異形墊片零件沖壓成形工藝及其落料沖孔級進模具設(shè)計

異形墊片零件沖壓成形工藝及其落料沖孔級進模具設(shè)計,異形墊片零件沖壓成形工藝及其落料沖孔級進模具設(shè)計,異形,墊片,零件,沖壓,成形,工藝,及其,沖孔,模具設(shè)計 附件4-4：任務(wù)書 任 務(wù) 書 茲發(fā)給 專業(yè) 班學(xué)生 設(shè)計（論文）任務(wù)書，內(nèi)容如下：1 1.畢業(yè)設(shè)計（論文）題目：異形墊片零件沖壓成形工藝及其落料沖孔級進模具設(shè)計2.應(yīng)完成的項目： （1）完成開題報告。要求完成10篇以上相關(guān)文章的閱讀量，撰寫字數(shù)不少于2500字，內(nèi)容包括工作任務(wù)分析、調(diào)研報告、方案擬定與分析、論文框架結(jié)構(gòu)、實施計劃、文獻綜述內(nèi)容等；撰寫格式參照附件4-5； （2）完成英文翻譯。要求閱讀3萬印刷符以上的外文參考資料。提交3000漢字（或1.2萬印刷符）以上的外文翻譯。翻譯外文內(nèi)容必須與畢業(yè)設(shè)計（論文）有緊密聯(lián)系，并說明出處；翻譯格式參照附件4-6； （3）完成沖壓工藝設(shè)計和模具結(jié)構(gòu)設(shè)計，具體工作包括： 1）零件的沖壓工藝方案和模具結(jié)構(gòu)方案的分析和制定； 2）各沖壓工序的沖壓工藝計算； 3）凸模、凹模的外形結(jié)構(gòu)和固定方式設(shè)計； 4）卸料機構(gòu)、定位機構(gòu)、導(dǎo)向機構(gòu)、連接固定機構(gòu)等選用和設(shè)計； （4）繪制圖紙。模具總裝圖繪制,模具零部件設(shè)計和零件圖繪制；（圖紙總量不少于3張A0圖紙；要求圖面整潔，布局合理，線條粗細均勻，圓弧連接光滑，尺寸標注規(guī)范符合機械工程制圖要求。） （5）編寫設(shè)計說明書。說明書內(nèi)容要求重點突出、觀點鮮明、論據(jù)充分、分析透徹、條理清晰、圖文并茂。字數(shù)不少于1.5萬字(20頁左右)；說明書的內(nèi)容、書寫規(guī)范和打印格式請嚴格按照2014屆本科生畢業(yè)設(shè)計工作指南文件中第3.2、第3.3、第3.4、第3.5的要求規(guī)定，具體格式請參照附件4-1. 3.參考資料以及說明：（1） 劉建超、張寶忠 主編. 沖壓模具設(shè)計與制造. 北京：高等教育出版社，2010 （2）吳詩惇，李淼泉. 沖壓工藝及模具設(shè)計.西安：西北工業(yè)大學(xué)出版社，2002 （3）沖模設(shè)計手冊編寫組.沖模設(shè)計手冊.機械工業(yè)出版社，1999.6 （4）王孝培主編. 沖壓設(shè)計資料 . 北京：機械工業(yè)出版社，1983 （5）李天佑主編. 沖模圖冊. 北京：機械工業(yè)出版社，1990 4.本畢業(yè)設(shè)計（論文）任務(wù)書于2013年12月23日發(fā)出，應(yīng)于2014年 5月 16日前完成，然后提交畢業(yè)設(shè)計（論文）答辯委員會進行答辯。 指導(dǎo)教師（導(dǎo)師組負責(zé)人） 簽發(fā)，2013年12月23日教研室負責(zé)人 審核，2013年12月23日XXXX 學(xué) 院畢 業(yè) 設(shè) 計（論 文）說 明 書題 目 異形墊片沖壓模具設(shè)計 學(xué) 生 系 別 機 電 工 程 系 專 業(yè) 班 級 學(xué) 號 指 導(dǎo) 教 師 摘要畢業(yè)設(shè)計是在模具專業(yè)理論教學(xué)之后進行的實踐性教學(xué)環(huán)節(jié)。是對所學(xué)知識的一次總檢驗，是走向工作崗位前的一次實戰(zhàn)演習(xí)。其目的是，綜合運用所學(xué)課程的理論和實踐知識,設(shè)計一副完整的模具訓(xùn)練、培養(yǎng)和提高自己的工作能力。鞏固和擴充模具專業(yè)課程所學(xué)內(nèi)容，掌握模具設(shè)計與制造的方法、步驟和相關(guān)技術(shù)規(guī)范。熟練查閱相關(guān)技術(shù)資料。掌握模具設(shè)計與制造的基本技能，如制件工藝性分析、模具工藝方案論證、工藝計算、加工設(shè)備選定、制造工藝、收集和查閱設(shè)計資料，繪圖及編寫設(shè)計技術(shù)文件等。本設(shè)計主要對異形墊片沖壓模具進行設(shè)計。結(jié)合公司實際生產(chǎn)要求和產(chǎn)品的特點，在廠原有的設(shè)計上，對模具進行了改進設(shè)計。