鎖片復(fù)合模具設(shè)計【鎖片不銹鋼門扣插銷防盜門鎖扣箱復(fù)合沖壓模具設(shè)計】【異形鎖芯】【說明書+CAD+ROE】

鎖片復(fù)合模具設(shè)計【鎖片不銹鋼門扣插銷防盜門鎖扣箱復(fù)合沖壓模具設(shè)計】【異形鎖芯】【說明書+CAD+ROE】,鎖片不銹鋼門扣插銷防盜門鎖扣箱復(fù)合沖壓模具設(shè)計,異形鎖芯,說明書+CAD+ROE,鎖片復(fù)合模具設(shè)計【鎖片不銹鋼門扣插銷防盜門鎖扣箱復(fù)合沖壓模具設(shè)計】【異形鎖芯】【說明書+CAD+ROE】,復(fù)合,模具設(shè)計 工 藝 過 程 卡 產(chǎn)品型號 零（部）件圖號 共1 頁 產(chǎn)品名稱 復(fù)合模具 零（部）件名稱 凸凹模 第1 頁 材料牌號 Cr12MoV 毛坯種類 精料 毛坯外形尺寸 每毛坯件數(shù) 1 每臺件數(shù) 1 備注 工序號 工序名稱 工 序 內(nèi) 容 車間 設(shè) 備 工 藝 裝 備 工 時 名稱、型號 編號 夾 具 輔具 刀、量具 準(zhǔn)終 單件 1 備 備料精料 2 CNC 銑臺階面，鉆穿絲 金工 法蘭克數(shù)控加工中心 電磁鐵 硬質(zhì)合金銑刀，游標(biāo)卡尺 3 CNC 掉頭銑槽 金工 法蘭克數(shù)控加工中心 電磁鐵 硬質(zhì)合金銑刀，游標(biāo)卡尺 4 熱處理 淬火處理HRC56-60 金工 5 線切割 線割輪廓 金工 日本牧野慢走絲 壓塊 銅絲，游標(biāo)卡尺 6 鉗工 去毛刺 金工 鉗工臺 7 終檢 入庫 編 制 審 核 會 簽 標(biāo)記 處數(shù) 更改文件號 簽 字 日 期 標(biāo) 記 處數(shù) 更改文件號 簽 字 日 期 工 藝 過 程 卡 產(chǎn)品型號 零（部）件圖號 共1 頁 產(chǎn)品名稱 復(fù)合模具 零（部）件名稱 沖孔凸模 第1 頁 材料牌號 Cr12MOV 毛坯種類 熱軋圓鋼 毛坯外形尺寸 每毛坯件數(shù) 1 每臺件數(shù) 1 備注 工序號 工序名稱 工 序 內(nèi) 容 車間 設(shè) 備 工 藝 裝 備 工 時 名稱、型號 編號 夾 具 輔具 刀、量具 準(zhǔn)終 單件 1 鋸 下棒料 鑄 2 熱處理 退火處理消除鑄件的內(nèi)應(yīng)力及改善機械加工性能 熱 3 車 粗車外圓柱面 金工 C6130 三爪卡盤 硬質(zhì)合金外圓車刀，游標(biāo)卡尺 4 車 半精車外圓柱面 金工 C6130 三爪卡盤 硬質(zhì)合金外圓車刀，游標(biāo)卡尺 5 熱處理 淬火處理HRC56-60 金工 6 車 精車外圓柱面 金工 C6130 三爪卡盤 硬質(zhì)合金外圓車刀，游標(biāo)卡尺 7 鉗工 去毛刺 鉗工臺 8 終檢 入庫 編 制 審 核 會 簽 標(biāo)記 處數(shù) 更改文件號 簽 字 日 期 標(biāo) 記 處數(shù) 更改文件號 簽 字 日 期 摘要 本次設(shè)計了一套沖壓模具在說明書中第一部分，主要敘述了沖壓模具的發(fā)展?fàn)顩r，說明了沖壓模具的重要性與本次設(shè)計的意義，對沖壓件的工藝分析，工藝方案的確定。通過，對零件排樣圖的設(shè)計，完成了材料利用率的計算。再進行沖裁工藝力的計算和沖裁模工作部分的設(shè)計計算。最后對主要零部件的設(shè)計和標(biāo)準(zhǔn)件的選擇，為本次設(shè)計模具的繪制和模具的成形提供依據(jù)，以及為裝配圖各尺寸提供依據(jù)。通過前面的設(shè)計方案畫出模具各零件圖和裝配圖。 