前端蓋沖壓成形工藝與模具設(shè)計(jì)【張力盤】【落料拉深復(fù)合模】
前端蓋沖壓成形工藝與模具設(shè)計(jì)【張力盤】【落料拉深復(fù)合?!?張力盤,落料拉深復(fù)合模,前端蓋沖壓成形工藝與模具設(shè)計(jì)【張力盤】【落料拉深復(fù)合模】,前端,沖壓,成形,工藝,模具設(shè)計(jì),張力,落料拉深,復(fù)合
2 河南機(jī)電高等??茖W(xué)校畢業(yè)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: 前端蓋沖壓成形工藝及模具設(shè)計(jì) 起 迄 日 期:指 導(dǎo) 教 師: 2014年4月 13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:該課題來源于楊占堯老師發(fā)放的畢業(yè)設(shè)計(jì)題目。在完成該課題之后,應(yīng)對(duì)沖裁工藝生產(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):(1)了解目前國內(nèi)外沖裁模具的發(fā)展現(xiàn)狀;(2)沖壓件的結(jié)構(gòu)工藝分析;(3)板體落料拉深模設(shè)計(jì),并編寫設(shè)計(jì)說明書一份;(4)繪制模具總裝圖一張,并畫出非標(biāo)準(zhǔn)零件的零件圖; (5)編制主要零件加工工藝過程卡。原始資料:零件件圖及其尺寸見說明書零件名稱:張力盤材料:08A厚度:1.5mm生產(chǎn)批量:大批量所在專業(yè)審查意見:負(fù)責(zé)人: 年 月 日系部意見:系領(lǐng)導(dǎo): 年 月 日機(jī) 械 加 工 工 序 卡 工序名稱粗銑工序號(hào)02零件名稱凹模零件號(hào)00-01零件重量同時(shí)加工零件數(shù)1材 料毛 坯牌 號(hào)硬 度型 號(hào)重 量Cr12設(shè) 備夾 具名 稱輔 助工 具名 稱型 號(hào)銑床虎鉗游標(biāo)卡尺安 裝工 步安裝及工步說明刀 具量 具走 刀長 度走 刀次 數(shù)切 削 深 度進(jìn)給量主 軸轉(zhuǎn) 速切 削速 度基 本工 時(shí)一次1銑上平面75面銑刀游標(biāo)卡尺0.521200/ min800r/min一次1銑下平面75面銑刀游標(biāo)卡尺0.521200/ min800r/min一次2銑兩端面20立銑刀游標(biāo)卡尺0.51160/ min300r/min一次2銑兩端面20立銑刀游標(biāo)卡尺0.51160/ min300r/min設(shè) 計(jì) 者指 導(dǎo) 教 師共 1 頁第1頁 機(jī) 械 加 工 工 藝 過 程 卡 模具號(hào)零件號(hào)零 件 名 稱00-21凹模21牌 號(hào)硬 度Cr125064HRC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01下料鋸床虎鉗直尺02錘鍛蒸汽錘虎鉗直尺03車數(shù)控車床三爪卡盤外圓車刀游標(biāo)卡尺04銑數(shù)控銑床虎鉗銑平面游標(biāo)卡尺05熱處理熱處理爐06磨平面磨床磁力吸盤砂輪游標(biāo)卡尺07檢驗(yàn) 編制 校對(duì) 審核 批準(zhǔn) 設(shè)計(jì)說明書畢業(yè)設(shè)計(jì)題目:前端蓋的沖壓成形工藝及模具設(shè)計(jì)系 部 專 業(yè) 班 級(jí) 學(xué)生姓名 學(xué) 號(hào) 指導(dǎo)教師 2014年 4 月 30日 前端蓋沖壓成形工藝及模具設(shè)計(jì) 摘要:本設(shè)計(jì)的題目為前端蓋沖壓成形工藝及模具設(shè)計(jì)的設(shè)計(jì),體現(xiàn)了薄板類沖裁零件的要求、內(nèi)容及方向,有一定的設(shè)計(jì)意義。通過對(duì)該零件模具的設(shè)計(jì),進(jìn)一步加強(qiáng)了本人沖壓模設(shè)計(jì)的基礎(chǔ)知識(shí),為設(shè)計(jì)更復(fù)雜的沖壓模具做好了鋪墊和吸取更深刻的經(jīng)驗(yàn)。 本設(shè)計(jì)運(yùn)用沖壓成形工藝及模具設(shè)計(jì)的基礎(chǔ)知識(shí),首先分析了沖裁件的沖壓工藝性,為確定沖裁工藝方案做好了準(zhǔn)備;然后計(jì)算沖裁力和模具刃口尺寸,便于選取壓力機(jī)及確定工作零件的尺寸和結(jié)構(gòu);最后分析了制件的特征,確定模具的設(shè)計(jì)參數(shù)、設(shè)計(jì)要點(diǎn)及推件裝置的選取。本沖裁件規(guī)則形狀的圓,為了便于落料凸模的加工,所以在設(shè)計(jì)時(shí)把落料凸模設(shè)計(jì)成直通式。此外,該制件的尺寸較大,本副模具采用倒裝結(jié)構(gòu)形式,同時(shí),為了簡化模具結(jié)構(gòu)采用彈性推件裝置。