柴油機(jī)飛輪鎖片沖壓模具設(shè)計【沖孔-落料復(fù)合?！?/h1>
柴油機(jī)飛輪鎖片沖壓模具設(shè)計【沖孔-落料復(fù)合模】,沖孔-落料復(fù)合模,柴油機(jī)飛輪鎖片沖壓模具設(shè)計【沖孔-落料復(fù)合?！?柴油機(jī),飛輪,沖壓,模具設(shè)計,沖孔,復(fù)合
內(nèi)容提要
本此設(shè)計說明書論述了模具的下模由下模座、下模墊板、下模固定板、凹模鑲塊、抬料釘、導(dǎo)料板、卸料板,導(dǎo)柱導(dǎo)套、卸料板彈釘、卸料板限位器等零部件組成以及其設(shè)計計算過程。其中下模固定板、凹模鑲塊、導(dǎo)料板、卸料板拉深翻邊凸模等是關(guān)鍵零部件。
該模具采用單出排樣，有6個工位，上、下模固定板具有高精度、長壽命?？煽焖俑鼡Q凸模和凹模鑲塊，并且重復(fù)裝配精度高，可延長模具的使用壽命。采用雙側(cè)刃定距，在側(cè)刃凹模鑲塊上設(shè)計一個與導(dǎo)料板一樣高的限位刃凸臺，既可初定位送料的步距，又可快速定位導(dǎo)料板。同時在上模座上設(shè)計剛性的卸料板限位器，卸料板既可彈性壓料又可剛性卸料﹐綜合而言﹐該模具有以下特點(diǎn)﹕
(1) 下模固定板具有高精度、長壽命
(2) 快速更換沖裁凹模鑲塊
目 錄
前言………………………………………………………………………… 1
緒論 …………………………………………………………………………2
第1章 沖壓工藝分析 ……………………………………………………3
第2章 主要工藝參數(shù)的計算 ……………………………………………4
2.1確定沖壓的基本工序…………………………………………………5
2.2確定基本工序尺寸公差………………………………………………6
2.3排樣及材料的選用率…………………………………………………7
2.4計算工序壓力…………………………………………………………8
2.5沖壓設(shè)備的選擇………………………………………………………9
2.6確定壓力中心…………………………………………………………10
2.7沖模刃口尺寸及公差的計算…………………………………………12
2.8確定各個零件的結(jié)構(gòu)尺寸……………………………………………13
第3章 確定工藝方案及模具結(jié)構(gòu)形式…………………………………15
3.1工藝方案的確定……………………………………………………‥17
3.2模具結(jié)構(gòu)形式選擇的基本原則………………………………………19
第4章 模具設(shè)計計算……………………………………………………21
4.1凹模板外形尺寸的確定……………………………………………23
4.2凸模固定板形外形尺寸確定 ……………………………………24
4.3 凸凹模墊板外形尺寸確定…………………………………………26
4.4卸料橡膠的選用……………………………………………………28
第5章 固定機(jī)構(gòu)的設(shè)計 ……………………………………………30
5.1 模板類零件的固定………………………………………………31
5.2凸模的固定 …………………………………………………………32
5.3凹模鑲塊的固定……………………………………………………33
第6章 設(shè)計并繪制總裝配圖并選取標(biāo)準(zhǔn)件……………………………34
6.1下模座的選用………………………………………………………35
6.2上模座的選用………………………………………………………36
第7章 繪制非標(biāo)準(zhǔn)零件圖 ……………………………………………37
第8章 本模具的工作過程及特點(diǎn)………………………………………38
8.1工作過程………………………………………………………………39
8.2本模結(jié)構(gòu)特點(diǎn)…………………………………………………………40
第9章 典型零件加工工藝編制…………………………………………41
9.1卸料板………………………………………………………………42
9.2擋料銷………………………………………………………………42
結(jié)束語 ……………………………………………………………………43
參考文獻(xiàn) …………………………………………………………………44
致謝 ………………………………………………………………………45
28
摘要：
隨著模具的迅速發(fā)展，在現(xiàn)代工業(yè)生產(chǎn)中，模具已經(jīng)成為生產(chǎn)各種工業(yè)產(chǎn)品不可缺少的重要工藝設(shè)備，為了擴(kuò)展在工藝方面的知識面為了適應(yīng)社會的要求，學(xué)校舉行了課程設(shè)計，這次課程設(shè)計是在學(xué)習(xí)完沖模、模具制造等課程的基礎(chǔ)上進(jìn)行的，是對我綜合能力的考核，是對我所學(xué)知識的綜合運(yùn)用，也是對我所學(xué)知識的回顧與檢查。
通過實例，分析了零件的沖壓工藝方案，闡述了模具結(jié)構(gòu)特點(diǎn)及工作過程，最后提出了模具設(shè)計應(yīng)該注意的問題。
關(guān)鍵詞：沖模；沖壓工藝；模具設(shè)計
Abstract
Through an example, the stamping process for forming the multi-direction bent parts is analyzed .The structure characteristics and working
process of the die for stamping the multi-direction bent parts are presented .The
parts needing attention in the design of the die are put forward .