本設(shè)計對彎曲件加工工藝進行了分析，得出了最佳加工方案，在充分保證零件質(zhì)量與精度的前提下，選擇高生產(chǎn)率的加工工藝，降低生產(chǎn)成本，從而有效地節(jié)約了材料。本設(shè)計中使用計算機軟件進行了輔助設(shè)計，在保證高精度的同時簡化了傳統(tǒng)的繁瑣計算過程，使設(shè)計更為便捷。隨著模具的迅速發(fā)展，在現(xiàn)代工業(yè)生產(chǎn)中，模具已經(jīng)成為生產(chǎn)各種工業(yè)產(chǎn)品不可缺少的重要工藝設(shè)備。這次畢業(yè)設(shè)計是在學(xué)習(xí)完所有機械課程的基礎(chǔ)上進行的，是對我綜合能力的考核，是對我所學(xué)知識的綜合運用，也是對我所學(xué)知識的回顧與檢查。本次設(shè)計是在指導(dǎo)老師認真、耐心的指導(dǎo)下，對模具的經(jīng)濟性、模具的壽命、生產(chǎn)周期、及生產(chǎn)成本等指標下進行全面、仔細的分析下而進行設(shè)計的。在此, 我表示衷心的感謝他們對我的教誨.沖模是模具設(shè)計與制造專業(yè)的主要專業(yè)課程之一。它具有很強的實踐性和綜合性，通過學(xué)習(xí)這門課程，使我對沖壓模具有了新的認識，從中也學(xué)到了不少知識，激發(fā)了我對沖壓模具的愛好。但因本人經(jīng)驗有限，因此很難避免的存在一些不合理之處，望各位老師批評和指正，以使我的畢業(yè)設(shè)計做到合理，同時也為我走出校門步入社會打下堅實的基礎(chǔ)。關(guān)鍵詞沖壓模具；彎曲模；輔助設(shè)計；模具結(jié)構(gòu)目 錄摘要2第一章、緒論51.1.沖壓的概念、特點及應(yīng)用51.2.沖壓的基本工序及模具6第二章、零件的工藝性分析.82.1.零件的工藝性分析82.2.沖裁件的精度與粗糙度82.3.沖裁件的材料82.4.確定工藝方案.9第三章、沖壓模具總體結(jié)構(gòu)設(shè)計103.1.模具類型103.2.操作與定位方式103.3.卸料與出件方式103.4.模架類型及精度10第四章、沖壓模具工藝與設(shè)計計算114.1.排樣設(shè)計與計算114.2.設(shè)計沖壓力與壓力中心,初選壓力機.124.2.1.沖裁力124.2.2.壓力機的選擇124.2.3.壓力中心134.2.4.計算凸凹模刃口尺寸及公差14第無章、模具的總張圖與零件圖165.1.模具結(jié)構(gòu)165.2.沖壓模具的零件圖175.2.1.凹模設(shè)計175.2.2.凸模設(shè)計185.2.3.選擇堅固件及定位零件205.2.4.設(shè)計和選用卸料與出件零件215.2.5.選擇模架及其它模具零件225.3.壓力機的校核245.3.1.公稱壓力245.3.2.滑塊行程245.3.3.行程次數(shù)245.3.4.工作臺面的尺寸255.3.5.閉合高度25第六章、沖壓模具零件加工工藝的編制266.1.凹模加工工藝過程266.2.凸模加工工藝過程266.3.卸料板加工工藝過程286.4.凸模固定板加工工藝過程286.5.上模座加工工藝過程296.6.下模座加工工藝過程29設(shè)計小結(jié)30致 謝31參考文獻32第一章、緒論1.1.沖壓的概念、特點及應(yīng)用模具主要類型有：沖模，鍛摸，塑料模，壓鑄模，粉末冶金模，玻璃模，橡膠模，陶瓷模等。除部分沖模以外的的上述各種模具都屬于腔型模，因為他們一般都是依靠三維的模具形腔是材料成型。模具所涉及的工藝繁多，包括機械設(shè)計制造，塑料，橡膠加工，金屬材料，鑄造（凝固理論），塑性加工，玻璃等諸多學(xué)科和行業(yè)，是一個多學(xué)科的綜合，其復(fù)雜程度顯而易見。隨著經(jīng)濟的發(fā)展，沖壓技術(shù)應(yīng)用范圍越來越廣泛，在國民經(jīng)濟各部門中，幾乎都有沖壓加工生產(chǎn)，它不僅與整個機械行業(yè)密切相關(guān)，而且與人們的生活緊密相連。沖壓是利用安裝在沖壓設(shè)備（主要是壓力機）上的模具對材料施加壓力，使其產(chǎn)生分離或塑性變形，從而獲得所需零件（俗稱沖壓或沖壓件）的一種壓力加工方法。沖壓通常是在常溫下對材料進行冷變形加工，且主要采用板料來加工成所需零件，所以也叫冷沖壓或板料沖壓。沖壓是材料壓力加工或塑性加工的主要方法之一，隸屬于材料成型工程術(shù)。沖壓所使用的模具稱為沖壓模具，簡稱沖模。沖模是將材料（金屬或非金屬）批量加工成所需沖件的專用工具。沖模在沖壓中至關(guān)重要，沒有符合要求的沖模，批量沖壓生產(chǎn)就難以進行；沒有先進的沖模，先進的沖壓工藝就無法實現(xiàn)。沖壓工藝與模具、沖壓設(shè)備和沖壓材料構(gòu)成沖壓加工的三要素，只有它們相互結(jié)合才能得出沖壓件。