保溫瓶?jī)?nèi)膽底沖壓模具設(shè)計(jì)【落料拉深復(fù)合?!?/h1>
保溫瓶?jī)?nèi)膽底沖壓模具設(shè)計(jì)【落料拉深復(fù)合?!?落料拉深復(fù)合模,保溫瓶?jī)?nèi)膽底沖壓模具設(shè)計(jì)【落料拉深復(fù)合?!?保溫瓶,內(nèi)膽,沖壓,模具設(shè)計(jì),落料拉深,復(fù)合
課程設(shè)計(jì)
題目 保溫瓶?jī)?nèi)膽底沖壓模具設(shè)計(jì)
系 別 機(jī)電工程系
年級(jí)專業(yè)
學(xué)生姓名 xxx
指導(dǎo)教師 xxx
專業(yè)負(fù)責(zé)人 xxx
答辯日期
第3頁 共19頁
摘 要
摘 要
隨著中國(guó)工業(yè)不斷地發(fā)展,模具行業(yè)也顯得越來越重要。本論文便是設(shè)計(jì)加工保溫瓶?jī)?nèi)膽底的模具。首先對(duì)加工零件進(jìn)行了加工工藝和結(jié)構(gòu)工藝的分析。通過計(jì)算毛坯尺寸和拉深系數(shù)提出了方案,最后確定采用落料、拉深復(fù)合模。對(duì)模具的排樣做出了合理的布置,使材料利用率達(dá)到較高的水平。計(jì)算了沖壓過程中所需要的各種沖壓工藝力,包括落料力、卸料力、壓邊力、拉深力、頂料力等,并對(duì)壓力機(jī)進(jìn)行了合理的噸位初選。復(fù)合模在結(jié)構(gòu)上采用了裝的形式,計(jì)算出了落料、拉深工作部分的尺寸。對(duì)模具的閉合高度進(jìn)行了合理的確定。列出了模具所需零件的詳細(xì)清單,并給出了合理的裝配圖。由于拉深的深度較大,對(duì)壓力機(jī)的電機(jī)也進(jìn)行了功率校核并提出了,能使拉深順利完成。最后對(duì)模具的一個(gè)主要零件導(dǎo)套進(jìn)行了簡(jiǎn)單的加工工藝路線的制定。本設(shè)計(jì)對(duì)于采用單動(dòng)壓力機(jī)進(jìn)行拉深具有一定的參考作用。
關(guān)鍵詞:課程論文;模具設(shè)計(jì);復(fù)合模;
Abstract
With the continuous development of Chinese industry, the mold industry has become increasingly important. This paper is designed to cover the mold machining. First of machined parts were analyzed process and structure the process. By calculating the rough size and drawing coefficient proposed plan to finalize the use of blanking, drawing compound die. Nesting on the mold to make a reasonable arrangement, the material utilization rate reached a higher level. Calculate the force of stamping process the stamping process needs, including blanking force, discharge power, BHF, drawing force, ejector force, etc., and press for a reasonable tonnage primaries. Composite mold in the structure adopted in the form of equipment, calculated blanking, drawing deep working portion size. The mold is closed for a reasonable determination of the height. Lists the detailed list of the required mold parts, and gives a reasonable assembly drawing. Since the depth of the larger drawing of the press motor were also checked and made power, enabling the successful completion of the drawing. Finally, a major part of the mold guide sleeve for a simple process route development. The design for a single-action press were drawing has a certain reference.
