墊板冷沖壓工藝模具設(shè)計(jì)【說明書+CAD】

墊板冷沖壓工藝模具設(shè)計(jì)【說明書+CAD】,說明書+CAD,墊板冷沖壓工藝模具設(shè)計(jì)【說明書+CAD】,墊板,沖壓,工藝,模具設(shè)計(jì),說明書,仿單,cad 設(shè)計(jì)作品：沖壓模具設(shè)計(jì)者：黃旭指導(dǎo)老師：胡淑芬設(shè)計(jì)說明設(shè)計(jì)說明v本零件毛坯為0.8mm的10號(hào)鋼板件。本次畢業(yè)設(shè)計(jì)是完成墊板冷沖壓工藝模具設(shè)計(jì)，采用落料；沖孔工藝。設(shè)計(jì)中分析了工件的沖壓工藝性，計(jì)算了毛坯排樣；沖壓力，刃口尺寸計(jì)算等。進(jìn)行了模具總體結(jié)構(gòu)；主要零部件的設(shè)計(jì)，繪制了落料；沖孔復(fù)合模的模具裝配圖和零部件圖。設(shè)計(jì)方案設(shè)計(jì)方案v1 產(chǎn)品的分析v2 模具的確定v3 相關(guān)數(shù)據(jù)的計(jì)算v4 工藝分析模具的確定模具的確定 v模具可分為正裝式復(fù)合模，倒裝式復(fù)合模和級(jí)進(jìn)模經(jīng)分析，此工件為多孔沖裁件，若采用倒裝復(fù)合模，由于孔與孔之間的間距過小，采用倒裝復(fù)合模則模具則剛度不夠，另外倒裝復(fù)合模是下模座自然卸料方式，會(huì)導(dǎo)致廢料積累從而膨脹擠壓凸凹模，會(huì)減少凸凹模的使用壽命。若采用級(jí)進(jìn)模則有側(cè)刃裝置，則模具精度達(dá)不到零件要求。因此本設(shè)計(jì)決定采用正裝復(fù)合模。設(shè)計(jì)原理設(shè)計(jì)原理v 此正裝復(fù)合模設(shè)計(jì)工作時(shí)，板料以導(dǎo)料銷和擋料銷進(jìn)行定位。上模下壓，凸凹模外形和凹模進(jìn)行落料，落下的沖件卡在凹模中，同時(shí)沖孔凸模和凸凹模內(nèi)孔進(jìn)行沖孔，沖孔廢料卡在凸凹?？變?nèi)?？ㄔ诎寄Ｖ械臎_件由頂件裝置頂出，卡在凸凹模內(nèi)孔中的沖孔廢料由推桿頂出。該模具采用裝在下模座座底的彈頂器推動(dòng)頂桿和頂件塊，可獲得較大的頂件力。每沖裁一次，沖孔廢料被推出一次，凸凹?？變?nèi)不積存廢料。模架的選擇模架的選擇v由于零件的尺寸較小，平直度要求也較高，因此 要求有較高的導(dǎo)向精度和穩(wěn)定性。本設(shè)計(jì)采用對角導(dǎo)柱模架，對角導(dǎo)柱滑動(dòng)模架其兩副導(dǎo)柱、導(dǎo)套均裝在模板的對角位置，既可橫向送料，又可縱向送料。模具剛性很好。適于各種沖裁模使用。為了避免上；下模的方向裝錯(cuò)，兩導(dǎo)柱直徑制成一大一小。主要適用于沖壓精度較高的零件。凸模的選擇凸模的選擇v在本設(shè)計(jì)中沖孔凸模采用60度錐頭直桿圓凸模。因?yàn)楸驹O(shè)計(jì)中有3個(gè)沖孔凸模，且凸模之間的距離較小，若采用階梯凸模雖然強(qiáng)度能夠保證，但是會(huì)導(dǎo)致凸模尾部相交，所以不適用。v且考慮到?jīng)_裁力，保證零件不至于承受太大的沖壓力，3個(gè)凸模采用階梯分布。頂件塊的設(shè)計(jì)頂件塊的設(shè)計(jì)v在本設(shè)計(jì)中頂件塊的厚度為21mm。v頂件塊的作用是將凹模中的落料件推出。v另外在本設(shè)計(jì)中，由于凸模采用60度錐頭直桿圓凸模，凸模的強(qiáng)度可能不夠，所以頂件塊設(shè)計(jì)較長能起到凸模護(hù)套的作用，也能夠保證凸模的強(qiáng)度。推桿的設(shè)計(jì)推桿的設(shè)計(jì)v正裝復(fù)合模每次沖裁結(jié)束時(shí)，卡在凸凹模內(nèi)孔中的廢料由推桿推出v在本設(shè)計(jì)中，凸凹模兩個(gè)孔直徑為5.2和6.0mm，廢料必須由推桿頂出才能進(jìn)行下次沖裁，因此推桿應(yīng)該保證有足夠的長度，本設(shè)計(jì)中推桿的長度為35mm。材料的選用材料的選用v在本設(shè)計(jì)中有各種材料的選用v由于模座不進(jìn)行加工，不需要有很大的韌性，只要保證有足夠的剛性和強(qiáng)度即可，因此考慮到經(jīng)濟(jì)性我選用灰口鑄鐵HT250v而凸模，凹模，凸凹模等要進(jìn)行沖裁的零件，要有足夠的韌性強(qiáng)度和尺寸穩(wěn)定性，因此我選用高碳中鉻工具鋼Cr5MoV,它們的含鉻量較低，共晶碳化物少，碳化物分布均勻，熱處理變形小，具有良好的淬透性和尺寸穩(wěn)定性。v其他大部分標(biāo)準(zhǔn)件選用45號(hào)鋼小結(jié)小結(jié)v通過本次畢業(yè)設(shè)計(jì)的鍛煉，使我對模具設(shè)計(jì)與模具制造的相關(guān)過程有了比較深刻的認(rèn)識(shí)和全面的掌握。認(rèn)真嚴(yán)謹(jǐn)?shù)耐瓿闪吮敬萎厴I(yè)設(shè)計(jì)也是大學(xué)四年里最后也最重要的一次設(shè)計(jì)。但是由于水平有限，錯(cuò)誤和不足之處在所難免，懇請各位老師批評指正，不勝感激。沖壓模具學(xué)校代碼：10410 序 號(hào)：0398本 科 畢 業(yè) 設(shè) 計(jì)題目： 沖壓模具 學(xué) 院： 工 學(xué) 院 姓 名： 黃 旭 學(xué) 號(hào)： 20050398 專 業(yè)： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 年 級(jí)： 機(jī)制051 指導(dǎo)教師： 胡淑芬 二OO九年 五 月33沖壓模具畢業(yè)設(shè)計(jì)材 料：10鋼板料厚度：t=0.8mm 生產(chǎn)批量：大批量任 務(wù)：編制沖壓工藝方案、設(shè)計(jì)模具結(jié)構(gòu)圖 8摘 要 本次畢業(yè)設(shè)計(jì)是完成墊板冷沖壓工藝模具設(shè)計(jì)，采用落料；沖孔工藝。設(shè)計(jì)中分析了工件的沖壓工藝性，計(jì)算了毛坯排樣；沖壓力，刃口尺寸計(jì)算等。進(jìn)行了模具總體結(jié)構(gòu)；主要零部件的設(shè)計(jì)，繪制了落料；沖孔復(fù)合模的模具裝配圖和零部件圖。關(guān)鍵詞： 沖壓工藝 模具設(shè)計(jì) 裝配圖一 引 言 隨著我國經(jīng)濟(jì)的發(fā)展，模具對于現(xiàn)代工業(yè)來說是十分重要的，尤其是沖壓技術(shù)的應(yīng)用。在各個(gè)經(jīng)濟(jì)部門中，幾乎都要沖壓加工生產(chǎn)，它不僅與整個(gè)機(jī)械行業(yè)密切相關(guān)，而且與人們的生活息息相關(guān)。模具，是工業(yè)生產(chǎn)的基礎(chǔ)工藝裝備，在電子、汽車、電機(jī)、電器、儀表、家電和通訊等產(chǎn)品中，60%-80%的零部件都依靠模具成形，模具質(zhì)量的高低決定著產(chǎn)品質(zhì)量的高低，因此，模具被稱之為“百業(yè)之母”。模具又是“效益放大器”，用模具生產(chǎn)的最終產(chǎn)品的價(jià)值，往往是模具自身價(jià)值的幾十倍、上百倍。模具生產(chǎn)的工藝水平及科技含量的高低，已成為衡量一個(gè)國家科技與產(chǎn)品制造水平的重要標(biāo)志，它在很大程度上決定著產(chǎn)品的質(zhì)量、效益、新產(chǎn)品的開發(fā)能力，決定著一個(gè)國家制造業(yè)的國際競爭力。改革開放以來，我國模具工業(yè)發(fā)展迅猛。1996至2001年間，我國模具工業(yè)的產(chǎn)值年平均增長14%左右。目前，全國共有模具生產(chǎn)廠點(diǎn)1.7萬個(gè)，從業(yè)人員50多萬人。2001年全國模具工業(yè)總產(chǎn)值達(dá)300億元人民幣，我國模具年產(chǎn)值已位居世界第四。我國模具工業(yè)的技術(shù)水平近年來也取得了長足的進(jìn)步。大型、精密、復(fù)雜、高效和長壽命模具上了一個(gè)新臺(tái)階。大型復(fù)雜沖模以汽車覆蓋件模具為代表，已能生產(chǎn)部分新型轎車的覆蓋件模具。體現(xiàn)高水平制造技術(shù)的多工位級(jí)進(jìn)模的覆蓋面，已從電機(jī)、電器鐵芯片模具，擴(kuò)展到接插件、電子槍零件、空調(diào)器散熱片等家電零件模具。在大型塑料模具方面，已能生產(chǎn)48英寸電視的塑殼模具、6.5Kg大容量洗衣機(jī)全套塑料模具，以及汽車保險(xiǎn)杠、整體儀表板等模具。在精密塑料模具方面，已能生產(chǎn)照相機(jī)塑料模具、多型腔小模數(shù)齒輪模具及塑封模具等。在大型精密復(fù)雜壓鑄模方面，國內(nèi)已能生產(chǎn)自動(dòng)扶梯整體踏板壓鑄模及汽車后橋齒輪箱壓鑄模。其他類型的模具，例如子午線輪胎活絡(luò)模具、鋁合金和塑料門窗異型材擠出模等，也都達(dá)到了較高的水平，并可替代進(jìn)口模具。 