與機械加工及塑性加工的其它方法相比，沖壓加工無論在技術(shù)方面還是經(jīng)濟方面都具有許多獨特的優(yōu)點。主要表現(xiàn)如下。(1) 沖壓加工的生產(chǎn)效率高，且操作方便，易于實現(xiàn)機械化與自動化。這是因為沖壓是依靠沖模和沖壓設(shè)備來完成加工，普通壓力機的行程次數(shù)為每分鐘可達幾十次，高速壓力要每分鐘可達數(shù)百次甚至千次以上，而且每次沖壓行程就可能得到一個沖件。（2）沖壓時由于模具保證了沖壓件的尺寸與形狀精度，且一般不破壞沖壓件的表面質(zhì)量,而模具的壽命一般較長,所以沖壓的質(zhì)量穩(wěn)定,互換性好,具有“一模一樣”的特征。（3）沖壓可加工出尺寸范圍較大、形狀較復(fù)雜的零件，如小到鐘表的秒表，大到汽車縱梁、覆蓋件等，加上沖壓時材料的冷變形硬化效應(yīng)，沖壓的強度和剛度均較高。（4）沖壓一般沒有切屑碎料生成，材料的消耗較少，且不需其它加熱設(shè)備，因而是一種省料，節(jié)能的加工方法，沖壓件的成本較低。但是，沖壓加工所使用的模具一般具有專用性，有時一個復(fù)雜零件需要數(shù)套模具才能加工成形，且模具 制造的精度高，技術(shù)要求高，是技術(shù)密集形產(chǎn)品。所以，只有在沖壓件生產(chǎn)批量較大的情況下，沖壓加工的優(yōu)點才能充分體現(xiàn)，從而獲得較好的經(jīng)濟效益。1.2.沖壓的基本工序及模具由于沖壓加工的零件種類繁多，各類零件的形狀、尺寸和精度要求又各不相同，因而生產(chǎn)中采用的沖壓工藝方法也是多種多樣的。概括起來，可分為分離工序和成形工序兩大類；分離工序是指使坯料沿一定的輪廓線分離而獲得一定形狀、尺寸和斷面質(zhì)量的沖壓（俗稱沖裁件）的工序；成形工序是指使坯料在不破裂的條件下產(chǎn)生塑性變形而獲得一定形狀和尺寸的沖壓件的工序。上述兩類工序，按基本變形方式不同又可分為沖裁、彎曲、拉深和成形四種基本工序，每種基本工序還包含有多種單一工序。在實際生產(chǎn)中，當沖壓件的生產(chǎn)批量較大、尺寸較少而公差要求較小時，若用分散的單一工序來沖壓是不經(jīng)濟甚至難于達到要求。這時在工藝上多采用集中的方案，即把兩種或兩種以上的單一工序集中在一副模具內(nèi)完成，稱為組合的方法不同，又可將其分為復(fù)合-級進和復(fù)合-級進三種組合方式。沖模的結(jié)構(gòu)類型也很多。通常按工序性質(zhì)可分為沖裁模、彎曲模、拉深模和成形模等；按工序的組合方式可分為單工序模、復(fù)合模和級進模等。但不論何種類型的沖模，都可看成是由上模和下模兩部分組成，上模被固定在壓力機工作臺或墊板上，是沖模的固定部分。工作時，坯料在下模面上通過定位零件定位，壓力機滑塊帶動上模下壓，在模具工作零件（即凸模、凹模）的作用下坯料便產(chǎn)生分離或塑性變形，從而獲得所需形狀與尺寸的沖件。上?；厣龝r，模具的卸料與出件裝置將沖件或廢料從凸、凹模上卸下或推、頂出來，以便進行下一次沖壓循環(huán)。沖壓件圖如下圖所示:沖壓技術(shù)要求:1. 材料:10F2. 材料厚度:3.0mm3. 生產(chǎn)批量:中批量4. 未注公差:按IT10確定.第二章、零件的工藝性分析.2.1.零件的工藝性分析該零件材料為10F鋼，結(jié)構(gòu)簡單,形狀復(fù)雜,產(chǎn)品寬度B=70+95+20=1851.2t(t為材料厚度) ,沖孔時有尺寸為20，45，60，根據(jù)沖壓模具設(shè)計手冊知沖孔時,因受凸模強度的限制,孔的尺寸不應(yīng)太小.沖孔的最小尺寸取決于材料性能,凸模的強度和模具結(jié)構(gòu)等.根據(jù)表3-3可查得圓形孔最小值得d=0.9t=0.9X3.0=2.7mm(1.52)t所以由沖件圖可知C1=35.141X3.0=3, 由以上可知孔與孔之間距離C1滿足工藝性要求, 由以上分析可得,沖件的尺寸很小,如圖21所示。在模具結(jié)構(gòu)上需要多考慮，確定后,我們才能繼續(xù)做下一步的設(shè)計。2.2.沖裁件的精度與粗糙度沖裁件的經(jīng)濟公差等級不高于IT12級,一般落料公差等級最好低于IT10級,沖孔件公差等級最好低于IT9級,由工件圖尺寸可查得落料公差,沖孔公差分別為0.40,0.08.而沖件落料公差,最高精度沖孔公差分別為0.5,0.15，孔中心距公差 0.15而沖件孔中心距最高精度公差為0.25,因此可用于一般精度的沖裁,普通沖裁可以達到要求10級。由于沖裁件沒有斷面粗糙度的要求,我們不必考慮.2.3.沖裁件的材料由材料方面的資料得,10F是優(yōu)質(zhì)碳素結(jié)構(gòu)鋼。