關(guān)鍵詞: 沖壓模 倒裝復(fù)合 凹模 彈性推件The front cover stamping process and die designAbstract: This design topic for the front cover design process and die design ofstamping forming, content and direction of the sheet metal blanking parts requirements, the design of a certain significance. Through the design of the die parts, further strengthen the stamping die design of the basic knowledge, which paves the way for more profound experience and lessons for the design of more complex stamping die.The design of the stamping process and die design of the basic knowledge, the first analysis of the stamping process of blanking, punching process scheme for determining ready; then the calculation of blanking force and die cutting edge size, easy to select the press and determine the size and structure of working parts; finally analyses the product characteristics, determination of designparameters, die design and the pushing device selection.The blanking piece shape circle, in order to facilitate the processing of blanking punch, so in the design of the blanking punch is designed through type. In addition, the size of the workpiece is larger, the mold using flip chip structure, at the same time, in order to simplify the mould structure with elastic pushing device.Keywords: push the stamping die compound die elastic 機(jī) 械 加 工 工 藝 過 程 卡 零件號(hào)零 件 名 稱00-03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01下料:10510537鋸床直尺02粗銑:銑六面,互為直角,留單邊余量0.5銑床虎鉗標(biāo)準(zhǔn)面銑刀游標(biāo)卡尺03磨削:磨六面,互為垂直,留單邊余量0.3磨床磁力夾具、虎鉗砂輪游標(biāo)卡尺04鉗工:劃線,按位置加工孔,并攻螺紋鉆床虎鉗鉆刀、鉸刀、攻絲刀高度尺、游標(biāo)卡尺05熱處理:按熱處理工藝,淬火回火達(dá)到5862HRC電熱爐火鉗06磨削:精磨上下平面磨床磁力夾具、虎鉗砂輪游標(biāo)卡尺07線切割:按圖紙要求進(jìn)行線切割線切割機(jī)床復(fù)式支撐夾具銅絲游標(biāo)卡尺08鉗工:鉗工精修、拋光研磨工具游標(biāo)卡尺 編制 校對(duì) 審核 批準(zhǔn) 目錄1 緒 論1 1.1 國內(nèi)模具的現(xiàn)狀和發(fā)展趨勢21.1.1 國內(nèi)模具的現(xiàn)狀21.1.2 國內(nèi)模具的發(fā)展趨勢4 1.2 國外模具的現(xiàn)狀和發(fā)展趨勢4 1.3 前端蓋零件模具設(shè)計(jì)與制造方面51.3.1 前端蓋零件模具設(shè)計(jì)的設(shè)計(jì)思路 51.3.2 前端蓋沖壓模具設(shè)計(jì)的進(jìn)度 6 2 前端蓋的沖壓工藝性分析7 2.1拉深件工藝性分析 7 2.1.2判斷能否一次拉成 8 2.1.3確定是否用壓邊圈8 3 沖壓工藝方案的確定 8 4 主要設(shè)計(jì)計(jì)算10 4.1 毛坯的計(jì)算 10 4.2 排樣10 4.3 計(jì)算工序壓力 114.3.1 落料力的計(jì)算11 4.3.2 卸料力的計(jì)算114.3.3 拉深力計(jì)算 11 4.3.4 壓邊力的計(jì)算 124.4 沖壓設(shè)備的選擇 13 5 主要工作部分尺寸計(jì)算14 5.1 落料刃口尺寸計(jì)算 14 6 彈性元件的設(shè)計(jì)計(jì)算17 6.1 橡膠的自由高度 176.2 橡膠的裝配高度17 7模具的主要工作部分及結(jié)構(gòu)設(shè)計(jì) 19 7.1模具主要工作部分的設(shè)計(jì) 19 8 模架的選用24 8.1其他零部件的說明 249 壓力機(jī)的校核26 9.1閉合高度的校核 26 9.2 