key words: die; stamping process ; die design
前 言
模具是現(xiàn)代化的生產(chǎn)重要工藝裝備，在國民經(jīng)濟(jì)的各個部門都越來越多地依
模具來進(jìn)行生產(chǎn)加工，越來越引起人們的重視，模具也趨向標(biāo)準(zhǔn)化。
隨著模具的迅速發(fā)展，在現(xiàn)代工業(yè)生產(chǎn)中，模具已經(jīng)成為生產(chǎn)各種工業(yè)產(chǎn)品不可缺少的重要工藝設(shè)備。這次畢業(yè)設(shè)計是在學(xué)習(xí)完所有機(jī)械課程的基礎(chǔ)上進(jìn)行的，是對我綜合能力的考核，是對我所學(xué)知識的綜合運(yùn)用，也是對我所學(xué)知識的回顧與檢查。
本次設(shè)計的是一副沖孔-落料的復(fù)合模，這次設(shè)計是在戴正強(qiáng)老師認(rèn)真、耐心的指導(dǎo)下，對模具的經(jīng)濟(jì)性、模具的壽命、生產(chǎn)周期、及生產(chǎn)成本等指標(biāo)下進(jìn)行全面、仔細(xì)的分析下而進(jìn)行設(shè)計的。在此, 我表示衷心的感謝他們對我的教誨.
沖模是模具設(shè)計與制造專業(yè)的主要專業(yè)課程之一。它具有很強(qiáng)的實踐性和綜合性，通過學(xué)習(xí)這門課程，使我對沖裁模具有了新的認(rèn)識，從中也學(xué)到了不少知識，激發(fā)了我對沖裁模具的愛好。
但因本人經(jīng)驗有限，因此很難避免的存在一些不合理之處，望各位老師批評和指正，以使我的課程設(shè)計做到合理，同時也為我走出校門步入社會打下堅實的基礎(chǔ)。
設(shè)計者：
緒 論
模具概述: 伴隨著現(xiàn)代工業(yè)的發(fā)展,模具產(chǎn)業(yè)發(fā)展迅速。現(xiàn)代模具產(chǎn)業(yè)已向大型化、多功能、高精度的方向發(fā)展,模具技術(shù)含量不斷提高,多功能復(fù)合模得到進(jìn)一步的發(fā)展,熱流道技術(shù)和模具標(biāo)準(zhǔn)件日益得到廣泛的應(yīng)用,同時塑料模比例不斷提高,快速經(jīng)濟(jì)型模具前景十分廣闊.我國模具產(chǎn)業(yè)也得到了較快的發(fā)展,九五期間年平均增速度約為13%,至2000年,我國模具總產(chǎn)值預(yù)計為260～270億元,模具行業(yè)結(jié)構(gòu)也有了較大的改善,模具商業(yè)化程度提高了近10%,中高檔模具占模具總量的比例有了明顯提高。
當(dāng)今世界,工業(yè)正日益朝著批量化的方向發(fā)展.這樣對沖壓生產(chǎn)提出了自動化,智能化的要求;從而使模具向簡單化、調(diào)試方便快速性方向發(fā)展,對生產(chǎn)人員要求的普遍性提高.同時伴隨生產(chǎn)還有許多的問題,比如噪音問題,生產(chǎn)的安全性問題,所有這些問題要獲得真正有效的解決都離不開沖壓生產(chǎn)設(shè)備,生產(chǎn)工藝方案的制訂,生產(chǎn)人員的狀況,生產(chǎn)現(xiàn)場的管理等;而最為重要的是模具設(shè)計與制造的能力的提高.展望未來,沖壓生產(chǎn)還有許多可提高之處.
沖模發(fā)展?fàn)顩r:目前,我國的模具工業(yè)已初具規(guī)模,但與先進(jìn)工業(yè)國家相比仍有較大差距.近年來對模具技術(shù)的探索和研究主要取得了以下成果:
1.研究了幾十種模具新鋼種及硬質(zhì)合金,鋼結(jié)硬質(zhì)合金等新型材料,并采用了一些熱處理新工藝,模具壽命有所提高.
2.發(fā)展了一些多任務(wù)位模具,硬質(zhì)合金模和簡單經(jīng)濟(jì)模具等新產(chǎn)品.
3.研究和應(yīng)用了一些新技術(shù)和新工藝.
4.模具加工設(shè)備的生產(chǎn)已具有一定的基礎(chǔ).目前已能小批量生產(chǎn)精密的坐標(biāo)磨床,計算器數(shù)控仿形銑床,電火花線切割機(jī)床,高精度的電火花機(jī)床等.
5.模具計算器輔助設(shè)計與制造已有多家單位正在研究開發(fā),有些已經(jīng)投入使用.
隨著工業(yè)的發(fā)展,國內(nèi)模具需求量都在激增,其中高精度,高效率,高壽命模具的應(yīng)用也正日趨廣泛.為了滿足這種需要,模具技術(shù)主要朝著如下幾個方面發(fā)展:
(1)發(fā)展高精度,高效率,高壽命的模具,.例如高速沖床所用的模具,多任務(wù)位模具,少無廢料模具等先進(jìn),經(jīng)濟(jì)的模具.
