鑰匙毛坯沖壓模具設(shè)計(jì)【說(shuō)明書(shū)+CAD】,說(shuō)明書(shū)+CAD,鑰匙毛坯沖壓模具設(shè)計(jì)【說(shuō)明書(shū)+CAD】,鑰匙,毛坯,沖壓,模具設(shè)計(jì),說(shuō)明書(shū),仿單,cad 附件三： 紫瑯職業(yè)技術(shù)學(xué)院 畢業(yè)設(shè)計(jì)任務(wù)書(shū) 系部名稱(chēng) 機(jī)電工程系 專(zhuān)業(yè)班級(jí) 模具 3091 學(xué)生姓名 林威 指導(dǎo)教師姓名 程洋 設(shè)計(jì)題目 鑰匙毛坯沖壓模具設(shè)計(jì) 撰寫(xiě)畢業(yè)論文的目的 撰寫(xiě)畢業(yè)設(shè)計(jì)的目的是總結(jié)和檢驗(yàn)學(xué)生在學(xué)校期間的學(xué)習(xí)成果，培養(yǎng)學(xué)生綜合運(yùn)用所學(xué)的專(zhuān)業(yè)知識(shí)以及專(zhuān)業(yè)技能進(jìn)行獨(dú)立分析和解決問(wèn)題的能力，使學(xué)生受到科學(xué)研究的基本訓(xùn)練，達(dá)到專(zhuān)業(yè)素質(zhì)培養(yǎng)目標(biāo)的要求。通過(guò)撰寫(xiě)畢業(yè)設(shè)計(jì)強(qiáng)化學(xué)生對(duì)專(zhuān)業(yè)理論知識(shí)和專(zhuān)業(yè)技能的理解和掌握,培養(yǎng)學(xué)生收集資料和調(diào)查研究的能力、培養(yǎng)學(xué)生進(jìn)行專(zhuān)業(yè)理論分析及論證的能力。 撰寫(xiě)畢業(yè)論文要求 1. 要求一定要有結(jié)合實(shí)際的對(duì)某具體課題進(jìn)行有獨(dú)立見(jiàn)解的設(shè)計(jì),并要求有一定的技術(shù)含量；. 2 . 設(shè)計(jì)應(yīng)該在所規(guī)定的時(shí)限內(nèi)完成； 3. 書(shū)面材料、框架及字?jǐn)?shù)應(yīng)符合規(guī)定； 4. 學(xué)會(huì)查閱有關(guān)的技術(shù)資料和相關(guān)的規(guī)范； 5 .掌握相關(guān)規(guī)范的選擇和運(yùn)用； 撰寫(xiě)畢業(yè)論文進(jìn)度安排 2011年11月中旬—12月上旬 依照任務(wù)書(shū)閱讀文獻(xiàn)，收集資料準(zhǔn)備草案 2011年12月上旬—12月中旬 確定方案，編寫(xiě)設(shè)計(jì)開(kāi)題報(bào)告，并交老師審核 2011年12月中旬—2012年3月中旬 完成初稿，交老師審核。 2012年3月中旬—4月下旬 完成二稿，交老師審核 2012年4月下旬—5月下旬 定稿并提交畢業(yè)設(shè)計(jì)相關(guān)資料，準(zhǔn)備答辯 2012年6月2日—6月3日 答辯 紫瑯職業(yè)技術(shù)學(xué)院 2012屆模具專(zhuān)業(yè)畢業(yè)設(shè)計(jì)開(kāi)題報(bào)告 姓名 林威 系部 機(jī)電工程系 專(zhuān)業(yè) 模具設(shè)計(jì)與制造 班級(jí) 模具3091 題目 鑰匙毛坯沖壓模具設(shè)計(jì) 一、選題背景、目的及意義 背景：鑰匙是與我們每個(gè)人生活息息相關(guān)的工具。隨著社會(huì)不停發(fā)展，鑰匙也越具特色。由于學(xué)校組織的崗位實(shí)習(xí)是在工廠的模具房實(shí)習(xí)，恰巧又以沖壓模具居多，所以就了解熟悉了沖壓模。 目的:在畢業(yè)之前自己設(shè)計(jì)一副模具，以便檢驗(yàn)自己三年所掌握的知識(shí)水平。 意義：鍛煉了自己的能力，也是為自己在大學(xué)所學(xué)的專(zhuān)業(yè)知識(shí)做總結(jié)。 