目 錄一 引言3二 沖壓工藝分析5 2.1 產(chǎn)品結(jié)構(gòu)形狀分析5 2.2 產(chǎn)品尺寸，精度，粗糙度，斷面質(zhì)量分析5三 沖壓方案的確定5四 墊板沖模結(jié)構(gòu)的確定7 4.1 模具的形式7 4.2 定位裝置7 4.3 卸料裝置8 4.4 導(dǎo)向裝置8 4.5 模架8五 沖壓工藝的計(jì)算8 5.1 排樣8 5.2 計(jì)算沖壓力9 5.3 計(jì)算模具的壓力中心10 5.4 計(jì)算模具的刃口尺寸11六 墊板復(fù)合模主要零件的設(shè)計(jì)計(jì)算16 6.1 落料凹模16 6.2 沖孔凸模長度及強(qiáng)度校核18 6.3 卸料裝置19 6.4凸凹模長度確定，壁厚的校核 20七 模座的設(shè)計(jì)21 7.1 模座的材料21 7.2 上模座21 7.3 下模座21八 其他零件的選用22 8.1 導(dǎo)柱模架的選用22 8.2 導(dǎo)柱導(dǎo)套的選擇23 8.3 定位元件的選擇24 8.4 模柄的選擇25 8.5 螺釘?shù)倪x擇26 8.6 推桿的選擇27 8.7 頂桿的選擇27九 沖壓模具的安全技術(shù)28十 沖模的安裝28十一 模具的分析29十二 心得體會(huì)30參考文獻(xiàn) 31二 沖壓工藝分析： 2.1 產(chǎn)品結(jié)構(gòu)形狀分析 由零件圖可知，產(chǎn)品為長條板型落料，圓片及其他沖孔，對稱，有尖角?？着c孔之間，孔與邊緣之間的最小距離C滿足C1.5t的要求（C1.2） 2.2 產(chǎn)品尺寸，精度，粗超度，斷面質(zhì)量分析 1：尺寸精度 查磨具設(shè)計(jì)手冊得：由于沖裁件的厚度為0.8mm 取 TT8到IT9 2：產(chǎn)品材料分析： 對于沖壓材料一般要求的力學(xué)性能是強(qiáng)度低；塑性高；表面質(zhì)量和厚度公差符合國家標(biāo)準(zhǔn)。本設(shè)計(jì)是10號(hào)鋼，屬于優(yōu)質(zhì)碳素結(jié)構(gòu)鋼，是低碳鋼。其力學(xué)性能是強(qiáng)度，硬度低；塑性，韌性好。經(jīng)退火后，沖裁的加工方法是完全可是成形的。另外，產(chǎn)品對于表面質(zhì)量沒有嚴(yán)格要求，所以盡量選用國家標(biāo)準(zhǔn)板材，其沖裁出餓表面質(zhì)量就可以保證。 3：產(chǎn)量 要求能夠大批量生產(chǎn)，很適合采用沖壓加工的方法。最好采用復(fù)合模或級(jí)進(jìn)模。 三 沖壓工藝方案的確定 完成此工件需要沖孔，落料兩道工序。其加工 工藝方案可分為以下三種。 （一）: 第一種方案：采用單工序逐步加工 1：沖孔，落料單工序模。工序簡圖見1-1 2: 落料，沖孔單工序模。工序簡圖見1-2特點(diǎn)：由于采用單工序模，模具制造簡單，維修方便，但生產(chǎn)率低，工件精度低，不適合大批量生產(chǎn)。 圖1-11 沖孔2 落料 圖2-21 落料 2 沖孔（二） 第二種方案：采用復(fù)合模加工成形，工序圖見圖1-3 圖1-3 特點(diǎn)： 生產(chǎn)率高，工件精度高，但模具制造較復(fù)雜，調(diào)整維修較麻煩，使用壽命低。（三） 第三種方案： 采用連續(xù)模加工成形，工序圖見圖14 圖14 第二工位 第一工位 特點(diǎn)： 生產(chǎn)率高，便于實(shí)現(xiàn)機(jī)械化，自動(dòng)化，但模具制造復(fù)雜，調(diào)整維修麻煩，工件精度低。根據(jù)本零件的設(shè)計(jì)要求，以及各種方案的特點(diǎn)，決定采用第二種方案較合理。四 墊板沖模結(jié)構(gòu)的確定 4.1 模具的形式 復(fù)合模又可以分為正裝式復(fù)合模和倒裝式復(fù)合模。（1） 正裝式復(fù)合模的特點(diǎn)：工件和沖孔的廢料的將落在凹模的表面上。必須加以清除后才能進(jìn)行下一次沖裁。因此，操作不方便，也不安全，對多孔工件不宜采用。但沖出的零件平直度較高，適合沖裁材質(zhì)較軟，板料較薄的沖裁件，還可以沖裁孔邊距較小的沖裁件。（2） 倒裝式復(fù)合模的特點(diǎn):沖孔廢料由沖孔凸模沖入凹模洞中積聚到一定數(shù)量，由下模漏料孔排出，不必清楚廢料。操作方便，應(yīng)用很廣，并為機(jī)械化出件提供了有利條件。但工件表面平直度較差。凸凹模承受的張力較大。 經(jīng)分析，此工件為多孔沖裁件，若采用倒裝復(fù)合模，由于孔與孔之間的間距過小，采用倒裝復(fù)合模則模具去剛度不夠。因此本設(shè)計(jì)決定采用正裝復(fù)合模。 4.2 定位裝置 采用固定擋料銷擋料，在上模座卸料板上給出讓位孔。 采用導(dǎo)料螺栓橫向定位。因?yàn)樗慕Y(jié)構(gòu)簡單，使用方便，對模具強(qiáng)度削弱小。 4.3卸料裝置 1：條料的卸除 采用固定卸料板，因?yàn)槭钦b復(fù)合模，卸料板安裝在上模座。 2：工件的卸除 采用彈性頂件裝置將工件從下模座中頂出 3：沖孔廢料的卸除 采用打桿推件將上模座中廢料沖出 4.4導(dǎo)向零件 導(dǎo)向零件有許多種，如用導(dǎo)板導(dǎo)向，則模具安裝不方便，而且阻擋操作者的視線，所以不用。若用滾珠式導(dǎo)柱導(dǎo)套進(jìn)行導(dǎo)向，則雖然導(dǎo)向精度高，壽命長，但結(jié)構(gòu)比較復(fù)雜，也不采用。針對本零件精度要求不是很高（ IT8到IT9），采用滑動(dòng)式導(dǎo)柱導(dǎo)套進(jìn)行導(dǎo)向即可。而且模具在壓力機(jī)上的安裝比較簡單，操作又方便，還可以降低成本。 4.5模架 若采用中間模架，則導(dǎo)柱對稱分布滑動(dòng)平穩(wěn)，但只能向一個(gè)方向送料，阻擋操作者的視線，操作不便，適用于單工序模和工位少的級(jí)進(jìn)模。若采用后側(cè)導(dǎo)柱，則操作方便，結(jié)構(gòu)緊湊，適用于大件邊緣沖裁，但其平穩(wěn)性不夠，常用于小型沖模。四導(dǎo)柱模架剛性很好，導(dǎo)向平穩(wěn)可靠，但其價(jià)格較高，一般用于精密沖裁模。對角導(dǎo)柱模架即可橫向送料，又可縱向送料，適合各種沖裁模使用。 綜合上述特點(diǎn)和零件特點(diǎn)，本設(shè)計(jì)決定采用對角導(dǎo)柱模架，但為避免上下模座的方向裝錯(cuò)，兩導(dǎo)柱直徑制成一大一小。五 沖壓工藝的計(jì)算5.1 排樣 1 搭邊 查冷沖壓模具設(shè)計(jì) 確定搭邊值a,b 當(dāng)t=0.8mm 時(shí) a=1.8 b=1.5 2 條料的寬度 采用無側(cè)壓裝置，所以= 條料寬度的單向偏差，mm 查表的 -0.5 = 3 材料的利用率 = 式中 n板料上實(shí)際沖裁的零件數(shù)量 零件的實(shí)際面積 L板料長度，mm B板料寬度，mm 若取工件數(shù)量n=10, 則料長為 L=10D+9b+2b=1018+91.5+21.5=196.5 取L=197 條料的規(guī)格為 19755.60.8 材料的利用率為=85.7% 5.2 計(jì)算沖壓力 沖裁力公式 F= 式中 F沖裁力 沖孔沖裁力 落料沖裁力 1：沖孔沖裁力 =K 式中K系數(shù) 查表去K=1.3 沖孔周長 =122+6.5+5.2+6 =75.6 t材料厚度 t=0.8mm 材料抗剪強(qiáng)度，Mpa 查模具設(shè)計(jì)與制造簡明手冊 10號(hào)鋼，=260340 取=300Mpa =K=1.375.60.8300=23587 取=23.6KN 2: 落料沖裁力 = 式中 落料周長 =（18+52）2=140 = =1.31400.8300=43680取=43.7KN 3：卸料力 = 式中 卸料系數(shù) 查表得為0.04到0.05 取=0.05 =0.0543.7 =2.185KN 4: 推料力 =n 式中 推料系數(shù) 查表取=0.055 n同時(shí)卡在凹模內(nèi)的件數(shù) n=3 =n=0.05523.63=3.9KN 5: 頂件力 =（+） 式中 頂件系數(shù) 查表去=0.06 =（+）=0.06（23.6+43.7）=4.038KN 6：模具總壓力 沖裁時(shí)，壓力機(jī)的壓力值必須大于或等于沖裁各工藝的總和，即大于總的沖裁力。根據(jù)模具不同，計(jì)算公式不同。 當(dāng)采用彈性卸料裝置和下出料方式的沖裁模為 =+=23.6+43.7+2.185+3.9=77.285KN 7: 初選壓力機(jī) 根據(jù)=77.285KN 選公稱壓力為100KN的壓力機(jī) 5.3 計(jì)算模具的壓力中心 由于零件在垂直于進(jìn)料方向左右對稱，因此壓力中心在進(jìn)料方向的中心線上。 沖孔所需的沖裁力為 、 F= 根據(jù)理論力學(xué)知道，合力對某軸之力矩等于各分力對同軸力矩之和。由此苛求出壓力中心坐標(biāo)（ ） = 1.3（24+6.5）0.830038+1.35.20.830022+ 1.363000.830012= 2.4 計(jì)算得=29.54 得出壓力中心為（29.54 0） 5.3 計(jì)算模具刃口尺寸 尺寸計(jì)算原則： 在確定沖模凹模和凸模刃口尺寸時(shí)，必須遵循以下原則：1） 根據(jù)落料和沖孔的特點(diǎn)：落料件的尺寸取決于凹模尺寸，因此落料模應(yīng)先決定凹模尺寸。故沖孔模應(yīng)先決定凸模尺寸，用增大凹模尺寸來保證合理間隙。2） 根據(jù)凹凸模刃口的磨損規(guī)律。