工作臺(tái)面尺寸的校核 26 9.3滑塊行程的校核26 10 模具的裝配和工作 2710.1沖裁間隙的調(diào)整27 10.2模架的裝配27 10.3 模具總裝 2810.4模具的總裝配圖28結(jié)束語 30致 謝31參 考 文 獻(xiàn).32 I前端蓋沖壓成形工藝與模具設(shè)計(jì)說明書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?,主要原因是我國在沖壓基礎(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 國內(nèi)模具的現(xiàn)狀和發(fā)展趨勢1.1.1 國內(nèi)模具的現(xiàn)狀我國模具近年來發(fā)展很快,據(jù)不完全統(tǒng)計(jì),2003年我國模具生產(chǎn)廠點(diǎn)約有2萬多家,從業(yè)人員約50多萬人,2004年模具行業(yè)的發(fā)展保持良好勢頭,模具企業(yè)總體上訂單充足,任務(wù)飽滿,2004年模具產(chǎn)值530億元。進(jìn)口模具18.13億美元,出口模具4.91億美元,分別比2003年增長18%、32.4%和45.9%。進(jìn)出口之比2004年為3.69:1,進(jìn)出口相抵后的進(jìn)凈口達(dá)13.2億美元,為凈進(jìn)口量較大的國家。在2萬多家生產(chǎn)廠點(diǎn)中,有一半以上是自產(chǎn)自用的。在模具企業(yè)中,產(chǎn)值過億元的模具企業(yè)只有20多家,中型企業(yè)幾十家,其余都是小型企業(yè)。近年來,模具行業(yè)結(jié)構(gòu)調(diào)整和體制改革步伐加快,主要表現(xiàn)為:大型、精密、復(fù)雜、長壽命中高檔模具及模具標(biāo)準(zhǔn)件發(fā)展速度快于一般模具產(chǎn)品;專業(yè)模具廠數(shù)量增加,能力提高較快;三資及私營企業(yè)發(fā)展迅速;國企股份制改造步伐加快等。雖然說我國模具業(yè)發(fā)展迅速,但遠(yuǎn)遠(yuǎn)不能適應(yīng)國民經(jīng)濟(jì)發(fā)展的需要。我國尚存在以下幾方面的不足: 第一,體制不順,基礎(chǔ)薄弱。 “三資”企業(yè)雖然已經(jīng)對(duì)中國模具工業(yè)的發(fā)展起了積極的推動(dòng)作用,私營企業(yè)近年來發(fā)展較快,國企改革也在進(jìn)行之中,但總體來看,體制和機(jī)制尚不適應(yīng)市場經(jīng)濟(jì),再加上國內(nèi)模具工業(yè)基礎(chǔ)薄弱,因此,行業(yè)發(fā)展還不盡如人意,特別是總體水平和高新技術(shù)方面。 第二,開發(fā)能力較差,經(jīng)濟(jì)效益欠佳.我國模具企業(yè)技術(shù)人員比例低,水平較低,且不重視產(chǎn)品開發(fā),在市場中經(jīng)常處于被動(dòng)地位。我國每個(gè)模具職工平均年創(chuàng)造產(chǎn)值約合1萬美元,國外模具工業(yè)發(fā)達(dá)國家大多是1520萬美元,有的高達(dá)2530萬美元,與之相對(duì)的是我國相當(dāng)一部分模具企業(yè)還沿用過去作坊式管理,真正實(shí)現(xiàn)現(xiàn)代化企業(yè)管理的企業(yè)較少。 第三,工藝裝備水平低,且配套性不好,利用率低雖然國內(nèi)許多企業(yè)采用了先進(jìn)的加工設(shè)備,但總的來看裝備水平仍比國外企業(yè)落后許多,特別是設(shè)備數(shù)控化率和CAD/CAM應(yīng)用覆蓋率要比國外企業(yè)低得多。由于體制和資金等原因,引進(jìn)設(shè)備不配套,設(shè)備與附配件不配套現(xiàn)象十分普遍,設(shè)備利用率低的問題長期得不到較好解決。裝備水平低,帶來中國模具企業(yè)鉗工比例過高等問題。 第四,專業(yè)化、標(biāo)準(zhǔn)化、商品化的程度低、協(xié)作差 由于長期以來受“大而全”“小而全”影響,許多模具企業(yè)觀念落后,模具企業(yè)專業(yè)化生產(chǎn)水平低,專業(yè)化分工不細(xì),商品化程度也低。目前國內(nèi)每年生產(chǎn)的模具,商品模具只占45%左右,其馀為自產(chǎn)自用。模具企業(yè)之間協(xié)作不好,難以完成較大規(guī)模的模具成套任務(wù),與國際水平相比要落后許多。模具標(biāo)準(zhǔn)化水平低,標(biāo)準(zhǔn)件使用覆蓋率低也對(duì)模具質(zhì)量、成本有較大影響,對(duì)模具制造周期影響尤甚。 第五,模具材料及模具相關(guān)技術(shù)落后模具材料性能、質(zhì)量和品種往往會(huì)影響模具質(zhì)量、壽命及成本,國產(chǎn)模具鋼與國外進(jìn)口鋼相比,無論是質(zhì)量還是品種規(guī)格,都有較大差距。塑料、板材、設(shè)備等性能差,也直接影響模具水平的提高。1.1.2 國內(nèi)模具的發(fā)展趨勢 巨大的市場需求將推動(dòng)中國模具的工業(yè)調(diào)整發(fā)展。