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紫瑯職業(yè)技術學院
畢業(yè)設計
題 目：
汽車輪速傳感器墊片模具設計
副 標 題：
學 生 姓 名：
吳向東
所在系、專業(yè)：
機電工程系、模具設計與制造
班 級：
模具5091
指 導 教 師：
金亞云
日 期：
2012.05.29
II
摘 要
摘 要
本文應用所學到的理論知識，分析了墊片的結構和成形工藝，計算了毛坯尺寸和沖壓力。為了提高墊片的生產(chǎn)效率，設計了級進模的結構,經(jīng)過工藝分析、結構設計，論證了其可能性，保證了制品的質量。在模具設計中,為了提高速度和效率,充分利用已經(jīng)掌握的知識和資源。利用沖模設計手冊軟件版快速設計沖壓模具。實踐證明,確實提高了設計的速度和效率。本模具設計中,由于卸料力較大,采用了組合彈簧力較大的優(yōu)點解決了這一問題。在模具結構中,用頂板做凸模的定位元件,由于配合定位的距離小,容易造成凸模的折斷,因而設計了凹模導向凸模,增強了凸模的強度。
關鍵詞：落料，墊片，級進模，模具設計
II
汽車輪速傳感器墊片模具設計
目 錄
摘 要 I
目 錄 I
1、緒論 1
2、設計課題及設計任務 1
2.1課題研究的目的和基本要求 1
2.1.1目的 1
2.1.2基本要求 1
2.2設計任務書 1
3、工藝方案分析及確定 2
3.1零件的工藝分析 2
3.1.1工藝方案的確定 2
3.1.2排樣的確定 2
3.1.3排樣及排樣方式的確定 2
3.1.4條料寬度 3
3.1.5搭邊及搭邊值 3
3.1.6材料的利用率 3
4、工藝設計與計算 4
4.1沖壓力與沖壓中心的計算 4
4.1.1沖裁力的計算 4
4.1.2卸料力、推件力計算 4
4.1.3壓力機公稱壓力的確定 5
4.2壓力中心的計算 5
5、凸、凹模刃口尺寸確定 5
5.1凹模尺寸 5
5.2凸模尺寸 5
5.3凸凹模刃口尺寸 6
6、其他零件 7
6.1導料板 7
6.2側刃、側刃擋塊 7
6.3卸料版 7
6.4凸模固定板 7
6.5上下墊板 8
6.6橡膠 8
6.7上下模座 8
7、典型零件加工工藝方案 8
8、沖壓設備選用 8
致 謝 1
參考文獻 2
1、緒論
沖壓模具是模具中最為廣泛的模具之一。特別是隨著汽車工業(yè)的迅速發(fā)展，沖壓工藝理論與技術的發(fā)展，以及計算機技術的發(fā)展，使得沖壓模具設計與制造方法發(fā)生了根本的變革。隨著汽車在現(xiàn)代生活中扮演越來越重要的角色，對汽車的零部件需求也是越來越大。此墊片用于汽車輪速傳感器與ESP(汽車電子穩(wěn)定系統(tǒng))之間，作為緊固件。本文通過所學知識分析墊片的結構和成形工藝，計算了毛坯尺寸和沖壓力。為了提高墊片的生產(chǎn)效率，設計了級進模的結構,經(jīng)過工藝分析、結構設計，論證了其可能性，保證了制品的質量。
2、設計課題及設計任務
2.1課題研究的目的和基本要求
2.1.1目的
①用本專業(yè)所學課程的理論和生產(chǎn)實踐知識，進行一項冷沖模設計的實際訓練，從而培養(yǎng)和提高學生獨立工作的能力。
②擴充“冷沖模設計”課程所學內(nèi)容，掌握冷沖壓模具設計的方法和步驟。
③掌握冷沖壓模具設計的基本知識。如查閱設計資料手冊、熟悉標準規(guī)范、計算和繪圖等。
2.1.2基本要求
①達到課題研究的目的所提的要求。
②以生產(chǎn)者的身份來設計模具，為求所設計模具適合在現(xiàn)有設備條件下生產(chǎn)，即要結合生產(chǎn)實際，又要滿足生產(chǎn)要求，更要提高生產(chǎn)效率和經(jīng)濟效益。
2.2設計任務書
本設計為墊片級進模具。工件如圖1所示：
圖1 零件圖
技術要求：
1.零件名稱：汽車輪速傳感器墊片
2.生產(chǎn)批量：大批
3.材料：H62-M
4.厚度：t=1.6mm
3、工藝方案分析及確定
3.1零件的工藝分析