凹模刃口磨損后使落料件尺寸變大，其刃口的基本尺寸應(yīng)取接近或等于工件的最小極限尺寸，凸模刃口磨損后使沖孔孔徑減小，故應(yīng)使尺寸接近或等于工件的最大極限尺寸3） 考慮工件精度與模具精度間的關(guān)系，在確定模具制造公差時(shí)，既要保證工件的精度要求，又要保證有合理的間隙數(shù)值，一般沖模精度較工件精度高2到3級(jí) 1：沖孔凸模 = = 以上各式中 沖孔凸模的刃口尺寸 沖孔凹模的刃口尺寸 沖孔件的最小極限尺寸，mm 系數(shù) 工件孔徑公差，mm 凸模刃口尺寸制造偏差，mm 凹模刃口尺寸制造偏差，mm 凸凹模最小初始雙面間隙，mm 查表 =0.072 由于本零件沖孔數(shù)量為3個(gè) 且大小不一 ，因此要求計(jì)算3個(gè)凸模的刃口尺寸 1） 孔11： =2.5 查表 =0.75 =0.25 =0.072 = = 由于此凸模非標(biāo)準(zhǔn)件 根據(jù)=0.06 =2.5 = = =mm =mm 2: =12 查表 =0.5 =0.5 =0.072 = = 由于此凸模非標(biāo)準(zhǔn)件 根據(jù)=0.125 =12 = = =mm =mm3：=4 查表 =0.75 =0.3 =0.072 = = 由于此凸模非標(biāo)準(zhǔn)件 根據(jù)=0.075 =4 = = =mm =mm2）孔2 同上 ： = = =5.2 查表得 =0.15 =0.072 =0.02 =0.02 = = = 校核 查表得 =0.104 +=0.02+0.02 =0.04 =0.1040.072=0.032 +2.3mm 滿足最小壁厚 n的要求，設(shè)計(jì)合理。七 模座的設(shè)計(jì)7.1 模座的材料 一般選用鑄鐵HT200 HT250， 也可以選用A3,A5結(jié)構(gòu)鋼，本設(shè)計(jì)中從降低模具成本考慮，選用鑄鐵HT250材料。查沖壓模具標(biāo)準(zhǔn)件選用與設(shè)計(jì)指南，選用標(biāo)準(zhǔn)結(jié)構(gòu)。7.2上模座 采用滑動(dòng)導(dǎo)向模架 上模座做選用“1008025 GB/T2855.5” 7.3 下模座 下模座選用“1008032 GB/T2855.6” 八 其他零件的選用 8.1 導(dǎo)柱模架的選用 標(biāo)準(zhǔn)件的規(guī)格，1)導(dǎo)柱“20150 GB/T2861.1” 導(dǎo)套“3280 GB/T2861.6”2)導(dǎo)柱“18150 GB/T2861.1” 導(dǎo)套“2880 GB/T2861.6” 后側(cè)導(dǎo)柱模架 技術(shù)條件：按GB/T80501999的規(guī)定 模架220160I GB/T2851.3 I級(jí)精度的后導(dǎo)柱模架 1 上模座 2 導(dǎo)套 3 導(dǎo)柱 4 下模座 8.2 導(dǎo)柱導(dǎo)套的選擇 選用A型直導(dǎo)柱結(jié)構(gòu)，材料20鋼，熱處理要求；滲碳深度0.8-1.2mm,硬度58-62HRC。 技術(shù)標(biāo)準(zhǔn) ISO91822 本設(shè)計(jì)取直徑d=20mm和d=18mm，公差帶h6，長度L=140mm。 選用A型直滑動(dòng)導(dǎo)套結(jié)構(gòu)，材料，熱處理同上，技術(shù)標(biāo)準(zhǔn)ISO9448-2。如圖所示： 導(dǎo)柱 導(dǎo) 套 8.3 定位元件的選擇 為了保證模具正常工作，必須保證坯料或工件對模具處于正確的相對位置，即必須定位。 1） 在本設(shè)計(jì)中采用A型固定擋料銷， 如圖： 直徑d=6mm，長度L=8mm的彈簧彈頂擋料裝置A10JB/T7649.10 材料:45號(hào)鋼，熱處理4348HRC 技術(shù)條件：按JB/T76531994的規(guī)定 2） 采用側(cè)邊導(dǎo)料銷進(jìn)去送料方向的定位，保證垂直進(jìn)料方向的精度。 本設(shè)計(jì)采用A型導(dǎo)料銷。 長度d=6mm , L=22mm的 A型導(dǎo)料銷 622GB/T7648.7 材料 T8A, 熱處理硬度5256HRC 技術(shù)條件按JB/T76531994的規(guī)定 8.4 模柄的選擇 中小型模具一般是通過模柄將上模固定在壓力機(jī)滑塊上。模柄是作為上模與壓力機(jī)滑塊連接的零件。對它的基本要求是:一要與壓力機(jī)滑塊上的模柄正確配合，安全可靠；二是與上模正確而可靠連接。 在本設(shè)計(jì)中采用壓入式的模柄。 如圖：采用A型壓入式模柄 材料：Q235AF 技術(shù)條件：按GB/T76531994的規(guī)定直徑D=20的A型壓入式模柄模柄A3280GB/T7646.28.5 螺釘?shù)倪x擇本設(shè)計(jì)選用圓柱頭內(nèi)六角螺釘 材料 45 熱處理硬度 35-40HRC 技術(shù)條件按JB/T3098.32000的規(guī)定 8.6 推桿的選擇 本設(shè)計(jì)采用A型帶肩推桿 材料 45 熱處理硬度 43-48HRC 技術(shù)條件按JB/T76531994的規(guī)定 8.7 頂桿的選擇 頂桿655JB/T7650.3 材料 45 熱處理硬度 43-48HRC 技術(shù)條件按JB/T76531994的規(guī)定 九 沖壓模具的安全技術(shù) 在設(shè)計(jì)沖壓模具時(shí)，必須滿足下列要求：1. 模具結(jié)構(gòu)應(yīng)能保證操作方便，安全可靠，操作者勿需手，臂，頭伸入危險(xiǎn)區(qū)即可順利完成沖壓工作。2. 調(diào)試，安裝，修理，搬運(yùn)和儲(chǔ)藏方便安全，不會(huì)因模具結(jié)構(gòu)問題而引起意外事故3. 模具零件要有足夠的強(qiáng)度，材料選擇合理，模具應(yīng)避免有與機(jī)能無關(guān)的外部凸凹，外部應(yīng)倒棱；倒柱倒套應(yīng)遠(yuǎn)離操作者，模具壓力中心應(yīng)通過或靠近模柄中心線，導(dǎo)向定位等重要部件要使操作者能看清楚4. 設(shè)計(jì)模具時(shí)應(yīng)考慮安裝機(jī)械化裝置的位置，以便必要時(shí)機(jī)械化自動(dòng)化裝置代替手工操作5. 頂件器，推件器以及卸料板等結(jié)構(gòu)必須可靠6. 不使操作者有不安全的感覺 十 沖模的安裝 沖模的使用壽命，工作安全和沖件質(zhì)量等對于沖模的正確安裝有著極大的關(guān)系： 1：沖模應(yīng)正確安裝在壓力機(jī)上，使模具上下部分不發(fā)生偏斜和位移，這樣就可以保證模具有較高的準(zhǔn)確性，避免產(chǎn)生廢品，而且可以保證模具壽命 2: 模具安裝時(shí)將帶有導(dǎo)向的模具上下應(yīng)同時(shí)搬到工作臺(tái)面上。應(yīng)先固定上模，然后根據(jù)上模的位置固定下模 3：在沖壓生產(chǎn)過程中，由于壓力機(jī)振動(dòng)，可能引起固定沖模的緊固零件松動(dòng)。操作者必須隨時(shí)注意和檢查各緊固零件的工作狀況 十一 模具的分析 模具的裝配圖： 1 下模座 2 墊板 3凸模固定板 4凸模墊塊 5頂件塊 6凹模 7卸料板 8彈性橡膠 9凸凹模固定板 10墊板 11模柄 12打桿 13上模座 14 推板 15 推桿 16導(dǎo)套 17卸料螺釘 18 凸凹模 19 導(dǎo)柱 20 凸模（1） 21 凸模（2） 22凸模（3） 23 頂桿 24 夾板 25 螺桿 26 螺母 27 圓柱頭螺釘 28 圓柱銷 29 導(dǎo)料銷 30 固定擋料銷此正裝復(fù)合模設(shè)計(jì)工作時(shí)，板料以導(dǎo)料銷和擋料銷進(jìn)行定位。上模下壓，凸凹模外形和凹模進(jìn)行落料，落下的沖件卡在凹模中，同時(shí)沖孔凸模和凸凹模內(nèi)孔進(jìn)行沖孔，沖孔廢料卡在凸凹?？變?nèi)?？ㄔ诎寄Ｖ械臎_件由頂件裝置頂出，卡在凸凹模內(nèi)孔中的沖孔廢料由推桿頂出。該模具采用裝置下模座底下的彈頂器推動(dòng)頂桿和頂件塊，可獲得較大的頂件力。每沖裁一次，沖孔廢料被推出一次，凸凹?？變?nèi)不積存廢料。 十二 心得與體會(huì) 通過本次畢業(yè)設(shè)計(jì)，在理論知識(shí)的指導(dǎo)下，結(jié)合生產(chǎn)實(shí)習(xí)中所獲得的實(shí)踐經(jīng)驗(yàn)，在老師和同學(xué)的幫助下，認(rèn)真并獨(dú)立的完成了本次畢業(yè)設(shè)計(jì)。在本次設(shè)計(jì)的過程中，通過自己實(shí)際的操作計(jì)算，我對以前所學(xué)過的專業(yè)知識(shí)有了更進(jìn)一步，更深刻的認(rèn)識(shí)，同時(shí)也認(rèn)識(shí)到了自己的不足。 本次畢業(yè)設(shè)計(jì)歷時(shí)1個(gè)月左右，從分析領(lǐng)會(huì)畢業(yè)設(shè)計(jì)的要求，到拿出自己的方案，然后對自己手上的沖壓件的性能進(jìn)行分析計(jì)算，比如材料，形狀等。因此對要設(shè)計(jì)的沖壓件有了一個(gè)比較全面深刻的認(rèn)識(shí)，并在此基礎(chǔ)上綜合考慮生產(chǎn)中的各種實(shí)際因素，最后確定本次畢業(yè)設(shè)計(jì)的工藝方案。然后進(jìn)行排樣，沖壓力，壓力中心等的計(jì)算，直到模具總裝配圖的繪制，經(jīng)歷了大量的計(jì)算過程，查閱了很多相關(guān)的書籍資料。因此通過本次畢業(yè)設(shè)計(jì)的訓(xùn)練，也培養(yǎng)和鍛煉了一種自己查閱資料，獲取有價(jià)值信息的能力。 總之，通過本次畢業(yè)設(shè)計(jì)的鍛煉，使我對模具設(shè)計(jì)與模具制造的相關(guān)過程有了比較深刻的認(rèn)識(shí)和全面的掌握。認(rèn)真嚴(yán)謹(jǐn)?shù)耐瓿闪吮敬萎厴I(yè)設(shè)計(jì)也是大學(xué)四年里最后也最重要的一次設(shè)計(jì)。但是由于水平有限，錯(cuò)誤和不足之處在所難免，懇請各位老師批評指正，不勝感激。 