(2).發(fā)展各種簡易模具,如低熔點(diǎn)合金模,超塑性模,鋅基合金模等.
(3).實現(xiàn)模具標(biāo)準(zhǔn)化,進(jìn)行模具專業(yè)化生產(chǎn).
(4).發(fā)展各種高效,精密,自動化的模具加工設(shè)備.如模具毛坯下料用的高速鋸床,陽極切割機(jī)床,砂線切割機(jī)床,激光切割機(jī)床等高級設(shè)備. 粗加工用的高速銑床,高速磨床等.精加工用的數(shù)控電氣仿形床,數(shù)控連續(xù)軌跡坐標(biāo)銑床.CNC低速走絲精密線切割機(jī)床,各種高精度電火花機(jī)床,精密電解成形機(jī),三坐標(biāo)測量機(jī)等精密加工設(shè)備和加工中心,并逐步實現(xiàn)模具自動加工系統(tǒng).
(5).開發(fā)和應(yīng)用模具CAD/CAM技術(shù),提高模具設(shè)計質(zhì)量和效率,提高制造精度,縮短制造周期.
(6).研究模具新材料,一方面研究高強(qiáng)度,高耐磨及有些特殊性能的合金模具鋼;另一方面研究簡易模具的材料.
沖壓墊片設(shè)計說明書
零件的名稱：沖壓墊片（如下圖所示）
生產(chǎn)批量：大批量
材料：A3 板厚：t =1.2 mm
要求設(shè)計落料，沖孔復(fù)合模
零件圖
第1章 沖壓件工藝的分析
工件如上圖所示，我開始考慮用模具，因為級進(jìn)沖模在設(shè)計上比較靈活，但后來想這種形狀較為簡單，由于產(chǎn)品批量較大，精度比較要求一般，我采用復(fù)合模，一套模具完成此工件的加工。
產(chǎn)品工藝分析包括技術(shù)和經(jīng)濟(jì)兩方面的內(nèi)容.在技術(shù)方面,根據(jù)產(chǎn)品圖紙,主要分析沖壓件的形狀特點(diǎn),尺寸大小,精度要求和材料性能等因素是否符合沖壓工藝的要求;在經(jīng)濟(jì)方面,主要根據(jù)沖壓件的生產(chǎn)批量,分析產(chǎn)品成本,闡明采用沖壓生產(chǎn)可以取得的經(jīng)濟(jì)效益.因此,中壓件的工藝分析,主要討論在不影響零件使用的前提下,能否以最簡單最經(jīng)濟(jì)的方法沖壓出來,能夠做到的,表示該沖壓件的工藝性好,反之，工藝性差.
影響沖壓件工藝性的因素主要有零件的形狀特點(diǎn),尺寸大小,設(shè)計基準(zhǔn),公差等級和形狀位置誤差要求,材料的厚度及成形后允許的變薄量,材料的機(jī)械性能和沖壓性能,在沖壓過程中產(chǎn)生的回彈,翹曲的可能性,毛刺大小和方向要求等.這些因素對確定沖壓工序的性質(zhì),數(shù)量和順序,對模具的結(jié)構(gòu)形式及制造精度要求等都有很大關(guān)系,因此,在制定沖壓工藝過程中必須根據(jù)零件圖認(rèn)真加以分析,尤其應(yīng)該注意分析零件在沖壓加工中的難點(diǎn)所在.良好的沖壓工藝性表現(xiàn)在材料消耗少,沖壓成形時不必采用特殊的控制措施,工藝過程簡單而且壽命長,產(chǎn)品質(zhì)量穩(wěn)定,操作方便等.如果發(fā)現(xiàn)零件的工藝性差,則應(yīng)該在不影響使用要求的前提下,對零件的形狀,尺寸及其它要求作必要的修改.
此零件外形對稱,無尖角,成品的精度要求不是很高,外形公差要求為±0.25mm,角度公差要求為±1.00°.
考慮到裝配的要求,抽孔必須保證抽起高度,孔距有位置要求,但孔徑無公差配合.因為要和下蓋接觸,所以兩側(cè)的小孔位置也必須保證.
由以上分析可知,該零件為板材沖壓件,尺寸精度要求不高,工藝上雖有難度,但易于刻服,又屬批量生產(chǎn),因此可以用沖壓方法生產(chǎn).
第2章 主要工藝參數(shù)的計算
2．1 確定沖壓的基本工序
如上圖零件圖所示，該零件行進(jìn)沖壓加工的基本工序為沖孔、落料。根據(jù)零件要求進(jìn)行工藝計算分析：
2．2 確定基本工序的尺寸公差
零件圖上的尺寸未標(biāo)注公差，按照IT14級確定工件的公差。經(jīng)查表（GB1800—79）得各尺寸的公差為：
查表的：
Φ62-0.620 φ200+0..52， 370+0..52，40+0..3
2.3 排樣及材料的利用率
排樣圖為
毛坯直徑為62，考慮操作方便，采用單排排樣，如下面所示。
首先查表明確搭邊值。根據(jù)零件形狀，兩零件之間按照圓形取搭邊值a=1.2mm，側(cè)邊搭邊值取a1=1.5 。
所以進(jìn)料步距為S0=43.2mm.