其力學(xué)性能： 抗拉強度 b (MPa)：300-360 抗剪強度，=220-310Mpa，伸長率 ()：32%此材料具有良好的塑性級較高的彈性,沖裁性較好,可以沖裁加工.2.4.確定工藝方案.該沖裁件包括落料和沖孔兩個基本工序,可采用的沖裁方案有單工序沖裁,復(fù)合沖裁和級進沖裁三種.零件屬于中批量生產(chǎn),因此采用單工序須要模具數(shù)量較多,生產(chǎn)率低,所用費用也高,不合理;若采用復(fù)合沖,可以得出沖件的精度和平直度較好,生產(chǎn)率較高,但因零件的孔邊距太小,模具強度不能保證;用用級進模沖裁時,生產(chǎn)率高,操作方便,通過合理設(shè)計可以達到較好的零件質(zhì)量和避免模具強度不夠的問題,根據(jù)以上分析,該零件采用級進沖裁工藝方案.第三章、沖壓模具總體結(jié)構(gòu)設(shè)計3.1.模具類型根據(jù)零件的沖裁工藝方案,采用級進沖裁模.3.2.操作與定位方式零件中批量生產(chǎn),安排生產(chǎn)可采用手工送料方式能夠達到批量生產(chǎn),且能降低模具成本,因此采用手工送料方式.零件尺寸較小，厚度較小，保證孔的精度及較好的定位，宜采用導(dǎo)料板導(dǎo)向，定位銷導(dǎo)正。3.3.卸料與出件方式考慮零件尺寸較大，厚度較厚，采用彈壓卸料方式，為了便于操作，提高生產(chǎn)率，沖件和廢料采用凸模直接從凹模洞口推下的下出件方式。3.4.模架類型及精度由于零件材料較厚，模具間隙比較大，又是級進模因此采用導(dǎo)向平穩(wěn)的四導(dǎo)柱模架，由于模具比較大，買標準件模價，從經(jīng)濟學(xué)角度出發(fā)，不實惠，不合理，因此，可以考慮自己制造的四導(dǎo)柱鋼板非標準模架。第四章、沖壓模具工藝與設(shè)計計算4.1.排樣設(shè)計與計算該沖裁件材料厚度較薄，尺寸小，因此可采用以下排樣比較合理,如圖4-11所示。圖4-1搭邊值要合理確定，值過大，材料利用率低；值過小，搭邊的強度與剛度不夠，沖裁時容易翹曲或被拉斷，不僅會增大沖裁件毛刺，有時甚至單邊拉入模具間隙，造成沖裁力不均，損壞模具刃口。因此，搭邊的最小寬度大于塑性變形區(qū)的寬度，一般可取等于材料的厚度。搭邊值的大小還與材料的力學(xué)性能、厚度、零件的形狀與尺寸、排樣的形式、送料及擋料方式、卸料方式等因素有關(guān)。搭邊值一般由經(jīng)驗確定，根據(jù)所給材料厚度=3.0mm，確定搭邊工作間a1為3.0mm, a為3.0mm。因此根據(jù)式3-13，條料的寬度為B=（Dmax+2a+z）=220+23+23=232mm進距為:s=45+a1=185+3.0=188mm根據(jù)3-14，導(dǎo)板間距為：B0=B+Z=Dmax+2a+2z=232+0.5=232.5mm由零件圖在CAD用計算機算得一個零件的面積為26347.74mm一個進距內(nèi)的坯料面積:BXS=232X188=43616mm,因此材料利用率為:=(A/BS)X100%=(26347.74/43616)X100%=60.41%4.2.設(shè)計沖壓力與壓力中心,初選壓力機.4.2.1.沖裁力 根據(jù)零件圖,用CAD可計算出沖一次零件內(nèi)外周邊之和L=686.22mm(首次沖裁除外),又因為=310Mpa,t=3.0mm,取K=1.3,則根據(jù)式3-18,F=KLt=1.3686.223.0310=829.64KN，沖孔力的大?。篎=KLt=1.3（3.1420+3.1445+3.1465）3.0310=493.51KN，切側(cè)刃力的大小：F=nKLt=21.33883.0310=938.18KN，總的力為829.64+493.15+938.18=2260.97卸料力:,取Kx=0.06,則Fx=KxF=0.062260.97=135.66KN推件力:根據(jù)材料厚度取凹模刃口直壁高度h3mm,為了修模時能保證模具仍具有足夠的強度,所以直壁高度取h=3mm,4.2.2.壓力機的選擇由式3-23應(yīng)選取的壓力機公稱壓力為:P0(1.11.2)F=(1.11.2)X（2260.97+135.66）=2636.293KN因此可選壓力機型號為J21-350.型號為J21350壓力機的基本參數(shù)如：（表一）公稱壓力/KN3500墊板尺寸/mm滑塊行程/mm200厚度80滑塊行程次數(shù)/（次/min）50模柄孔尺寸/mm最小封閉高度/mm120滑塊底面積尺寸/mm封閉高度調(diào)節(jié)量80滑塊中心線至床身距離/mm床身最大可傾角30工作臺尺寸/mm前后880左右15504.2.3.