二、主要內(nèi)容及提綱 摘 要 目 錄 1、沖壓模具的設(shè)計(jì)步驟 1.1分析沖壓件零件圖 1.2選擇卸料方案 1.3工藝方案的確定 2.1合理的排樣 2.2模具結(jié)構(gòu)設(shè)計(jì)與工作過(guò)程 3、工作零件的加工 3.1模具的主要部分及加工 3.4沖壓力計(jì)算及壓力機(jī)選擇 3.3組裝工藝要求 4.定位裝置的確定 4.3選擇模架及其他模架零件 致 謝 參考文獻(xiàn) 三、主要方法和措施 對(duì)鑰匙外形進(jìn)行分析，采用倒裝復(fù)合模的加工工藝，通過(guò)合理的排樣與沖壓力的計(jì)算，進(jìn)行了模具結(jié)構(gòu)設(shè)計(jì)以及注意問(wèn)題。實(shí)踐證明，該模具沖出來(lái)的零件毛刺小，斷面平整光滑，生產(chǎn)率高，成本低，達(dá)到了預(yù)期目的。 四、主要參考文獻(xiàn) （1） 《冷沖壓工藝與模具設(shè)計(jì)》 中國(guó)勞動(dòng)社會(huì)保障出版社。2006 （2） 《冷沖模設(shè)計(jì)》中國(guó)勞動(dòng)社會(huì)保障出版社。1998 （3） 《冷沖壓技術(shù)問(wèn)答》 機(jī)械工業(yè)出版社。2004 （4） 《沖模設(shè)計(jì)編寫(xiě)組》 機(jī)械工業(yè)出版社。2007 （5） 《冷沖壓技術(shù)》 機(jī)械工業(yè)出版社。2000 （6） 《沖壓模具設(shè)計(jì)與制造》 高等教育出版社。2002 五、畢業(yè)設(shè)計(jì)推進(jìn)計(jì)劃 2011年11月中旬—12月上旬 依照任務(wù)書(shū)閱讀文獻(xiàn)，收集資料準(zhǔn)備草案 2011年12月上旬—12月中旬 確定方案，編寫(xiě)設(shè)計(jì)開(kāi)題報(bào)告，并交老師審核 2011年12月中旬—2012年3月中旬 完成初稿，交老師審核。 2012年3月中旬—4月下旬 完成二稿，交老師審核 2012年4月下旬—5月下旬 定稿并提交畢業(yè)設(shè)計(jì)相關(guān)資料，準(zhǔn)備答辯 2012年6月2日—6月3日 答辯 學(xué)生簽名： 2011 年12 月16 日 指導(dǎo)教師意見(jiàn)（對(duì)選題的有效性、研究方法的正確性、課題的廣度、深度的意見(jiàn)及開(kāi)題是否通過(guò)）： 通過(guò)（ ） 修改后通過(guò) （ ） 未通過(guò) （ ） 指導(dǎo)教師簽名： 2011 年 12 月 16日 注：開(kāi)題報(bào)告裝訂在畢業(yè)設(shè)計(jì)（論文）任務(wù)書(shū)后 開(kāi)題是否通過(guò)請(qǐng)指導(dǎo)教師在括號(hào)內(nèi)打“ √” 紫瑯職業(yè)技術(shù)學(xué)院 畢業(yè)設(shè)計(jì) 題 目： 鑰匙毛坯沖壓模具設(shè)計(jì) 副 標(biāo) 題： 學(xué) 生 姓 名： 林威 所在系、專(zhuān)業(yè)： 機(jī)電工程系,模具設(shè)計(jì)與制造 班 級(jí)： 模具3091 指 導(dǎo) 教 師： 程洋 日 期： 2012年5月29日 I 摘 要 摘 要 本文主要根據(jù)鑰匙的形狀及工藝特點(diǎn)，分析了工序集中的可能性，提出制造鑰匙外形的工藝方案，介紹了復(fù)合模的結(jié)構(gòu)及設(shè)計(jì)中應(yīng)注意的問(wèn)題。