L形板落料工藝與模具設(shè)計(jì)【L型塊沖壓模具】【墊板】【墊塊】

L形板落料工藝與模具設(shè)計(jì)【L型塊沖壓模具】【墊板】【墊塊】,L型塊沖壓模具,墊板,墊塊,L形板落料工藝與模具設(shè)計(jì)【L型塊沖壓模具】【墊板】【墊塊】,形板落料,工藝,模具設(shè)計(jì),沖壓,模具 摘要沖壓模具在實(shí)際工業(yè)生產(chǎn)中應(yīng)用廣泛。在傳統(tǒng)的工業(yè)生產(chǎn)中，工人生產(chǎn)的勞動(dòng)強(qiáng)度大、勞動(dòng)量大，嚴(yán)重影響生產(chǎn)效率的提高。隨著當(dāng)今科技的發(fā)展，工業(yè)生產(chǎn)中的模具的使用已經(jīng)越來越引起人們的重視，而被大量應(yīng)用到工業(yè)生產(chǎn)中來。沖壓模具的自動(dòng)送料技術(shù)也投入到實(shí)際生產(chǎn)中，沖壓模具可以大大的提高勞動(dòng)成產(chǎn)率，減輕工人的負(fù)擔(dān)，具有重要的技術(shù)進(jìn)步意義和經(jīng)濟(jì)價(jià)值。本文對(duì)冷沖壓技術(shù)的分類、特點(diǎn)及發(fā)展方向作了簡(jiǎn)略的概述：論述了沖壓零件的成形原理、基本模具結(jié)構(gòu)與運(yùn)動(dòng)過程及其設(shè)計(jì)原理；對(duì)典型的沖壓件零件進(jìn)行了設(shè)計(jì)：此設(shè)計(jì)解決了沖壓模具的加工難題,沖壓模具的設(shè)計(jì)充分利用了機(jī)械壓力機(jī)的功用特點(diǎn)，在室溫的條件下對(duì)坯件進(jìn)行沖壓成形，生產(chǎn)效率高，經(jīng)濟(jì)效益顯著。關(guān)鍵詞：沖壓、模具、模具設(shè)計(jì)、工藝AbstractPunching die has been widely used in the actual industrial production. In traditional industrial production,the worker work hard ,and there are too much works,so the efficiency is low.With the development of the science and technology nowdays,the use of punching die in the industial production gain more attention,and be used in the industrail production more and more.Self-acting feed technology of punching die is also used in production,punching die could increase the efficience of production and could alleviate the work burden,so it has signification meaning in technologic progress and economic value.The article mainly discussed the classification,feature and the developmental direction of the punching technology. Elaborated the punching comonents formation principle, the basic dies structure and the rate process and the principle of design; and designed some conventional punching die : the die for big diameter three direction pipe which solved the problem of traditional maching, the darwing and punching compound die with float punch-matrix, the