工藝性其實也就是從成本、制造性、使用性方面考慮，比方?jīng)_裁件,在不必要的情況下去掉銳角，倒成圓角，以降低凸凹模磨損崩刃的可能性，且對后續(xù)的涂裝有好處（涂料在銳角處的附著性差），沖孔工序圓孔的工藝性最好，對于一些不宜用形狀定位的可前序增設工藝孔，這些都是從制造工藝上考慮的，從成本上考慮就是落料件的搭邊和排樣、在滿足技術要求的情況下盡量使用最小允許值，以提高材料利用率。
(1)材料：H62-M軟黃銅，具有良好的沖壓性能。
(2)該零件形狀簡單，孔邊距遠大于凸、凹模允許的最小壁厚，故可以考慮采用復合沖壓工序。
(3)零件尺寸按未注公差確定，而在沖壓工序中一般按IT14級確定。
3.1.1工藝方案的確定
零件包括落料和沖孔兩個基本工序，可采用級進沖裁，生產(chǎn)效率高，操作方便，通過設計合理的模具結構和排樣方案可以達到較好的零件質量和避免模具強度不夠的問題。
根據(jù)以上分析，該零件采用級進沖裁工藝方案。
由于級進模工位數(shù)較多，因而用級進模沖制零件，必須解決條料或帶料的準確定位問題，才可能保證沖壓件的質量。根據(jù)級進模定位零件的特征，級進模有以下兩種典型結構。
方案一：固定擋料銷和導正銷定位的級進模
工作時，用手按入始用擋料銷限定條料的初始位置，進行沖孔。始用擋料銷在彈簧作用下復位后，條料再送進一個步距，以固定擋料銷粗定位，落料時以裝在落料凸模端面上的導正進行精定位，保證零件上的孔與外圓的相對位置精度。模具的導板兼作卸料板和導料板。采用這種級進模，當沖壓件的形狀不適合在工件上直接定位時，可在條料上的廢料部分沖出工藝孔。利用裝在凸模固定板上的導正銷進行導正。
方案二：側刃定距的級進模
側刃是特殊功用的凸模，其作用是在壓力機每次沖壓行程中，沿條料邊緣切下一塊等于步距的料邊。由于沿送料方向上，在側刃前后兩導料間距不同，前寬后窄形成一個凸肩，所以條料上只有切去料邊的部分方能通過，通過的距離即等于步距。為了減少料尾損耗，尤其工位較多的級進模，可采用兩個側刃前后對角排列，該模具就是這樣排列的。
綜合考慮以上方案，由于零件尺寸較小，材料厚度較薄，為了便于操作和保證零件的精度，宜采用方案二，即導料板導向、側刃定距的定位方式。為了減小料頭和料尾的材料消耗和提高定距的可靠性，采用雙側刃前后對角布置。
3.1.2排樣的確定
在沖壓生產(chǎn)中，節(jié)約金屬和減少廢料具有非常重要的意義，特別是在大批量生產(chǎn)中，較好地確定沖件尺寸和合理排樣是降低成本的有效措施之一。
3.1.3排樣及排樣方式的確定
排樣是指沖裁件在條料、帶料或板料上的布置方法。本產(chǎn)品排樣方式采用有廢料排樣，模具沿工件的外輪廓進行沖裁，工件周邊都留有搭邊。
3.1.4條料寬度
因模具采用側刃定距，故采用下式計算：
B-Δ0=（Lmax+1.5a+nb1）-Δ0
式中： Lmax --- 條料寬度方向沖裁件最大尺寸
a --- 側搭邊值，見表2.5.2[5]
n --- 側刃數(shù)
b1 --- 側刃沖切的料邊寬度，見表2.5.6[2]
B-0.60=[(90.5+1.5×2.2+2×2)]-0.60=97.5-0.60
3.1.5搭邊及搭邊值
排樣時工件之間以及工件與條料側邊之間留下的余料叫搭邊。搭邊的作用是補償條料的定位誤差，保證沖出合格的工件，保持條料有一定的剛度，便于送料。
考慮到材料的利用，以及采用手工送料、有側壓裝置的模具，搭邊值一般由經(jīng)驗確定，表2.5.2[3]列出常用的沖裁的最小搭邊值。
圖2 排樣圖
查表得 工件間a1取2.0 側面a取2.2。
綜合上述計算得出圖2。
3.1.6材料的利用率
一個進距的材料利用率η的計算公式為：
η=×100％
式中： A --- 沖裁面積
B --- 條料寬度
s --- 進距
η=≈84.47%
根據(jù)采購的鋼板規(guī)格為900mm×1250mm， 每張鋼板可以剪成12張（97.5mm×900mm）條料，每張條料可以沖下37個零件。
一張板料上總的材料利用率：
η總=
式中 N --- 一張板料上沖裁件總數(shù)
As--- 一個沖裁件的實際面積
L --- 板料長度
B --- 板料寬度
η總=≈83.34%
4、工藝設計與計算
4.1沖壓力與沖壓中心的計算
4.1.1沖裁力的計算