參考文獻(xiàn) 1 翁其金，徐新成 沖壓工藝及沖模設(shè)計(jì) 機(jī)械工業(yè)出版社 2 于永泗 齊民 機(jī)械工程材料第五版 大連理工大學(xué)出版社 3 夏巨堪 李志剛 中國模具設(shè)計(jì)大典電子版 中國機(jī)械工程學(xué)會(huì) 4 中國磨具設(shè)計(jì)大典 第三卷 5 簡明冷沖壓手冊編寫租 簡明冷沖壓手冊 第三版 機(jī)械工業(yè)出版社 6 陳于萍 周兆元 互換性與測量技術(shù) 第二版 機(jī)械工業(yè)出版社 江西農(nóng)業(yè)大學(xué)畢業(yè)設(shè)計(jì)(論文)任務(wù)書設(shè)計(jì)（論文）課題名稱沖壓模具學(xué)生姓名黃旭院（系）工學(xué)院專 業(yè)機(jī)械設(shè)計(jì)制造及其自動(dòng)化指導(dǎo)教師胡淑芬職 稱副教授學(xué) 歷本科畢業(yè)設(shè)計(jì)（論文）要求：1 設(shè)計(jì)說明書按工學(xué)院規(guī)定的格式要求編寫。2 設(shè)計(jì)說明書編寫條理與順序清晰，并達(dá)到規(guī)定字?jǐn)?shù)。3 希望同學(xué)們能用proi等軟件制作模具裝配及工作動(dòng)畫。4 按院規(guī)定要求制作設(shè)計(jì)PP。畢業(yè)設(shè)計(jì)（論文）內(nèi)容與技術(shù)參數(shù)：1. 裝配圖按國標(biāo)要求繪制，左下角須是國標(biāo)的明細(xì)欄。2. 裝配圖的右上部繪制零件圖和排樣圖。3. 零件圖要標(biāo)注設(shè)計(jì)尺寸，下方須標(biāo)注零件材料及厚度。4. 排樣圖上須標(biāo)注條料的寬度、搭邊值、步距。(另還須在設(shè)計(jì)說明書中說明選擇的條料的規(guī)格)5. 裝配圖的中下處要用“技術(shù)要求”，字體及大小按國標(biāo)。6. 裝配圖上的每個(gè)零件必須按順序標(biāo)號(hào)(相同零件可不標(biāo)，但須在圖中及明細(xì)欄中標(biāo)明數(shù)量。7. 零件圖上的相關(guān)尺寸、形位公差及表面粗糙度必須標(biāo)注清晰。8. 如果該零件有熱處理要求及制作要求須在“技術(shù)要求”中說明。9. 在明細(xì)欄中標(biāo)明該零件的材料。畢業(yè)設(shè)計(jì)（論文）工作計(jì)劃：1查閱資料 共1周2編寫設(shè)計(jì)計(jì)算說明書（畢業(yè)論文）一份 共2周3繪制主要零件圖若干張 共2周4繪制裝配圖一套 共5周接受任務(wù)日期 2008 年 12 月 01 日 要求完成日期 2009 年 05 月 10 日學(xué) 生 簽 名 年 月 日指導(dǎo)教師簽名 年 月 日院長（主任）簽名 年 月 日 Int J Adv Manuf Technol (2002) 19:253259 2002 Springer-Verlag London Limited An Analysis of Draw-Wall Wrinkling in a Stamping Die Design F.-K. Chen and Y.-C. Liao Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan Wrinkling that occurs in the stamping of tapered square cups and stepped rectangular cups is investigated. A common characteristic of these two types of wrinkling is that the wrinkles are found at the draw wall that is relatively unsup- ported. In the stamping of a tapered square cup, the effect of process parameters, such as the die gap and blank-holder force, on the occurrence of wrinkling is examined using finite- element simulations. The simulation results show that the larger the die gap, the more severe is the wrinkling, and such wrinkling cannot be suppressed by increasing the blank-holder force. In the analysis of wrinkling that occurred in the stamping of a stepped rectangular cup, an actual production part that has a similar type of geometry was examined. The wrinkles found at the draw wall are attributed to the unbalanced stretching of the sheet metal between the punch head and the step edge. An optimum die design for the purpose of eliminating the wrinkles is determined using finite-element analysis. The good agreement between the simulation results and those observed in the wrinkle-free production part validates the accuracy of the finite-element analysis, and demonstrates the advantage of using finite-element analysis for stamping die design. Keywords: Draw-wall wrinkle; Stamping die; Stepped rec- tangular cup; Tapered square cups 1. Introduction Wrinkling is one of the major defects that occur in the sheet metal forming process. For both functional and visual reasons, wrinkles are usually not acceptable in a finished part. There are three types of wrinkle which frequently occur in the sheet metal forming process: flange wrinkling, wall wrinkling, and elastic buckling of the undeformed area owing to residual elastic compressive stresses. In the forming operation of stamp- ing a complex shape, draw-wall wrinkling means the occurrence Correspondence and offprint requests to: Professor F.-K. Chen, Depart- ment of Mechanical Engineering, National Taiwan University, No. 1 Roosevelt Road, Sec. 4, Taipei, Taiwan 10617. E-mail: fkchenL50560 w3.me.ntu.edu.tw of wrinkles in the die cavity. Since the sheet metal in the wall area is relatively unsupported by the tool, the elimination of wall wrinkles is more difficult than the suppression of flange wrinkles. It is well known that additional stretching of the material in the unsupported wall area may prevent wrinkling, and this can be achieved in practice by increasing the blank- holder force; but the application of excessive tensile stresses leads to failure by tearing. Hence, the blank-holder force must lie within a narrow range, above that necessary to suppress wrinkles on the one hand, and below that which produces fracture on the other. This narrow range of blank-holder force is difficult to