條料寬度的計算：
B =（D+2a1）-Δ0查表2-12得Δ=0.5
所以B =（62+2X1.5）-0.50=65-0.50mm
2.4 計算工序壓力
P0=P＋P推
P沖=KL沖tτ=1.3×66.5×2×188÷1000=32.5KN
P落=KLt 08鋼查表抗剪強(qiáng)度～360,取
P落=KL落tτ=1.3×131.9×2×188÷1000
=64.5KN
P= P沖＋P落=32.5＋64.5
=97KN
計算推料力：
P推=n×K2×P沖
查表1-7得K2=0.050
取n=4
P推=4×0.055×32.5=7.15KN
計算總的沖壓力：
P0=P+P推=97＋7.15=104.15KN
卸料力有兩種即下模卸條料的力PS1和上模卸工件的力PS2：
PS1=0.05×64.5=3.225KN
PS2=0.05×（64.5＋32.5）=4.85KN
式中：P0—— 理論上總的沖壓力；
P — 總的沖裁力；
P推——總的推件力；
P沖 ——沖孔時所用的沖裁力；
P落 ——落料時所用的沖裁力；
Τ ——為材料的抗剪強(qiáng)度；
L沖——為沖孔輪廓的周長；
L落——為落料輪廓的周長；
2.5 沖壓設(shè)備的的選擇
為使壓力機(jī)能安全工作，取：
≥（1.6-1.8）p.=177.055KN
公稱壓力：250KN
滑塊塊行程：100mm
最大封閉高度：270mm
連桿調(diào)節(jié)量：55mm]
滑塊底面尺寸：左右 250
前后 220
工作臺尺寸：1345X950mm
模柄孔尺寸：40X60mm
工作臺板厚度：50mm
最大大角度：30
電動機(jī)功率：2.2KW
2.6確定壓力中心
根據(jù)圖形分析，因為工件圖形對稱，故落料和沖孔的中心都在工件的幾何中心，根據(jù)力矩平衡原理得：
PX=(43.2-X)P
由此計算得X=14.474mm
2.7 沖模刃口尺寸及公差的計算：
①. 沖孔凸模刃口尺寸計算：
dp=（dmin+ΧΔ）-δp0
內(nèi)孔基本尺寸為20㎜的刃口尺寸dp1：
因為 d1min=20㎜ 查公差表得Δ=0.52 δp=0.25×Δ=0.13
查表2-21得 Χ=0.5
所以 dp1=20.26-0.130㎜
內(nèi)孔基本尺寸為22㎜的刃口尺寸dp2：
因為d2min=22㎜ 查公差表得Δ=0.52 δp=0.13
所以 dp2=22.26-0.130㎜
內(nèi)孔基本尺寸為4㎜的刃口尺寸dp3：
因為d3min=4㎜ 查公差表得Δ=0.3 δp=0.075
所以dp3=4.150-0.075㎜
②. 落料凹模刃口尺寸：
壓圈外圓基本尺寸為42mm，
查公差表得Δ=0.62mm δd=0.155
因為 Dmax=42mm
Dd=（Dmax-ΧΔ）0+δ =41.690+0.155mm
③．凸凹模內(nèi)部刃口尺寸根據(jù)凸模刃口實際尺寸配作保證雙面間隙為0.25-0.36㎜。
凸凹模外部刃口尺寸根據(jù)凹模刃口實際尺寸配作保證雙面間隙為0.25-0.36㎜。
2.8 確定個主要零件的結(jié)構(gòu)尺寸：
(1) 凹模外形尺寸的確定
凹模厚度H的確定：
H=（0.1×104150）1/3 P0=104150N
所以H=21.8㎜
查≤模具設(shè)計與制造實訓(xùn)≥表6-2取H=25mm C=34㎜
根據(jù)壓力中心圖可以得出凹模外徑D=110㎜
（2）．取凸凹模墊板的厚度為9㎜，直徑為110㎜。
（3）．取凸凹模固定板的厚度為15㎜，直徑為110㎜.
（4）．取回程卸料板的厚度為10㎜，直徑為110㎜。
（5）．取凹模墊板的厚度為8㎜，直徑為110㎜。
（6）．取凸模固定板的厚度為20㎜，直徑為110㎜。
（7）．取凸模墊板的厚度為8㎜，直徑為110㎜。
（8）．凸模長度的確定：
L凸=h1+h2+h3=25＋8＋20=53㎜
其中h1為凹模厚度25㎜，h2為凹模墊板厚度8㎜，h3為凸模固定板厚度20㎜。
（9）．模架的選用：
選用125×125×160-190I GB/T 285.3-90（滑動導(dǎo)向后側(cè)導(dǎo)柱模架）
第3章 確定工藝方案及模具結(jié)構(gòu)形式
3．1 工藝方案的確定
在工藝分析的基礎(chǔ)上,根據(jù)產(chǎn)品圖紙進(jìn)行必要的工藝計算,然后分析沖壓件的沖壓性質(zhì),沖壓次數(shù),沖壓順序和工序組合方式,提出各種可能的沖壓工藝方案.通過對產(chǎn)品質(zhì)量,生產(chǎn)效率,設(shè)備條件,模具制造和壽命,操作安全以及經(jīng)濟(jì)效益等方面的綜合分析和比較,確定出一種適合于本單位生產(chǎn)的最佳工藝方案.確定工藝方案時應(yīng)考慮到以下內(nèi)容:
3．1．1 沖壓性質(zhì):剪裁,落料,沖孔,是常見的沖壓工藝各沖壓工序有其不同的性質(zhì),特點(diǎn)和用途.編制沖壓工藝時,可以根據(jù)產(chǎn)品圖和生產(chǎn)批量等要求,合理地選擇這些工序.