計算沖裁力的目的是為了確定壓力機的額定壓力，因此要計算最大沖裁力。則沖裁力可按下式計算：
F=KLtτb≈Ltσb
式中：K --- 系數(shù)(一般取1.3)
L --- 沖裁件周長，mm
T --- 材料厚度，mm
τ --- 材料抗剪強度，MP
σb--- 材料抗拉強度，MP
F落料=1.3Ltτ≈Ltσb =220.6×1.6×300=105.9kN
F沖孔=1.3Ltτ≈Ltσb =98.84×1.6×300=47.4kN
查表7.4[1]得H62-M抗拉強度為300MP
4.1.2卸料力、推件力計算
由于影響卸料力、推件力的因素很多，無法準確計算。在生產(chǎn)中均采用下列經(jīng)驗公式計算：
卸料力 Fx=KxF
推件力 Ft=nKtF
式中： F --- 沖裁力
Kx、Kt--- 卸料力、推件力系數(shù) 見表2.6.1[2]
n --- 卡在凹模內(nèi)的沖裁件數(shù)
卸料力:Fx=KxF=0.06×105.9=6.3kN
推件力:Ft=nKtF=0.09×12×47.4=51.2kN
4.1.3壓力機公稱壓力的確定
FZ=F落料+Fx+Ft+F沖孔=105.9+47.4+6.3+51.2=210.8kN
4.2壓力中心的計算
該零件是對稱的，所以壓力中心在該零件的幾何中心。如圖3所示：
圖3 產(chǎn)品圖
5、凸、凹模刃口尺寸確定
5.1凹模尺寸
（1）凹模厚度
H=Kb(≥15mm)
式中K系數(shù)查表2.9.5[2]得90，b-垂直于送料方向度量的凹?？鬃畲蟪叽?。
H=Kb=90×0.3=27mm
（2) 凹模邊緣壁厚
C=(1.5～2)H=40.5～54mm，實取C=50mm
（3) 凹模邊長L
L=b+2C=89.57+2×50=189.57mm
（4) 凹模寬度B
B=l+2C=21.74+2×50=121.74mm
查國家標準手冊UDC 621.961.02 GB 2873.1-81查得：
凹模板長度A=200mm寬度B=160mm。
5.2凸模尺寸
落料凸模刃口部分為非圓形，為便于凸模和固定板的加工，可設計成階梯形結構，并將安裝部分設計成便于加工的長圓形，通過鉚接方式與凸模固定板固定。凸模的尺寸根據(jù)刃口尺寸、卸料裝置和安裝固定要求確定。如圖5所示：
圖5 凸、凹模
5.3凸凹模刃口尺寸
凸、凹模分開加工由于材料薄，模具間隙小，故凸、凹模采用配作加工為宜。配作法就是先按設計尺寸制造出一個基準件（凸?；虬寄＃?，然后根據(jù)基準件的實際尺寸按間隙配制另一件。這種加工方法特點是模具的間隙有配制保證，刃口尺寸的計算方法如下表4：
表4 刃口尺寸計算
基本尺寸及分類
沖裁間隙
磨損系數(shù)
計算公式
制造公差
計算結果
落料凹模
900 -0.87
Zmin=0.22
Zmax=0.26
Zmax-Zmin=0.26-0.22=0.04
工件公差等級為IT14級，故x=0.5
Aj=（Amax-XΔ）0+0.25Δ
89.570+0.217
220 -0.52
21.740+0.13
20 -0.25
1.870+0.0625
沖孔凸模
46+0.62 0
Bj=（Bmin+XΔ）0-0.25Δ
46.310-0.155
6+0.3 0
6.150-0.075
6、其他零件
6.1導料板
在固定卸料式?jīng)_模和級進模沖裁中，條料的橫向定位使用導料板。
導料板一般由兩塊組成，稱為分體式導料板。在簡單落料模上，有時將導料板與固定卸料板制成一體，稱為整體式導料板。采用整體式導料板的模具，結構簡單，但是，固定卸料板的加工量較大，且不便于安裝調整。為了使條料順利通過，兩導料板間距離應該等于條料最大寬度加上一個間隙值。導料板高度取決于擋料方式和板料厚度，導料板高度見表9-2[3]。查表得h為8mm。
導料板的平面形狀與凹模相同，l=160mm，B=100mm，其厚度h=8mm。
6.2側刃、側刃擋塊
按側刃的工作端面形狀分平面型和臺階型兩類，每類又有三個型號（A型、B型、C型）臺階型的多用于厚度為1mm 以下的板料的沖裁，沖裁前凸出部分先進入凹模導向，以免由于側壓力導致側刃損壞。
