風(fēng)罩拉伸成形工藝及模具設(shè)計(jì)【有凸緣的筒形件】【落料拉深復(fù)合?!?/h1>
風(fēng)罩拉伸成形工藝及模具設(shè)計(jì)【有凸緣的筒形件】【落料拉深復(fù)合模】,有凸緣的筒形件,落料拉深復(fù)合模,風(fēng)罩拉伸成形工藝及模具設(shè)計(jì)【有凸緣的筒形件】【落料拉深復(fù)合模】,拉伸,成形,工藝,模具設(shè)計(jì),凸緣,筒形件,落料拉深,復(fù)合
風(fēng)罩拉伸成形工藝及模具設(shè)計(jì) 摘要:設(shè)計(jì)著重介紹了制件的成型工藝,及模具結(jié)構(gòu)設(shè)計(jì)。通過對(duì)制件的工藝分析,確定了工藝方案。并設(shè)計(jì)了一套落料拉伸復(fù)合模具。在設(shè)計(jì)同時(shí)利用參考資料,確定了各工作零件的尺寸。并較多的考慮了模具結(jié)構(gòu)的調(diào)整性、易更換性及模具成本。同時(shí)在模具設(shè)計(jì)內(nèi)容中融匯了沖壓模具的不同加工方法、加工工藝及裝配工藝,對(duì)初學(xué)沖壓模具模設(shè)計(jì)者有一定的參考價(jià)值。本設(shè)計(jì)從模具設(shè)計(jì)到零部件的加工工藝以及裝配工藝等進(jìn)行詳細(xì)的闡述,并應(yīng)用CAD進(jìn)行各重要零件的設(shè)計(jì)。 關(guān)鍵詞: 拉伸模 復(fù)合模。 Air shield forming process and die designAbstract:Design focused on parts of the forming process and die structure design. Parts of the process through the analysis of the process program. And designed a tensile composite blanking die. At the same time, the use of reference materials in the design to determine the size of the working parts. And more to consider the restructuring of the mold, and easy to replace and the cost of mold. At the same time, the contents of the mold design stamping die in a combination of different processing methods, processing technology and assembly process, stamping die mold for novice designers have a certain reference value. The design of the parts from the mold design process and the assembly process, such as described in detail, and the application of CAD for the design of the important parts.Keywords:Drawing Die;Compound Die設(shè)計(jì)任務(wù)書系 部: 專 業(yè): 學(xué)生姓名: 學(xué) 號(hào): 設(shè) 計(jì) 題 目: 風(fēng)罩拉伸成形工藝及模具設(shè)計(jì) 起 迄 日 期: 指 導(dǎo) 教 師: 2014 年 4 月 22 日畢 業(yè) 設(shè) 計(jì) 任 務(wù) 書1本畢業(yè)設(shè)計(jì)課題來源及應(yīng)達(dá)到的目的:該課題來源于一一六廠生產(chǎn)一線的沖壓制件。在完成該課題之后,應(yīng)對(duì)沖壓工藝生產(chǎn)較為熟悉,能熟練掌握相關(guān)設(shè)計(jì)手冊(cè)的使用,能獨(dú)立完成一套模具的設(shè)計(jì)及模具工作零件加工工藝的編制,能夠運(yùn)用模具設(shè)計(jì)軟件完成模具裝配圖及零件圖的繪制。2本畢業(yè)設(shè)計(jì)課題任務(wù)的內(nèi)容和要求(包括原始數(shù)據(jù)、技術(shù)要求、工作要求等):課題資料:厚度:2mm材料:08鋼批量:大批量設(shè)計(jì)任務(wù):(1)了解目前國內(nèi)外沖壓模具的發(fā)展現(xiàn)狀;(2)分析筒形件拉深沖壓成形工藝并確定其工藝方案;(3)成形設(shè)備的選用及校核;(4)模具的整體設(shè)計(jì),繪制模具總裝圖與拆畫非標(biāo)準(zhǔn)件零件圖;(5)編寫設(shè)計(jì)說明書一份;(6)編制主要零件加工工藝過程卡。 