關(guān)鍵字：沖壓；工藝:模具結(jié)構(gòu) Abstract In text file the first part, described to wash the development condition that press the molding tool primarily, explain to wash the importance that press the molding tool and the meaning of this design, to craft that washing and pressing the piece analyzes, the craft project really settles.Pass, line up the design of the kind diagram to the spare parts, complete the calculation of the material utilization.Proceed again the calculation that wash cut the craft dint with wash to cut mold work part of designs calculation.Finally to the design of the main the parts of zero with the choice of the standard piece, draw for this design molding tool to take shape the offering with the molding tool according to, and for assemble each size of diagram offering according to.The design project passing before draws an each spare parts of molding tool diagram with assemble the diagram. Keyword:Wash to press;Fal 目錄 摘要 1 Abstract 2 目錄 3 1 緒論 5 2 零件的分析 7 3 工藝方案分析 8 3.2.1方案種類 8 3.2.2方案的比較 8 3.2.3方案的確定 8 4 模具間隙和凸凹模尺寸的確定 9 4.1 模具間隙的確定 9 4.2 凸凹模刃口尺寸計算 10 5 沖載力和壓力中心的計算 12 5.1 沖壓力的計算 12 5.2 壓力中心的計算 14 5.3 設(shè)備的選擇 15 6 排樣設(shè)計 18 6.1 沖裁件的排樣 18 6.2 材料利用率 19 7 模具總體設(shè)計 20 7.1 模具總體結(jié)構(gòu)設(shè)計 20 7.2 凸凹模固定板 20 7.3凸模固定板 20 7.4墊板 21 7.5 卸料板 21 7.6操作與定位方式 22 8 模具工作過程 23 9 模具的裝配 24 結(jié)論與展望 26 致謝 27 參考文獻 28 1 緒論 (1)中國模具行業(yè)發(fā)展現(xiàn)狀 鑒于模具作為包括機床工具、汽車制造、食品包裝等在內(nèi)的機械行業(yè)中機械基礎(chǔ)件產(chǎn)業(yè)，以及電工電器、電子及信息行業(yè)的支持產(chǎn)業(yè)，在發(fā)展先進生產(chǎn)力當(dāng)中，處于非常關(guān)鍵并服務(wù)全行業(yè)的地位，其發(fā)展對產(chǎn)業(yè)配套能力的提升和促進產(chǎn)業(yè)聚集優(yōu)勢的形成將起到重要作用。改革開放以來，中國模具工業(yè)企業(yè)的所有制成分也發(fā)生了巨大變化，國內(nèi)已能生產(chǎn)精度達2微米的精密多工位級進模，工位數(shù)最多已達160個，壽命1～2億次。在大型塑料模具方面，現(xiàn)在已能生產(chǎn)48英寸電視的塑殼模具、6.5公斤大容量洗衣機的塑料模具，以及汽車保險杠、整體儀表板等模具。在精密塑料模具方面，國內(nèi)已能生產(chǎn)照相機塑料模具、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)自動扶梯整體踏板壓鑄模及汽車后橋齒輪箱壓鑄模。