由于學(xué)校大部分的學(xué)生對(duì)鑰匙的需求量都很大，因此設(shè)計(jì)出一份合理的鑰匙外形模具很有現(xiàn)實(shí)意義 關(guān)鍵詞：間隙沖裁 沖孔落料 工藝分析 I 目 錄 目 錄 摘 要 I 目 錄 I 1、鑰匙模具分析 1 1.1分析零件圖 1 1.1.1分析模具的結(jié)構(gòu) 1 1.1.2制定沖壓方案 1 1.1.3設(shè)計(jì)工藝方案 1 1.2卸料方案的確定 1 1.2.1彈性卸料方式 1 1.2.2模具設(shè)計(jì)計(jì)算 2 1.2.3制作圖紙 2 1.3工藝方案的確定 2 1.3.1方案選擇 2 2、排樣 3 2.1合理的排樣 3 2.1.1排樣方式的確立 3 2.1.2 鑰匙零件圖 3 2.2模具結(jié)構(gòu)設(shè)計(jì) 4 2.2.1模具結(jié)構(gòu)設(shè)計(jì) 4 2.3 模具工作過(guò)程 4 3、工作零件的結(jié)構(gòu) 5 3.1模具的主要部分 5 3.2凹模結(jié)構(gòu) 5 3.3凸模結(jié)構(gòu) 7 3.4沖壓力計(jì)算及壓力機(jī)選擇 8 3.5凸凹模刃口尺寸計(jì)算方法 9 3.6模具工作過(guò)程 11 3.3組裝工藝要求 11 3.3.1選擇基準(zhǔn)件 11 3.3.2組建裝配 11 3.3.3總體裝配 11 4.定位裝置的確定 12 4.1壓力中心計(jì)算 12 4.2裝配原則 12 4.3選擇模架及其他模架零件 12 4.3.1模架 12 4.3.2墊板 12 4.4試驗(yàn) 12 致 謝 13 參考文獻(xiàn) 14 I 鑰匙毛坯沖壓模具設(shè)計(jì) 1、鑰匙模具分析 1.1分析零件圖 1.1.1分析模具的結(jié)構(gòu) 產(chǎn)品零件圖是制定沖壓工藝方案和模具設(shè)計(jì)的重要依據(jù)，制定沖壓工藝要從分析產(chǎn)品的零件圖入手。分析零件圖包括技術(shù)性和經(jīng)濟(jì)性兩個(gè)方面： 1. 根據(jù)沖壓件的生產(chǎn)綱領(lǐng)，分析產(chǎn)品的成本，闡明采用沖壓生產(chǎn)可采取的經(jīng)濟(jì)效益。 2. 沖壓件的工藝性是指該零件沖壓加工的難易程度。在技術(shù)方面，主要分析該零件的形狀特點(diǎn)、尺寸大小、精度要求和材料性能等因素是否符合沖壓工藝的特點(diǎn)。如果發(fā)現(xiàn)沖壓工藝性差，則需要對(duì)沖壓件產(chǎn)品提出修改意見(jiàn) 1.1.2制定沖壓方案 1．在分析了沖壓件的工藝性質(zhì)后，通常在對(duì)工序性質(zhì)、工序數(shù)目、工序順序及組合方式基礎(chǔ)上，制定幾種不同的沖壓工藝方案。 2．從產(chǎn)品質(zhì)量、生產(chǎn)效率、設(shè)備占用情況、模具制造的難易程度和使用壽命高低、工藝成本、操作方便和安全程度等方面進(jìn)行綜合考慮，比較，最后確定經(jīng)濟(jì)合理的工藝方案。 1.1.3設(shè)計(jì)工藝方案 依據(jù)所確定的零件成形的總體方案，確定沖壓工序的工藝方案。沖壓工序的工藝方案的內(nèi)容如下： 1 確定完成本工序成形的加工方法； 2 確定本工序的主要工藝參數(shù)； 3 根據(jù)各沖壓工序的成形極限，進(jìn)行必要的工藝設(shè)計(jì)； 4 確定各工序的成形力； 5 計(jì)算并確定每個(gè)工序的形狀和尺寸、繪出各工序圖。 1.2卸料方案的確定 1.2.1彈性卸料方式 為了將沖壓后卡篩在凸模上、凸凹模上的制件或廢料卸掉，將制件從凹模中推出來(lái)，以保證下次沖壓正常進(jìn)行，設(shè)計(jì)模具時(shí)，必須正確選擇卸料方式和裝置。 對(duì)于沖裁料厚度在0.8mm-1.5mm下并且要求沖裁件比較平整的，可選用彈性卸料方式；卸料裝置設(shè)計(jì)的是否正確，直接影響工件的質(zhì)量、生產(chǎn)效率和操作安全程度 1.2.2模具設(shè)計(jì)計(jì)算 計(jì)算或估算模具各主要零件（凹模、凸模固定板、墊板、凸模、打料板）的外形尺寸，并確定標(biāo)準(zhǔn)模架以及卸料橡膠或彈簧的自由高度。 確定凸、凹模的間隙，計(jì)算凸、凹模工作部分尺寸 1.2.3制作圖紙 根據(jù)分析、計(jì)算及圖形繪制本產(chǎn)品的設(shè)計(jì)說(shuō)明書(shū)。 本次設(shè)計(jì)一套沖孔、落料的模具。