所在專業(yè)審查意見:負(fù)責(zé)人: 年 月 日系部意見:系領(lǐng)導(dǎo): 年 月 日模具設(shè)計(jì)與制造專業(yè)機(jī) 械 加 工 工 藝 過 程 卡 片零件號(hào)零 件 名 稱00-02凸凹模工序號(hào)工 序 名 稱設(shè) 備夾 具刀 具量 具工 時(shí)名 稱型 號(hào)名 稱規(guī) 格名 稱規(guī) 格名 稱規(guī) 格1下料(3070)鋸床直尺2車外圓車床三爪卡盤標(biāo)準(zhǔn)車刀游標(biāo)卡尺,螺旋測(cè)微器3磨削磨床磁力夾具、虎鉗砂輪游標(biāo)卡尺4鉗工虎鉗劃針剛尺、游標(biāo)卡尺5熱處理(淬火、回火)電熱爐火鉗6磨削磨床磁力夾具、虎鉗砂輪游標(biāo)卡尺7鉗工研磨工具游標(biāo)卡尺設(shè) 計(jì) 者指 導(dǎo) 教 師共 3 頁第 3 頁 專業(yè):模具設(shè)計(jì)與制造 機(jī) 械 加 工 工 藝 過 程 卡 零件號(hào)零 件 名 稱01-03落料凹模工序號(hào)工 序 名 稱設(shè) 備夾 具刀 具量 具工 時(shí)名 稱型 號(hào)名 稱規(guī) 格名 稱規(guī) 格名 稱規(guī) 格1下料鋸床直尺2鍛造鍛床鍛錘直尺3熱處理(退火)4鉗工劃線臺(tái)虎鉗虎鉗劃針、樣沖游標(biāo)卡尺5粗銑平面臥式銑床X6132銑刀游標(biāo)卡尺6粗銑孔臥式銑床X6132銑刀游標(biāo)卡尺7粗磨坐標(biāo)磨床CNC314砂輪千分尺8熱處理電熱爐火鉗9精磨平面磨床M7120A砂輪千分尺10檢驗(yàn)編制 校對(duì) 審核 批準(zhǔn) 河南機(jī)電高等??茖W(xué)校畢業(yè)設(shè)計(jì)評(píng)語學(xué)生姓名: 劉乾 班級(jí): 模具113 學(xué)號(hào): 111304314題 目: 風(fēng)罩成形工藝及模具設(shè)計(jì) 綜合成績: 指導(dǎo)者評(píng)語: 指導(dǎo)者(簽字): 年 月 日畢業(yè)設(shè)計(jì)評(píng)語評(píng)閱者評(píng)語: 評(píng)閱者(簽字): 年 月 日答辯委員會(huì)(小組)評(píng)語: 答辯委員會(huì)(小組)負(fù)責(zé)人(簽字): 年 月 日1、緒論31.1 冷沖壓的概念特點(diǎn)及應(yīng)用31.1.1 冷沖壓的概念31.1.2 冷沖壓的特點(diǎn)及應(yīng)用31.2 冷沖壓現(xiàn)狀與發(fā)展41.2.1 冷沖壓的現(xiàn)狀41.2.2 冷沖壓的發(fā)展41.3冷沖壓基本工序分類51.3.1分離工序51.3.2成形工序52、風(fēng)罩的沖壓工藝性分析63、工藝方案及主要工藝計(jì)算73.1工藝方案的確定73.2主要工藝計(jì)算73.2.1計(jì)算毛坯尺寸73.2.2判斷能否一次拉深成形83.2.3確定是否使用壓邊圈83.2.4試制定首次拉伸系數(shù)83.2.5確定拉伸次數(shù)83.2.6排樣設(shè)計(jì)93.2.7條料寬度、導(dǎo)料板間距離和材料利用率的計(jì)算104、模具的結(jié)構(gòu)設(shè)計(jì)134.1、模具工作部分的計(jì)算134.1.1、拉深模的間隙134.1.2、拉深模的圓角半徑134.1.3、凸凹模工作部分的尺寸和公差134.2、模具各部件的設(shè)計(jì)144.2.1、模柄144.2.4、凸凹模固定板174.2.5落料凹模184.2.6、拉深凸模194.2.7、卸料板194.2.8、壓邊圈194.2.9、凸凹模204.2.10、模具其它部件的選用215、沖壓工藝力計(jì)算及設(shè)備選擇235.1、落料力235.2、卸料力235.3、拉深力235.4、壓邊力245.5、推件力245.6、頂件力245.7沖壓設(shè)備的選擇256、模具零件主要工作零件的設(shè)計(jì)266.1、落料凸、凹模尺寸得計(jì)算266.2.拉深凸、凹模尺寸的計(jì)算277、選用模架、確定閉合高度及總體尺寸298、模具總裝圖319、結(jié)束語33致 謝34參 考 文 獻(xiàn)35風(fēng)罩沖壓成形工藝模具設(shè)計(jì) 1、緒論 目前,我國沖壓技術(shù)與工業(yè)發(fā)達(dá)國家相比還相當(dāng)?shù)穆浜螅饕蚴俏覈跊_壓基礎(chǔ)理論及成形工藝、模具標(biāo)準(zhǔn)化、模具設(shè)計(jì)、模具制造工藝及設(shè)備等方面與工業(yè)發(fā)達(dá)的國家尚有相當(dāng)大的差距,導(dǎo)致我國模具在壽命、效率、加工精度、生產(chǎn)周期等方面與工業(yè)發(fā)達(dá)國家的模具相比差距相當(dāng)大。1.1 冷沖壓的概念特點(diǎn)及應(yīng)用1.1.1 冷沖壓的概念 冷沖壓是在室溫下,利用安裝在壓力機(jī)上的沖模對(duì)材料施加壓力,使材料在沖模內(nèi)產(chǎn)生分離或塑性變形,從而獲得所需要零件的一種壓力加工方法。1.1.2 冷沖壓的特點(diǎn)及應(yīng)用 冷沖壓生產(chǎn)是利用沖模和沖壓設(shè)備完成加工的,與其他加工方法相比,它具有如下特點(diǎn): 1)冷沖壓所用的原材料多是表面質(zhì)量好的板料或帶料,沖壓件的尺寸精度由沖模來保證,所以產(chǎn)品尺寸穩(wěn)定,互換性好。 