壓力中心根據(jù)排樣,我們可以在CAD里使用查詢便能得出沖孔的壓力中心,F1沖側(cè)刃力 F1=Ltb ，得F1=469.09KNF2沖側(cè)刃力 F2=Ltb ，得F2=469.09KNF3沖孔力65 F3=Ltb ，得F3=246.76KNF4沖孔力20 F4=Ltb , 得F4=76KNF5沖孔力45 F5= Ltb , 得F5=170.83KNF6落料力 F6= Ltb , 得F6=829.64KNY1F1到X軸的力臂 Y1=116X1F1到Y(jié)軸的力臂 X1=282Y2F2到X軸的力臂 Y2=-116X2F2到Y(jié)軸的力臂 X2=282Y3F3到X軸的力臂 Y3=15X3F3到Y(jié)軸的力臂 X3=93Y4F4到X軸的力臂 Y4=90X4F4到Y(jié)軸的力臂 X4=0Y5F5到X軸的力臂 Y5=-70X5F5到Y(jié)軸的力臂 X5=-65Y6F6到X軸的力臂 Y6=15X6F6到Y(jié)軸的力臂 X6=-260.5根據(jù)合力距定理：YG = （Y1F1+ Y2F2+ Y3F3）/（F1+ F2+ F3）XG = （X1F1+ X2F2+ X3F3）/（F1+ F2+ F3）XGF沖壓力到X軸的力臂；XG=1.08YGF沖壓力到Y(jié)軸的力臂；YG=4.877所以由以上可以算得壓力中心為G(1.08,4.877)4.2.4.計算凸凹模刃口尺寸及公差由于材料厚度中等，模具間隙較小,模具的間隙由配作保證,工藝比較簡單,并且還可以放大基準件的制造公差,(一般可取沖件公差的1/4),使制造容易,因此采用配作加工為宜.由落料尺寸得,凹模會變小,所以得以凹模為基準,配作凸模.由沖孔尺寸得,凸模尺寸變小,所以以凸模為基準,配作凹模.由材料厚度可得Zmin=0.08mm, Zmax=0.12mm.由落料,凹模磨損后變大,磨損系數(shù)X1=0.50,X2=0.20所以:Ad1=(A1max-x)=(70-0.20X0.14) =69.98Ad2=(A2max-x)=(40-0.20X0.14) =39.98Ad3=(A3max-x)=(30-0.20X0.14) =29.98Ad4=(A4max-x)=(20-0.20X0.14) =19.98由于Ad1,為落料尺寸,故以凹模為基準,配作凸模，所以落料凸模刃口尺寸按凹模實際尺寸配作，保證雙面間隙值為0.180.22mm。取0.20。落料凸模尺寸：Ah1=(Ad1-Z)+ =60-0.10=59.9+0.02; Ah2=(Aj2-Z)+ =40-0.10=39.9+0.02; Ah3=(Aj3-Z)+ =30-0.10=30.1+0.02; Ah4=(Aj4-Z)+ =20-0.04=19.96+0.02; 由沖孔尺寸凸模磨損后變小有:b1=20, b2=45, b3=65,磨損系數(shù)X1=X20.5,故bp6不需采用刃口尺寸公式計算,而直接取bp6=2bp5.所以:bp1=(b1min+X11)=(20+0.5X0.04)=20.02bp2=(b2min+X22)=(45+0.5X0.04)=45.02bp3=(b3min+X33)=(65X0.04)=65.02 凸,凹模磨損后不變的尺寸Cp1=85，Cp1=95， Cp1=106， 未注公差為IT10,所以20的公差為0.04, 35的公差為0.06,60的公差為0.06,得:Cp=(Cmin+0.5),所以:Cp1=(Cmin+0.5)=850.01Cp2=(Cmin+0.5)=950.01Cp3=(Cmin+0.5)=1060.01第五章、模具的總張圖與零件圖5.1.模具結(jié)構(gòu)根據(jù)前面的設(shè)計與分析,我們可以得出如級進模具的總張圖如圖5-1所示:圖5-1 級進?？傃b圖1.下模板；2.導(dǎo)柱；3.凹模；4.落料凸模；5.卸料板；6.樹脂；7.導(dǎo)套；8.沖頭固定板；9.上墊板；10.上模板；11.內(nèi)六角螺釘；12.導(dǎo)正銷；13.中間孔沖頭；14.切側(cè)刃凸模；15.圓柱銷；16.內(nèi)六角螺釘；17.卸料螺釘；18.中間大孔沖頭；19.中間孔沖頭；20.導(dǎo)料板；21.內(nèi)六角螺釘；22.圓柱銷；23.內(nèi)六角螺釘。5.2.沖壓模具的零件圖5.2.1.凹模設(shè)計凹模采用矩形板狀結(jié)構(gòu)和直接通過螺釘,圓柱銷與下模座固定的固定方式.考慮凹模的磨損和保證沖件的質(zhì)量根據(jù)表3-28,凹模刃口采用直筒形刃口壁結(jié)構(gòu),刃口高度根據(jù)前面“4.2”計算沖裁力時所取h=3mm,漏料部分刃口輪廓適當擴大，可以擴大0.51mm,取1mm,(為便于加工,落料凹模漏料孔可設(shè)計成近似于刃口輪廓的簡化形狀,如圖所示),凹模輪廓尺寸計算如下:凹模輪廓尺寸的確定，凹模輪廓輪廓尺寸包括凹模板的平面尺寸LXB(長X寬)及厚度尺寸H.