經(jīng)過(guò)查閱資料，首先要對(duì)零件進(jìn)行工藝分析，經(jīng)過(guò)工藝分析和對(duì)比，采用沖孔落料工序，通過(guò)沖裁力、頂件力、卸料力等計(jì)算，確定壓力機(jī)的型號(hào)。再分析對(duì)沖壓件加工的模具適用類(lèi)型選擇所需設(shè)計(jì)的模具。得出將設(shè)計(jì)的模具類(lèi)型后將模具的各工作零部件設(shè)計(jì)過(guò)程表達(dá)出來(lái)。 1.3工藝方案的確定 1.3.1方案選擇 上述零件看該零件圖看，加工該零件的一般的方法即是采用先沖孔，后落料兩道工序內(nèi)容。但由于用級(jí)進(jìn)模沖壓時(shí)，進(jìn)料過(guò)程中零件中間有一個(gè)直徑4的孔,在模具中的位置不能保證，還對(duì)材料的寬度的要求較嚴(yán)格。 用倒裝復(fù)合模，即一次行程中在模具的同一部位可以同時(shí)完成幾道工序，減少了工序數(shù)量和模具數(shù)量，減少操作人員和設(shè)備占用量，減低生產(chǎn)成本。該種模具對(duì)板料定位精度要求比級(jí)進(jìn)模低，沖模的輪廓尺寸較小，沖出的沖件平整度較高。適用于像鑰匙外形這樣形狀的零件而且沖出后尺寸精度和表面質(zhì)量都能滿足以上工序分析中的要求。經(jīng)過(guò)對(duì)該零件的工藝分析以及生產(chǎn)實(shí)踐，應(yīng)選擇后者。 2、排樣 2.1合理的排樣 2.1.1排樣方式的確立 設(shè)計(jì)條料排樣圖,要考慮到材料的利用率及板料的纖維方向。因?yàn)榱慵男螤顬檠?，因此可采用有廢料排樣。 圖1排樣圖 .影響排樣形式的因素 (1)零件的形狀。零件的合理排樣與其形狀有密切關(guān)系，例如圓形零件不可能實(shí)現(xiàn)無(wú)廢料排樣。在使用條件許可時(shí)，也可改變零件形狀，以設(shè)計(jì)最佳排樣方式。 (2)零件的斷面質(zhì)量、精度要求。當(dāng)零件的斷面質(zhì)量和尺寸精度要求較高且形狀較復(fù)雜時(shí)，應(yīng)采用有廢料排樣形式。 (3)沖模結(jié)構(gòu)。有廢料排樣的沖模結(jié)構(gòu)比較復(fù)雜。少、無(wú)廢料排樣沖裁多用連續(xù)模、導(dǎo)板模，當(dāng)零件孔與外形相對(duì)位置公差很小時(shí)，可用復(fù)合模。在無(wú)廢料沖裁中，多數(shù)凸模單面切割，受到很大的側(cè)向力，為此，凸模側(cè)面要有支撐結(jié)構(gòu)零件，如反側(cè)壓擋塊。 (4)模具壽命。有廢料排樣模具全部刃口參與沖裁，受力均勻，模壽命較高；少、無(wú)廢料排樣凸模單面切割，有時(shí)毛刺會(huì)被凸模帶入間隙，導(dǎo)致模具壽命較短。 (5)操作的方便與安全。有廢料排樣模具的零部件較為安全，操作方便、安全；少、無(wú)廢料排樣的模具結(jié)構(gòu)簡(jiǎn)單，操作時(shí)往往欠方便與安全。 (6)生產(chǎn)率。有的少、無(wú)廢料排樣模具一次沖裁可獲得兩個(gè)以上的零件，有利于提高生產(chǎn)率。 2.1.2 鑰匙零件圖 材料的選擇 根據(jù)使用要求，如圖2所示，材料為1Cr18Ni9,（不銹剛）厚度為0.5㎜。零件成形后要求有精確的尺寸及較小的表面粗糙度值。 （2）沖孔工藝的確定，考慮到Φ4孔是起懸掛作用，因此對(duì)孔的精度與位置要求并不高，一般沖孔方案就可以滿足要求。因受凸模強(qiáng)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(qiáng)度和模具結(jié)構(gòu)等 圖2 零件圖 2.2模具結(jié)構(gòu)設(shè)計(jì) 2.2.1模具結(jié)構(gòu)設(shè)計(jì) 模具在設(shè)計(jì)制造過(guò)程中本生精度要比產(chǎn)品進(jìn)度高。只有提高了模具精度才能近一步提高產(chǎn)品精度 零件質(zhì)量與模具結(jié)構(gòu)以及工作零件精度有關(guān)，合理的模具結(jié)構(gòu)是制造合格零件的關(guān)鍵之一。