側刃斷面的關鍵尺寸的寬度b其它尺寸按GB/7648.1---1994規(guī)定。寬度b原則上等于送料步距，但對于長方形側刃和導正銷兼用的模具，其寬度為：
b=[s+(0.05～0.1)]
式中： b --- 側刃寬度（mm）
S --- 送進步距（mm）
b=24+0.1=24.1mm
側刃擋塊選擇為長方體，尺寸為8×6×35mm。
6.3卸料版
彈性卸料板的平面外形尺寸等于或稍大于凹模板尺寸，厚度取凹模厚度的0.6～0.8倍。所以卸料板厚度取H=0.6×27=16.2mm 取17mm。
綜上所述卸料板長度A=200mm寬度B=160mm厚度H=17mm
當卸料板對凸模起導向作用時，卸料板與凸模間按H7/h6配合，但其間隙應該比凸、凹模間隙小，此時凸模與固定板按H7/h6或H8/h7配合。此外，為了便于可靠卸料，在模具開啟狀態(tài)時，卸料板工作平面應該高出凸模刃口端面0.3～0.5mm。
卸料板凸臺部分的高度為
h=H-（0.1～0.3）t
式中: h --- 卸料板凸臺高度
H --- 導料板高度
t --- 條料厚度
h=8-（0.1～0.3）×1.6≈7.6mm
彈性卸料板的壓料面應凸出凸模端面0.2～0.5mm ，所以取臺階高度H1=7.1mm 。
6.4凸模固定板
標準凸模固定板有圓形、矩形和單固定板等多種型式。選用時，根據(jù)凸模固定和緊固件合理布置的需要確定其輪廓尺寸，其厚度一般為凹模厚度的60%～80%。
凸模固定板的平面形狀與凹模相同，L=200mm，B=160mm，其厚度一般為凹模厚度的60%～80%，所以凸模固定板的尺寸為200×160×18mm。
6.5上下墊板
在凸模固定板與上模座之間加一塊淬硬的墊板，可避免硬度較低的模座因局部受凸模較大的沖擊力而出現(xiàn)凹陷，致使凸模松動，拼塊凹模與下模座之間也加墊板。
墊板的平面形狀尺寸與固定板相同，L=200mm，B=160mm，其厚度一般為6～10mm.取8mm。
6.6橡膠
根據(jù)工藝性質和模具結構確定橡膠性能、形狀和數(shù)量。沖裁卸料用較硬橡膠；拉伸用較軟橡膠。本模具采用較硬橡膠。材料選用聚氨酯。
橡膠板高度為
H0=
式中：ΔH1 --- 壓縮高度
H0 --- 橡膠原高度
設ΔH1為5mm
則 H0=20mm
橡膠外形 為 200×160×20mm。
6.7上下模座
采用對角導柱模架（標準間），與上下墊板配合。
7、典型零件加工工藝方案
以凹模板的加工為例，典型零件的加工工藝為：備料——熱處理——洗平面——鉗工——磨平面——熱處理——線切割。工藝過程如表 6。
表6工藝過程
序號
工序名稱
工序的主要內(nèi)容
1
備料
根據(jù)圖紙下適合的毛胚料
2
熱處理
退火
3
銑平面
銑六平面
4
鉗工
劃線、打螺紋孔、銷釘孔和穿絲孔
5
磨平面
光上下平面至圖紙要求
6
熱處理
淬火、回火達到硬度要求
7
線切割
線割內(nèi)型,保證間隙達到要求
8、沖壓設備選用
根據(jù)總的沖裁力必須小于或等于壓力機的公稱壓力，故選壓力機型號。
故選壓力機型號為開式壓力機其技術規(guī)格如下：
標準壓力：110kN
滑塊行程：40mm
行程次數(shù)：200次/min
最大封閉高度：160mm
封閉高度調節(jié)量：35mm
8
致謝
致 謝
五年的大學生活就快走入尾聲，我的校園生活即將就要劃上句號，心中是無盡的難舍與眷戀。從這里走出，對我的人生來說，將是踏上一個新的征程，要把所學的知識應用到實際工作中去。
回首五年，取得了很多成績，生活中有快樂也有艱辛。感謝老師們五年來對我孜孜不倦的教誨和無微不至關懷，使我在關心和愛護下度過難忘的五年大學生活。
學友情深，情同兄妹。五年的風風雨雨，我們一同走過，充滿著關愛，給我留下了值得珍藏而又最美好的回憶。
在我的十幾年求學歷程里，離不開家長的鼓勵和支持，是他們辛勤的勞作，無私的付出，為我創(chuàng)造良好的學習條件，我才能順利完成學業(yè)，感激他們一直以來對我的撫養(yǎng)與培育。
最后，我要特別感謝我的論文輔導老師和參加我論文答辯老師。是他們在我畢業(yè)的最后關頭給了我巨大的幫助與不斷的鼓勵,使我能夠順利完成畢業(yè)論文設計。
我在此表示真誠的感謝!