從凹模外邊緣的最短距離稱為凹模壁厚C.對于簡單對稱形狀刃口凹模,由于壓力中心即對稱中心,所以凹模和平面尺寸即可沿刃口型孔向四周擴大一個凹模壁厚來確定,所以:L=l+2C=220+2X62=344 B=840C值可根據(jù)資料查得.整體式凹模板的厚度可按如下經(jīng)驗公式估算:H=K1K2=35mm, K1取1,K2根據(jù)資料取2.5.由以上算得凹模輪廓尺寸LBH=84035041,查有關(guān)國家標準,并無厚度合適,因此我選LB為標準尺寸,得LBH=84035040。凹模材料的選用:材料選用Cr12MoV，孔與孔的校核:校核最小A值為20,以上都能達到要求,因此得以校核.凹模刃口尺寸及其它具體見零件圖5-21。后面所附的零件圖。設(shè)計中,因為壓力中心與凹模板的幾何中心相差不太,壓力中心仍在模柄投影面積,可設(shè)他們在同軸線上.圖5-2 凹模5.2.2.凸模設(shè)計落料凸模刃口部分為異形,又在它里面開孔,裝配導(dǎo)正銷,為便于凸模和固定板的加工,可通這設(shè)計成鉚接方式與固定板固定.沖孔凸模采用階梯結(jié)構(gòu),設(shè)計成鉚接方式.凸模的尺寸根據(jù)導(dǎo)料板尺寸、卸料板尺寸和安裝固定要求尺寸h，取h1520，因為這里的凹模刃口尺寸為4 mm,在范圍之內(nèi)取18mm所以凸模的尺寸為L=18+20+25+2=65mm.凸模材料：參照沖壓模具設(shè)計與制造選用Cr12MoV.考慮沖孔凸模的直徑很小，故需對最小凸模20進行強度和鋼度校核：根據(jù)表3-26可得：L90d/=(90X20X20)/=50.6mm.L為凸模的允許最大工作尺寸，而設(shè)計中，凸模的工作尺寸為6550.6,所以鋼度不需要校核。具體零件圖如后面所附零件圖為準， 5.2.3.選擇堅固件及定位零件螺釘規(guī)格的選用: 由凹模板的厚度可選用M10,在根據(jù)實際要求,查標準選用GB 70-85 M10X60,這里要8個,卸料板的螺釘選用GB 70-85 M8X60,這里要4個。銷釘規(guī)格的選用: 銷釘?shù)墓Q直徑可取與螺釘大徑相同或小一個規(guī)格,因此根據(jù)標準選用GB 119-86 10X60, 選取材料為45鋼.根據(jù)定位方式及坯料的形狀與尺寸,選用合適的標準定位零件.導(dǎo)料板: 根據(jù)凹模LXB=840X350,查標準GB2865.5-81,選規(guī)格為:長度L=840,寬度B=350,厚度H=12,材料為45#的導(dǎo)料板,即導(dǎo)料板:270X62X12 如圖5-10所示:5.2.4.設(shè)計和選用卸料與出件零件卸料以卸料板卸料,出件是以凸模往下沖即可,因此不用設(shè)計出件零件.固定卸料板的平面外形尺寸一般與凹模板相同,其厚度可取凹模厚度的0.51倍,所以卸料板的LBH=84035040/0.545=84013522.5，本設(shè)計中取25厚，卸料板在此僅起卸料作用,凸模與卸料板間的雙邊間隙一般取0.050.1mm,這里取0.1mm,材料為45#.由以上根據(jù)凸模和凹?？稍O(shè)計出卸料板如圖5-13.5.2.5.選擇模架及其它模具零件選擇模架:根據(jù)GB/T 2851.5-90,由凹模周界840350,及安裝要求,選取凹模周界:LB=840350,閉合高度:H=170219,上模座:100042040，下模座:100042045,導(dǎo)柱:38170,導(dǎo)套:5570.由以上可得模架及其零件如圖5-14所示.墊板: 墊板的作用是承受并擴散凸模傳遞的壓力,以防止模座被擠壓損傷,因此在與模座接觸面之間加上一塊淬硬磨平的墊板.墊板的外形尺寸與凸模固定板相同,厚度可取310mm,這里設(shè)計時,由于壓力較大,根據(jù)GB2865.2-81選取規(guī)格為LXBXH=840X350X10.凸模固定板: 凸模固定板的外形尺寸與凹模的外形尺寸一致,厚度為凹模的0.40.6h,h為凹模的厚度,這里取0.4h,即0.4X45=18mm,根據(jù)核準選取板的規(guī)格為LXBXH=840X35X18;凸模與凸模固定板的配合為H7/n6,裝配可通過2個銷釘定位,8個螺釘與上模座連接固定,各形孔的位置尺寸與凹模的保持一致,頂部與凸模鉚接,因此必須倒角,由以上可得凸模固定板的零件圖如圖5-16所示:5.3.壓力機的校核5.3.1.公稱壓力根據(jù)公稱壓力的選取壓力機型號為J21-350,它的壓力為35002636.293,所以壓力不需要校核;5.3.2.滑塊行程滑塊行程應(yīng)保證坯料能順利地放入模具和沖壓能順利地從模具中取出.