2)冷沖壓加工不像切削加工那樣大量切除金屬,因而節(jié)省能源,節(jié)省原材料。 3)冷沖壓生產(chǎn)便于實(shí)現(xiàn)自動(dòng)化,生產(chǎn)率高,操作簡(jiǎn)便,對(duì)人工的技術(shù)等級(jí)要求也不高。普通壓力機(jī)每分鐘可生產(chǎn)幾件到幾十件沖壓件,而高速壓力機(jī)每分鐘可生產(chǎn)數(shù)百件甚至上千件的沖壓件。 4)可以獲得其他加工方法所不能或難以制造的壁薄、質(zhì)量輕、剛度好、表面質(zhì)量高、形狀復(fù)雜的零件,小到鐘表的秒針,大到汽車縱梁、覆蓋件等。 但是,冷沖壓必須具備相應(yīng)的沖模,而沖模制造的主要特征是單件小批量生產(chǎn)、精度高、技術(shù)要求高,屬于技術(shù)密集型。因而,在一般情況下,只有在產(chǎn)品生產(chǎn)批量大的情況下,才能獲得較高的經(jīng)濟(jì)效益。綜上所述,冷沖壓與其他加工方法相比,由于冷沖壓在技術(shù)上和經(jīng)濟(jì)上的特別之處,因而在現(xiàn)代工業(yè)生產(chǎn)中占有重要地位。在汽車、拖拉機(jī)、電器、電子、儀表、國防、航空航天以及日用品中隨處可見的龍沖壓產(chǎn)品,如不銹鋼飯盒、高壓鍋、汽車覆蓋件、冰箱門板等。拒不完全統(tǒng)計(jì),沖壓件在汽車、拖拉機(jī)行業(yè)中約占60%,在電子工業(yè)約占85%,而在日用五金產(chǎn)品占到約90%.如一輛汽車投產(chǎn)所需配套2000副以上各類專用模具;一臺(tái)冰箱投產(chǎn)則需要350副以上各類專用模具。可以這么說,一個(gè)國家模具工業(yè)發(fā)展的水平能反映出這個(gè)國家的現(xiàn)代化、工業(yè)化發(fā)展的程度,對(duì)于一個(gè)地區(qū)來說也是如此。1.2 冷沖壓現(xiàn)狀與發(fā)展1.2.1 冷沖壓的現(xiàn)狀冷沖壓技術(shù)從最初的作坊式生產(chǎn)到現(xiàn)在的專業(yè)化模具工業(yè)生產(chǎn),從無到有發(fā)展迅速。而我國模具工業(yè)在近二十年來的發(fā)展更是迅速,模具及模具加工設(shè)備市場(chǎng)需求潛力巨大,發(fā)展前景廣闊。隨著工業(yè)的發(fā)展,工業(yè)產(chǎn)品的品種、數(shù)量越來越多,對(duì)產(chǎn)品的質(zhì)量、數(shù)量越來越多,對(duì)產(chǎn)品質(zhì)量外觀的要求,更是日趨嚴(yán)格。所以改革開放以來,我國已成為使用模具的大國,其中,汽車、摩托車與家電產(chǎn)品生產(chǎn)用的各類模具的年需求量已占全故模具需求總量的60%以上。但是,我國模具生產(chǎn)能力和水平與國外相比則差距頗大,造成20世紀(jì)90年代模具進(jìn)口量占全國模具銷售總額的三分之一以上,達(dá)6-10億美元。1.2.2 冷沖壓的發(fā)展 模具技術(shù)的發(fā)展應(yīng)該為適應(yīng)模具生產(chǎn)“交貨期短”、“精度高”、“質(zhì)量好”、“價(jià)格低”的要求服務(wù)。達(dá)到這一要求急需發(fā)展如下幾項(xiàng): (1)全面推廣CAD/CAM/CAE技術(shù) 模具CAD/CAM/CAE技術(shù)是模具設(shè)計(jì)制造的發(fā)展方向。隨著計(jì)算機(jī)軟件的發(fā)展與進(jìn)步,普及CAD/CAM/CAE技術(shù)的條件已基本成熟,各企業(yè)將加大CAD/CAE/CAM技術(shù)培訓(xùn)和技術(shù)服務(wù)的力度。 (2)模具掃面及數(shù)字化系統(tǒng) 高速掃描機(jī)和模具掃描系統(tǒng)提供了從模型或?qū)嵨飹呙璧郊庸こ銎谕哪P退璧闹T多功能,大大縮短了模具的研制周期。 (3)模具制造方面 國外近年來發(fā)展的高速銑削加工,大幅度提高了加工效率,并可以獲得極低的表面粗糙值。模具自動(dòng)加工系統(tǒng)應(yīng)有多臺(tái)機(jī)床合理組合,配有隨行定位夾具或定位盤,有完整的機(jī)具、刀具數(shù)控庫與數(shù)控柔性同步系統(tǒng),以及質(zhì)量監(jiān)控系統(tǒng)。 (4)提高模具標(biāo)準(zhǔn)化程度 我國模具標(biāo)準(zhǔn)化正在不斷提高,估計(jì)目前我國模具標(biāo)準(zhǔn)件使用覆蓋率已達(dá)到30%左右;國外發(fā)達(dá)國家一般為80%左右。 (5)優(yōu)質(zhì)材料及先進(jìn)表面處理技術(shù) 選用優(yōu)質(zhì)材料和應(yīng)用先進(jìn)的表面處理技術(shù)提高模具壽命十分重要。 (6)開發(fā)和引進(jìn)新裝備、新技術(shù) 開發(fā)和引進(jìn)高速壓力機(jī)和多工位自動(dòng)壓力機(jī)、數(shù)控壓力機(jī),沖壓柔性制造系統(tǒng)及各種專用壓力機(jī),以滿足大批量、高精度生產(chǎn)的需求。 (7)冷沖壓基本原理的研究 沖壓成形基本理論的研究是提高沖壓技術(shù)的基礎(chǔ)。