drawing and cutting compound dies with unaltered press, the compound die for the back bowl of the noise keeper, the design of the compound die which could produce two workpieces in one punching, the bending die for ring shape part , the bending die which used the gemel, automate loading die for cutting, the drawing, punching and burring compound die with sliding automated loading, the punching die for the long pipe with two row of hole, the drawing die for the square box shape workpiece and the burring die for the box shape workpiece . KeyWord： punching, die, die design, punching, bending, drawing目錄摘要1Abstract2前 言5第1章 緒論6第2章 落料模的設(shè)計(jì)82.1 零件工藝性分析82.2 模具分析及制定工藝方案92.3 確定模具類型和模具結(jié)構(gòu)92.4 排樣設(shè)計(jì)及材料利用率的計(jì)算92.5 沖裁力與壓力中心的計(jì)算112.5.1 沖載力的計(jì)算校核112.5.2 沖裁模刃口形式112.5.3 壓力中心的計(jì)算122.6 模具刃口尺寸及公差確定122.7 凹模的設(shè)計(jì)132.7.1 凹模刃口結(jié)構(gòu)132.7.2 凹模厚度計(jì)算132.10 凸模的設(shè)計(jì)132.10.1 凸模類型132.10.2 凸模長(zhǎng)度計(jì)算和凸凹模長(zhǎng)度計(jì)算132.10.3 凸模結(jié)構(gòu)形式和凸凹模的結(jié)構(gòu)形式142.11 定位元件的設(shè)計(jì)142.12 模具閉合高度的計(jì)算142.13 彈性卸料元件的設(shè)計(jì)142.13.1 彈性元件的設(shè)計(jì)142.13.2 卸料螺釘?shù)脑O(shè)計(jì)152.14 導(dǎo)向元件的設(shè)計(jì)與選擇152.14.1 導(dǎo)柱的設(shè)計(jì)152.14.2 導(dǎo)套的設(shè)計(jì)162.15 緊固件的設(shè)計(jì)與選擇162.15.1 緊固螺釘?shù)脑O(shè)計(jì)與選擇162.15.2 銷釘?shù)脑O(shè)計(jì)與選擇17第3章 模具的裝配及工作過程183.1 模具的裝配183.2 沖裁模具的試沖19第4章 模具工作過程1結(jié)果與建議2致 謝3參考文獻(xiàn)4前 言首先，對(duì)零件做整體的分析。包括：材料的使用、精度的要求、工序的要求以及成本的要求等。為了降低成本，對(duì)排樣方式進(jìn)行了合理的設(shè)計(jì)；其次，對(duì)零件整體進(jìn)行工藝設(shè)計(jì)。通過工藝目的的設(shè)計(jì)、工序的順序設(shè)計(jì)、壓力機(jī)的選擇等來實(shí)現(xiàn)所要達(dá)到的要求；再次，想要保證制件精度的要求，就要考慮模具刃口尺寸的計(jì)算。因?yàn)槿锌谑菦_制工件的主要工作部分，刃口處的精度就決定了制件的精度，就必須根據(jù)公差來進(jìn)行精確計(jì)算。最后，根據(jù)計(jì)算出的模具刃口尺寸設(shè)計(jì)出相應(yīng)的凸凹模，并且查找資料選擇冷沖壓模的標(biāo)準(zhǔn)零件，符合標(biāo)準(zhǔn)后，就把凸凹模與其它各零部件進(jìn)行總體裝配。在確定了模具體閉合高度后，選出合適的壓力機(jī)在調(diào)試校驗(yàn)后并進(jìn)行試沖加工，以達(dá)到符合的標(biāo)準(zhǔn)，最終完成加工。