在汽車模具方面，現(xiàn)已能制造新轎車的部分覆蓋件模具。 (2)沖壓模具行業(yè)遇到的問題和解決方法 阻力一：機械化、自動化程度低 美國680條沖壓線中有70%為多工位壓力機，日本國內(nèi)250條生產(chǎn)線有32%為多工位壓力機，而這種代表當(dāng)今國際水平的大型多工位壓力機在我國的應(yīng)用卻為數(shù)不多；中小企業(yè)設(shè)備普遍較落后，耗能耗材高，環(huán)境污染嚴(yán)重；封頭成形設(shè)備簡陋，手工操作比重大；精沖機價格昂貴，是普通壓力機的5-10倍，多數(shù)企業(yè)無力投資阻礙了精沖技術(shù)在我國的推廣應(yīng)用；液壓成形，尤其是內(nèi)高壓成形，設(shè)備投資大，國內(nèi)難以起步。 突破點：加速技術(shù)改造 阻力二：生產(chǎn)集中度低 許多汽車集團大而全，形成封閉內(nèi)部配套，導(dǎo)致各企業(yè)的沖壓件種類多，生產(chǎn)集中度低，規(guī)模小，易造成低水平的重復(fù)建設(shè)，難以滿足專業(yè)化分工生產(chǎn)，市場競爭力弱。 突破點：走專業(yè)化道路 阻力三：科技成果轉(zhuǎn)化慢先進工藝推廣慢 在我國，許多沖壓新技術(shù)起步并不晚，有些還達到了國際先進水平，但常常很難形成生產(chǎn)力。先進沖壓工藝應(yīng)用不多，有的僅處于試用階段，吸收、轉(zhuǎn)化、推廣速度慢。技術(shù)開發(fā)費用投入少，導(dǎo)致企業(yè)對先進技術(shù)的掌握應(yīng)用慢，開發(fā)創(chuàng)新能力不足，中小企業(yè)在這方面的差距更甚。目前，國內(nèi)企業(yè)大部分仍采用傳統(tǒng)沖壓技術(shù)，對下一代輕量化汽車結(jié)構(gòu)和用材所需的成形技術(shù)缺少研究與技術(shù)儲備。 突破點：走產(chǎn)、學(xué)、研聯(lián)合之路 (3)中國模具行業(yè)發(fā)展前景 模具是工業(yè)生產(chǎn)中的基礎(chǔ)工藝裝備，是一種高附加值的高技術(shù)密集型產(chǎn)品，也是高新技術(shù)產(chǎn)業(yè)的重要領(lǐng)域，其技術(shù)水平的高低已成為衡量一個國家制造水平的重要標(biāo)志。隨著國民經(jīng)濟總量和工業(yè)產(chǎn)品技術(shù)的不斷發(fā)展，各行各業(yè)對模具的需求量越來越大，技術(shù)要求也越來越高。目前我國模具工業(yè)的發(fā)展步伐日益加快，“十一五期間”產(chǎn)品發(fā)展重點主要應(yīng)表現(xiàn)在： ①汽車覆蓋件模； ②精密沖模； ③大型及精密塑料模； ④主要模具標(biāo)準(zhǔn)件； ⑤其它高技術(shù)含量的模具； 2 零件的分析 由圖可知，產(chǎn)品形狀結(jié)構(gòu)較簡單，無狹槽、尖角；孔與孔之間、孔與零件之間的最小距離滿足要求。 （1）尺寸精度 任務(wù)書對沖件的尺寸精度要求為IT12級， 查參考文獻[2]知，普通沖裁時對于該沖件的精度要求為IT12～IT11級，所以尺寸精度滿足要求。 （2）沖裁件斷面質(zhì)量 因為一般用普通沖裁方式?jīng)_2mm以下的金屬板料時，其斷面粗糙度Ra可達12.5～3.2，毛刺允許高度為0.05～0.1mm；本產(chǎn)品在斷面粗糙度上沒有太嚴(yán)格的要求，單要求孔及輪廓邊緣無毛刺，所以只要模具精度達到一定要求，在沖裁后加修整工序，沖裁件斷面的質(zhì)量就可以保證。 （3）產(chǎn)品材料分析 對于沖壓件材料一般要求的力學(xué)性能是強度低，塑性高，表面質(zhì)量和厚度公差符合國家標(biāo)準(zhǔn)。