雖然我國的模具工業(yè)和技術(shù)在過去的十多年得到了快速發(fā)展,但與國外工業(yè)發(fā)達(dá)國家相比仍存在較大差距,尚不能完全滿足國民經(jīng)濟(jì)高速發(fā)展的需求。未來的十年,中國模具工業(yè)和技術(shù)的主要發(fā)展方向包括以下幾方面: 1) 模具日趨大型化; 2)在模具設(shè)計(jì)制造中廣泛應(yīng)用CAD/CAE/CAM技術(shù); 3)模具掃描及數(shù)字化系統(tǒng); 4)在塑料模具中推廣應(yīng)用熱流道技術(shù)、氣輔注射成型和高壓注射成型技術(shù); 5)提高模具標(biāo)準(zhǔn)化水平和模具標(biāo)準(zhǔn)件的使用率;6)發(fā)展優(yōu)質(zhì)模具材料和先進(jìn)的表面處理技術(shù);7)模具的精度將越來越高; 8)模具研磨拋光將自動(dòng)化、智能化; 9)研究和應(yīng)用模具的高速測量技術(shù)與逆向工程;10)開發(fā)新的成形工藝和模具。1.2 國外模具的現(xiàn)狀和發(fā)展趨勢模具是工業(yè)生產(chǎn)關(guān)鍵的工藝裝備,在電子、建材、汽車、電機(jī)、電器、儀器儀表、家電和通訊器材等產(chǎn)品中,6080的零部件都要依靠模具成型。用模具生產(chǎn)制作表現(xiàn)出的高效率、低成本、高精度、高一致性和清潔環(huán)保的特性,是其他加工制造方法所無法替代的。模具生產(chǎn)技術(shù)水平的高低,已成為衡量一個(gè)國家制造業(yè)水平高低的重要標(biāo)志,并在很大程度上決定著產(chǎn)品的質(zhì)量、效益和新產(chǎn)品的開發(fā)能力。近幾年,全球模具市場呈現(xiàn)供不應(yīng)求的局面,世界模具市場年交易總額為600650億美元左右。美國、日本、法國、瑞士等國家年出口模具量約占本國模具年總產(chǎn)值的三分之一。國外模具總量中,大型、精密、復(fù)雜、長壽命模具的比例占到50%以上;國外模具企業(yè)的組織形式是大而專、大而精。2004年中國模協(xié)在德國訪問時(shí),從德國工、模具行業(yè)組織-德國機(jī)械制造商聯(lián)合會(huì)(VDMA)工模具協(xié)會(huì)了解到,德國有模具企業(yè)約5000家。2003年德國模具產(chǎn)值達(dá)48億歐元。其中(VDMA)會(huì)員模具企業(yè)有90家,這90家骨干模具企業(yè)的產(chǎn)值就占德國模具產(chǎn)值的90%,可見其規(guī)模效益。 隨著時(shí)代的進(jìn)步和技術(shù)的發(fā)展,國外的一些掌握和能運(yùn)用新技術(shù)的人才如模具結(jié)構(gòu)設(shè)計(jì)、模具工藝設(shè)計(jì)、高級(jí)鉗工及企業(yè)管理人才,他們的技術(shù)水平比較高故人均產(chǎn)值也較高我國每個(gè)職工平均每年創(chuàng)造模具產(chǎn)值約合1萬美元左右,而國外模具工業(yè)發(fā)達(dá)國家大多1520萬美元,有的達(dá)到 2530萬美元。國外先進(jìn)國家模具標(biāo)準(zhǔn)件使用覆蓋率達(dá)70%以上,而我國才達(dá)到451.3 前端蓋零件模具設(shè)計(jì)與制造方面1.3.1 前端蓋零件模具設(shè)計(jì)的設(shè)計(jì)思路沖裁是沖壓工藝的最基本工序之一,它是利用模具使板料沿著一定的輪廓形狀產(chǎn)生分離的一種沖壓工序。它包括落料、沖孔、切邊、修邊、切舌、剖切等工序,其中落料和沖孔是最常見的兩種工序。沖裁在沖壓加工中應(yīng)用極廣。它既可直接沖出成品零件,還可以對(duì)已成形的工件進(jìn)行再加工。普通沖裁加工出來的制件的精度不高,一般情況下,沖裁件的尺寸精度應(yīng)在IT12級(jí)以下,不宜高于IT10級(jí)。只有加強(qiáng)沖裁變形基礎(chǔ)理論的研究,才能提供更加準(zhǔn)確、實(shí)用、方便的計(jì)算方法,才能正確地確定沖裁工藝參數(shù)和模具工作部分的幾何形狀與尺寸,解決沖裁變形中出現(xiàn)的各種實(shí)際問題,從而,進(jìn)一步提高制件質(zhì)量。前端蓋是典型的沖壓件,該模具工作過程很簡單就是沖壓、落料、拉深,根據(jù)零件圖的結(jié)構(gòu)和尺寸精度以及材料的性能確定完成該沖件所需要的模具類型.因此,綜合考慮各種因素后采用復(fù)合模。根據(jù)計(jì)算的結(jié)果和選用的標(biāo)準(zhǔn)模架,判斷此次沖裁能不能采用標(biāo)準(zhǔn)的模架。為了保證制件的順利加工和順利取件,模具必須有足夠高度。要改變模具的高度,只有從改變導(dǎo)柱和導(dǎo)套的高度,改變導(dǎo)柱和導(dǎo)套的高度的同時(shí),還要注意保證導(dǎo)柱和導(dǎo)套的強(qiáng)度. 導(dǎo)柱和導(dǎo)套的高度可根據(jù)沖裁凸凹模與落料凹模工作配合長度決定設(shè)計(jì)時(shí)可能高度出現(xiàn)誤差,應(yīng)當(dāng)邊試沖邊修改高度。1.3.2 前端蓋沖壓模具設(shè)計(jì)的進(jìn)度1.了解目前國內(nèi)外沖壓模具的發(fā)展現(xiàn)狀,所用時(shí)間10天;2.確定加工方案,所用時(shí)間5天;3.