第1章 緒論模具是成批和大量生產(chǎn)各種機(jī)電與家電必備的基礎(chǔ)工藝裝備，是進(jìn)行少無切削加工的主要工具，是制造業(yè)發(fā)展的前提。國(guó)內(nèi)模具產(chǎn)業(yè)近幾年以12%15%的增速，持續(xù)、穩(wěn)定、高速發(fā)展，支撐并保證國(guó)內(nèi)制造業(yè)，特別是機(jī)械、汽車、電子、石化及建筑業(yè)等國(guó)民經(jīng)濟(jì)的五大支柱產(chǎn)業(yè)持續(xù)高速發(fā)展。1953年，長(zhǎng)春第一汽車制造廠在中國(guó)首次建立了沖模車間，該汽車廠于1958年開始制造汽車覆蓋件模具。我國(guó)于20世紀(jì)60年代開始生產(chǎn)精沖模具。走過漫長(zhǎng)的發(fā)展道路，目前我國(guó)已形成約300多億元沖壓模具的生產(chǎn)能力。形成了如浙江寧波和黃巖地區(qū)的“模具之鄉(xiāng)”；廣東一些大集團(tuán)公司和鄉(xiāng)鎮(zhèn)企業(yè)迅速崛起，科龍、美的、康佳等集團(tuán)紛紛建立了自己的模具制造中心；中外合資和外商獨(dú)資的模具企業(yè)現(xiàn)已有幾千家。隨著與國(guó)際接軌的腳步不斷加快，市場(chǎng)競(jìng)爭(zhēng)的日益加劇，模具的生產(chǎn)和設(shè)計(jì)已經(jīng)越來越認(rèn)識(shí)到產(chǎn)品質(zhì)量、成本和新產(chǎn)品的開發(fā)能力的重要性。模具制造技術(shù)現(xiàn)已成為衡量一個(gè)國(guó)家制造業(yè)水平高低的重要標(biāo)志，并在很大程度上決定企業(yè)的生存空間。目前我國(guó)沖壓模具無論在數(shù)量上，還是在質(zhì)量、技術(shù)和能力等方面都已有了很大發(fā)展，但與國(guó)民經(jīng)濟(jì)需求和世界先進(jìn)水平相比，差距仍很大。在國(guó)際競(jìng)爭(zhēng)的局勢(shì)下，我過的模具工業(yè)得到飛速的發(fā)展，很多的專門模具研究中心不斷的建立起來，模具結(jié)構(gòu)和鋼材的研究取得了顯著的成就，但還是存在很大的差距。 一是進(jìn)口模具大部分是技術(shù)含量高的大型精密模具，而出口模具大部分是技術(shù)含量較低的中低檔模具，因此技術(shù)含量高的中高檔模具市場(chǎng)滿足率低于沖壓模具總體滿足率，這些模具的發(fā)展已滯后于沖壓件生產(chǎn)，而技術(shù)含量低的中低檔模具市場(chǎng)滿足率要高于沖壓模具市場(chǎng)總體滿足率。成批與大量生產(chǎn)的各類機(jī)電與家電產(chǎn)品零部件及半成品坯件，都需要大量、不同種類的模具進(jìn)行加工。其中，約65%的零件要用各種金屬板、條、帶卷料，沖成個(gè)種形狀復(fù)雜、精度高、用其他加工方法無法完成的板料沖壓零件，所使用的冷沖模種類繁多，結(jié)構(gòu)各異而又千變?nèi)f化。沖壓加工在技術(shù)上有以下優(yōu)勢(shì)：(1）在壓力機(jī)滑塊上下往復(fù)的簡(jiǎn)單沖擊下，使用的沖?？梢詻_制其他加工方法難以制造的、形狀復(fù)雜的沖壓零件。 (2)板料沖壓零件質(zhì)量輕，剛度大，承載能力強(qiáng)，長(zhǎng)期使用不變形，是各類機(jī)電與家電產(chǎn)品結(jié)構(gòu)輕型化，取代笨重鑄、鍛及切削加工零部件的首選。因而對(duì)沖模數(shù)量的需求日益增多，沖模結(jié)構(gòu)的復(fù)雜程度和沖壓工藝水平日益提升。 (3）沖壓零件的一致性好，互換性強(qiáng)，尺寸和形位精度高，一般只需局部甚至不再進(jìn)行切削加工，即可進(jìn)行產(chǎn)品的裝配。 (4）便于實(shí)現(xiàn)沖壓過程機(jī)械化、自動(dòng)化及組建CNC復(fù)合作業(yè)生產(chǎn)線。當(dāng)設(shè)計(jì)與使用自動(dòng)沖模時(shí)也可實(shí)現(xiàn)單機(jī)自動(dòng)化作業(yè)。