材料成型的工藝性能,沖壓成形中應(yīng)力與應(yīng)變的分析和計(jì)算機(jī)模擬。金屬變形規(guī)律與模具相互關(guān)系。1.3冷沖壓基本工序分類 冷沖壓加工的零件,由于其形狀、尺寸、精度要求、生產(chǎn)批量、原材料性能等各不相同,因此生產(chǎn)中所采用的冷沖壓工藝方法也是多種多樣的。概括起來可以分為兩大類,即分離工序和成形工序。1.3.1分離工序 分離工序是指板料按一定的輪廓線分離而獲得一定形狀、尺寸和切斷質(zhì)量的沖壓件工序。1.3.2成形工序 成型工序是指坯料在不破裂的條件下生產(chǎn)塑性變形而獲得一定形狀和尺寸的沖壓件的工序。2、風(fēng)罩的沖壓工藝性分析零件名稱:風(fēng)罩 生產(chǎn)批量:大批量材料:08F料厚:1mm零件簡(jiǎn)圖:(見下圖) 此工件為有凸緣的筒形件,且底部帶有圓孔,拉深高度不高,拉深前后厚度不變,工件材料為08F,拉深性能比較好,且此工件的形狀滿足拉深工藝要求,可用拉深工序加工。工件底部上有一直徑15mm的圓孔,孔邊與筒壁之間的距離為L=7.5mmR+0.5t=3.5mm,滿足沖裁尺寸條件要求。30的公差等級(jí)為IT12級(jí),滿足拉深工序?qū)ぜ畹燃?jí)的要求,15的公差等級(jí)為IT9級(jí),精度比較高,應(yīng)在拉深后增加整形工序,以提高其精度,又由于材料的各向異性的影響,拉深件的口部或凸緣外緣一般是不整齊的,出現(xiàn)“突耳”現(xiàn)象,需要在最后增加切邊工序。3、工藝方案及主要工藝計(jì)算3.1工藝方案的確定 因?yàn)楣ぜ閹咕壡业撞坑袌A孔的筒形零件,零件形狀比較對(duì)稱,零件名稱為風(fēng)罩,該工件有落料、拉深、校形、沖孔、切邊五個(gè)基本工序,通過分析有2種工作方案: 方案1:落料拉深校形沖孔-切邊。采用單工序模模生產(chǎn)。 方案2:先落料拉深,再校形沖孔切邊,采用一套復(fù)合模具生產(chǎn)。 方案1模具結(jié)構(gòu)簡(jiǎn)單,但需要四道工序四副模具,生產(chǎn)效率低,難以滿足該工件大批量生產(chǎn)的要求。方案2需要兩副模具,雖然比方案二多了一副模具,但由于每套模具只進(jìn)行兩個(gè)工序,且零件的幾何形狀簡(jiǎn)單對(duì)稱,模具制造、裝配和維修并不困難,模具采用復(fù)合形式,簡(jiǎn)化了工序,生產(chǎn)效率比方案1高,能滿足大批量生產(chǎn)的要求,所以經(jīng)綜合考慮,工件采用方案2進(jìn)行生產(chǎn)。我只做了一套落料拉深復(fù)合模,另一套校形沖孔切邊復(fù)合模由另一位學(xué)生做。3.2主要工藝計(jì)算 3.2.1計(jì)算毛坯尺寸 由工件簡(jiǎn)圖可得,d= 50 mm,d= (32 - 1)mm = 31mm,由凸緣的相對(duì)直徑d/ d = 50mm / 31mm = 1.6,查表4.2得修邊余量 = 2.0mm,因零件底部圓角半徑r與凸緣圓角半徑R相等,即r = R時(shí),有凸緣筒形件的毛坯直徑 D = 將d = 50 + 2 = (50 + 22)mm = 54mm ,d = 31mm,H = (31 1 )mm = 30mm,R = 3mm,代入上式中,得毛胚的直徑為 D = =80.25mm3.2.2判斷能否一次拉深成形 工件總的拉深系數(shù)m= d / D = 31mm / 80.25mm = 0.39,工件總的拉深相對(duì)高度H / d = 30mm / 31mm = 0.97。 由 d/ d = 54mm / 31mm = 1.74,t /D100 = 1mm / 80.25mm100 = 1.25,查表4.9得有凸緣筒形件第一次拉深的極限拉深系數(shù)m = 0.46。 由表4.10查得,有凸緣筒形件首次拉深的極限相對(duì)高度h/d= 0.50,由于m = 0.39 h/d= 0.50,所以工件不能一次拉出。3.2.3確定是否使用壓邊圈 因?yàn)閠 /D100 = 1mm / 80.25mm100 = 1.25 1.5, m = 0.46 0.6,由表4.7查得需要采用壓邊裝置。首次拉伸一般采用平面壓邊裝置,再次拉伸采用筒形壓邊圈,所以要使用限位裝置。3.2.4試制定首次拉伸系數(shù)取d/ d,=1.1,查表4-9得m1=0.53,而第一次拉深系數(shù)m1=d1/D,則第一次拉深的半成品直徑為d1=m1xD=0.53x80.25=42.5mm(調(diào)整為43mm)經(jīng)計(jì)算得r=r凸1=4.5mm,為了以后的拉深不使已拉深好的半成品工序件變形,第一次拉深要將坯料多拉入凹模所需要量的5%,則需對(duì)坯料相應(yīng)的放大。經(jīng)計(jì)算得第一次相對(duì)高度(H1/d)工件= 27/43=0.63,由表4-10查得,有凸緣圓筒形件的第一次拉深的最大相對(duì)高度h/d=0.65,因?yàn)椋℉1/d)工件小于等于h/d,所以第一次拉深直徑43合理。3.2.5確定拉伸次數(shù)1)計(jì)算直徑 根據(jù)毛坯的相對(duì)高度(t /D100)=(1mm/80.25mm)x100=1.25mm,由表4.11取值為m1=0.75,m2=0.78,m3=0.80,m4=0.82.