9
參考文獻
參考文獻
1.吳元徽，趙利群.模具材料與熱處理[M].大連：大連理工大學出版社，2007.1
2.馬朝興. 沖壓工藝與模具設計[M].北京：機械工業(yè)出版社，2006.4
3.徐政坤. 沖壓模具設計與制造[M].北京：化學工業(yè)出版社，2005.1
4.曾珊琪，丁毅.模具壽命與失效[M].北京：化學工業(yè)出版社，2002.5
5.吳兆祥，高楓.模具材料及表面處理[M].北京：高等教育出版社，2006.2
6.王德文. 提高模具壽命應用技術實例[M].北京：機械工業(yè)出版社，2004.5
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第 26 頁 共 27 頁
e pos 模具工業(yè)現(xiàn)狀Process simulation in stamping – recent
applications for product and process design
Abstract
Process simulation for product and process design is currently being practiced in industry. However, a number of input variables have a significant effect on the accuracy and reliability of computer predictions. A study was conducted to evaluate the capability of FE-simulations for predicting part characteristics and process conditions in forming complex-shaped, industrial parts.
In industrial applications, there are two objectives for conducting FE-simulations of the stamping process; (1) to optimize the product design by analyzing formability at the product design stage and (2) to reduce the tryout time and cost in process design by predicting the deformation process in advance during the die design stage. For each of these objectives, two kinds of FE-simulations are applied. Pam-Stamp, an incremental dynamic-explicit FEM code released by Engineering Systems Int'l, matches the second objective well because it can deal with most of the practical stamping parameters. FAST_FORM3D, a one-step FEM code released by Forming Technologies, matches the first objective because it only requires the part geometry and not the complex process information.
In a previous study, these two FE codes were applied to complex-shaped parts used in manufacturing automobiles and construction machinery. Their capabilities in predicting formability issues in stamping were evaluated. This paper reviews the results of this study and summarizes the recommended procedures for obtaining accurate and reliable results from FE simulations.
In another study, the effect of controlling the blank holder force (BHF) during the deep drawing of hemispherical, dome-bottomed cups was investigated. The standard automotive aluminum-killed, drawing-quality (AKDQ) steel was used as well as high performance materials such as high strength steel, bake hard steel, and aluminum 6111. It was determined that varying the BHF as a function of stroke improved the strain distributions in the domed cups.
Keywords: Stamping; Process ;stimulation; Process design
1. Introduction
The design process of complex shaped sheet metal stampings such as automotive panels, consists of many stages of decision making and is a very expensive and time consuming process. Currently in industry, many engineering decisions are made based on the knowledge of experienced personnel and these decisions are typically validated during the soft tooling and prototyping stage and during hard die tryouts. Very often the soft and hard tools must be reworked or even redesigned and remanufactured to provide parts with acceptable levels of quality.
The best case scenario would consist of the process outlined in Fig. 1. In this design process, the experienced product designer would have immediate feedback using a specially design software called one-step FEM to estimate the formability of their design. This would allow the product designer to make necessary changes up front as opposed to down the line after expensive tooling has been manufactured. One-step FEM is particularly suited for product analysis since it does not require binder, addendum, or even most process conditions. Typically this information is not available during the product design phase. One-step FEM is also easy to use and computationally fast, which allows the designer to play “what if” without much time investment.
Fig. 1. Proposed design process for sheet metal stampings.
Once the product has been designed and validated, the development project would enter the “time zero” phase and be passed onto the die designer. The die designer would validate his/her design with an incremental FEM code and make necessary design changes and perhaps even optimize the process parameters to ensure not just minimum acceptability of part quality, but maximum achievable quality. This increases product quality but also increase process robustness. Incremental FEM is particularly suited for die design analysis since it does require binder, addendum, and process conditions which are either known during die design or desired to be known.