(5）現(xiàn)代沖壓高技術(shù)的大力推廣與實(shí)施，可對(duì)各種復(fù)雜形狀沖壓零件，用多工位復(fù)合形成，實(shí)現(xiàn)安全生產(chǎn)，達(dá)到優(yōu)質(zhì)、高產(chǎn)、低能耗。按照沖模適用沖壓零件生產(chǎn)性質(zhì)（投產(chǎn)批量大小）、結(jié)構(gòu)復(fù)雜及制模費(fèi)用大小、沖壓精度高低，可將沖模大致劃分如下幾類：（1）制造經(jīng)濟(jì)的簡(jiǎn)易沖模 適用于新產(chǎn)品樣式與批式，需要單件、小批量生產(chǎn)的沖壓零件所使用各種簡(jiǎn)易結(jié)構(gòu)，用新材料與新工藝及簡(jiǎn)易制模方法制造的經(jīng)濟(jì)、簡(jiǎn)易沖模。其制模工藝簡(jiǎn)便，制模周期短，造價(jià)低，但模具使用壽命也低。（2）萬能通用沖模與組合沖模 使用中小批量、多品種生產(chǎn)低精度沖壓零件。萬能通用沖?？梢荒６嘤?；組合沖模是備有多種工作元件，按需要隨時(shí)組合成個(gè)種沖模，將沖壓零件分解成多工序，加工用多套組合沖模沖制。（3）普通全鋼沖模 適用于成批和大批量生產(chǎn)各種沖壓零件，是應(yīng)用廣泛的標(biāo)準(zhǔn)結(jié)構(gòu)與非標(biāo)準(zhǔn)結(jié)構(gòu)的全鋼材質(zhì)普通沖壓用模具。（4）精沖模 用于各種精沖工藝專用的精沖模具。（5）大型、特種、高精度與高壽命沖模 適用于大量生產(chǎn)的汽車覆蓋件沖模、高精度硅鋼片硬質(zhì)合金模等。第2章 落料模的設(shè)計(jì)2.1 零件工藝性分析該零件為圓形零件形，簡(jiǎn)單且對(duì)稱，無懸臂、凹槽。結(jié)論：從結(jié)構(gòu)分析，該零件適合沖裁生產(chǎn)。注：沖壓模具及設(shè)備194頁該零件材料為H62，其抗拉強(qiáng)度： =322441Mpa，抗剪強(qiáng)度：=265343Mpa，延伸率：=29%。而該零件要求拉深性能較好，即塑性較好，從該材料的這三個(gè)方面可見，符合該零件。結(jié)論：綜上分析，符合零件要求。注：沖壓模具及設(shè)備28頁表2-3。該零件落料尺寸按IT14級(jí)，普通沖裁落料可達(dá)IT10級(jí)，故普通沖裁可以達(dá)到該零件精度要求。該零件斷面粗糙度、飛邊毛刺都無特殊要求，普通沖裁可以達(dá)到=3.26.4m，故普通沖裁可達(dá)到零件要求。結(jié)論：綜上所述，該零件適合普通沖裁。注：沖壓模具及設(shè)備191頁。2.2 模具分析及制定工藝方案該零件只有落料1個(gè)基本工序2.3 確定模具類型和模具結(jié)構(gòu)根據(jù)上述分析，采用導(dǎo)柱式模具（導(dǎo)柱式落料模。雖然零件生產(chǎn)批量大，一般選用手工送料操作方式，故選擇手工送料。定位方式分析如下：采用導(dǎo)料銷導(dǎo)料；擋料銷擋料結(jié)論：采用手工送料；導(dǎo)料銷+擋料銷。注：沖壓模具及設(shè)備143-146頁。由于該零件形狀簡(jiǎn)單且工作環(huán)境要求滑動(dòng)平穩(wěn)，導(dǎo)向準(zhǔn)確，故選用導(dǎo)柱式模座。該零件精度要求不高，因此選擇I級(jí)模座精度。結(jié)論：導(dǎo)柱式I級(jí)精度模座。2.4 排樣設(shè)計(jì)及材料利用率的計(jì)算根據(jù)工件的開關(guān)，確定采用無廢料的排樣方法不可能做到，但能采用有廢料和少廢料的排樣方法。經(jīng)多次排樣計(jì)算決定采用， 1）搭邊設(shè)計(jì) 板料厚度t=2mm, 工件邊長(zhǎng)L50mm, 所以a=2mm, a=2mm。送料步距A=54mm, 條料寬度B=55mm。 2）排樣布局3）材料利用率計(jì)算：S=518mm=100%=100%=100%=76.7%式中，材料利用率；S工件的實(shí)際面積；S所用材料面積，包括工件面積與廢料面積；A步距（相鄰兩個(gè)制件對(duì)應(yīng)點(diǎn)的距離）B條料寬度。2.5 沖裁力與壓力中心的計(jì)算2.5.1 沖載力的計(jì)算校核落料力=KLt （3.2） 式中： K系數(shù)，K=1.3； L沖裁周邊長(zhǎng)度（mm）； t沖裁件的厚度（mm）；材料的抗剪強(qiáng)度（MPa）。