本設(shè)計的產(chǎn)品材料為1CR18NI9TI,厚度1mm，屬優(yōu)質(zhì)碳素結(jié)構(gòu)鋼，其力學(xué)性能是強度、硬度低而塑性較好，非常適合沖裁加工。另外產(chǎn)品對于厚度與表面質(zhì)量沒有嚴(yán)格要求，所以盡量采用國家標(biāo)準(zhǔn)的板材，其沖裁出的產(chǎn)品表面質(zhì)量和厚度公差就可以保證 經(jīng)上述分析，產(chǎn)品的材料性能符合冷沖壓加工要求。 3 工藝方案分析 3.2.1方案種類 該工件包括落料、沖孔兩個基本工序，可有以下三種工藝方案： 方案一：先沖孔，后落料,采用單工序模生產(chǎn)。 方案二：沖孔－－落料級進沖壓,采用級進模生產(chǎn)。 方案三：采用落料－－沖孔同時進行的復(fù)合模生產(chǎn)。 3.2.2方案的比較 方案一，模具結(jié)構(gòu)簡單，制造方便，但需要兩道工序，兩副模具，成本相對較高，生產(chǎn)效率低，且更重要的是在第一道工序完成后，進入第二道工序必然會增大誤差，使工件精度、質(zhì)量大打折扣，達不到所需的要求，難以滿足生產(chǎn)需要。故而不選此方案。 方案二，級進模是一種多工位、效率高的一種加工方法。但級進模輪廓尺寸較大，制造復(fù)雜，成本較高，一般適用于大批量，小型沖壓件。而本工件尺寸輪廓較大，采用此方案，勢必會增大模具尺寸，使加工難度提高，進而也排除此方案。 方案三，只需要一套模具，工件的精度及生產(chǎn)效率要求都能滿足，模具輪廓尺寸、制造相對前面兩種方案都有比較好。 3.2.3方案的確定 綜上所述，本套模具采用復(fù)合模。 4 模具間隙和凸凹模尺寸的確定 4.1 模具間隙的確定 由以上分析可見，凸模、凹模間間隙對沖裁件質(zhì)量、沖裁工藝力、模具壽命都有很大的影響。因此，設(shè)計模具時一定要選擇一個合理的間隙，以保證沖裁件的斷面質(zhì)量、尺寸精度滿足產(chǎn)品的要求、所需沖裁力小、模具壽命高。考慮到模具在使用過程中的磨損使間隙值增大，故設(shè)計與制造新模具時要采用最小合理間隙值Cmin。確定合理間隙的方法有理論確定法與經(jīng)驗法。 1.理論確定法 理論確定法的主要依據(jù)是保證上下裂紋會合，以便獲得良好的斷面。 2.經(jīng)驗確定法 根據(jù)近年來的研究與使用經(jīng)驗，在確定間隙值時要按要求分類選用。對尺寸精度、斷面垂直度要求高的制件應(yīng)選用較小間隙值，對斷面垂直度與尺寸精度要求不高的制件，應(yīng)以降低沖裁力、提高模具壽命為主，可用較大間隙值 本論文設(shè)計的產(chǎn)品經(jīng)查《沖壓工藝與模具設(shè)計》書中表2.2.3得：材料為08F鋼，厚度為0.8的鐵芯片間隙值為：Z=0.072；Z=0.104 彎曲模間隙是指單面間隙。間隙的大小對彎曲力、彎曲件的質(zhì)量、彎曲模的壽命都有影響。若值太小，凸緣區(qū)變厚的材料通過間隙時，校直與變形的阻力增加，與模具表面間的摩擦、磨損嚴(yán)重，使彎曲力增加，零件變薄嚴(yán)重，甚至拉破，模具壽命降低。間隙小時得到的零件側(cè)壁平直而光滑，質(zhì)量較好，精度較高。 間隙過大時，對毛坯的校直和擠壓作用減小，彎曲力降低，模具的壽命提高，但零件的質(zhì)量變差，沖出的零件側(cè)壁不直。 因此彎曲模的間隙值也應(yīng)合適，確定時要考慮壓邊狀況、彎曲次數(shù)和工件精度等。其原則是：既要考慮板料本身的公差，又要考慮板料的增厚現(xiàn)象，間隙一般都比毛坯厚度略大一些。采用壓邊彎曲時其值可按下式計算： ??????????????????????(3) 4.2 凸凹模刃口尺寸計算 材料是1CR18NI9TI，料厚2mm 對于精度為IT9的工件，磨損系數(shù)χ=0.5 采用凸模與凹模配合加工，沖孔情況，磨損后凸模減小。 