The validated die design would then be manufactured directly into the hard production tooling and be validated with physical tryouts during which the prototype parts would be made. Tryout time should be decreased due to the earlier numerical validations. Redesign and remanufacturing of the tooling due to unforeseen forming problems should be a thing of the past. The decrease in tryout time and elimination of redesign/remanufacturing should more than make up for the time used to numerically validate the part, die, and process.
Optimization of the stamping process is also of great importance to producers of sheet stampings. By modestly increasing one's investment in presses, equipment, and tooling used in sheet forming, one may increase one's control over the stamping process tremendously. It has been well documented that blank holder force is one of the most sensitive process parameters in sheet forming and therefore can be used to precisely control the deformation process.
By controlling the blank holder force as a function of press stroke AND position around the binder periphery, one can improve the strain distribution of the panel providing increased panel strength and stiffness, reduced springback and residual stresses, increased product quality and process robustness. An inexpensive, but industrial quality system is currently being developed at the ERC/NSM using a combination of hydraulics and nitrogen and is shown in Fig. 2. Using BHF control can also allow engineers to design more aggressive panels to take advantage the increased formability window provided by BHF control.
Fig. 2. Blank holder force control system and tooling being developed at the ERC/NSM labs.
Three separate studies were undertaken to study the various stages of the design process. The next section describes a study of the product design phase in which the one-step FEM code FAST_FORM3D (Forming Technologies) was validated with a laboratory and industrial part and used to predict optimal blank shapes. Section 4 summarizes a study of the die design stage in which an actual industrial panel was used to validate the incremental FEM code Pam-Stamp (Engineering Systems Int'l). Section 5 covers a laboratory study of the effect of blank holder force control on the strain distributions in deep drawn, hemispherical, dome-bottomed cups.
2. Product simulation – applications
The objective of this investigation was to validate FAST_FORM3D, to determine FAST_FORM3D's blank shape prediction capability, and to determine how one-step FEM can be implemented into the product design process. Forming Technologies has provided their one-step FEM code FAST_FORM3D and training to the ERC/NSM for the purpose of benchmarking and research. FAST_FORM3D does not simulate the deformation history. Instead it projects the final part geometry onto a flat plane or developable surface and repositions the nodes and elements until a minimum energy state is reached. This process is computationally faster than incremental simulations like Pam-Stamp, but also makes more assumptions. FAST_FORM3D can evaluate formability and estimate optimal blank geometries and is a strong tool for product designers due to its speed and ease of use particularly during the stage when the die geometry is not available.
In order to validate FAST_FORM3D, we compared its blank shape prediction with analytical blank shape prediction methods. The part geometry used was a 5?in. deep 12?in. by 15?in. rectangular pan with a 1?in. flange as shown in Fig. 3. Table 1 lists the process conditions used. Romanovski's empirical blank shape method and the slip line field method was used to predict blank shapes for this part which are shown in Fig. 4.
Fig. 3. Rectangular pan geometry used for FAST_FORM3D validation.
Table 1. Process parameters used for FAST_FORM3D rectangular pan validation
Fig. 4. Blank shape design for rectangular pans using hand calculations.
(a) Romanovski's empirical method; (b) slip line field analytical method.
Fig. 5(a) shows the predicted blank geometries from the Romanovski method, slip line field method, and FAST_FORM3D. The blank shapes agree in the corner area, but differ greatly in the side regions. Fig. 5(b)–(c) show the draw-in pattern after the drawing process of the rectangular pan as simulated by Pam-Stamp for each of the predicted blank shapes. The draw-in patterns for all three rectangular pans matched in the corners regions quite well. The slip line field method, though, did not achieve the objective 1?in. flange in the side region, while the Romanovski and FAST_FORM3D methods achieved the 1?in. flange in the side regions relatively well. Further, only the FAST_FORM3D blank agrees in the corner/side transition regions. Moreover, the FAST_FORM3D blank has a better strain distribution and lower peak strain than Romanovski as can be seen in Fig. 6.
Fig. 5. Various blank shape predictions and Pam-Stamp simulation results for the rectangular pan.
(a) Three predicted blank shapes; (b) deformed slip line field blank; (c) deformed Romanovski blank; (d) deformed FAST_FORM3D blank.
Fig. 6. Comparison of strain distribution of various blank shapes using Pam-Stamp for the rectangular pan.
(a) Deformed Romanovski blank; (b) deformed FAST_FORM3D blank.