=KLt=1.31083252=91.26 (kN）卸料力由2得卸料力的計(jì)算公式F卸料=K卸料F落料 （3.3）式中： K卸料卸料力系數(shù)F卸料=K卸料F落料 =0.03491.260=3.1 kN總沖壓力F卸料+ =91.26 +3.1=94.36KN.所以選擇壓力機(jī)必須要大于總沖壓力2.5.2 沖裁模刃口形式由于選用具沖裁的方式，采用臺(tái)階式的。結(jié)論：采用臺(tái)階式刃口形式。注：沖壓模具設(shè)計(jì)指導(dǎo)書37頁表2-1。2.5.3 壓力中心的計(jì)算如對(duì)毛坯進(jìn)行加工必須要用到壓力機(jī)。而壓力機(jī)位置的確定必須先確定壓力中心。其出公式如下： （2-5a） （2-5b） 壓力中心即在中心2.6 模具刃口尺寸及公差確定注：?jiǎn)挝粸閙m。落料時(shí)，有沖件精度為IT14，查得；由表得，、，凹模刃口： 凸模刃口：查表得，、，校核間隙：，說明所取凸、凹模公差不能滿足但相差不大，此時(shí)可調(diào)整如下：2.7 凹模的設(shè)計(jì)2.7.1 凹模刃口結(jié)構(gòu)根據(jù)沖裁模刃口形式的分析，采用臺(tái)階式刃口結(jié)構(gòu)。2.7.2 凹模厚度計(jì)算根據(jù)凹模刃口的最大尺寸，查表得，那么厚度：H1=K1K230.1F=1.31.373120637.6080.1=24.323,H1=25mm注：沖壓模具設(shè)計(jì)指導(dǎo)書38頁，沖壓模具標(biāo)準(zhǔn)件選用與設(shè)計(jì)指南103頁。2.10 凸模的設(shè)計(jì)2.10.1 凸模類型根據(jù)該零件外形內(nèi)孔分析，模具的凸模為圓凸模和方形凸模。2.10.2 凸模長(zhǎng)度計(jì)算和凸凹模長(zhǎng)度計(jì)算由于采用具剛性卸料，那么H凸=H固+H凹=43注：沖壓模具及設(shè)備136頁。2.10.3 凸模結(jié)構(gòu)形式和凸凹模的結(jié)構(gòu)形式凸模結(jié)構(gòu)選擇：由于矩形凸模尺寸相對(duì)稍大，為方便加工，選用 注：沖壓模具標(biāo)準(zhǔn)件選用與設(shè)計(jì)指南87頁表4-1。2.11 定位元件的設(shè)計(jì)導(dǎo)料銷用以導(dǎo)料，數(shù)量為2個(gè)。具體設(shè)計(jì)如下圖所示，2.12 模具閉合高度的計(jì)算根據(jù)以上設(shè)計(jì)，那么模具閉合高度Hb=H1+H1+t+H2+Hxm=175注：沖壓模具設(shè)計(jì)指導(dǎo)書31頁。2.13 彈性卸料元件的設(shè)計(jì)2.13.1 彈性元件的設(shè)計(jì)彈性元件的選擇模具工作平穩(wěn)，模具尺寸中等，從經(jīng)濟(jì)方面考慮，選用常用的橡膠作為彈性元件即可。彈性元件高度計(jì)算自由高度：，H0=2+t+(410)0.250.3=2+1+70.3=33根據(jù)其高度范圍，查標(biāo)準(zhǔn)，得H=35安裝高度： Ha=0.9H0=0.9x35=31.5彈性元件其他尺寸。注：沖壓模具標(biāo)準(zhǔn)件選用與設(shè)計(jì)指南158-160頁，沖壓模具設(shè)計(jì)指導(dǎo)書233頁表9-36。2.13.2 卸料螺釘?shù)脑O(shè)計(jì)螺釘類型：由于卸料螺釘無特殊要求，故采用一般的圓柱頭卸料螺釘。結(jié)構(gòu)設(shè)計(jì)：由橡膠的內(nèi)徑d=8.5,查表得，卸料螺釘。查表得，其螺紋公稱直徑為，其長(zhǎng)度查標(biāo)準(zhǔn)取h=50。結(jié)論：卸料螺釘?shù)某叽鐬?。卸料螺釘?shù)亩ㄎ辉O(shè)計(jì)：注：沖壓模具標(biāo)準(zhǔn)件選用與設(shè)計(jì)指南128-129頁表5-5、133頁。2.14 導(dǎo)向元件的設(shè)計(jì)與選擇由于該模具為沖裁模，故選用適用于沖裁?；瑒?dòng)導(dǎo)向模座的A型導(dǎo)柱導(dǎo)套。注：沖壓模具標(biāo)準(zhǔn)件選用與設(shè)計(jì)指南66頁。