各次拉伸的半成品的直徑為d2=m2xd1=0.75x43=32.25mm(調(diào)整為34mm)d3=m3xd2=0.78x34=26.52mm31mm所以應(yīng)該兩次拉深成型。由于每次最好不要以極限拉深系數(shù)進(jìn)行拉深,所以要調(diào)整極限拉深系數(shù)為:m1=0.55mm,m2=0.77.m3=0.80各次半成品的直徑為d1=m1xD=0.55x80.25=44.14mm(調(diào)整為45mm)d2=m2xd1=0.77x45=34.65mm(調(diào)整為35mm)d3=m3xd2=0.80x35=28mm31mm所以最終是3次拉深成形。選定d3為工件的直徑31mm。2)計(jì)算圓角半徑第二次拉深的凹模圓角半徑為3.3mm,則r凸2=r凹2=3.3mm第二次拉深的工件r=3.3+0.5=4mm最后一次拉深,凸凹模的圓角半徑應(yīng)取工件的圓角半徑,即r凸3=r凹3=3mm。3)計(jì)算高度第一次拉深要將坯料多拉入凹模所需要的5%,則需要對(duì)坯料相應(yīng)的放大。經(jīng)計(jì)算得第一次拉深的高度為24mm,第二次的拉深高度為27mm。最后一次的拉伸高度31mm。各半成品的外形總高度用;Hn+1mm來計(jì)算,分別為h1=24mm h2=28mm h3=31mm。 3.2.6排樣設(shè)計(jì)設(shè)計(jì)模具時(shí),條料的排樣很重要。中軸碗具有左右對(duì)稱的特點(diǎn),單向排列時(shí)(如圖所示)的排樣方案可以提高材料的利用率,減少廢料。 3.2.7條料寬度、導(dǎo)料板間距離和材料利用率的計(jì)算 查表取得搭邊值為a = 1.8mm,a = 2.2mm。 條料寬度的計(jì)算:擬采用無側(cè)壓裝置的送料方式,由 條料寬度 B=【D+ 2a + C】 B_條料寬度(mm)D條料寬度方向沖裁件的最大尺寸;a側(cè)搭邊的最小值; 條料寬度的單向(負(fù)向)偏差; C_導(dǎo)料板與最寬條料之間的單面最小間隙; 把D= 77.3mm,a = 2.2mm,查表得C = 0.5, = 0.8mm,代入上式得B = 82.2mm。 材料利用率的計(jì)算:由書 材料利用率通用計(jì)算公式 =100%式中 S一個(gè)零件的實(shí)際面積,mm2; n一個(gè)步距內(nèi)實(shí)際沖裁件數(shù)量; B條料寬度,mm; A送料步距, mm把S = 3.14 38.65 = 4690.6mm,n = 1,B = 82.2mm,A = D + a = 77.3mm + 1.8mm = 79.1mm。代入上式得 = 4960.6 mm1/82.2mm79.1mm100% = 76.3% 導(dǎo)料板間距離的計(jì)算: A = B + C = D+ 2a + 2C 式中 B_條料寬度(mm)D條料寬度方向沖裁件的最大尺寸;a側(cè)搭邊的最小值; C_導(dǎo)料板與最寬條料之間的單面最小間隙; 把B = 82.2mm,C = 0.5, a = 2.2mm, D= 77.3mm,代入上式得 A = 77.3mm + 22.2mm + 20.5mm = 82.7mm。 4、模具的結(jié)構(gòu)設(shè)計(jì)4.1、模具工作部分的計(jì)算4.1.1、拉深模的間隙 深間隙對(duì)拉深過程有較大的影響。它不僅影響拉深件的質(zhì)量與尺寸精度,而且影響拉深模的壽命以及拉深是否能夠順利進(jìn)行。因此,應(yīng)該綜合考慮各種影響因素,選取適當(dāng)?shù)睦铋g隙值,既可保證工件的要求,又能使拉深順利進(jìn)行。 由前面計(jì)算的:Z/2 = 2.35mm 4.1.2、拉深模的圓角半徑 凸模、凹模的選用在制件拉深過程中有著很大的作用。凸模圓角半徑的選用可以大些,這樣會(huì)減低板料繞凸模的彎曲拉應(yīng)力,工件不易被拉裂,極限拉深因數(shù)會(huì)變小些;凹模的圓角半徑也可以選大些,這樣沿凹模圓角部分的流動(dòng)阻力就會(huì)小些,拉深力也會(huì)減小,極限拉深因數(shù)也會(huì)相應(yīng)減小。但是凸、凹模的圓角半徑也不易過大,過大的圓角半徑,就會(huì)減少板料與凸模和凹模端面的接觸面積及壓邊圈的壓料面積,板料懸空面積增大,容易產(chǎn)生失穩(wěn)起皺。拉深凸凹模的圓角半徑已有前面計(jì)算得出結(jié)果: r=3mm4.1.3、凸凹模工作部分的尺寸和公差 拉深以凹模為基準(zhǔn),模具的制造公差按IT6級(jí)選取。