公式： 沖孔時： d= (d+x) （3—10） d= (d+x+Z) (3—11) 落料時： D= (D+x) （3—12） D= (D+x+Z) (3—13) 孔距尺寸：L= (L+0.5+)±△／8 （3—14） 式中 d， d－分別為沖孔凸模和凹模的刃口尺寸； D ，D－分別為落料凸模和凹模的刃口尺寸； d，D－分別為沖孔件和落料件的最小和最大極限尺寸； L－兩孔中心距的最小極限尺寸； △－工件公差； Z－最小合理間隙； X－磨損系數(shù)。 工件精度IT14,取x=0.5。 沖孔是以凸模為基準(zhǔn) 8 mm=（8+0.5×0.36）=8.18 落料是以凹模為基準(zhǔn) 5.9mm =（5.9-0.5×0.25）=5.775 11.5mm =（11.5-0.5×0.25）=11.375 10mm =（10-0.5×0.25）=9.875 7mm =（7-0.5×0.25）=6.875 5 沖載力和壓力中心的計算 5.1 沖壓力的計算 沖孔力 由[2]得沖裁力的計算公式 F沖孔孔=KLtτ （3.1） 式中： K—系數(shù)，K=1.3； L—沖裁周邊長度（mm）； t—沖裁件的厚度（mm）； τ—材料的抗剪強度（MPa）。 F沖孔孔=KLtτ =1.3×25.13×350×1 =11.43（kN） 落料力 =KLtτ （3.2） 式中： K—系數(shù)，K=1.3； L—沖裁周邊長度（mm）； t—沖裁件的厚度（mm）； τ—材料的抗剪強度（MPa）。 =KLtτ =1.3×145.45×350×1 =66.18 (kN） 卸料力 由[2]得卸料力的計算公式 F卸料=K卸料F落料 （3.3） 式中： K卸料—卸料力系數(shù)，查表3.1。 F卸料=K卸料F落料 =0.034×66.18 =2.25（kN） 推件力 由[2]中推件力的計算公式 F推件=nK推件F沖孔（3.4） 式中： K推件—推件力系數(shù)，查表3.1。 n—同時梗塞在凹模內(nèi)的工件數(shù)（廢料數(shù)）； F推件=nK推件F沖孔 =2×0.045×11.43 =1.03（kN） 頂件力 由[2]中頂件力的計算公式 F頂件=K頂件F落料 （3.5） 式中： K頂件—頂件力系數(shù)，查表3.1。 F頂件=K頂件F落料 =0.06×66.18 =3.97（kN） 5.2 壓力中心的計算 因為該零件是對稱圖形，并按照如下式進行計算得： 沖孔：（3.8） （3.9） 沖裁邊：（3.10） （4.11） 式中：——沖孔時指各種孔的中心位置； 沖裁邊時指各線段中心坐標(biāo)； ——沖各孔時所用壓力； ——各線段長度； ——壓力中心坐標(biāo)。 具體見圖3.2； 圖3.2 壓力中心線 5.3 設(shè)備的選擇 (一) 常用壓力機的分類 壓力機的種類很多,按照不同的觀點可以把壓力機分成不同的類別.如:按驅(qū)動滑塊力的種類分機械的、液壓的、氣動的等；按滑塊個數(shù)可分為單動的、雙動的、三動的等；按驅(qū)動滑塊的機構(gòu)的種類又可分為曲軸式、肘桿式、摩擦式；按機身結(jié)構(gòu)形式可分為開式的、閉式的等等。另外還有許多種分類方法，一般按驅(qū)動滑塊力的種類而把壓力機分為機械壓力機、液壓機。 (二) 壓力機類型的選擇 壓力機類型的選擇，主要是根據(jù)沖壓工藝的性質(zhì)、生產(chǎn)批量大小、制件的幾何形狀、尺寸及精度要求，以及安全操作等因素來確定的。 開式曲柄壓力機雖然剛度差，降低了模具壽命和沖件的質(zhì)量。但是它成本低，且有三個方向可以操作的優(yōu)點，故廣泛應(yīng)用于中小型沖裁件、彎曲件或拉深件的生產(chǎn)中。 閉式曲柄壓力機剛度好、精度高，只能兩個方向操作,適于大中型沖壓件的生產(chǎn)。 雙動曲柄壓力機有兩個滑塊,壓邊可靠易調(diào)，適用于較復(fù)雜的大中型拉深件的生產(chǎn)。 高速壓力機或多工位自動壓力幾適用于大批量生產(chǎn)。 液壓機沒有固定的行程,不會因為板材厚度超差而過載,全行程中壓力恒定,但是壓力機的速度低、生產(chǎn)效率低.適用于小批量,尤其是大型厚板沖壓件的生產(chǎn)。 