因此，根據(jù)具體的零件形狀、尺寸以及材料，必須要合理設(shè)計(jì)模具結(jié)構(gòu)。根據(jù)以上工藝分析，設(shè)計(jì)了倒裝復(fù)合模，模具結(jié)構(gòu)如圖3所示 2.3 模具工作過(guò)程 模具的沖孔凸模和落料凹模裝在上模，凸凹模裝在下模上。所以由其結(jié)構(gòu)我們可以看出，該模具屬于倒裝式復(fù)合模。 如圖所示，該模具處于閉合位置。當(dāng)沖模開(kāi)始運(yùn)行的時(shí)候，滑塊的移動(dòng)會(huì)帶動(dòng)其模柄向上運(yùn)動(dòng)，與模柄連接的上模座會(huì)與墊板、凸模固定板、凸模、凹模、推件塊等相關(guān)零件發(fā)生聯(lián)鎖的向上運(yùn)動(dòng)，自動(dòng)送料裝置將條料送到模具的正確位置。模具中導(dǎo)料銷(xiāo)和擋料銷(xiāo)與加工條料相接觸，對(duì)條料起到固定和導(dǎo)向的作用，這樣可以確保其在沖壓時(shí)處于正確的位置且不發(fā)生位移。壓力機(jī)帶動(dòng)滑塊向下運(yùn)動(dòng)，這時(shí)卸料板和凹模將毛坯固定壓緊，接著就開(kāi)始沖裁。被沖下來(lái)的毛坯材料會(huì)被凸凹模壓在孔內(nèi)，而外部的毛坯材料則在凸凹模上被壓緊。然后，沖床滑塊開(kāi)始它的回程運(yùn)動(dòng)。坯料會(huì)在彈簧的作用下，通過(guò)卸料板推出凸凹模，剩下工件則被留在了凹模的孔內(nèi)。當(dāng)推桿接觸到?jīng)_床的打料橫梁后，會(huì)向下移動(dòng)帶動(dòng)推板，推板則會(huì)推動(dòng)推銷(xiāo)向下運(yùn)動(dòng)，而推銷(xiāo)會(huì)推動(dòng)推件塊向下運(yùn)動(dòng)，最終將工件從凹?？字许敵雎湎?。 3、工作零件的結(jié)構(gòu) 3.1模具的主要部分 凸模和凹模分開(kāi)加工 一般在制造的沖裁模批量較大時(shí)采用此種方法,在這種情況下,需要分別計(jì)算和標(biāo)注凸模和凹模的尺寸和公差,落料時(shí),間隙取在凸模上. 圖3模具圖 1.上模座2導(dǎo)柱3凹模4凸凹模5下模座6銷(xiāo)釘7凸模8銷(xiāo)釘9螺釘10凹模11導(dǎo)柱12固定板 3.2凹模結(jié)構(gòu) 圖4凹模及加工步驟 工序號(hào) 工序名稱(chēng) 工序內(nèi)容 設(shè)備 1 備料 將毛坯鍛成 2 熱處理 退火 3 銑 銑六面,厚度留單邊磨量0.2~0.3mm 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(xiāo)孔位置劃漏孔輪廓線 6 鉗工 加工好凸模,配作沖孔凹模達(dá)要求 7 銑 銑漏料孔達(dá)要求 銑床 8 鉗工 鉆鉸6×φ10,鉆攻4XM12 鉆床 9 熱處理 淬火,回火,保證HRC60~62 10 平磨 磨厚度及基面達(dá)到要求 平面磨床 11 線切割 按圖切割各型孔,留0.005~0.01單邊研量 線切割機(jī)床 12 鉗工 研光各型孔達(dá)要求 13 檢驗(yàn) 確定模板尺寸 1) 凹模的厚度： H=Kb 式中 b— 凹?？椎淖畲髮挾?(mm ) K― 系數(shù) H― 凹模厚度 通過(guò)差表 可得凹模厚度 通過(guò)凹模板的確定，可算出其他板的厚度 包括 下模座厚度 導(dǎo)向板厚度 凸模固定板厚度 墊板厚度 上模座厚度 2﹚可得模板尺寸及其它零件： 下模座 凹模板 導(dǎo)向板 凸模固定板 墊板 上模座 3)．