2.14.1 導(dǎo)柱的設(shè)計(jì)根據(jù)模具閉合高度，查表得，導(dǎo)柱尺寸 注：沖壓模具設(shè)計(jì)指導(dǎo)書245頁表9-46、50頁表2-27。2.14.2 導(dǎo)套的設(shè)計(jì)根據(jù)模具閉合高度，查表得，導(dǎo)套尺寸注：沖壓模具設(shè)計(jì)指導(dǎo)書245頁表9-46、51頁表2-28。2.15 緊固件的設(shè)計(jì)與選擇2.15.1 緊固螺釘?shù)脑O(shè)計(jì)與選擇螺釘類型：在沖裁模中，為使螺釘頭部外露，模具外形美觀，一般采用內(nèi)六角螺釘。螺釘?shù)某叽缬?jì)算：根據(jù)凹模厚度，查表得，所用螺釘都為。上模座、,凹模板 ，墊板，固定板之間的螺釘：四塊板厚度查表得，螺釘尺寸，數(shù)量為4個(gè)。下模座、墊板，固定板之間的螺釘： 查表得，螺釘尺寸，數(shù)量為4個(gè)。注：沖壓模具及設(shè)備160-161頁，沖壓模具標(biāo)準(zhǔn)件選用與設(shè)計(jì)指南124頁表5-2。2.15.2 銷釘?shù)脑O(shè)計(jì)與選擇銷釘?shù)念愋停涸撃＞邔?duì)銷釘無特殊要求，故采用常用的圓柱銷。銷釘?shù)某叽缬?jì)算：根據(jù)緊固件設(shè)計(jì)參考原則，查表得，所用銷釘公稱直徑都為。 凹模板 ，墊板，固定板之間的銷釘： 查表得，銷釘尺寸，數(shù)量為2個(gè)。、墊板，固定板之間的螺釘： 查表得，銷釘尺寸，數(shù)量為2個(gè)。注：沖壓模具標(biāo)準(zhǔn)件選用與設(shè)計(jì)指南134頁表5-11。第3章 模具的裝配及工作過程3.1 模具的裝配根據(jù)沖壓模具裝配要點(diǎn)，選凹模作為裝配基準(zhǔn)件，先裝下模，再裝上模，并調(diào)整間隙、試沖、返修，具體裝配見表9.1。表9.1 沖壓模具的裝配序號(hào)工序工藝說明1凸、凹模預(yù)配（1）裝配前仔細(xì)檢查各凸模形狀以及凹模形孔，是否符合圖紙要求尺寸精度、形狀（2）將各凸模分別與相應(yīng)的凹?？紫嗯洌瑱z查其間隙是否加工均勻。不合適者應(yīng)重新修磨或更換2凸模裝配以凹?？锥ㄎ唬瑢⒏魍鼓７謩e壓入凸模固定板8的形孔中，并擰緊牢固3裝配下模（1）在下模座1上劃中心線，按中心預(yù)裝凹模17、導(dǎo)料板5；（2）在下模座1、導(dǎo)料板5上，用已加工好的凹模分別確定其螺孔位置，并分別鉆孔，攻絲（3）將下模座1、導(dǎo)料板5、凹模17、擋料銷20、凹?？蜓b在一起，并用螺釘緊固，打入銷釘4裝配上模（1）在已裝好的下模上放等高墊鐵，再在凹模中放入0.12片，然后將凸模與固定板的組合裝入凹模（2）預(yù)裝上模座，劃出與凸模固定板相應(yīng)螺孔。銷孔位置并鉆絞螺孔、銷孔（3）用螺釘將固定板組合，墊板、上模座連接在一起，但不要擰緊（4）將卸料板套裝在已裝入固定板的凸模上，裝上橡膠14和卸料螺釘12，并調(diào)節(jié)橡膠的預(yù)壓量，使卸料板高出凸模下端約1；復(fù)查凸、凹模間隙并調(diào)整合適后，緊固螺釘；切紙檢查，合適后打入銷釘5試沖與調(diào)整裝機(jī)試沖并根據(jù)試沖結(jié)果作相應(yīng)調(diào)整3.2 沖裁模具的試沖模具裝配以后，必須在生產(chǎn)條件下進(jìn)行試沖。通過試沖可以發(fā)現(xiàn)模具設(shè)計(jì)和制造的不足，并找出原因給與糾正。并能夠?qū)δ＞哌M(jìn)行適當(dāng)?shù)恼{(diào)整和修理，直到模具正常工作中沖出合格的制件為止。沖裁模具經(jīng)試沖合格后，應(yīng)在模具模座正面打上編號(hào)、沖模圖號(hào)、制件號(hào)、使用壓力機(jī)型號(hào)、制造日期等。并涂油防銹后經(jīng)檢驗(yàn)合格入庫。沖裁模具試沖時(shí)常見的缺陷、產(chǎn)生原因和調(diào)整方法見表9.2。表9.2 沖裁模具試沖時(shí)常見的缺陷、產(chǎn)生原因和調(diào)整方法缺陷產(chǎn)生原因調(diào)整方法沖件毛刺過大1刃口不鋒利或淬火硬度不夠2間隙過大或過小，間隙不均勻1修磨刃口使其鋒利2重新調(diào)整間隙，使其均勻沖件不平整1凸模有倒錐，沖件從孔中通過時(shí)被壓彎2頂出件與頂出器接觸零件面積大小3頂出件、頂出器分布不均勻1修磨凹?？