3．1．2 沖壓次數(shù):沖壓次數(shù)是指同一性質(zhì)的工序重復(fù)進(jìn)行的次數(shù).對于拉深件,可根據(jù)它的形狀和尺寸,以及板料許可的變形程度,計算出拉深次數(shù).彎曲件或沖裁件的沖壓次數(shù)也是根據(jù)具體形狀和尺寸及極限變形程度來決定.
3．1．3 沖壓順序:沖壓件各工序的先后順序,主要依據(jù)工序的變形特點(diǎn)和質(zhì)量要求等安排的,一般按列原則進(jìn)行:
(1) 對于帶孔的或有缺口的沖裁件,如果選用簡單模,一般先落料,再沖孔或切口.使用連續(xù)模時,則應(yīng)先沖孔或切口,后落料.
(2) 對于帶孔的彎曲件,孔邊與彎曲線的間距較大時,可以先沖孔,后彎曲.如果孔邊在彎曲線附近,必須在零件壓彎后再沖也.孔與基準(zhǔn)面的間距有嚴(yán)格要求時,也應(yīng)先壓彎后沖孔.
(3) 對于帶孔的拉深件,一般來說,都是先拉深,后沖孔,但是孔的位置在零件底部,且孔徑尺寸要求不高時 ,也可以先在毛坯上沖孔,后拉深.
(4) 多角彎曲件,應(yīng)從材料變形和彎曲時材料流動兩方面安排彎曲的先后順序.一般情況下,先彎外角,再彎內(nèi)角.
(5) 對于形狀復(fù)雜的拉深件,為了便于材料變形和流動,應(yīng)先成形內(nèi)部形狀,再拉深外部形狀.
(6) 整形或校平工序,應(yīng)在沖壓件基本成形以后進(jìn)行.
該零件進(jìn)行沖壓加工的基本工序為沖孔、落料。其中，沖孔和落料屬于簡單分離。
3．1．4 組合方式:工序的組合方式可以選用復(fù)合模和連續(xù)模,主要取決于沖壓件的生產(chǎn)批量,尺寸大小和精度等因素.一般按下列原則進(jìn)行:
(7) 對于多孔的沖裁件,當(dāng)孔之間的間距, 孔與材料邊的距離大于允許值時,最好落料與沖孔在一道復(fù)合工序中完成.
(8) 當(dāng)彎曲件的平直高度大于10mm時,彎曲工序一般與沖裁工序分開單獨(dú)進(jìn)行.
對于形狀復(fù)雜的彎曲件,為簡化模具設(shè)計過程,降低模具制造成本,一般安排由兩道劃兩道以上的工序來完成;而形狀較簡單的彎曲件(如V形,U形,Z形等),應(yīng)盡量采用一道工序彎曲成形.
3．2 模具結(jié)構(gòu)形式選擇的基本原則:
(1) 能沖出符合技術(shù)要求的工件
(2) 能提高生產(chǎn)率
(3) 模具制造和修磨方便
(4) 模具有足夠的壽命
(5) 模具易于安裝調(diào)整,且操作方便,安全
3．2．1卸料裝置:
沖孔時,由于孔口部分的回彈,料片卡在沖子上隨沖子一起向上運(yùn)動,因此需要有卸料裝置把料片推下.在實際沖裁時,由于彈性卸料裝置可以平整工件,且使模具結(jié)構(gòu)簡單,因此采用彈性卸料裝置.
3．2．2導(dǎo)向裝置:
分析工件可知,雖然模具間隙很小,但由于其料厚為1.0,且此網(wǎng)孔的作用系散熱,精度要求不是太高,所以可以不用外導(dǎo)柱來導(dǎo)向,只需用內(nèi)導(dǎo)柱即可.