To continue this validation study, an industrial part from the Komatsu Ltd. was chosen and is shown in Fig. 7(a). We predicted an optimal blank geometry with FAST_FORM3D and compared it with the experimentally developed blank shape as shown in Fig. 7(b). As seen, the blanks are similar but have some differences.
Fig. 7. FAST_FORM3D simulation results for instrument cover validation.
(a) FAST_FORM3D's formability evaluation; (b) comparison of predicted and experimental blank geometries.
Next we simulated the stamping of the FAST_FORM3D blank and the experimental blank using Pam-Stamp. We compared both predicted geometries to the nominal CAD geometry (Fig. 8) and found that the FAST_FORM3D geometry was much more accurate. A nice feature of FAST_FORM3D is that it can show a “failure” contour plot of the part with respect to a failure limit curve which is shown in Fig. 7(a). In conclusion, FAST_FORM3D was successful at predicting optimal blank shapes for a laboratory and industrial parts. This indicates that FAST_FORM3D can be successfully used to assess formability issues of product designs. In the case of the instrument cover, many hours of trial and error experimentation could have been eliminated by using FAST_FORM3D and a better blank shape could have been developed.
Fig. 8. Comparison of FAST_FORM3D and experimental blank shapes for the instrument cover.
(a) Experimentally developed blank shape and the nominal CAD geometry; (b) FAST_FORM3D optimal blank shape and the nominal CAD geometry.
3. Die and process simulation – applications
In order to study the die design process closely, a cooperative study was conducted by Komatsu Ltd. of Japan and the ERC/NSM. A production panel with forming problems was chosen by Komatsu. This panel was the excavator's cabin, left-hand inner panel shown in Fig. 9. The geometry was simplified into an experimental laboratory die, while maintaining the main features of the panel. Experiments were conducted at Komatsu using the process conditions shown in Table 2. A forming limit diagram (FLD) was developed for the drawing-quality steel using dome tests and a vision strain measurement system and is shown in Fig. 10. Three blank holder forces (10, 30, and 50?ton) were used in the experiments to determine its effect. Incremental simulations of each experimental condition was conducted at the ERC/NSM using Pam-Stamp.
Fig. 9. Actual product – cabin inner panel.
Table 2. Process conditions for the cabin inner investigation
Fig. 10. Forming limit diagram for the drawing-quality steel used in the cabin inner investigation.
At 10?ton, wrinkling occurred in the experimental parts as shown in Fig. 11. At 30?ton, the wrinkling was eliminated as shown in Fig. 12. These experimental observations were predicted with Pam-stamp simulations as shown in Fig. 13. The 30?ton panel was measured to determine the material draw-in pattern. These measurements are compared with the predicted material draw-in in Fig. 14. Agreement was very good, with a maximum error of only 10?mm. A slight neck was observed in the 30?ton panel as shown in Fig. 13. At 50?ton, an obvious fracture occurred in the panel.
Fig. 11. Wrinkling in laboratory cabin inner panel, BHF=10?ton.
Fig. 12. Deformation stages of the laboratory cabin inner and necking, BHF=30?ton.
(a) Experimental blank; (b) experimental panel, 60% formed; (c) experimental panel, fully formed; (d) experimental panel, necking detail.
Fig. 13. Predication and elimination of wrinkling in the laboratory cabin inner.
(a) Predicted geometry, BHF=10?ton; (b) predicted geometry, BHF=30?ton.
Fig. 14. Comparison of predicted and measured material draw-in for lab cabin inner, BHF=30?ton.
Strains were measured with the vision strain measurement system for each panel, and the results are shown in Fig. 15. The predicted strains from FEM simulations for each panel are shown in Fig. 16. The predictions and measurements agree well regarding the strain distributions, but differ slightly on the effect of BHF. Although the trends are represented, the BHF tends to effect the strains in a more localized manner in the simulations when compared to the measurements. Nevertheless, these strain prediction show that Pam-Stamp correctly predicted the necking and fracture which occurs at 30 and 50?ton. The effect of friction on strain distribution was also investigated with simulations and is shown in Fig. 17.
Fig. 15. Experimental strain measurements for the laboratory cabin inner.
(a) measured strain, BHF=10?ton (panel wrinkled); (b) measured strain, BHF=30?ton (panel necked); (c) measured strain, BHF =50?ton (panel fractured).
Fig. 16. FEM strain predictions for the laboratory cabin inner.
(a) Predicted strain, BHF=10?ton; (b) predicted strain, BHF=30?ton; (c) predicted strain, BHF=50?ton.