摩擦壓力機結(jié)構(gòu)簡單、造價低、不易發(fā)生超負荷損壞。在小批量生產(chǎn)中用來完成彎曲、成形等沖壓工件。 肘桿式精壓機剛度大、滑塊行程小，在行程末端停留時間長，適用于校正、校平和整形等類沖壓工序。 (三) 確定設(shè)備規(guī)格 (1) 壓力機的行程大小，應(yīng)該能保證成形零件的取出與毛坯的放進，例如拉伸所用壓力機的行程，至少應(yīng)大于成品零件高度的兩倍以上。 (2) 壓力機工作臺面的尺寸應(yīng)大于沖模的平面尺寸，且還需留有安裝固定的余地，但過大的工作臺面上安裝小尺寸的沖模時,工作臺的受力條件也是不利的。 (3) 所選壓力機的封閉高度應(yīng)與沖模的封閉高度相適應(yīng)。模具的閉合高度是指上模在最低的工作位置時，下模板的底面到上模板的頂面的距離.壓力機的閉合高度是指滑塊在下死點時，工作臺面到滑塊下端面的距離。大多數(shù)壓力機,其連桿長短能調(diào)節(jié)，也即壓力機的閉合高度可以調(diào)節(jié)，故壓力機有最大閉合高度和最小閉合高度。 設(shè)計模具時，模具閉合高度的數(shù)值應(yīng)滿足下式： 無特殊情況應(yīng)取上限值，即最好取在：,這是為了避免連桿調(diào)節(jié)過長，螺紋接觸面積過小而被壓壞。如果模具閉合高度實在太小，可以在壓床臺面上加墊板。 綜合上述，考慮到所設(shè)計的沖裁件尺寸不大，精度要求不是很高，所以選擇開式曲柄壓力機。其參數(shù)如下： 公稱壓力/ 550 固定行程/ 80 調(diào)節(jié)行程/ 80 行程次數(shù)/(次/) 100 最大閉合高度/ 250 閉合高度調(diào)節(jié)量/70 工作臺尺寸/ 左右 560 前后 200 工作臺孔尺寸/ 左右 260 前后 130 直徑180 工作臺板厚度/ 70 6 排樣設(shè)計 在沖壓生產(chǎn)中，節(jié)約金屬和減少廢料具有非常重要的意義，特別是在大批量生產(chǎn)中，較好地確定沖件尺寸和合理排樣是降低成本的有效措施之一。 6.1 沖裁件的排樣 排樣是指沖件在條料、帶料或板料上布置的方法。沖件的合理布置（即材料的經(jīng)濟利用），與沖件的外形有很大關(guān)系。 根據(jù)不同幾何形狀的沖件，可得出于其相適應(yīng)的排樣類型，而根據(jù)排樣的類型，又可分為少或無工藝余料的排樣與工藝余料的排樣兩種。 排樣時，沖件之間以及沖件與條料側(cè)邊之間留下的余料叫搭邊。它的作用是補償定位誤差，保證沖出合格的沖件，以及保證條料有一定剛度，便于送料。 搭邊數(shù)值取決于以下因素: (1) 工件的尺寸和形狀。 (2) 材料的硬度和厚度。 (3) 排樣的形式（直排、斜排、對排等）。 (4) 條料到的送料方法（是否有側(cè)壓板）。 檔料裝置的形式（包括檔料銷、導(dǎo)料銷和定距側(cè)刃等的形式）。搭邊值一般由經(jīng)驗在經(jīng)過簡單計算確定的。 考慮到該制造件的生產(chǎn)綱領(lǐng)與加工條件，采用條料加工余料的排樣。排樣如下： 圖2.1 6.2 材料利用率 衡量材料經(jīng)濟利用的指標(biāo)是材料利用率。 一個進距內(nèi)的材料利用率為： *100% A— 沖裁件面積（包括沖出小孔在內(nèi)）（㎜2）; B— 條斜寬度（㎜）； H—近距（㎜）； η=*100% =52% 7 模具總體設(shè)計 7.1 模具總體結(jié)構(gòu)設(shè)計 廢料由凸模入凹模洞口中，積累到一定數(shù)量，由下模漏料孔排出，不必清除廢料，操作方便，應(yīng)用很廣，但工件表面平直度較差，凸凹模承受的張力較大，因此凸凹模的壁厚應(yīng)嚴(yán)格控制，以免強度不足。 7.2 凸凹模固定板 凸凹模固定板形狀與凹模板一致，如圖所示： 7.3 凸模固定板 凸模固定板將凸模固定在模座上，其平面輪廓尺寸與凹模板外形尺寸相同，但還應(yīng)考慮緊固螺釘及銷釘?shù)奈恢?。