針對與該水管壓蓋零件而言﹐該零件進(jìn)行沖壓加工的基本工序為沖孔且拉深后翻邊﹐再落料。其中沖孔和落料屬于簡單的分離工序﹐而拉深翻邊則屬于彎曲成型。
綜合分析，沖裁件的尺寸精度不高，形狀不大，但產(chǎn)量大，根據(jù)材料較厚（t=1.5）工序較多的特點(diǎn)，為保證孔位精度和較高的生產(chǎn)率，以及防止拉深開裂等。實行工序集中的工藝方案，即采用吊裝式導(dǎo)正釘定位、雙側(cè)刃定距、固定卸料裝置、壓邊裝置、自然漏料方式的連續(xù)沖裁模結(jié)構(gòu)。
第4章 模具設(shè)計
4.1 凹模板外形尺寸的確定
凹模結(jié)構(gòu)設(shè)計包括：確定凹模的外形尺寸和凹模板的厚度，選擇凹模形孔側(cè)壁的形狀，布置凹模板上形孔，螺孔和銷孔的位置以及標(biāo)注尺寸等。
凹模板厚度H的確定：
H = （F取總壓力）
所以，H =25 mm
凹模板長度L的確定：
L = b+ 2 c
t=2.5 mm, b = 25mm，查表得，c = 34 mm
L = 35 + 2×34 = 93 mm
為使凹模板板獲得更好的受力，可以將凹模的長度和厚度適當(dāng)增大。由此，確定凹模板的外形尺寸為：400×110×36
4.2 凸模固定板外形尺寸的確定
凸模固定板的外形尺寸同凹模板相同，厚度為凹模板0.8～1倍
故凸模固定板外形尺寸為，400×110×15
4.3凸凹模墊板外形尺寸確定
墊板的平面形狀與尺寸與固定板相同，其厚度一般為6～10 mm，
故墊板的外形尺寸為，400×110×10
4.4．卸料橡膠的選用：
下模卸料橡膠
(1)選用牌號為1120的合成橡膠體切割制作。
(2)計算彈性體的預(yù)壓力Fy：
Fy=3.225×1000=3225 N
(3)．橡膠高度的確定
考慮橡膠塊的工作壓縮量較小，取預(yù)壓縮率ξy=15%
極限壓縮率取ξj=35%
橡膠塊的工作壓縮量 hg=t＋1=3㎜
H= hg÷（ξj－ξy）=15㎜
(4)確定橡膠體的截面面積A：
(5)查表2-27得Fq=2.1MPa
A= Fy÷Fq=3225÷2.1=1535.7㎜2
采用M6×45的卸料螺釘加工制得，取橡膠塊穿卸料螺釘?shù)目字睆綖閐因為
膠塊穿過凸凹模，取單邊間隙為3㎜所以橡膠的外徑不能少于65㎜。為提高橡膠的使用壽命取橡膠的外徑為108㎜。
下模卸料橡膠采用聚氨脂彈性體制得，外徑為42㎜，內(nèi)徑為26㎜，高度為15㎜。
第5章 固定機(jī)構(gòu)的設(shè)計
5．1 模板類零件的固定：
模板類零件包括凸模固定板、凹模板、導(dǎo)料板等，一般采用銷釘定位，內(nèi)六角螺釘連接．當(dāng)模板層少于三層時，可用一個螺釘連接，超過三層,應(yīng)分層連接.本模具設(shè)計中，因使用快速換凸模機(jī)構(gòu)．故將上模座，上模墊板，上模固定板，用一螺釘連接，它們間用銷釘定位．凸模蓋板只起固定凸模上下方向作用，只需用螺釘固定在凸模固定板上，無需銷釘定位.
5．2 凸模的固定：
標(biāo)準(zhǔn)圓凸模采用臺階式，即在凸模固定板上開臺階孔，將標(biāo)準(zhǔn)圓凸模放入，上面蓋上凸模墊板，用六角螺釘和銷釘將墊板以及凸模固定板與上模座一起固定。鉚裝式凸模是直痛結(jié)構(gòu)，鉚頭一端材料需要保持軟狀態(tài)，必須限定淬火長度，固定板型孔按凸模配作成過渡配合（取m6），同時型孔上端沿周邊制成（1.5～2.5）×45斜角，做成鉚窩。
5.3 凹模鑲塊的固定：
本設(shè)計為快速更換沖裁凹模鑲塊,因為凹模(尤其沖裁凹模)是易損件，需經(jīng)常更換。該復(fù)合模按下圖所示設(shè)計凹模鑲塊，凹模鑲塊外側(cè)不帶臺階。更換凹模時，用一個銷釘從下模墊板的廢料漏孔將凹模鑲塊從固定板內(nèi)頂出，不必拆卸聯(lián)接固定板的螺釘和銷釘，有時還無需將模具從高速沖床上卸下，因此更換凹模速度快，而且可保證模具的重復(fù)裝配精度，提高模具的使用壽命。因為卸料板能彈性壓料，所以在生產(chǎn)過程中不帶臺階的凹模鑲塊不會從下模固定板中形跳出。
第6章 設(shè)計并繪制總裝配圖、選取標(biāo)準(zhǔn)件（附圖）
按已確定的模具形式及參數(shù)，從冷沖模標(biāo)準(zhǔn)中選取標(biāo)準(zhǔn)模架。
凹模周界 L=400 mm、B=160 mm、厚度H=45 mm的對角上模座；
上模座 400×160×45 GB/T2855.1-90
材料 HT200 GB9436-88
6．1 下模座的選用
原則:
6．1．1 排配有墊腳螺釘側(cè)(如圖1-4中尺寸E),單邊加大30MM.