determine. For wrinkles occurring in the central area of a stamped part with a complex shape, a workable range of blank-holder force does not even exist. In order to examine the mechanics of the formation of wrinkles, Yoshida et al. 1 developed a test in which a thin plate was non-uniformly stretched along one of its diagonals. They also proposed an approximate theoretical model in which the onset of wrinkling is due to elastic buckling resulting from the compressive lateral stresses developed in the non-uniform stress field. Yu et al. 2,3 investigated the wrinkling problem both experimentally and analytically. They found that wrinkling could occur having two circumferential waves according to their theoretical analysis, whereas the experimental results indi- cated four to six wrinkles. Narayanasamy and Sowerby 4 examined the wrinkling of sheet metal when drawing it through a conical die using flat-bottomed and hemispherical-ended punches. They also attempted to rank the properties that appeared to suppress wrinkling. These efforts are focused on the wrinkling problems associa- ted with the forming operations of simple shapes only, such as a circular cup. In the early 1990s, the successful application of the 3D dynamic/explicit finite-element method to the sheet- metal forming process made it possible to analyse the wrinkling problem involved in stamping complex shapes. In the present study, the 3D finite-element method was employed to analyse the effects of the process parameters on the metal flow causing wrinkles at the draw wall in the stamping of a tapered square cup, and of a stepped rectangular part. A tapered square cup, as shown in Fig. 1(a), has an inclined draw wall on each side of the cup, similar to that existing in a conical cup. During the stamping process, the sheet metal on the draw wall is relatively unsupported, and is therefore 254 F.-K. Chen and Y.-C. Liao Fig. 1. Sketches of (a) a tapered square cup and (b) a stepped rectangular cup. prone to wrinkling. In the present study, the effect of various process parameters on the wrinkling was investigated. In the case of a stepped rectangular part, as shown in Fig. 1(b), another type of wrinkling is observed. In order to estimate the effectiveness of the analysis, an actual production part with stepped geometry was examined in the present study. The cause of the wrinkling was determined using finite-element analysis, and an optimum die design was proposed to eliminate the wrinkles. The die design obtained from finite-element analy- sis was validated by observations on an actual production part. 2. Finite-Element Model The tooling geometry, including the punch, die and blank- holder, were designed using the CAD program PRO/ ENGINEER. Both the 3-node and 4-node shell elements were adopted to generate the mesh systems for the above tooling using the same CAD program. For the finite-element simul- ation, the tooling is considered to be rigid, and the correspond- ing meshes are used only to define the tooling geometry and Fig. 2. Finite-element mesh. are not for stress analysis. The same CAD program using 4- node shell elements was employed to construct the mesh system for the sheet blank. Figure 2 shows the mesh system for the complete set of tooling and the sheet-blank used in the stamping of a tapered square cup. Owing to the symmetric conditions, only a quarter of the square cup is analysed. In the simulation, the sheet blank is put on the blank-holder and the die is moved down to clamp the sheet blank against the blank-holder. The punch is then moved up to draw the sheet metal into the die cavity. In order to perform an accurate finite-element analysis, the actual stressstrain relationship of the sheet metal is required as part of the input data. In the present study, sheet metal with deep-drawing quality is used in the simulations. A tensile test has been conducted for the specimens cut along planes coinciding with the rolling direction (0) and at angles of 45 and 90 to the rolling direction. The average flow stress H9268, calculated from the equation H9268H11005(H9268 0 H11001 2H9268 45 H11001H9268 90 )/4, for each measured true strain, as shown in Fig. 3, is used for the simulations for the stampings of the tapered square cup and also for the stepped rectangular cup. All the simulations performed in the present study were run on an SGI Indigo 2 workstation using the finite-element pro- gram PAMFSTAMP. To complete the set of input data required Fig. 3. The stressstrain relationship for the sheet metal. Draw-Wall Wrinkling in a Stamping Die Design 255 for the simulations, the punch speed is set to 10 m s H110021 and a coefficient of Coulomb friction equal to 0.1 is assumed. 