模具的設(shè)計(jì),所用時(shí)間30天;4.模具的調(diào)試所用時(shí)間5天2 前端蓋的沖壓工藝性分析2.1拉深件工藝性分析零件名稱:前端蓋生產(chǎn)批量:大批量材 料:08AL厚 度:1.5mm工件圖:如圖1.圖1 零件圖 此工件為有凸緣圓筒形件,要求零件尺寸標(biāo)注在外形,零件尺寸厚度不變。此工件的形狀滿足拉深工藝要求,可用拉深工序加工。 各圓角r=32t,滿足拉深對(duì)圓角半徑的要求。為IT12級(jí),滿足拉深工序?qū)ぜ墓畹燃?jí)要求。 08鋼拉深性能良好。 此零件的拉深次數(shù)可由下列工序計(jì)算來確定。2.1.1計(jì)算毛坯尺寸=248mm,d=(212-1.5)=210.5mm,由凸緣的相對(duì)直徑/d=248 mm/210.5mm=1.2,查表4.3.2得修邊余量R=5mm,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=d=210.5mm,H=(14.5-1.5)mm=13mm,R=3mm代入上式中,得毛坯的直徑為: D=278.5mm2.1.2判斷能否一次拉成 工件總的拉深系數(shù)=d/D=210.5 mm/28.5mm =0.76 ,工件總的拉深相對(duì)高度H/d=13mm/212mm =0.06. 由/d=278.5mm/210.5mm=1.32,t/D100=1.5mm/278.5mm100=0.53,查表4.9得,有凸緣圓筒形件第一次拉深的極限拉深系數(shù)=0.5;由表4.10查得,有凸緣圓筒形件首次拉深的極限相對(duì)高度/=0.53,由于,H/d/,故此工件能一次拉出。2.1.3確定是否用壓邊圈因?yàn)閠D100%=0.541.5,由表4.9查得需要用壓料裝置。拉深時(shí)一般采用平面壓邊裝置。 3 沖壓工藝方案的確定方案一:先落料,再拉深,采用兩套模具生產(chǎn)方案二:落料拉深復(fù)合模,用一套復(fù)合模具生產(chǎn)分析方案一,其加工復(fù)雜,模具太多,生產(chǎn)成本太高,不便采用。方案二與一相比較,其模具的設(shè)計(jì)與 制造比較復(fù)雜困難,但能縮短生產(chǎn)周期,降低模具制造成本,提高生產(chǎn)效益,因此,采用方案二最好。4 主要設(shè)計(jì)計(jì)算4.1 毛坯的計(jì)算 根據(jù)等面積原則,用解析法求該零件的毛坯直徑。首先將該零件分析成圓,圓臺(tái)、二個(gè)簡單的幾何體。由2.1.1計(jì)算可得毛坯D=278.5mm4.2 排樣 該工件排樣根據(jù)落料工序設(shè)計(jì),考慮操作方便及模具結(jié)構(gòu)簡單,故采用單排樣設(shè)計(jì)。根據(jù)表2.9查得搭邊值a1= 1.5 mm,a= 2 mm。采用雙排導(dǎo)料銷導(dǎo)料條料的寬 b=278.5mm+2a= 282.5 mm 條料的進(jìn)距為 h=278.5+a1= 280 mm 沖裁單件時(shí)料的利用率根據(jù)公式2.41計(jì)算 %=77.0% 圖4-1 排樣圖4.3 計(jì)算工序壓力4.3.1 落料力的計(jì)算按式(2.18): F落=1.3Lt F落-落料力(N) L -工件外輪廓周長L=D=3.14278.5=874.49 mm t-材料的厚度 t=1.5 mm -材料的抗剪強(qiáng)度 由鋼材力學(xué)性能表查得=310 Mpa落料力則為:F落=1.3874.491.5310KN=528.6 KN4.3.2 卸料力的計(jì)算 按照式(2.20): F卸=K卸F落 K卸-卸料力因數(shù) 其值由表(2.7)查得K卸=0.03 K卸=0.03528.6KN=15.9 KN4.3.3 拉深力計(jì)算 該零件為淺伸,故可以按照由壓邊圈的圓筒形的工件近似計(jì)算。按照式(4.15): F拉=Kdt F拉-拉深力(N) d-拉深件的直徑 d=212mm -材料的強(qiáng)度極限(Mpa)。由鋼材力學(xué)性能表得 =380Mpa K-修正因數(shù) 拉深因數(shù) m=d/D=212/278.5=0.76 由表(4.6)查得修正因數(shù)K=0.66則拉深力為: F拉=0.663.142121.5380=250.43KN4.3.4 壓邊力的計(jì)算 壓邊力FQ用以下計(jì)算 FQ=AP 式中 A-壓邊圓面積 A=(278.5-212)=25605mm P-單位壓邊力 由表(4.8)查得P=3.0Mpa則壓邊力為: FQ=256053.0=76.8KN故總沖壓力為: F總=F落+F卸+F拉+F壓 =528.6+15.9+250.4+76.8 =871.7KN4.3.5 計(jì)算模具壓力中心沖壓力合理的作用點(diǎn)稱為模具的壓力中心。模具的壓力中心應(yīng)該通過壓力機(jī)滑塊的中心線。對(duì)于有曲柄的沖模來說,虛實(shí)壓力中心通過曲柄的中心線。以便于沖模平穩(wěn)工作,減少導(dǎo)向件的磨損,從而提高模具的壽命。 由于該工件的毛坯和各工序工件均為軸對(duì)稱圖形,而且只有一個(gè)工位,因此壓力機(jī)的中心必定與制件的幾何中心重合,所以模具的壓力中心就在圓心部位,無需再次計(jì)算。