由前面計(jì)算得凹模的尺寸和公差為 : D= ( D 0.75) =(40.175 0.750.2) = 40.025凸模的尺寸和公差為: D= ( D - 0.75 - Z)=(40.175 - 0.750.2 4.7) = 35.325 4.2、模具各部件的設(shè)計(jì)4.2.1、模柄因?yàn)槟>叱叽绮皇翘?,綜合考慮選用垂直度和同軸度較好的壓入式模柄,根據(jù)JB/T 7646.1選取基本尺寸標(biāo)準(zhǔn)為40mm的模柄,具體如下圖所示: .4.2.2、墊板 因?yàn)橥拱寄:吐淞习寄6紴閳A形,所以采用圓形墊板,由JB/T 76531994的規(guī)定,選取規(guī)格為160mm 8mm的墊板如下 4.2.3、拉深凸模固定板凸模固定板主要用來固定拉深凸模,使其在工作過程中保持穩(wěn)定和精度,所以根據(jù)JB/T 76531994選取規(guī)格標(biāo)準(zhǔn)為160mm 18mm的凸凹模固定板,為了使其均勻固定,需要在其上加工三個(gè)螺紋孔和三個(gè)銷釘孔,又因?yàn)槔罴庸ば枰獕哼吶Γ赃€需要在凸模固定板上加工三個(gè)頂桿孔,使壓邊圈起到壓邊作用,另外還要加工固定凸模的階梯孔,如下圖所示: 4.2.4、凸凹模固定板 凸凹模固定板是用來固定凸凹模,使其在工作過程中能穩(wěn)定的工作,保持模具的精度,它通過螺釘與上模座進(jìn)行緊固連接,同時(shí)通過銷釘進(jìn)行定位,以保證安裝位置的精度,另外卸料螺釘通過安裝在固定板的彈簧達(dá)到彈性卸料的目的,所以需要在凸凹模固定板上加工三個(gè)螺釘孔和兩個(gè)銷釘孔,另外還要加工一個(gè)固定凸凹模的階梯孔和三個(gè)卸料螺釘孔,各部分工作尺寸如下圖所示:4.2.5落料凹模落料凹模是模具的主要工作零件,需要較高的強(qiáng)度和精度,所以凹模材料選用Cr12,淬火硬度為:5862HRC,凹模刃口尺寸為77.15mm,可通過鏜、銑削、磨削等加工方法進(jìn)行加工制造,安裝時(shí)通過螺釘與銷釘和下模座進(jìn)行連接和定位,所以凹模上要加工螺釘孔和銷釘孔,刃口部分采用階梯孔形式,以方便安裝壓邊圈,如下圖所示:4.2.6、拉深凸模 拉深凸模是模具的主要工作零部件,用于工件的拉深成形,需要很高的精度以保證工件的精度,同時(shí)對(duì)強(qiáng)度要求也較高,綜合考慮拉深凸模材料采用Cr12,凸模刃口尺寸為35.325mm,圓角半徑為3mm,其外形可通過車削、磨削等進(jìn)行加工,與凸模固定板采用過盈配合,以進(jìn)行緊固安裝。4.2.7、卸料板 卸料板是模具的主要卸料零件,它與卸料螺釘、彈簧組成彈性卸料裝置,以卸除卡在凸凹模上的條料,使工作快速進(jìn)行,與凸凹模之間采用間隙配合,卸料板需加工卸料螺釘孔與卸料螺釘進(jìn)行連接, 4.2.8、壓邊圈 在拉深工序中,為保證拉深件的表面質(zhì)量,防止拉深過程中材料的起皺,常采用壓邊圈用合適的壓邊力使毛坯的變形區(qū)部分被壓在凹模平面上,并使毛坯從壓邊圈與凹模平面之間的縫隙中通過,從而制止毛坯的起皺現(xiàn)象。壓邊圈的內(nèi)形與拉深凸模間隙配合,一般與頂料桿(三根以上)、橡皮等構(gòu)成彈性卸料系統(tǒng)。4.2.9、凸凹模 凸凹模即是落料的凸模又是拉深的凹模,做為模具的主要成形零部件,凸凹模的精度和強(qiáng)度都有較高的要求,其凸模和凹模部分的刃口尺寸分別為76.79 mm和35.325mm,其外部形狀可以通過車削、鏜削、磨削等加工方法進(jìn)行加工制造,材料可選用Cr12,淬火硬度為5862HRC,4.2.10、模具其它部件的選用 模具其它部件的選用見表21 表21 模具其它部件的選用序號(hào)名稱數(shù)量材料規(guī)格/ mm標(biāo)準(zhǔn)熱處理1銷釘240Cr10602打桿140111504045HRC3螺釘345M12604打料塊14040404045HRC5卸料螺釘340CrM12853035HRC6螺釘345M12957頂桿3T8AM10904045HRC8銷釘340Cr10909彈簧3209067010橡皮15、沖壓工藝力計(jì)算及設(shè)備選擇 5.1、落料力 P = 1.3t 式中 _材料抗剪強(qiáng)度 D_毛胚直徑 t_材料厚度 查表得15鋼得抗剪強(qiáng)度 = 289MPa 。把D = 77.3mm,t = 2.5mm代入上式得 P = 1.3 3.14 77.3mm 289MPa2.5mm =227976.638 227.977kN。 5.2、卸料力 P = K P K_卸料力系數(shù); P落料力; 查表得K = 0.06,P =227.977kN,所以代入上式得 P = 0.06227.977kN = 13.6786kN 13.679kN 。 5.3、拉深力 P = Kdt 式中 K_修正系數(shù),查表4.6; d_拉深后工序件中徑; t_材料厚度; _材料的抗拉強(qiáng)度; 查表得K = 1.0, = 375MPa,把K = 1.0, = 375MPa,d = 37.5mm,t = 2.5mm,代入上式得 P = 13.1437.5mm2.5mm375Mpa =110.39KN。 5.4、壓邊力 P = P 式中 D_毛胚直徑(mm); d_第一次拉深后工件的直徑(mm); r_拉深凹模圓角半徑(mm); P_單位壓邊力(Mpa); 查表得 P = 2.5Mpa, 取r = 6mm。D = 77.3mm,d = 37.5mm。代入上式得 P= 2.5Mpa = 6917.89 6.92kN。 5.5、推件力 P = nK P 式中 n_沖孔時(shí)卡在凹模內(nèi)的廢料數(shù); K_推件力系數(shù); P_沖孔力; 查表得K = 0.05,取n = 3,把K = 0.05,n = 3,P = 56.036kN。代入上式得 P = 30.0556.036 kN = 7.9554 kN。 