3. Wrinkling in a Tapered Square Cup A sketch indicating some relevant dimensions of the tapered square cup is shown in Fig. 1(a). As seen in Fig. 1(a), the length of each side of the square punch head (2W p ), the die cavity opening (2W d ), and the drawing height (H) are con- sidered as the crucial dimensions that affect the wrinkling. Half of the difference between the dimensions of the die cavity opening and the punch head is termed the die gap (G) in the present study, i.e. G H11005 W d H11002 W p . The extent of the relatively unsupported sheet metal at the draw wall is presumably due to the die gap, and the wrinkles are supposed to be suppressed by increasing the blank-holder force. The effects of both the die gap and the blank-holder force in relation to the occurrence of wrinkling in the stamping of a tapered square cup are investigated in the following sections. 3.1 Effect of Die Gap In order to examine the effect of die gap on the wrinkling, the stamping of a tapered square cup with three different die gaps of 20 mm, 30 mm, and 50 mm was simulated. In each simulation, the die cavity opening is fixed at 200 mm, and the cup is drawn to the same height of 100 mm. The sheet metal used in all three simulations is a 380 mm H11003 380 mm square sheet with thickness of 0.7 mm, the stressstrain curve for the material is shown in Fig. 3. The simulation results show that wrinkling occurred in all three tapered square cups, and the simulated shape of the drawn cup for a die gap of 50 mm is shown in Fig. 4. It is seen in Fig. 4 that the wrinkling is distributed on the draw wall and is particularly obvious at the corner between adjacent walls. It is suggested that the wrinkling is due to the large unsupported area at the draw wall during the stamping process, also, the side length of the punch head and the die cavity Fig. 4. Wrinkling in a tapered square cup (G H11005 50 mm). opening are different owing to the die gap. The sheet metal stretched between the punch head and the die cavity shoulder becomes unstable owing to the presence of compressive trans- verse stresses. The unconstrained stretching of the sheet metal under compression seems to be the main cause for the wrink- ling at the draw wall. In order to compare the results for the three different die gaps, the ratio H9252 of the two principal strains is introduced, H9252 being H9280 min /H9280 max , where H9280 max and H9280 min are the major and the minor principal strains, respectively. Hosford and Caddell 5 have shown that if the absolute value of H9252 is greater than a critical value, wrinkling is supposed to occur, and the larger the absolute value of H9252, the greater is the possibility of wrinkling. The H9252 values along the cross-section MN at the same drawing height for the three simulated shapes with different die gaps, as marked in Fig. 4, are plotted in Fig. 5. It is noted from Fig. 5 that severe wrinkles are located close to the corner and fewer wrinkles occur in the middle of the draw wall for all three different die gaps. It is also noted that the bigger the die gap, the larger is the absolute value of H9252. Consequently, increasing the die gap will increase the possibility of wrinkling occurring at the draw wall of the tapered square cup. 3.2 Effect of the Blank-Holder Force It is well known that increasing the blank-holder force can help to eliminate wrinkling in the stamping process. In order to study the effectiveness of increased blank-holder force, the stamping of a tapered square cup with die gap of 50 mm, which is associated with severe wrinkling as stated above, was simulated with different values of blank-holder force. The blank-holder force was increased from 100 kN to 600 kN, which yielded a blank-holder pressure of 0.33 MPa and 1.98 MPa, respectively. The remaining simulation conditions are maintained the same as those specified in the previous section. An intermediate blank-holder force of 300 kN was also used in the simulation. The simulation results show that an increase in the blank- holder force does not help to eliminate the wrinkling that occurs at the draw wall. The H9252 values along the cross-section Fig. 5. H9252-value along the cross-section MN for different die gaps. 256 F.