4.4 沖壓設(shè)備的選擇對(duì)于淺拉深可按照式F壓(1.61.8)F總。估算壓力來選取壓力機(jī),參照書末附錄由F壓(1.61.8)F總可得:1394.8F壓1569.1 (KN)從滿足沖壓力要求看,可以初選1600KN規(guī)格的壓力機(jī) (查表13.9),其主要技術(shù)參數(shù)為: 公稱壓力:1600KN滑塊行程:160mm最大閉合高度:450mm封閉高度調(diào)節(jié)量:130mm工作臺(tái)尺寸:1120mm710mm模柄孔尺寸:70mm80mm工作臺(tái)厚度:130mm 最大傾斜角:255 主要工作部分尺寸計(jì)算 模具的落料凹模,凸凹模,及鑲拼凸凹模的工作關(guān)系:見裝配圖所示。對(duì)于工件未標(biāo)注公差尺寸的應(yīng)按照IT12計(jì)算,也可以按照書末附錄查得尺寸的未標(biāo)注公差。根據(jù)表(2.4)查得沖裁模刃口雙面間隙: Zmin=0.132mm Zmax=0.24mm5.1 落料刃口尺寸計(jì)算根據(jù)題目尺寸要求基本尺寸278.50-0.46mm。在查表(2.5)得:凹=0.045mm 凸=0.030mm由于凹+凸Zmax-Zmin故采用用分別加工法。有磨損系數(shù)表(2.6)查得X=0.5由公式2.3、2.4可得: =(278.5-0.50.46 =278.27mm =(278.27-0.50.46-0.132 =278.14mm 、分別為落料凹、凸模刃口尺寸; D落料件外徑的最大極限尺寸; 沖裁件制造公差; X磨損系數(shù),其值在0.51之間,與沖裁件精度等級(jí)有關(guān); 最小初始雙面間隙; 、分別為凹、凸模的制造公差;根據(jù)工件的基本尺寸計(jì)算該工件能進(jìn)行一次拉深成形。5.2 拉深工作部分尺寸計(jì)算拉深凸模和凹模的單邊間隙可以按照課本(圖2.10)中式計(jì)算: =1.5mm, =3mm。由于拉深工件的公差為IT12級(jí),故凸凹模的制造公差可按IT10級(jí)來執(zhí)照。查標(biāo)準(zhǔn)公差數(shù)值表2-1得=0.185mm。按照式2.3式2.4可以求拉深凹凸模尺寸及公差如下 =(212-0.50.46) =211.780+0.185 =(212-0.50.46-3) =208.770+0.1856 彈性元件的設(shè)計(jì)計(jì)算為了得到較為平整的原件,此模具采用彈壓式卸料結(jié)構(gòu),使條料在落料拉深過程中始終處在一個(gè)穩(wěn)定的壓力之下,從而改善了毛坯的穩(wěn)定性,避免材料在切向應(yīng)力的作用下起皺的可能。6.1 橡膠的自由高度 上卸料采用橡膠作為彈性元件,按照式(1-4)計(jì)算橡膠的自由高度: H自由=(3.54)S工作 H自由-橡膠的自由高度(mm) S工作-工作行程與模具修磨量或調(diào)整量(46mm)之和 S工作=(14.5+5+1)=20.5mm H自由=(3.54)20.5=71.7582mm取H自由=77mm由式(1-5)計(jì)算橡膠的裝配高度為: H2=(0.850.9)H自由=(0.850.9)77mm=65.4569.3mm取H2=67mm 橡膠的斷面面積在模具裝配時(shí)按照模具空間大小來裝配。6.2 橡膠的裝配高度 下頂塊壓邊采用橡膠作為彈性元件,按照式(1-4)計(jì)算橡膠的自由高度:H自由=(3.54)S工作S工作=(14.5+5)=19.5mm 則H自由=(3.54)19.5=68.2578mm 取H自由=73mm由式(1-5)計(jì)算橡膠的裝配高度H2=(0.850.9)H自由=(0.850.9)73mm =62.05 65.7mm取H2=64mm橡膠斷面面積在模具裝配時(shí)按照模具空間大小確定 7模具的主要工作部分及結(jié)構(gòu)設(shè)計(jì)7.1模具主要工作部分的設(shè)計(jì)本設(shè)計(jì)采用落料拉深復(fù)合模,首先要考慮凹凸模的壁厚是否過薄,本次設(shè)計(jì)凹凸模的最小壁厚查表(查表2.48)為3.8mm,滿足最小壁厚a1.5t=2.25mm的要求,能夠保證強(qiáng)度,所以采用復(fù)合模。(1)落料凹模高度的確定落料凹模高度為 H=KB =(0.135278)mm =37.5mm B凹模空的最大寬度; K凹模厚度系數(shù)(查1表2.41),考慮板料厚度的影響根據(jù)公式2.16得凹??妆谥涟寄_吘壍淖钚【嚯x C1.2H=45mm 考慮總體布局,選擇圓形凹模板,尺寸為DH=400mm55mm,材料采用Cr12,工作部分熱處理硬度為6064HRC,結(jié)構(gòu)圖如下: 圖7-1 落料凹模 (2)固定板設(shè)計(jì)凸模的固定方式有直接固定在模座、用固定板固定和快換式固定三種固定方式,這里選用固定板固定,固定板與凸模為過渡配合(H7/n6),根據(jù)GB2858.581及凹模尺寸選取凸模固定板尺寸DH=400mm18mm,其結(jié)構(gòu)簡圖如下:圖7-2 凸模固定板同理,選擇凹凸模固定板尺寸為DH=400mm45mm,其結(jié)構(gòu)簡圖如下: 圖7-3 凹凸模固定板(3)壓邊圈設(shè)計(jì)為了防止拉深時(shí)起皺,需用壓邊圈,壓邊圈與凸模的單面間隙選為0.3mm,與凹模的單邊間隙取0.5mm,壓邊圈采用45鋼制造,熱處理硬度為4245HRC。