5.6、頂件力 P = K P 式中 K_頂件力系數(shù); P_拉深力; 查表得 K = 0.06,P = 110.39KN,代入上式得 P = 0.06110.39KN = 6.6234kN。 所以綜上可得,落料拉深模得總沖裁力 P = P+ P+ P+ P+ P = 227.977kN +220.39 kN +13.679 Kn+6.92 kN+6.623 kN =365.589 kN。 P = P+ P = 56.036kN +7.9554 kN = 63.9914kN。5.7沖壓設(shè)備的選擇 為了使壓力機(jī)能安全工作,取 P (1.6 1.8)P 所以落料拉深的壓力機(jī) P (1.6 1.8)P = 1.6 365.589 kN = 584.9424 kN。 沖孔壓力機(jī) P (1.6 1.8)P = 1.7 63.9914kN = 108.78538kN。故落料拉深模選用630kN的開式壓力機(jī)。其主要技術(shù)參數(shù)如下。公稱壓力:630kN 滑塊行程:130mm 最大封閉高度:360mm 最大封閉高度調(diào)節(jié)量:80mm 工作臺(tái)尺寸:480mm710mm 工作臺(tái)墊板孔尺寸: 250模柄孔尺寸:50mm80mm 工作臺(tái)墊板厚度:80mm 沖孔模選用150kN的開式壓力機(jī)。6、模具零件主要工作零件的設(shè)計(jì) 6.1、落料凸、凹模尺寸得計(jì)算由于落料是一個(gè)簡(jiǎn)單的圓形,因沖裁此類工件的凸、凹模制造相對(duì)簡(jiǎn)單,精度容易保證,所以擬采用分別加工。設(shè)計(jì)時(shí),需在圖紙上分別標(biāo)注凸模和凹模刃口尺寸及制造工差。查表2.4得間隙值Z=0.360mm,Z=0.500mm。查表2.5得凸、凹模制造公差:= 0.020mm,= 0.030mm。校核:Z- Z = 0.140mm,而+ = 0.050mm滿足Z- Z +的條件。查表2.6得:IT11級(jí)時(shí)磨損系數(shù)x = 0.75根據(jù)設(shè)計(jì)原則,落料時(shí)以凹模為設(shè)計(jì)基準(zhǔn)。由書式(2.3)和(2.4)得 D= ( D - x) D= ( D - Z) 式中 D、 D落料凹凸模尺寸; D落料件的最大基本尺寸; x磨損系數(shù); 工件制造公差; Z最小合理間隙; 、凸、凹模的制造公差。 把D = 77.3mm,x = 0.75, = 0.20, = 0.020mm,= 0.030mm,Z=0.360mm代入上式得 D= (77.3mm 0.750.20) = 77.15mm D= (77.15mm 0.360mm) = 76.79 mm6.2.拉深凸、凹模尺寸的計(jì)算 由于外形尺寸精度較高,所以以凹模為基準(zhǔn)進(jìn)行設(shè)計(jì)加工,由式4.35和4.36得 D= ( D 0.75) D= ( D - 0.75 - Z) 式中: D、 D凹、凸模的尺寸; D_零件外徑的最大極限尺寸;零件的公差; 、凹、凸模制造公差; Z拉深模雙面間隙。 查表得 = 0.2, = = 0.016mm,因?yàn)楣ぜ木纫筝^高,為了拉深后的回彈小,表面光潔,所以采用負(fù)間隙拉深模,其單面間隙值為 = (0.9 0.95)t = 0.94 2.5 = 2.35mm所以取Z = 4.7mm 代入上式得 D= ( D 0.75) =(40.175 0.750.2) = 40.025 D= ( D - 0.75 - Z)=(40.175 - 0.750.2 4.7) = 35.325 凸、凹模的圓角半徑得計(jì)算 考慮到實(shí)際采用的拉深系數(shù)均接近其極限值,故拉深凹模圓角半徑應(yīng)大些,可按公式,計(jì)算拉深凸模和凹模的圓角半徑 r = 0.8 = 2.828mm 所以取 r = 3mm7、選用模架、確定閉合高度及總體尺寸 由于拉深凹模外形尺寸不大,且工件精度要求較高,為了工作過程穩(wěn)定和保證工件精度,選用中間導(dǎo)柱模架。再按其標(biāo)準(zhǔn)選擇具體結(jié)構(gòu)尺寸見表5-1。表3-1 拉深落料模架規(guī)格選用名稱尺寸材料熱處理上模座16016040HT200下模座16016045HT200導(dǎo)柱28170、3217020滲碳5862HRC導(dǎo)套2810038、321003820滲碳5862HRC最小閉合高度H= 180mm, 最大閉合高度H = 220mm。模具的閉合高度 H = 上模座厚 + 墊板厚 + 凸凹模厚 + 凸模厚 + 下模座厚 + 墊板厚 - (料厚 +工件高度) = 40mm + 8mm + 64mm + 50mm + 45mm + 10mm (2.5mm + 14mm) =200.5mm因?yàn)槟>叩姆忾]高度H應(yīng)該介于壓力機(jī)的最大封閉高度Hmax和最小封閉高度Hmin之間,一般?。篐max-5mmHHmin+10mm由此可知,要使工件能順利的加工和從模具上取出,必須要模具有足夠的封閉高度 HmaxH+5mm=200.5mm + 5mm = 205.5mm HminH-10mm=200.5mm 10mm = 190.5mm 因H = 220mm 205.5mm, H= 180mm 190.5mm,所以可以選用標(biāo)準(zhǔn)模架。