這里只是材料的厚度t=3.0,導(dǎo)料板的厚度H=12及凸模沖入凹模的最大深度2,即S1=3+12+2=17S=130,所以不需要校核.5.3.3.行程次數(shù)行程次數(shù)為80/min.因為生產(chǎn)批量為中批量,又是手工送料,不能太快。5.3.4.工作臺面的尺寸根據(jù)下模座LB=1000X420,且每邊留出60100,即L1B1=1200X620,而壓力機的工作臺面L2B2=1550X880,沖壓件和廢料從下模漏出。故符合要求;5.3.5.閉合高度 由壓力機型號知Hmax=380 M=90 H1=120Hmin=HmaxM=380-90=290(M為閉合高度調(diào)節(jié)量/mm,H1為墊板厚度/mm)由式(1-24):( HmaxH1)-5H( HminH1)+10,得(380120)-5194(290120)+10即 275194180 ,所以所選壓力機合適.第六章、沖壓模具零件加工工藝的編制6.1.凹模加工工藝過程表6-1 凹模加工工藝過程工序號工序名稱工序內(nèi)容設(shè)備1備料將毛坯鍛成850mm360mm45mm2熱處理退火3銑銑六面,厚度留單邊磨量0.20.3mm銑床4平磨磨厚度到上限尺寸,磨側(cè)基面保證互相垂直平面磨床5鉗工劃各型孔,螺孔,銷孔位置劃漏孔輪廓線6鉗工加工好凸模,配作沖孔凹模達要求7銑銑漏料孔達要求銑床8鉗工鉆鉸410,鉆攻8XM10鉆床9熱處理淬火,回火,保證HRC606210平磨磨厚度及基面達到要求平面磨床11線切割按圖切割各型孔,留0.0050.01單邊研量線切割機床12鉗工研光各型孔達要求13檢驗6.2.凸模加工工藝過程 表6-2-1 落料凸模加工工藝過程工序號工序名稱工序內(nèi)容設(shè)備1備料將毛坯鍛成195mm230mm65mm2熱處理退火3銑銑六面,厚度留單邊磨量0.20.3mm銑床4平磨磨厚度到上限尺寸,磨側(cè)基面保證互相垂直平面磨床5鉗工劃刃口輪廓尺寸及螺釘孔位置尺寸6鉗工加工好凹模,配作落料凸模達要求7鉗工鉆孔攻絲鉆床8熱處理淬火,回火,保證HRC60649線切割按圖切割外形,留0.0050.01單邊研量線切割機床10鉗工磨各配合面達要求11檢驗表6-2-2 沖孔凸模20加工工藝過程工序號工序名稱工序內(nèi)容設(shè)備1備料備料30mm70mm2熱處理退火3車外圓車外圓達配合尺寸車床4車工作尺寸車工作尺寸達要求車床5倒角倒角達要求車床6鉗工拋光達表面要求7熱處理淬火,回火,保證HRC58628鉗工磨平上下表面達要求9檢驗表6-2-3 沖孔凸模45加工工藝過程工序號工序名稱工序內(nèi)容設(shè)備1備料備料55mm70mm2熱處理退火3車外圓車外圓達配合尺寸車床4車工作尺寸車工作尺寸達要求車床5倒角倒角達要求車床6鉗工拋光達表面要求7熱處理淬火,回火,保證HRC58628鉗工磨平上下表面達要求9檢驗6.3.卸料板加工工藝過程 表6-3 卸料板加工工藝過程工序號工序名稱工序內(nèi)容設(shè)備1備料將毛坯鍛成850mm360mm30mm2熱處理退火3銑銑六面,厚度留單邊磨量0.20.3mm，銑臺階銑床4平磨磨厚度到上限尺寸,磨側(cè)基面保證互相垂直平面磨床5鉗工劃各型孔,螺孔,銷孔位置劃漏孔輪廓線6線切割按圖切割各型孔,保證雙面間隙0.5mm線切割機床7鉗工鉆沉，攻絲，6-M8鉆床8平磨磨厚度及基面見光平面磨床9鉗工研光各型孔達要求10檢驗6.4.凸模固定板加工工藝過程表6-4 凸模固定板加工工藝過程工序號工序名稱工序內(nèi)容設(shè)備1備料將毛坯鍛成850mm360mm20mm2熱處理退火3銑銑六面,厚度留單邊磨量0.20.3mm銑床4平磨磨厚度到上限尺寸,磨側(cè)基面保證互相垂直平面磨床5鉗工劃各型孔,螺孔,銷孔位置劃漏孔輪廓線6線切割按圖切割各型孔,保證配合尺寸線切割機床7鉗工鉆鉸410,鉆攻8M10鉆床8鉗工鉚接處倒角9平磨磨厚度及基面見光平面磨床10鉗工研光各型孔達要求11檢驗6.5.上模座加工工藝過程 表6-5 上模座加工工藝過程工序號工序名稱工序內(nèi)容設(shè)備1備料取標準上模座2熱處理退火4平磨平磨上下平面達要求平面磨床5鉗工劃螺孔,銷孔位置劃模柄孔輪廓線6線切割按圖切割各型孔,保證配合尺寸線切割機床7鉗工鉆鉸410,鉆孔及沉孔,鉆床8鉗工去毛刺9檢驗6.6.下模座加工工藝過程表6-6 下模座加工工藝過程工序號工序名稱工序內(nèi)容設(shè)備1備料取標準上模座2熱處理退火4平磨平磨上下平面達要求平面磨床5鉗工劃螺孔,銷孔位置劃線6線切割按圖切割各型孔 線切割機床7鉗工鉆鉸410,鉆沉孔鉆床8鉗工去毛刺9檢驗設(shè)計小結(jié)此次畢業(yè)設(shè)計是在學(xué)完沖壓工藝與模具設(shè)計，模具制造工藝和大部分專業(yè)課并進行了生產(chǎn)實習(xí)的基礎(chǔ)上進行的，這次設(shè)計使我能夠綜合運用沖壓工藝與模具設(shè)計中的基本理論，結(jié)合生產(chǎn)中所學(xué)的新知識、獨立分析和解決工藝問題，初步具備了設(shè)計一個中等復(fù)雜程度的冷沖壓模具的能力。