祝コ龑?dǎo)錐現(xiàn)象2更換頂出桿，加大與零件的接觸面積尺寸超差和形狀不準(zhǔn)確凸模、凹模形狀及尺寸精度差修整凸模、凹模形狀及尺寸，使其達(dá)到形狀及尺寸精度要求凸模折斷1沖裁時(shí)產(chǎn)生側(cè)壓力2卸料板傾斜1在模具上設(shè)置擋塊抵消側(cè)向力2修整卸料板或使凸模增加導(dǎo)向裝置凹模被脹裂1凹?？子械瑰F度形象2凹?？變?nèi)卡住廢料1修磨凹?？?，消除倒錐現(xiàn)象2修抵凹?？赘叨韧?、凹模刃口相咬1上、下模座，固定板、凹模、墊板等零件安裝基面不平行2凸、凹模錯(cuò)位3凸模、導(dǎo)柱、導(dǎo)套與安裝基面不垂直4導(dǎo)向精度差，導(dǎo)柱、導(dǎo)套配合間隙過大5卸料板孔位偏斜使凸模位移1調(diào)整有關(guān)兩件重新安裝2重新安裝凸、凹模，使之對(duì)正3調(diào)整其垂直度重新安裝4更換導(dǎo)柱、導(dǎo)套5調(diào)整及更換卸料板沖裁件剪切斷面光亮帶寬，甚至出現(xiàn)毛刺沖裁間隙過小適當(dāng)放大沖裁間隙，對(duì)于模間隙加大在凹模方向上，對(duì)落料間隙加大在凸模方向上剪切斷面光亮帶寬窄不均勻，局部有毛刺沖裁間隙不均勻修磨或重新調(diào)整凸?；虬寄?，調(diào)整間隙保證均勻外型與內(nèi)孔偏移1在連續(xù)模中孔與外形偏心，并且所偏的方向一致，表明側(cè)刃的長(zhǎng)度與布局不一致2連續(xù)模多件沖裁時(shí)，其它孔形正確，只有一孔偏心，表明該孔凸凹模相對(duì)位置有變化3孔形不正確，表明凸凹模相對(duì)位置有偏移1加大(減小)側(cè)刃長(zhǎng)度或磨?。哟螅趿蠅K尺寸2重新裝配凸模并調(diào)整其位置使之正確3更換凸（凹）模，重新進(jìn)行裝配調(diào)整合適送料不暢通，有時(shí)被卡死易發(fā)生在連續(xù)模中1兩導(dǎo)料板之間的尺寸過小或有斜度2凸模與卸料板之間的間隙太大，致使搭邊翻轉(zhuǎn)而堵塞3導(dǎo)料板的工作面與側(cè)刃不平行，卡住條料，形成毛刺大1粗修或重新調(diào)整裝配導(dǎo)料板2減小凸模與導(dǎo)料板之間的配合間隙，或重新調(diào)整澆注卸料板孔3重新調(diào)整裝配導(dǎo)料板，使之平行4修整側(cè)刃及擋塊之間的間隙，使之達(dá)到嚴(yán)密卸料及卸料困難1卸料裝置不動(dòng)作2卸料力不夠3卸料孔不暢，卡住廢料4凹模有錐度5漏料孔太小6推桿長(zhǎng)度不夠1重新裝配卸料裝置，使之靈活2增加卸料力3修整卸料孔4修整凹模5加大漏料孔6加長(zhǎng)打料桿第4章 模具工作過程有上面可知模具為落料模。上模部分有落料凹模與凸模，通過凸模固定板、墊板由銷釘定位、螺釘固定裝在上模座上。凸凹模通過凸凹模固定、墊板裝在下模座上。采用導(dǎo)柱導(dǎo)套導(dǎo)向，導(dǎo)柱布置在兩側(cè)。為防止裝反，兩個(gè)導(dǎo)柱的直徑有同。為了推件與卸料，上模裝有由推桿、推板、推桿與推件板組成的剛性系統(tǒng)。下模裝有由卸料、卸料螺釘與橡皮組成的彈性卸料系統(tǒng)。彈性卸料對(duì)條料起校平作用。沖載時(shí)，落料凹模將彈性卸料板壓下，凸模也進(jìn)入凹?？字?，同時(shí)完成與落料。當(dāng)上?；爻虝r(shí)，彈性卸料板在橡作用下將條料從凸凹模上卸下，而推桿受到橫桿的推動(dòng)，通過推板、推桿與推件板將沖件從落料凹中推出，廢料由凸凹?？字新┏?。條料的定位依靠左側(cè)的兩個(gè)活動(dòng)導(dǎo)料的方法在復(fù)合模中的應(yīng)用較多，它不影響彈性卸料板對(duì)條料的壓平作用。而的主要的優(yōu)點(diǎn)是廢料能直接從壓力機(jī)漏料孔落下，沖載件從上模落下，比較容易取出這些排出件，因此操作方便安全，有利于的安裝送料裝置，生產(chǎn)效率較高，所以應(yīng)用比較廣泛。結(jié)果與建議通過這次設(shè)計(jì)，我收獲很多，感悟也很多。這是對(duì)我?guī)啄晁鶎W(xué)知識(shí)的一次綜合的運(yùn)用和檢驗(yàn)。首先是鞏固并加深了我對(duì)模具知識(shí)的了解，進(jìn)一步鞏固了我對(duì)AUTOCAD的運(yùn)用能力。