固定板的凸模安裝孔與凸模采用過渡配合H7/m6、H7/n6，壓裝后將凸模端面與固定板一起磨平。凸模固定板為圓形，厚度一般取凹模厚度的0.6~0.8倍。 7.4 墊板 沖裁時，如果凸模的端部對模座的壓應(yīng)力超過模座材料的許用壓應(yīng)力，這時需要在凸模端部與模座之間加上一塊強度較高的墊板。即下列情況下雨加墊板。 式中 —凸模端面的壓應(yīng)力，其數(shù)值為； —模座材料下雨壓應(yīng)力，其數(shù)值：鑄鐵約為100MPa，鋼約為200 MPa； —沖裁力； —凸模上端面面積。 墊板的下載與凸模固定板一致，厚度一般取4～12mm。墊板淬硬后兩面應(yīng)磨平，表面粗糙度Ra≤0.32～0.63。 由于本套模具選用壓入式模柄，在上模座與凸模固定板之間也必須安裝墊板 7.5 卸料板 卸料板同樣為和凹模板一致，卸料板材料選A3或（45）鋼，不用熱處理淬硬。 取卸料板與凸凹模的雙面間隙為0.1～0.3mm. 卸料板上設(shè)置幾個卸料螺釘。卸料釘尾部應(yīng)留有足夠的行程空間。卸料螺釘擰緊后，應(yīng)使卸料板超出凸模端面lmm，有誤差時通過在螺釘與卸料板之間安裝墊片來調(diào)整。如下圖所示： 7.6 操作與定位方式 零件中批量生產(chǎn),安排生產(chǎn)可采用手工送料方式能夠達到批量生產(chǎn),且能降低模具成本,因此采用手工送料方式.零件尺寸較大，厚度較高，保證孔的精度及較好的定位，宜采用導(dǎo)料板導(dǎo)向，導(dǎo)正銷導(dǎo)正，為了提高材料利用率采用始用擋料銷和固定擋料銷。 8 模具工作過程 有上面可知模具為沖孔落料倒裝復(fù)合沖裁模。上模部分有落料凹模與沖孔凸模，通過沖孔凸模固定板、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)。彈性卸料對條料起校平作用。沖載時，落料凹模將彈性卸料板壓下，沖孔凸模也進入沖孔凹?？字校瑫r完成沖孔與落料。當(dāng)上?；爻虝r，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，通過推板、推桿與推件板將沖件從落料凹中推出，沖孔廢料由凸凹模孔中漏出。條料的定位依靠左側(cè)的兩個活動導(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條料的壓平作用。 而倒裝復(fù)合模的主要的優(yōu)點是廢料能直接從壓力機漏料孔落下，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，有利于倒裝復(fù)合模的安裝送料裝置，生產(chǎn)效率較高，所以應(yīng)用比較廣泛。 9 模具的裝配 根據(jù)沖壓模具裝配要點，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，具體裝配看下表。 序號 工序 工藝說明 1 凸、凹模預(yù)配 （1）裝配前仔細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?，檢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、凹模框裝在一起，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 裝機試沖并根據(jù)試沖結(jié)果作相應(yīng)調(diào)整 結(jié)論與展望 在大學(xué)的學(xué)習(xí)過程中，設(shè)計是一個重要的環(huán)節(jié)。是我們步入社會參與實際工作的一次極好的演示，我十分有幸提早把設(shè)計和實際工作有機的結(jié)合起來。 此次的設(shè)計是我們從大學(xué)走向未來工作的重要一步，從最初的選題、開題到計算、繪圖直到完成設(shè)計，期間查找資料、老師們的指導(dǎo)與同學(xué)的交流，每一個過程都是對自己能力的一次檢驗和充實。