6．1．2 裝有外導(dǎo)柱側(cè)(如圖1-4中尺寸F),
Φ50有珠:單邊加大125MM; Φ50無珠:單邊加大110MM;
Φ36有珠:單邊加大100MM; Φ36無珠:單邊加大100MM;
Φ25有珠:單邊加大90MM; Φ25無珠:單邊加大90MM.
c.未排外導(dǎo)柱又未排墊腳螺釘側(cè),單邊加大10MM.
注意:下模座到下墊腳的螺釘,在下模座上不需要沉頭,設(shè)計成身過孔即可.
6．2 上模座的選用
原則:
6．2．1 上模座不具有上托板的功能時,可取上模座與下模座規(guī)格(長X寬)相同.
6．1．2 如果模具無上托板,上模座兼具有上托板的功能時,還應(yīng)注意:
L與W及L2,L4取值要盡量符合上托板的標(biāo)準(zhǔn)L1取值要符合上托板的標(biāo)準(zhǔn).
U型鎖固溝的數(shù)量及布置形式,可根據(jù)模具大小選取.模座厚度大于30MM時,影線部分背面銑深后要保證余下的模板厚度為30.0MM.C值要保證不小于零.
第7章 繪制非標(biāo)準(zhǔn)零件圖（附模具零件圖）
本設(shè)計繪制了落料凸模、、沖孔凸模、、、凹模固定板、凹模墊板、導(dǎo)料板、壓料板、凸模固定板、凸模墊板、等零件圖樣。
第8章 本模具的工作過程及特點(diǎn)
8．1 工作過程:
1). 準(zhǔn)備工作:將條料順著乘料板導(dǎo)向槽全部拉入乘料板中,然后把條料拖出一步一步手工送料.(手工送料到全部工位后讓其在步進(jìn)電動機(jī)的帶動下自動送料.)
2). 沖床滑塊帶動上模從最高點(diǎn)開始向下運(yùn)動.
3). 上模繼續(xù)下行,外導(dǎo)柱進(jìn)入導(dǎo)套對上模導(dǎo)向起粗定位作用.
4). 壓料彈釘與卸料板壓板接觸,壓著卸料板下行,內(nèi)導(dǎo)柱進(jìn)入下模導(dǎo)套孔進(jìn)行精確導(dǎo)向起精確定位作用.
5). 導(dǎo)正銷進(jìn)入條料上導(dǎo)正孔,壓料板接觸條料,隨著上模下行條料被壓向下運(yùn)動. 壓料板壓著帶料下行。
6). 條料接觸凹模板時壓料板停止運(yùn)動,沖床滑塊繼續(xù)向下運(yùn)動,上模壓料彈釘彈簧開始壓縮.壓料板受彈簧壓力壓緊條料,經(jīng)一定的行程,沖裁和拉深凸模開始工作，同時拉深工位上的壓邊圈，緊壓條料，保證拉深工序順利完成。
7). 沖床滑塊繼續(xù)向下運(yùn)動,在接近下死點(diǎn)(閉模狀態(tài))時,沖頭完全進(jìn)入下?？變?nèi),完成沖孔、落料等工序.此時上模的最下表面,與下模的最上表面接觸.
8). 沖孔廢料從凹模板到凹模墊板到下模座落料孔落下.
9). 在沖床經(jīng)過下死點(diǎn)后,沖床滑塊帶動上模開始回升,凸模退回一段距離后此時由于壓料彈釘壓力漸漸退去。
10). 沖床滑塊帶動上模繼續(xù)上行,回到開模狀態(tài)的最高點(diǎn)完成一次沖壓過程.
11) 帶料送進(jìn)一個步距,帶料掉下,至送料高度.準(zhǔn)備下一個工作循環(huán).
8．2 本模具結(jié)構(gòu)特點(diǎn):
該模具的下模由下模座、下模墊板、下模固定板、凹模鑲塊、抬料釘、導(dǎo)料板、卸料板,導(dǎo)柱導(dǎo)套、卸料板彈釘、卸料板限位器等零部件組成，其中下模固定板、凹模鑲塊、導(dǎo)料板、卸料板等是關(guān)鍵零部件。
8．2．1 下模固定板具有高精度、長壽命
下模固定板與凸模固定板一樣，選用淬透性好、淬火變形小的合金模具鋼材料，熱處理達(dá)HRC50—55，線切割加工，以保證下模固定板的高精度和長壽命。
8．2．2 快速更換沖裁凹模鑲塊
因為凹模(尤其沖裁凹模)是易損件，需經(jīng)常更換。該復(fù)合模設(shè)計凹模鑲塊，凹模鑲塊外側(cè)不帶臺階。更換凹模時，用一個銷釘從下模墊板的廢料漏孔將凹模鑲塊從固定板內(nèi)頂出，不必拆卸聯(lián)接固定板的螺釘和銷釘，有時還無需將模具從高速沖床上卸下，因此更換凹模速度快，而且可保證模具的重復(fù)裝配精度，提高模具的使用壽命。因為卸料板能彈性壓料，所以在生產(chǎn)過程中不帶臺階的凹模鑲塊不會從下模固定板中跳出。
拉深之前需要壓料，所以卸料板又需作壓料板使用，因此在上模設(shè)計了壓料彈釘。在彎曲之前，壓料彈釘將卸料板壓住，從而使卸料板將片料壓住。沖床完成一次工作行程后，壓料彈釘隨上模一起上行；送料時，下模的卸料板彈釘將卸料板抬起，但卸料板彈釘?shù)膹椓Ρ仨氝h(yuǎn)小于上模壓料彈釘?shù)膹椓ΑＴ谙履Ｗ显O(shè)計剛性的卸料板限位器，既可控制卸料板的抬起高度，又可承受很大的卸料力。因此卸料板既可彈性壓料，又可剛性卸料。
為了保證落料、翻邊上模的位置精度，在落料凸模底部安裝了導(dǎo)正銷、用于落料前的導(dǎo)正。而將翻邊凸模底部設(shè)計成為半球狀。有利于翻邊的準(zhǔn)確定位。
此下模的結(jié)構(gòu)簡單,動作可靠,避免了結(jié)構(gòu)復(fù)雜的側(cè)沖機(jī)構(gòu)的設(shè)計,可大大降低模的成本,以及調(diào)試,維護(hù)難度.