-K. Chen and Y.-C. Liao MN, as marked in Fig. 4, are compared with one another for the stamping processes with blank-holder force of 100 kN and 600 kN. The simulation results indicate that the H9252 values along the cross-section MN are almost identical in both cases. In order to examine the difference of the wrinkle shape for the two different blank-holder forces, five cross-sections of the draw wall at different heights from the bottom to the line M N, as marked in Fig. 4, are plotted in Fig. 6 for both cases. It is noted from Fig. 6 that the waviness of the cross-sections for both cases is similar. This indicates that the blank-holder force does not affect the occurrence of wrinkling in the stamp- ing of a tapered square cup, because the formation of wrinkles is mainly due to the large unsupported area at the draw wall where large compressive transverse stresses exist. The blank- holder force has no influence on the instability mode of the material between the punch head and the die cavity shoulder. 4. Stepped Rectangular Cup In the stamping of a stepped rectangular cup, wrinkling occurs at the draw wall even though the die gaps are not so significant. Figure 1(b) shows a sketch of a punch shape used for stamping a stepped rectangular cup in which the draw wall C is followed by a step DE. An actual production part that has this type of geometry was examined in the present study. The material used for this production part was 0.7 mm thick, and the stress strain relation obtained from tensile tests is shown in Fig. 3. The procedure in the press shop for the production of this stamping part consists of deep drawing followed by trimming. In the deep drawing process, no draw bead is employed on the die surface to facilitate the metal flow. However, owing to the small punch corner radius and complex geometry, a split occurred at the top edge of the punch and wrinkles were found to occur at the draw wall of the actual production part, as shown in Fig. 7. It is seen from Fig. 7 that wrinkles are distributed on the draw wall, but are more severe at the corner edges of the step, as marked by AD and BE in Fig. 1(b). The metal is torn apart along the whole top edge of the punch, as shown in Fig. 7, to form a split. In order to provide a further understanding of the defor- mation of the sheet-blank during the stamping process, a finite- element analysis was conducted. The finite-element simulation was first performed for the original design. The simulated shape of the part is shown from Fig. 8. It is noted from Fig. 8 that the mesh at the top edge of the part is stretched Fig. 6. Cross-section lines at different heights of the draw wall for different blank-holder forces. (a) 100 kN. (b) 600 kN. Fig. 7. Split and wrinkles in the production part. Fig. 8. Simulated shape for the production part with split and wrinkles. significantly, and that wrinkles are distributed at the draw wall, similar to those observed in the actual part. The small punch radius, such as the radius along the edge AB, and the radius of the punch corner A, as marked in Fig. 1(b), are considered to be the major reasons for the wall breakage. However, according to the results of the finite- element analysis, splitting can be avoided by increasing the above-mentioned radii. This concept was validated by the actual production part manufactured with larger corner radii. Several attempts were also made to eliminate the wrinkling. First, the blank-holder force was increased to twice the original value. However, just as for the results obtained in the previous section for the drawing of tapered square cup, the effect of blank-holder force on the elimination of wrinkling was not found to be significant. The same results are