Fig. 17. Predicted effect of friction for the laboratory cabin inner, BHF=30?ton.
(a) Predicted strain, μ=0.06; (b) predicted strain, μ=0.10.
A summary of the results of the comparisons is included in Table 3. This table shows that the simulations predicted the experimental observations at least as well as the strain measurement system at each of the experimental conditions. This indicates that Pam-Stamp can be used to assess formability issues associated with the die design.
Table 3. Summary results of cabin inner study
4. Blank holder force control – applications
The objective of this investigation was to determine the drawability of various, high performance materials using a hemispherical, dome-bottomed, deep drawn cup (see Fig. 18) and to investigate various time variable blank holder force profiles. The materials that were investigated included AKDQ steel, high strength steel, bake hard steel, and aluminum 6111 (see Table 4). Tensile tests were performed on these materials to determine flow stress and anisotropy characteristics for analysis and for input into the simulations (see Fig. 19 and Table 5).
Fig. 18. Dome cup tooling geometry.
Table 4. Material used for the dome cup study
Fig. 19. Results of tensile tests of aluminum 6111, AKDQ, high strength, and bake hard steels.
(a) Fractured tensile specimens; (b) Stress/strain curves.
Table 5. Tensile test data for aluminum 6111, AKDQ, high strength, and bake hard steels
It is interesting to note that the flow stress curves for bake hard steel and AKDQ steel were very similar except for a 5% reduction in elongation for bake hard. Although, the elongations for high strength steel and aluminum 6111 were similar, the n-value for aluminum 6111 was twice as large. Also, the r-value for AKDQ was much bigger than 1, while bake hard was nearly 1, and aluminum 6111 was much less than 1.
The time variable BHF profiles used in this investigation included constant, linearly decreasing, and pulsating (see Fig. 20). The experimental conditions for AKDQ steel were simulated using the incremental code Pam-Stamp. Examples of wrinkled, fractured, and good laboratory cups are shown in Fig. 21 as well as an image of a simulated wrinkled cup.
Fig. 20. BHF time-profiles used for the dome cup study.
(a) Constant BHF; (b) ramp BHF; (c) pulsating BHF.
Fig. 21. Experimental and simulated dome cups.
(a) Experimental good cup; (b) experimental fractured cup; (c) experimental wrinkled cup; (d) simulated wrinkled cup.
Limits of drawability were experimentally investigated using constant BHF. The results of this study are shown in Table 6. This table indicates that AKDQ had the largest drawability window while aluminum had the smallest and bake hard and high strength steels were in the middle. The strain distributions for constant, ramp, and pulsating BHF are compared experimentally in Fig. 22 and are compared with simulations in Fig. 23 for AKDQ. In both simulations and experiments, it was found that the ramp BHF trajectory improved the strain distribution the best. Not only were peak strains reduced by up to 5% thereby reducing the possibility of fracture, but low strain regions were increased. This improvement in strain distribution can increase product stiffness and strength, decrease springback and residual stresses, increase product quality and process robustness.
Table 6. Limits of drawability for dome cup with constant BHF
Fig. 22. Experimental effect of time variable BHF on engineering strain in an AKDQ steel dome cup.
Fig. 23. Simulated effect of time variable BHF on true strain in an AKDQ steel dome cup.
Pulsating BHF, at the frequency range investigated, was not found to have an effect on strain distribution. This was likely due to the fact the frequency of pulsation that was tested was only 1?Hz. It is known from previous experiments of other researchers that proper frequencies range from 5 to 25?Hz [3]. A comparison of load-stroke curves from simulation and experiments are shown in Fig. 24 for AKDQ. Good agreement was found for the case where μ=0.08. This indicates that FEM simulations can be used to assess the formability improvements that can be obtained by using BHF control techniques.
Fig. 24. Comparison of experimental and simulated load-stroke curves for an AKDQ steel dome cup.
5 Conclusions and future work
In this paper, we evaluated an improved design process for complex stampings which involved eliminating the soft tooling phase and incorporated the validation of product and process using one-step and incremental FEM simulations. Also, process improvements were proposed consisting of the implementation of blank holder force control to increase product quality and process robustness.
Three separate investigations were summarized which analyzed various stages in the design process. First, the product design phase was investigated with a laboratory and industrial validation of the one-step FEM code FAST_FORM3D and its ability to assess formability issues involved in product design. FAST_FORM3D was successful at predicting optimal blank shapes for a rectangular pan and an industrial instrument cover. In the case of the instrument cover, many hours of trial and error experimentation could have been eliminated by using FAST_FORM3D and a better blank shape could have been developed.
Second, the die design