkles were still found at the draw wall of the cup. This result implies that wrinkles are introduced because of the uneven stretch between the whole punch head edge and the whole step edge, not merely between the punch corner and Fig. 10. Wrinkle formed when the sheet blank touches the stepped edge. Fig. 11. Cut-off of the stepped corner. the step corner. In order to verify this idea, two modifications of the die design were suggested: one is to cut the whole step off, and the other is to add one more drawing operation, that is, to draw the desired shape using two drawing operations. The simulated shape for the former method is shown in Fig. 12. Since the lower step is cut off, the drawing process is quite similar to that of a rectangular cup drawing, as shown in Fig. 12. It is seen in Fig. 12 that the wrinkles were eliminated. In the two-operation drawing process, the sheet blank was first drawn to the deeper step, as shown in Fig. 13(a). Sub- sequently, the lower step was formed in the second drawing operation, and the desired shape was then obtained, as shown in Fig. 13(b). It is seen clearly in Fig. 13(b) that the stepped rectangular cup can be manufactured without wrinkling, by a two-operation drawing process. It should also be noted that in the two-operation drawing process, if an opposite sequence is applied, that is, the lower step is formed first and is followed by the drawing of the deeper step, the edge of the deeper step, as shown by AB in Fig. 1(b), is prone to tearing because the metal cannot easily flow over the lower step into the die cavity. The finite-element simulations have indicated that the die design for stamping the desired stepped rectangular cup using one single draw operation is barely achieved. However, the manufacturing cost is expected to be much higher for the two- operation drawing process owing to the additional die cost and operation cost. In order to maintain a lower manufacturing cost, the part design engineer made suitable shape changes, and modified the die design according to the finite-element Fig. 12.

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