選用標(biāo)準(zhǔn)螺釘： 凹模采用整體式凹模，為了制造方便各沖裁的凹模孔均可以采用線切割中走絲加工，也可以保證精度 3.3凸模結(jié)構(gòu) 圖5凸模 凸模材料為Cr12，加工時(shí)應(yīng)先按圖紙要求加工臺(tái)階孔，應(yīng)注意刃口部分先打φ4的小孔，然后進(jìn)行熱處理達(dá)到要求，利用線切割加工刃口部分達(dá)到圖樣要求 3.4沖壓力計(jì)算及壓力機(jī)選擇 根據(jù)沖裁力計(jì)算公式為 模具采用彈性卸料裝置和推件結(jié)構(gòu)，根據(jù)所需卸料力和推件力 根據(jù)計(jì)算得出數(shù)據(jù),查表可知所需沖壓力,可選設(shè)備為開(kāi)式壓力機(jī)J23—35 3.5凸凹模刃口尺寸計(jì)算方法 由于加工模具的方法不同，凸模與凹模刃口部分尺寸的計(jì)算公式與制造公差的標(biāo)注也不同，刃口尺寸的計(jì)算方法可分為以下兩種情況：凹模與凸模分開(kāi)加工，凸模和凹模配合加工，從此工件的結(jié)構(gòu)上分析，選擇凸模與凹模分開(kāi)加工的制造方法：采用這種方法，凸模和凹模分別按圖紙加工至尺寸，要分別標(biāo)注凸模和凹模的刃口尺寸及制造公差（凸模δp、凹模δd），適用于圓形或簡(jiǎn)單形狀的制件。為了保證初始間隙值小于最大合理間隙2Cmax，必須滿足下列條件： 或取： 也就是說(shuō)，新制造模具應(yīng)該是，否則制造的模具部隙已超過(guò)允許變動(dòng)范圍2Cmin～2Cmax,影響模具的使作壽命。 刃口尺寸及公差 由于材料較厚,模具間隙較小,模具的間隙由配作保證,工藝比較簡(jiǎn)單,并且還可以放大基準(zhǔn)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(huì)變小,所以得以凹模為基準(zhǔn),配作凸模.刃口尺寸由沖孔尺寸得,凸模尺寸變小,所以以凸模為基準(zhǔn),配作凹模. 圖7模具結(jié)構(gòu)圖 注意: 在進(jìn)行模具結(jié)構(gòu)及零件設(shè)計(jì)時(shí)，需首先根據(jù)條料排樣圖確定總體結(jié)構(gòu)，然后一次為基礎(chǔ)，詳細(xì)設(shè)計(jì)其中的組成零件。這一過(guò)程實(shí)際上就是自頂向下的設(shè)計(jì)過(guò)程。模具組成零件的形狀除受成形工藝形狀約束外，還受其在模具中所處的位置及其他零件的關(guān)系約束，只有總裝在結(jié)構(gòu)基礎(chǔ)上，才能獲得零件的相關(guān)約束，進(jìn)行零件的設(shè)計(jì)。 為此，在利用CAD畫(huà)圖時(shí)，應(yīng)采用自頂向下的設(shè)計(jì)模式，依次實(shí)現(xiàn)模具結(jié)構(gòu)及零件的設(shè)計(jì)。具體表述為：首先，根據(jù)條料排樣圖確定模具的總體框架結(jié)構(gòu)，從典型結(jié)構(gòu)庫(kù)中實(shí)體化一種導(dǎo)向結(jié)構(gòu)圖，然后直接在該總體結(jié)構(gòu)下，設(shè)計(jì)其他相關(guān)模具零件，以使零件設(shè)計(jì)和裝配設(shè)計(jì)相關(guān)聯(lián)。這樣，在設(shè)計(jì)某一零件時(shí)，其相關(guān)零件的形狀變化可被自動(dòng)處理，從而保證設(shè)計(jì)結(jié)構(gòu)一致性。當(dāng)零件設(shè)計(jì)完成后，可將裝配結(jié)構(gòu)中的每一零件輸出到相應(yīng)的文件中，用來(lái)產(chǎn)生相應(yīng)零件的裝配圖，并標(biāo)注相關(guān)尺寸、技術(shù)要求等。 搭邊: 在進(jìn)行模具結(jié)構(gòu)及零件設(shè)計(jì)時(shí)，需首先根據(jù)條料排樣圖確定總體結(jié)構(gòu)，然后一次為基礎(chǔ)，詳細(xì)設(shè)計(jì)其中的組成零件。這一過(guò)程實(shí)際上就是自頂向下的設(shè)計(jì)過(guò)程。模具組成零件的形狀除受成形工藝形狀約束外，還受其在模具中所處的位置及其他零件的關(guān)系約束，只有總裝在結(jié)構(gòu)基礎(chǔ)上，才能獲得零件的相關(guān)約束，進(jìn)行零件的設(shè)計(jì)。 連接零件 此類(lèi)零件包括螺釘、銷(xiāo)釘?shù)?