通過分析，擬定設(shè)計方案，完成模具結(jié)構(gòu)設(shè)計等一系列復(fù)雜工作，最終完成此次的設(shè)計任務(wù)。通過這次設(shè)計使我初步具備了設(shè)計一個中等復(fù)雜程度的沖壓模具的工藝規(guī)程和掌握運用模具設(shè)計的基本原理和方法，同時也學(xué)會了熟練運用有關(guān)參考資料，圖表等基本技能，增強了自我的讀圖和繪圖能力，從而使我在能力方面又提高了一個臺階，為今后從事的工作打下了良好的基礎(chǔ)。致 謝 對三年來辛勤教導(dǎo)我的老師和學(xué)校致以最崇高的敬意！ 對本次畢業(yè)設(shè)計指導(dǎo)我和給予我最多的老師表示我最衷心的感謝!畢業(yè)設(shè)計開始以來，有幸多次聆聽老師的教誨。老師以他寬廣的知識、高瞻遠矚的學(xué)識、在實際生產(chǎn)中所積累的經(jīng)驗。拓寬了我的視野和思維，更為重要的是老師以他對事業(yè)孜孜不倦的追求和待人接物謙遜的態(tài)度和豁達的胸襟，時刻都在潛移默化地影響著我，這將使我終生受益。參考文獻1朱光力主編. 模具設(shè)計與制造實訓(xùn).第1版. 北京：高等教育出版社. 2002. 1341562溫松明主編. 互換性與測量技術(shù)基礎(chǔ). 第2版. 長沙：湖南大學(xué)出版社. 1998. 453馮炳堯 韓泰榮 殷振海 蔣文森編. 模具設(shè)計與制造簡明手冊. 第1版.上海：上?？茖W(xué)技術(shù)出版社. 1985. 1 804劉朝儒 彭福蔭 高政一主編. 機械制圖. 第3版. 北京：高等教育出版社.20015張代東主編. 機械工程材料應(yīng)用基礎(chǔ). 第1版.北京：機械工業(yè)出版社.2001.851036王衛(wèi)衛(wèi)主編. 材料成型設(shè)備. 第1版.北京：機械工業(yè)出版.2004. 47487傅建軍主編. 模具制造工藝. 第1版.北京：機械工業(yè)出版社.2005. 24258王新華 袁聯(lián)富主編.沖模結(jié)構(gòu)圖冊. 第1版. 北京：機械工業(yè)出版社. 2003.9中國模具設(shè)計大典編委會.中國模具設(shè)計大典第2卷.南昌:江西科學(xué)技術(shù)出版社,2003.10傅建軍. 模具制造工藝M.北京:機械工業(yè)出版社,2004.11單巖，王蓓，王剛.Moldflow模具分析技術(shù)基礎(chǔ).北京：清華大學(xué)出版社，2004.9 12王衛(wèi)衛(wèi). 彎曲與塑料成型設(shè)備M. 北京:機械工業(yè)出版社,2004.13馮開平，左宗義主編.畫法幾何與機械制圖.廣州：華南理工大學(xué)出版社，2001.9.14R. A. Harris, H. A. Newlyn, R. J. M. Hague and P. M. Dickens, The future direction of stamping dies , Volume 43, Issue 9, July 2003, Pages 879-88715王昆，何小柏，汪信遠主編.機械設(shè)計、機械設(shè)計基礎(chǔ)課程設(shè)計.北京：高等教育出版社，1996.16開思論壇 www.icax.cn17F. Chan, C. K. Law and K. K. Chan, Technical summary sheet metal stamping dies18姜奎華.沖壓工藝及模具設(shè)計M.北京:機械工業(yè)出版社,1998.萬戰(zhàn)勝.沖壓工藝及模具設(shè)計M.北京:中國鐵道出版社,1995.19陳文亮. 板料成形CAE分析教程.北京:機械工業(yè)出版社，2005.20中國機械工程學(xué)會塑性工程學(xué)會.鍛模手冊.北京:機械工業(yè)出版社，2008. 21自編. 沖模設(shè)計課程設(shè)計指導(dǎo)書. 廣東工業(yè)大學(xué)，2008. 22自編. 沖模圖冊. 廣東工業(yè)大學(xué)，2008 23羅益旋主編. 最新沖壓新工藝新技術(shù)及模具設(shè)計實用手冊M. 長春: 吉林出版發(fā)行集團, 2004年. 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.