高度選為20mm,其結(jié)構(gòu)如下圖: 圖7-4 壓邊圈 (4)凹凸模設(shè)計(jì)結(jié)合工件外形并考慮加工,將凸凹模設(shè)計(jì)成帶肩臺(tái)階式圓凸凹模,一方面加工簡單,另一方面又便于裝配與更換,采用車床加工,與凸凹模固定板的配合按H7/m6,材料采用Cr12,工作部分熱處理淬硬6064HRC,其高度為: L= =67mm+10mm+15mm+10mm+8mm =110mm 彈性原件安裝高度; 卸料板高度; 凸凹模工作高度; 凸凹模臺(tái)肩高度; 蓋板高度;結(jié)構(gòu)圖如下: 圖7-5 凹凸模(5)模柄的設(shè)計(jì) 模柄選擇壓入式模柄,材料選用45鋼,熱處理硬度4348HRC,依據(jù)模具設(shè)計(jì)尺寸,參考GB2862.190,選用B型,具體結(jié)構(gòu)如下: 圖7-5 模柄8 模架的選用 模具的閉合高度是指模具在最低工作位置時(shí)上下模座之間的距離,它應(yīng)與壓力機(jī)的裝模高度相適應(yīng),從生產(chǎn)量、模具結(jié)構(gòu)、產(chǎn)品規(guī)格和操作方便等方面考慮,選擇滑動(dòng)導(dǎo)向中間導(dǎo)柱圓形模架,查GB/T 2851.690,所選模架具體參數(shù)如下:凹模周界:400mm閉合高度(參考)最?。?05mm閉合高度(參考)最大:350mm上模座 數(shù)量1 規(guī)格:400mm55mm下模座 數(shù)量1 規(guī)格:400mm65mm 導(dǎo)柱 數(shù)量2 規(guī)格:45mm360mm 50mm360mm 導(dǎo)套 數(shù)量2 規(guī)格:60mm150mm53mm 65mm150mm53mm導(dǎo)柱與導(dǎo)套結(jié)構(gòu)從標(biāo)準(zhǔn)中選取,尺寸由模架中的參數(shù)決定。導(dǎo)柱的長度應(yīng)保證沖模在最低工作位置時(shí),導(dǎo)柱上端面與上模座頂面的距離不小于1015mm,而下模座底面與導(dǎo)柱底面的距離應(yīng)為12mm。導(dǎo)柱與導(dǎo)套之間的配合為H7/h6,導(dǎo)套與上模座之間、導(dǎo)柱與下模座之間采用過渡配合H7/m6。導(dǎo)柱與導(dǎo)套材料采用Cr12,熱處理硬度為(滲碳)5662HRC。上下模座材料采用HT200鋼,熱處理硬度為調(diào)質(zhì)2832HRC8.1其他零部件的說明 選用4個(gè)卸料螺釘,公稱直徑為16mm,螺紋部分為M1218mm;凹凸模緊固螺釘選取M16x80mm,選用四個(gè);凸模緊固螺釘選取M16x90mm選用四個(gè);擋料銷采用A型固定擋料銷,d=10mm;導(dǎo)料銷選用兩個(gè),取d=10mm;圓柱銷選取10x100mm,上下模座各兩個(gè)。選用四個(gè)頂桿,取10x200mm。頂件裝置兼起壓邊的作用。 9 壓力機(jī)的校核9.1閉合高度的校核 所選壓力機(jī)的最大閉合高度為450mm,閉合高度調(diào)節(jié)量為130mm,墊板高度為90mm,所以: 450mm-90mm=360mm本次模具設(shè)計(jì)的閉合高度為H=408mm, 5mm=445mm 370mm滿足 H5 所選壓力機(jī)閉合高度滿足要求。9.2 工作臺(tái)面尺寸的校核所選壓力機(jī)工作臺(tái)尺寸為 :前后710mm,左右1120mm ,模具外形尺寸為D=400mm,模具底座外形尺寸為:前后510mm ,左右675mm,根據(jù)工作臺(tái)面尺寸一般應(yīng)大于模具底座尺寸5070mm,所以工作臺(tái)尺寸滿足要求。9.3滑塊行程的校核滑塊行程應(yīng)保證能夠方便地放入毛坯和取出零件,對(duì)于拉深工序,滑塊行程應(yīng)大于零件高度的2倍,零件高度2=14.5mm2=29mm,所選壓力機(jī)的滑塊行程為160mm,所以滑塊行程滿足要求。10 模具的裝配和工作模具的裝配就是按照規(guī)定的技術(shù)要求,將若干個(gè)零件結(jié)合形成零部件,再將若干個(gè)零件和部件組合成模具的整個(gè)工藝過程,裝配工作通常可以分為部件裝配和總裝配。10.1沖裁間隙的調(diào)整對(duì)于沖裁模,即便模具零件的加工精度已經(jīng)得到保證,但是在裝配時(shí),如不能保護(hù)沖裁間隙仍然會(huì)影響制件的質(zhì)量和模具的使用壽命。10.2模架的裝配(1)模柄的裝配此模具采用的是凸緣模柄中B型壓入式模柄,模柄與上模座的配合為H7/h6,將模柄裝上模座,用角尺檢查模柄圓柱面和上模座上平面的垂直度,其誤差不大于0.05mm,然后用銷釘將其固定在上模座上,應(yīng)該在裝模柄前先裝入推板。(2)導(dǎo)柱和導(dǎo)套的裝配導(dǎo)柱導(dǎo)套與上下模座均采用壓入式連接,導(dǎo)套和導(dǎo)柱與模座的配合分別為H7/h6和H7/m6壓入時(shí)要注意校正導(dǎo)柱對(duì)模座底面的垂直度,裝配后的導(dǎo)柱的固定端面與下模座底面距離要求不小于12mm。