，主要作用是?lián)接其它零部伯，使之共同完成工件的制造 3.6模具工作過(guò)程 如圖所示，該模具的沖孔凸模和落料凹模裝在上模，凸凹模裝在下模上。所以由其結(jié)構(gòu)我們可以看出，該模具屬于倒裝式復(fù)合模。 如圖所示，該模具處于閉合位置。當(dāng)沖模開(kāi)始運(yùn)行的時(shí)候，滑塊的移動(dòng)會(huì)帶動(dòng)其模柄向上運(yùn)動(dòng)，與模柄連接的上模座會(huì)與墊板、凸模固定板、凸模、凹模、推件塊等相關(guān)零件發(fā)生聯(lián)鎖的向上運(yùn)動(dòng)，自動(dòng)送料裝置將條料送到模具的正確位置。模具中導(dǎo)料銷(xiāo)和擋料銷(xiāo)與加工條料相接觸，對(duì)條料起到固定和導(dǎo)向的作用，這樣可以確保其在沖壓時(shí)處于正確的位置且不發(fā)生位移。壓力機(jī)帶動(dòng)滑塊向下運(yùn)動(dòng)，這時(shí)卸料板和凹模將毛坯固定壓緊，接著就開(kāi)始沖裁。被沖下來(lái)的毛坯材料會(huì)被凸凹模壓在孔內(nèi)，而外部的毛坯材料則在凸凹模上被壓緊。然后，沖床滑塊開(kāi)始它的回程運(yùn)動(dòng)。坯料會(huì)在彈簧的作用下，通過(guò)卸料板推出凸凹模，剩下工件則被留在了凹模的孔內(nèi)。當(dāng)推桿接觸到?jīng)_床的打料橫梁后，會(huì)向下移動(dòng)帶動(dòng)推板，推板則會(huì)推動(dòng)推銷(xiāo)向下運(yùn)動(dòng)，而推銷(xiāo)會(huì)推動(dòng)推件塊向下運(yùn)動(dòng)，最終將工件從凹?？字许敵雎湎?。 3.3組裝工藝要求 3.3.1選擇基準(zhǔn)件 選擇裝配基準(zhǔn)件。 選擇基準(zhǔn)件的原則是按照模具主要零件加工時(shí)的依賴(lài)關(guān)系來(lái)確定 3.3.2組建裝配 組件裝配。 組件裝配是指模具在總裝配前，將兩個(gè)以上的零件按照規(guī)定技術(shù)要求連接成一個(gè)組件的裝配工作 3.3.3總體裝配 總體裝配。 總裝是將零件和組件結(jié)合成一幅完整的模具過(guò)程。在總裝前，應(yīng)選好裝配的基準(zhǔn)件和安裝好上、下模的裝配順序。 在裝配模具時(shí)必須嚴(yán)格控制和調(diào)整凸、凹模間隙的均勻性。間隙調(diào)整后，才能緊固銷(xiāo)釘21A及螺釘。 檢驗(yàn)、調(diào)試。 模具裝配完畢后，必須保證裝配精度，滿足規(guī)定的各項(xiàng)技術(shù)要求，檢驗(yàn)?zāi)＞吒鞑糠值墓δ堋Ｔ趯?shí)際生產(chǎn)條件下進(jìn)行試模，當(dāng)試模合格后，模具加工、裝配才算基本完成。 4.定位裝置的確定 因?yàn)榘辶虾穸萾=5mm,屬于較小厚度的板材,且制件尺寸不大,固采用側(cè)面兩個(gè)固定擋料銷(xiāo)定位導(dǎo)向,在送料方向由于受凸模和凹模的影響,為了不至于削弱模具的強(qiáng)度,在送給方向采用一個(gè)彈簧擋料裝置的活動(dòng)擋料銷(xiāo). 4.1壓力中心計(jì)算 此零件的外形為對(duì)稱(chēng)件，中間的異形孔不是對(duì)稱(chēng)的，但孔的尺寸很小，左右兩邊的圓弧各自的壓力中心和零件中心線的距離差距不大，所以該零件的壓力中心可近似認(rèn)為就是零件外形中心線的交點(diǎn) 4.2裝配原則 裝配應(yīng)以凹凸模作裝配基準(zhǔn)件。