also obtained by increasing the friction or increasing the blank size. We conclude that this kind of wrinkling cannot be suppressed by increasing the stretching force. Since wrinkles are formed because of excessive metal flow in certain regions, where the sheet is subjected to large com- pressive stresses, a straightforward method of eliminating the wrinkles is to add drawbars in the wrinkled area to absorb the redundant material. The drawbars should be added parallel to the direction of the wrinkles so that the redundant metal can be absorbed effectively. Based on this concept, two drawbars are added to the adjacent walls, as shown in Fig. 9, to absorb the excessive material. The simulation results show that the Draw-Wall Wrinkling in a Stamping Die Design 257 Fig. 9. Drawbars added to the draw walls. wrinkles at the corner of the step are absorbed by the drawbars as expected, however some wrinkles still appear at the remain- ing wall. This indicates the need to put more drawbars at the draw wall to absorb all the excess material. This is, however, not permissible from considerations of the part design. One of the advantages of using finite-element analysis for the stamping process is that the deformed shape of the sheet blank can be monitored throughout the stamping process, which is not possible in the actual production process. A close look at the metal flow during the stamping process reveals that the sheet blank is first drawn into the die cavity by the punch head and the wrinkles are not formed until the sheet blank touches the step edge DE marked in Fig. 1(b). The wrinkled shape is shown in Fig. 10. This provides valuable information for a possible modification of die design. An initial surmise for the cause of the occurrence of wrink- ling is the uneven stretch of the sheet metal between the punch corner radius A and the step corner radius D, as indicated in Fig. 1(b). Therefore a modification of die design was carried out in which the step corner was cut off, as shown in Fig. 11, so that the stretch condition is changed favourably, which allows more stretch to be applied by increasing the step edges. However, wrinkles were still found at the draw wall of the cup. This result implies that wrinkles are introduced because of the uneven stretch between the whole punch head edge and the whole step edge, not merely between the punch corner and Fig. 10. Wrinkle formed when the sheet blank touches the stepped edge. Fig. 11. Cut-off of the stepped corner. the step corner. In order to verify this idea, two modifications of the die design were suggested: one is to cut the whole step off, and the other is to add one more drawing operation, that is, to draw the desired shape using two drawing operations. The simulated shape for the former method is shown in Fig. 12. Since the lower step is cut off, the drawing process is quite similar to that of a rectangular cup drawing, as shown in Fig. 12. It is seen in Fig. 12 that the wrinkles were eliminated. In the two-operation drawing process, the sheet blank was first drawn to the deeper step, as shown in Fig. 13(a). Sub- sequently, the lower step was formed in the second drawing operation, and the desired shape was then obtained, as shown in Fig. 13(b). It is seen clearly in Fig. 13(b) that the stepped rectangular cup can be manufactured without wrinkling, by a two-operation drawing process. It should also be noted that in the two-operation drawing process, if an opposite sequence is applied, that is, the lower step is formed first and is followed by the drawing of the deeper step, the edge of the deeper step, as shown by AB in Fig. 1(b), is prone to tearing because the metal cannot easily flow over the lower step into the die cavity. The finite-element simulations have indicated that the die design for stamping the desired stepped rectangular cup using one single draw operation is barely achieved. However, the manufacturing cost is expected to be much higher for the two- operation drawing process owing to the additional die cost and operation cost. In order to maintain a lower manufacturing cost, the part design engineer made suitable shape changes, and modified the die design according to the finite-element Fig. 12.