第9章 模具零件加工工藝的編制
9.1 卸料板
工序1.備料 板料145X15mm
工序2.車 平內(nèi)孔42.4 mm
工序3.刨 刨上下面達(dá)圖
工序4.磨 磨上下面見光
工序5.鉗 畫線，制孔
工序6.銑 以內(nèi)孔定位銑外型
工序7.鏜 鏜導(dǎo)料銷和擋料銷孔
9.2 擋料銷
1.備料 圓料棒10mm
2.車 a 車平端面
b車8mm車6mm的外圓
c 倒0.5X45角
d 車2mmX0.4槽
e 切斷保證尺寸3mm
f 倒0.5X45度
3.熱處理 表面淬火43-48HBC
結(jié)束語
由于社會的發(fā)展,人民生活水平的提高,物品不斷更新?lián)Q代以及人們對個性化的物品喜好,致使商家為了搶奪市場,須不斷推出新產(chǎn)品,這樣樣品制造就顯得極為重要.樣品制造具有很大的靈活性,為了滿足市場的需求,其制造周期不斷在縮短,因此,樣品制造的方法簡易可行,其設(shè)備是先進(jìn)的快速加工設(shè)備.當(dāng)然,樣品制造并沒有完全脫離沖壓生產(chǎn),它還須用到?jīng)_壓的一些知識.
模具是工業(yè)之母,模具設(shè)計的好壞關(guān)系到產(chǎn)品的質(zhì)量及成本.當(dāng)前,模具設(shè)計制造朝著CAD/CAM/CAE技術(shù)展,使設(shè)計人員節(jié)省了大量的繪圖時間,把精力花在模具結(jié)構(gòu)的改進(jìn)和模具技術(shù)的研究.現(xiàn)在是多品種小批量生產(chǎn)的時代,要求模具的生產(chǎn)周期愈短愈好,開發(fā)快速經(jīng)濟(jì)模具越來越引起人們的重視.
模具設(shè)計在要求首先要在經(jīng)濟(jì)考慮，經(jīng)濟(jì)時代不可能去虧本開和模具，能節(jié)省的就要盡量節(jié)省；其次，要在復(fù)雜程度上去設(shè)計模具，能做復(fù)合的就做復(fù)合模具，免得浪費(fèi)材料和時間；再次我們在要精度上去考慮，精度高的我們不能做簡單模具設(shè)計，
不要偷工簡料，做一個實事求是的人，做一個有責(zé)任心的人。
致謝
本畢業(yè)設(shè)計,我的是一副復(fù)合模設(shè)計，在規(guī)定的時間內(nèi)完成從模具裝配.結(jié)構(gòu)及零件的設(shè)計經(jīng)歷了了兩個月.除了自己的努力外,更多的是要感謝各位老師在我設(shè)計過程中對我的指導(dǎo)。
在此,我要感謝我的指導(dǎo)老師,沖壓模具專業(yè)老師以及在這次設(shè)計給我?guī)椭耐瑢W(xué)，他們的指導(dǎo),讓我修正了設(shè)計中一個又一個的錯誤,更重要的是我從中學(xué)到了很多東西,這些在原來學(xué)過的教材中是無法找到了,這些也是我以后工作中很寶貴的財富。
參考文獻(xiàn)
1．《模具設(shè)計與制造實訓(xùn)》 朱光力 主編 高等教育出版社
2. 《沖壓工藝與模具設(shè)計》 姜奎華 主編 機(jī)械工業(yè)出版社
3．《互換性與測量技術(shù)基礎(chǔ)》 溫松明 主編 湖南大學(xué)出版社
4.《中國模具設(shè)計大典》 電子版 中國模具設(shè)計大典編委會 互聯(lián)網(wǎng)資料
5《沖壓工藝模具設(shè)計》 鐘毓斌 主編 機(jī)械工業(yè)出版社
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.