8、模具總裝圖 由以上設(shè)計(jì),可得模具的總裝配圖,見下圖 1下模座 2墊板 3凸模固定板 4落料凹模 5螺釘 6導(dǎo)柱 7導(dǎo)套 8上模座 9彈簧 10卸料螺釘 11模柄 12打桿 13圓柱銷 14螺釘 15墊板 16凸凹模固定板 17推件塊 18卸料板 19凸凹模 20壓邊圈 21圓柱銷 22拉深凸模 23橡皮 24托板 25螺柱 26螺母 27頂桿 28擋料銷模具工作過程:條形板材由前后通過凹模上的擋料銷送進(jìn)定位,上模下行,落料拉深凸凹模19與落料凹模4首先完成落料工序,上模繼續(xù)下行,拉深凸模22開始接觸壓邊圈20壓住是落料毛胚并將其壓入落料拉深凸凹模19孔內(nèi),完成拉深工序,上?;爻虝r(shí),彈性卸料板18從拉深落料凸凹模上卸下廢料,壓邊圈在彈頂裝置的作用下將工件從拉深凸模上推掉,若工件卡在落料拉深凸凹??變?nèi),可通過推件塊17在上?;爻痰揭欢ň嚯x后,將工件推出。9、結(jié)束語風(fēng)罩件屬于簡(jiǎn)單拉深沖孔件,分析其工藝性,并確定工藝方案。根據(jù)計(jì)算確定本制件可以一次拉深成形,所以工件的生產(chǎn)可通過落料拉深和切邊沖孔兩道工序完成,然后相應(yīng)選取各工序的壓力機(jī)。本設(shè)計(jì)主要是第一次落料拉深模具的設(shè)計(jì),需要計(jì)算拉深時(shí)的間隙、工作零件的圓角半徑、尺寸和公差,并且還需要確定模具的總體尺寸和模具零件的結(jié)構(gòu),然后根據(jù)上面的設(shè)計(jì)繪出模具的總裝圖。 由于在零件制造前進(jìn)行了預(yù)測(cè),分析了制件在生產(chǎn)過程中可能出現(xiàn)的缺陷,采取了相應(yīng)的工藝措施。因此,模具在生產(chǎn)零件的時(shí)候才可以減少廢品的產(chǎn)生。 風(fēng)罩件的形狀結(jié)構(gòu)較為簡(jiǎn)單,拉深高度不是太高,所以在保證零件的順利加工和取件的前提下,可以選用標(biāo)準(zhǔn)模架。模具工作零件的結(jié)構(gòu)也較為簡(jiǎn)單,它可以相應(yīng)的簡(jiǎn)化了模具結(jié)構(gòu)。便以以后的操作、調(diào)整和維護(hù)。風(fēng)罩模具的設(shè)計(jì),是理論知識(shí)與實(shí)踐有機(jī)的結(jié)合,更加系統(tǒng)地對(duì)理論知識(shí)做了更深切貼實(shí)的闡述。也使我認(rèn)識(shí)到,要想做為一名合理的模具設(shè)計(jì)人員,必須要有扎實(shí)的專業(yè)基礎(chǔ),并不斷學(xué)習(xí)新知識(shí)新技術(shù),樹立終身學(xué)習(xí)的觀念,把理論知識(shí)應(yīng)用到實(shí)踐中去,并堅(jiān)持科學(xué)、嚴(yán)謹(jǐn)、求實(shí)的精神,大膽創(chuàng)新,突破新技術(shù),為國民經(jīng)濟(jì)的騰飛做出應(yīng)有的貢獻(xiàn)。致 謝首先感謝本人的導(dǎo)師翟德梅老師,她幫我仔細(xì)審閱了本文的全部內(nèi)容并對(duì)我的畢業(yè)設(shè)計(jì)內(nèi)容提出了許多建設(shè)性建議。翟德梅老師淵博的知識(shí),誠懇的為人,使我受益匪淺,在畢業(yè)設(shè)計(jì)的過程中,特別是遇到困難時(shí),她給了我鼓勵(lì)和幫助,在這里我向他表示真誠的感謝!感謝母校河南機(jī)電高等??茖W(xué)校的辛勤培育之恩!感謝材料工程系系給我提供的良好學(xué)習(xí)及實(shí)踐環(huán)境,使我學(xué)到了許多新的知識(shí),掌握了一定的操作技能。最后,我非常慶幸在三年的的學(xué)習(xí)、生活中認(rèn)識(shí)了很多可敬的老師和可親的同學(xué),并感激師友的教誨和幫助!參 考 文 獻(xiàn)1翟德梅. 模具制造技術(shù). 北京 機(jī)械工業(yè)出版社 20042楊占堯.模具制造工藝課程設(shè)計(jì). 北京 化學(xué)工業(yè)出版社20083原紅玲 沖壓工藝與模具設(shè)計(jì) 北京 機(jī)械工業(yè)出版社 20044李學(xué)鋒 模具設(shè)計(jì)與制造實(shí)訓(xùn)教程 北京 化學(xué)工業(yè)出版社20045高為國 模具材料 北京 機(jī)械工業(yè)出版社 20046寇世瑤 機(jī)械制圖 北京 高等教育出版社7陳于萍 互換性與測(cè)量技術(shù) 北京 高等教育出版社8李紹林 實(shí)用模具技術(shù)手冊(cè) 上??茖W(xué)技術(shù)出版社20019李曉沛 尺寸極限與配合的設(shè)計(jì)和選用 中國標(biāo)準(zhǔn)出版199910萬良輝 萬秀鳳 冷沖壓模具設(shè)計(jì)與制造 北京航空航天大學(xué)出版 200531Int 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.