先將裝有凹凸模的固定板用螺栓和銷(xiāo)釘安裝，固定在指定的相應(yīng)位置上；再按凹凸模的內(nèi)形裝配和調(diào)整沖孔凸模固定板的相對(duì)位置，使沖孔凹凸模的間隙趨于均勻，用螺栓固定；然后再以凹凸模的外形為基準(zhǔn)，裝配和調(diào)整落料凹模相對(duì)凹凸模的位置，調(diào)整間隙，用螺栓固定 4.3選擇模架及其他模架零件 4.3.1模架 根據(jù)GB/T 2851.5-90,由凹模周界200X160,及安裝要求,選取 凹模周界:LXB=250X200,閉合高度:H=220~265,上模座:250X200X50 下模座:250X200X60,導(dǎo)柱:32X210,35X210, 導(dǎo)套:32X115X48,35X115X48 4.3.2墊板 墊板的作用是承受并擴(kuò)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3~10mm,這里設(shè)計(jì)時(shí),由于壓力較大,根據(jù)GB2865.2-81選取規(guī)格為L(zhǎng)XBXH=200X160X8. 4.4試驗(yàn) 零件裝配完成以后，個(gè)別零件之間可能出現(xiàn)型號(hào)干涉的情況，需對(duì)裝配體進(jìn)行干涉檢查；否則零件有可能無(wú)法安裝或正常工作。需對(duì)零件重新進(jìn)行裝配或修改零件尺寸，直到消除干涉為止，表明各個(gè)零部件被正確安裝，可以正常工作 12 致 謝 致 謝 以上對(duì)鑰匙外形進(jìn)行分析，采用倒裝復(fù)合模的加工工藝，通過(guò)合理的排樣與沖壓力的計(jì)算，進(jìn)行了模具結(jié)構(gòu)設(shè)計(jì)以及注意問(wèn)題。實(shí)踐證明，該模具沖出來(lái)的零件毛刺小，斷面平整光滑，生產(chǎn)率高，成本低，達(dá)到了預(yù)期目的。 三年的大學(xué)生活就快走入尾聲，我的校園生活即將就要?jiǎng)澤暇涮?hào)，心中是無(wú)盡的難舍與眷戀。從這里走出，對(duì)我的人生來(lái)說(shuō)，將是踏上一個(gè)新的征程，要把所學(xué)的知識(shí)應(yīng)用到實(shí)際工作中去。 回首三年，取得了很多成績(jī)，生活中有快樂(lè)也有艱辛。感謝老師們?nèi)陙?lái)對(duì)我孜孜不倦的教誨和無(wú)微不至關(guān)懷，使我在關(guān)心和愛(ài)護(hù)下度過(guò)難忘的三年大學(xué)生活。 最大收獲就是學(xué)會(huì)了做一次設(shè)計(jì)項(xiàng)目的具體流程。從策劃構(gòu)思、總體設(shè)計(jì)到各個(gè)模塊的的具體設(shè)計(jì)及其組合，再到編寫(xiě)需要提交的論文，這一切如今仍歷歷在目。我想，這種對(duì)整體設(shè)計(jì)流程的把握應(yīng)該是以后走上工作崗位所必需的技能，而這種技能卻只能通過(guò)自己的親身實(shí)踐才能獲得。這也是為什么我認(rèn)為機(jī)械設(shè)計(jì)大作業(yè)這種教學(xué)實(shí)踐模式值得推廣的原因。 畢業(yè)設(shè)計(jì)是我在大學(xué)生涯完成的最后一項(xiàng)內(nèi)容,此時(shí)此刻，我感覺(jué)自己有很多想要說(shuō)的話，有很多需要感謝的人。首先感謝指導(dǎo)老師程洋給予的支持與指導(dǎo),以及但由于工作的原因和條件的限制,我在外面所做的畢業(yè)設(shè)計(jì)并不完善。自從回校之后,向老師們請(qǐng)教和指導(dǎo),他們都在百忙之中給予了我悉心的指導(dǎo)和幫助。師生之情無(wú)法言表，在此，謹(jǐn)向恩師們深表謝意 13 參考文獻(xiàn) 參考文獻(xiàn) u 圖書(shū)： （1） 《冷沖壓工藝與模具設(shè)計(jì)》 中國(guó)勞動(dòng)社會(huì)保障出版社。2006 （2） 《冷沖模設(shè)計(jì)》中國(guó)勞動(dòng)社會(huì)保障出版社。1998 （3） 《冷沖壓技術(shù)問(wèn)答》 機(jī)械工業(yè)出版社。2004 （4） 《沖模設(shè)計(jì)編寫(xiě)組》 機(jī)械工業(yè)出版社。2007 （5） 《冷沖壓技術(shù)》 機(jī)械工業(yè)出版社。2000 （6） 《沖壓模具設(shè)計(jì)與制造》 高等教育出版社。2002 15 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.