不但使我更進一步理解和懂得了以前學(xué)到的知識而且還把以前課本上學(xué)到的知識連接在了一起。使我能更好的融會貫通。 此次設(shè)計是對我專業(yè)知識和專業(yè)基礎(chǔ)知識一次實際檢驗和鞏固，設(shè)計收獲很多，提高自己的繪圖能力。但是設(shè)計也暴露出自己專業(yè)基礎(chǔ)的很多不足之處，比如缺乏綜合應(yīng)用專業(yè)知識的能力，對材料的不了解。 這次實踐是對自己大學(xué)所學(xué)的一次大的檢閱，使我明白了自己知識還很淺薄。雖然馬上要了但是自己的求學(xué)之路還很長，以后更應(yīng)在工作中學(xué)習(xí)，努力使自己成為一個對社會有所貢獻的人。 致謝 設(shè)計是對幾年的大學(xué)生活的一個總結(jié)，是幾年來的一個綜合考評，現(xiàn)在終于圓滿完成了，感謝我所有的老師，是你們無私的奉獻把我?guī)нM機械殿堂，讓我在機械行業(yè)快樂翱翔。 本次設(shè)計是在老師的悉心指導(dǎo)和關(guān)懷下完成的。在設(shè)計過程中，導(dǎo)師給了我許多指導(dǎo)和幫助，并提出了很多寶貴的意見尤老師的嚴(yán)謹治學(xué)，不斷探索的科研作風(fēng)，敏銳深邃的學(xué)術(shù)洞察力，孜孜不倦的敬業(yè)精神，給我留下了深刻的印象。值此設(shè)計完成之際，謹向我的導(dǎo)師致以崇高的敬意和衷心的感謝！ 在做設(shè)計時，在老師的推薦下我借閱了關(guān)于模具的書籍，查閱相關(guān)的標(biāo)準(zhǔn)是我我設(shè)計時思路清晰，充滿信息，圓滿地完成了本次設(shè)計。 在設(shè)計撰寫時，得到了機械系多位老師和同學(xué)的幫助，，在忙碌的工作中，仍給予我專業(yè)知識上的指導(dǎo)，而且交給我學(xué)習(xí)的方法和思路，是我在實際設(shè)計中不斷有新的認識和提高，在此，我對他們的幫助表示由衷的感謝！ 最后再次向幫助過我的老師及同學(xué)致以最崇高的敬意！ 參考文獻 1、王孝培主編.沖壓手冊.北京：機械工業(yè)出版社，1990 2、《沖壓模具設(shè)計與制造》　劉建超、張寶忠主編　高等教育出版社 3、《模具設(shè)計與制造簡明手冊》(第二版)　馮炳堯編　上海科學(xué)技術(shù)出版社 4、李碩本主編.沖壓工藝學(xué).北京：機械工業(yè)出版社，1982 5、模具實用技術(shù)叢書編委會.沖壓設(shè)計應(yīng)用實例.北京：機械工業(yè)出版社，1994 6、高鴻庭，劉建超主編.冷沖壓設(shè)計及制造.北京：機械工業(yè)出版社，2002 7、《沖模圖冊》李天佑主編　機械工業(yè)出版社 8、丁松聚主編.冷沖模設(shè)計.北京：機械工業(yè)出版社，1994 9、成虹主編.沖壓工藝與模具設(shè)計.北京：高等教育出版社，2000 10、李天佑主編.沖模圖冊.北京：機械工業(yè)出版社，1988 11、國家技術(shù)監(jiān)督局.沖模模架.北京：中國標(biāo)準(zhǔn)出版社，1991 12、中國機械工程學(xué)會鍛壓學(xué)會編.鍛壓手冊 第2冊.北京：機械工業(yè)出版社，1993 13、王同海編著.實用沖壓設(shè)計技術(shù).北京：機械工業(yè)出版社，1995 14、模具實用技術(shù)叢書編委會.模具制造工藝裝備及應(yīng)用。北京：機械工業(yè)出版社，1999 15、杜東福等編。冷沖壓模具設(shè)計.長沙：湖南科學(xué)技術(shù)出版社，1985 16、趙孟棟主編.冷沖模設(shè)計.北京：機械工業(yè)出版社，2000 . 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.