在整個(gè)過程中，由于平時(shí)不注意知識(shí)的積累，又缺少實(shí)踐經(jīng)驗(yàn)，導(dǎo)致我遇到許多難以解決的困難，但很慶幸我們遇到好的指導(dǎo)老師，帶領(lǐng)我們?nèi)スS見到了模具的實(shí)物，讓我們和模具有了零距離的接觸，更細(xì)心的指導(dǎo)我們完成了整個(gè)巨大設(shè)計(jì)過程?？傊?，這次的設(shè)計(jì)讓我收獲很大，我很高興，也很榮幸有這次的經(jīng)歷。在此也對(duì)我們的導(dǎo)師和老師表示由衷的感謝，沒有指導(dǎo)老師的指導(dǎo)，我們的設(shè)計(jì)不可能順利的完成。導(dǎo)師嚴(yán)謹(jǐn)負(fù)責(zé)的態(tài)度，平易近人的作風(fēng)也是值得學(xué)習(xí)的榜樣。也感謝學(xué)校對(duì)此設(shè)計(jì)的重視，為我們提供良好的環(huán)境。同時(shí)我也要感謝我的同學(xué)們給予的幫助。致 謝本文是在老師的精心指導(dǎo)和悉心關(guān)懷下完成的，在設(shè)計(jì)的撰寫過程中，我得到了老師的耐心指教，提出了許多寶貴意見。老師嚴(yán)謹(jǐn)求實(shí)的治學(xué)風(fēng)范、平易近人的工作作風(fēng)和及循循善誘的教誨等，給我留下了深刻的印象，得到了學(xué)術(shù)上和工作上的進(jìn)步，這些都是我終身受益，值此設(shè)計(jì)完成之際，謹(jǐn)向尊敬的老師致以深深的感謝和崇高的敬意！最后，感謝審閱本文的各位老師、同學(xué)和同事。本文的完成和他們的無私奉獻(xiàn)是分不開的。隨著科學(xué)技術(shù)的發(fā)展，設(shè)備越來越向智能化、集成化等方向發(fā)展，車間的生產(chǎn)也越來越多的向依靠設(shè)備生產(chǎn)轉(zhuǎn)變，生產(chǎn)的車身質(zhì)量與設(shè)備密切相關(guān)。因此，如何維護(hù)、維修及管理好設(shè)備是車間的一項(xiàng)重要工作。參考文獻(xiàn)1 王立剛沖模設(shè)計(jì)手冊(cè).機(jī)械工業(yè)出版社， 2002.52劉建超.沖壓模具設(shè)計(jì)與制造.北京.高等教育出版社,2002.113郭景儀.沖壓模具手冊(cè).北京.北京出版社,1991.44牟林,魏崢.冷沖壓工藝及模具設(shè)計(jì)教程.北京.清華大學(xué)出版社,2005.45李天佑.沖壓圖冊(cè).山西.機(jī)械工業(yè)出版社,1988.116王芳冷沖壓模具設(shè)計(jì)指導(dǎo)機(jī)械工業(yè)出版社，1998.107張超英沖壓模具與制造北京.化學(xué)工業(yè)出版社，2003.68萬本善. 實(shí)用沖模結(jié)構(gòu)圖解與沖壓新工藝詳圖及常用數(shù)據(jù)速查速用手冊(cè).北京. 科大電子出版社,2004.89 彭建生. 模具設(shè)計(jì)與加工速查手冊(cè). 機(jī)械工業(yè)出版社，2005.710韓洪濤. 機(jī)械制造技術(shù).北京.化學(xué)工業(yè)出版社,2003.711李志剛,夏巨諶.中國(guó)模具設(shè)計(jì)大典.中國(guó)機(jī)械工程學(xué)會(huì),2003.512余最康冷沖壓模具設(shè)計(jì)與制造南京.江蘇技術(shù)出版社，198313太田哲沖壓模具結(jié)構(gòu)與設(shè)計(jì)圖解北京.國(guó)防工業(yè)出版社，198314肖景容沖壓工藝學(xué)北京.機(jī)械工業(yè)出版社，199215黃毅宏模具制造工藝北京.機(jī)械工業(yè)出版社，198716許發(fā)樾模具標(biāo)準(zhǔn)應(yīng)用手冊(cè)北京.機(jī)械工業(yè)出版社，198417成虹沖壓工藝與模具設(shè)計(jì)（第二版）北京.高等教育出版社，200618周勤芳公差與技術(shù)測(cè)量（第二版）上海.上海交通大學(xué)出版社，2001Int 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.