(3)凸模和凹凸模的裝配該模具的凸模與凸模固定板的配合按H7/m6,凸模裝入固定板后,其固定端面應(yīng)和固定板的支承面應(yīng)處于同一平面內(nèi),在壓力機(jī)上調(diào)整好凸模與固定板的垂直度,將凸模壓入固定板內(nèi),凸模對(duì)固定支承面的垂直度經(jīng)檢查合格后將固定板用螺釘上緊,裝配前在平面磨床上將凸模的上端面和固定板一起磨平,并以固定板支承面定位將凸模工作端面磨平。凹凸模與固定板的配合按H7/m6,總裝前應(yīng)將凹凸模壓入固定板內(nèi),壓在平面磨床將上下平面磨平。10.3 模具總裝 (1)把組裝上了凸模的固定板放在下模座上,按中心線打正固定板的位置,用平行夾頭夾緊,通過螺釘孔在下模座上鉆出錐窩,拆去凸模固定板,在下模座上按錐窩鉆螺紋底孔并攻絲,重新將凸模固定板置于下模座上并找正,用螺釘緊固,鉆孔,打入銷釘定位。 (2)配鉆卸料螺釘孔時(shí),將卸料板套在已裝入固定板的凹凸模上,在固定板與卸料板之間墊上適當(dāng)高度的等高墊鐵,并用平行夾頭將其夾緊,按卸料板上螺孔位置在模座上鉆錐窩,然后拆開,按錐窩鉆孔。 (3)在凹凸模固定板的彈性孔中裝入卸料原件,將卸料板套入凹凸模;用(1)中同樣的方法配鉆墊板和上模座上的螺釘孔,推桿孔,然后依次將墊片和卸料板、凹凸模、凹凸模固定板的組合部件裝入上模座,用緊固螺釘固定,打入銷釘定位。 (4)在落料凹模上裝入擋料銷,將推件塊裝入落料凹模,并將推桿裝入固定板上的推桿孔,用緊固螺釘將落料凹模與凸模固定板固定,鉆孔,打入銷釘定位。10.4模具的總裝配圖 按以上步驟進(jìn)行安裝后,生成模具總裝配圖,其具體結(jié)構(gòu)如下(各部件名稱、數(shù)量、材料、規(guī)格及相關(guān)技術(shù)要求見裝配圖) 圖10-1 模具的總裝圖結(jié)束語前端蓋屬于典型的沖裁件,分析其工藝性,并確定工藝方案。根據(jù)計(jì)算確定該制件的沖裁力及模具刃口尺寸,然后選取相應(yīng)的壓力機(jī)。本設(shè)計(jì)主要是凸凹模及拉深凸模,需要計(jì)算凸凹模的間隙、工作零件的尺寸和公差。此外,還需要確定模具工藝零件和結(jié)構(gòu)零件以及模具的總體尺寸,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,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。前端蓋落料拉深模具的設(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,要想做為一名合格的模具設(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)師楊占堯老師,他幫我仔細(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。楊占堯老師淵博的知識(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),他給了我鼓勵(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 中國機(jī)械工程協(xié)會(huì)、李春勝、黃德彬主編.金屬材料手冊(cè).北京:化學(xué)工業(yè)出版社,2004.112 肖祥芷、王孝培主編.中國模具工程大典第4卷.北京:電子工業(yè)出版社,2007.33 機(jī)械工業(yè)部編.機(jī)械產(chǎn)品目錄(1996)第5卷.北京:機(jī)械工業(yè)出版社,19964 王孝培主編.實(shí)用沖壓技術(shù)手冊(cè). 北京:機(jī)械工業(yè)出版社,2003.35 中國機(jī)械工程學(xué)會(huì)、中國模具設(shè)計(jì)大典編委會(huì)編.中國模具設(shè)計(jì)大典(第3卷).南昌:江西科學(xué)技術(shù)出版社,2003.16 任嘉卉主編.公差與配合手冊(cè).北京:機(jī)械工業(yè)出版社,1997.47 王建中、李洪主編.公差與制圖技術(shù)手冊(cè).沈陽:遼寧科學(xué)技術(shù)出版社,1999.18 郭成、儲(chǔ)家佑主編.現(xiàn)代沖壓技術(shù)手冊(cè).北京:中國標(biāo)準(zhǔn)出版社,2005.109 中國標(biāo)準(zhǔn)出版社、全國模具標(biāo)準(zhǔn)化技術(shù)委員會(huì)編.中國機(jī)械工業(yè)標(biāo)準(zhǔn)匯編:沖壓模具卷(下).北京:中國標(biāo)準(zhǔn)出版社,1998.1210 許發(fā)越主編.模具標(biāo)準(zhǔn)應(yīng)用手冊(cè).北京:機(jī)械工業(yè)出版社,1994.1011 林慧國等主編.模具材料應(yīng)用手冊(cè).北京:機(jī)械工業(yè)出版社,2004.712 陳錫東、周小玉主編.實(shí)用模具技術(shù)手冊(cè).北京:機(jī)械工業(yè)出版社,2001.7 - 29 -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.
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