Key words:mold design; composite mold;
目錄
目 錄
第1章 沖壓工藝設(shè)計(jì) 5
1.1 零件的工藝分析 5
1.2 制定沖壓工藝方案 6
1.3 畫工序圖 7
1.4 初選沖壓設(shè)備 7
第2章 沖壓模具設(shè)計(jì) 8
2.1 沖模類型及結(jié)構(gòu)形式 8
2.2 模具設(shè)計(jì)計(jì)算 8
第3章 選用模架、確定閉合高度 11
3.1 模架的選用 11
3.2 模具的閉合高度 11
3.3 壓力中心 12
第4章 模具的主要零部件結(jié)構(gòu)設(shè)計(jì) 12
4.1落料凹模 12
4.2 凸凹模 12
4.3拉深凸模 12
4.4彈性卸料板 12
4.5上墊板 13
4.6凹模固定板 14
第5章 模具的整體安裝 15
5.1模具的總裝配 15
5.2模具零件 15
第6章 選定沖壓設(shè)備 16
6.1壓力機(jī)的規(guī)格 16
6.2電動(dòng)機(jī)功率的校核 16
總結(jié) 17
致謝 18
參考文獻(xiàn) 19
第19頁 共19頁
保溫瓶?jī)?nèi)膽底沖壓模具設(shè)計(jì)
第1章 沖壓工藝設(shè)計(jì)
1.1 零件的工藝分析
此零件形狀為階梯圓筒形件,需要采用落料,拉深三道工序,通過計(jì)算確定拉深次數(shù)。
零件材料為SVS304鋼,根據(jù)參考文獻(xiàn)[1]表1.4.1得:SVS304鋼的抗剪強(qiáng)度=210MPa。
由此可見,其塑性較好,有較高的強(qiáng)度,適合于成形加工。=260~440MPa、抗拉強(qiáng)度b=300~440MPa﹑伸長(zhǎng)率10=29%、屈服強(qiáng)度=210MPa。
由此可見,其塑性較好,有較高的強(qiáng)度,適合與成形加工。
此零件毛坯形狀為圓形,故采用沖裁工藝中的落料工序。
首先計(jì)算出毛坯的尺寸,根據(jù)毛坯尺寸要求計(jì)算出凸凹模的尺寸,但要注意落料見的尺寸應(yīng)增加修邊余量,以保證零件的高度。后面還有拉深等其它工序,最重要的是毛坯外形尺寸精度要保證下一道工序的完成。
拉深見工藝性的好壞,直接影響到該零件能否用拉深方法生產(chǎn)出來,不僅能滿足產(chǎn)品的使用要求,同時(shí)也能夠用最簡(jiǎn)單,最經(jīng)濟(jì)和最快的方法生產(chǎn)出來。
拉深見外形尺寸的要求應(yīng)根據(jù)零件的高度以及厚度等選擇一次拉深還是多次拉深。
1.計(jì)算落料毛坯尺寸:
t=0.6mm<1mm. 故可以按外形尺寸計(jì)算
由《指導(dǎo)》表4-4.將零件分為序號(hào)9和序號(hào)11兩部分
由序號(hào)9得:
由序號(hào)11得: D2=
∴ 毛坯的總面積 A=A1+A2=11060mm2
∴ 所以毛坯直徑
因此毛坯直徑為127mm
查書得修邊余留為2.5,那么圓整取毛坯的直徑為132
2.確定拉深次數(shù):
查《指導(dǎo)》表4-8得:當(dāng) ×100%=1.25(<1.5~1),一次拉深可得最大相對(duì)高度為0.84~0.65,故零件以以一次拉深成形。
3.計(jì)算拉深系數(shù)
因該零件兼有凸緣見拉深與階梯圓筒件拉深的持性,所以近似按此兩種拉深方法估算總拉深系數(shù).
1.2 制定沖壓工藝方案
1.2.1 工藝方案分析比較
此零件外殼形狀表明它為拉深件,所以拉深為基本工序,其毛坯可用落料工序完成。根據(jù)前面的計(jì)算,只需要一次拉深,故根據(jù)該零件所需基本沖壓工序,做出一個(gè)合格的零件,可以有三種工藝方案:
第一種方案是把落料、拉深、二道工序做一個(gè)簡(jiǎn)單復(fù)合模。
第二種方案是以落料、拉深工序分開,各做一副單工序模。
第三種方案是把落料、拉深工序并在一起,做一副多工位的級(jí)進(jìn)模。
三種方案的比較:
第一種方案:落料、拉深是一個(gè)簡(jiǎn)單復(fù)合模,設(shè)計(jì)簡(jiǎn)便,制造也不難生產(chǎn)效率高,裝夾方便,只要保證一個(gè)尺寸精度要求,方便、簡(jiǎn)單。
第二種方案:2道工序分開,分布鮮明,有序進(jìn)行,看得懂,弄得請(qǐng),但效率不高,占用設(shè)備多,若單用一個(gè)設(shè)備,則需拆下來,裝上去次數(shù)多,比較麻煩。
第三種方案:2道工序一起進(jìn)行,效率比較高,但是制造麻煩,周期長(zhǎng),成本高,只有大批量生產(chǎn)中才適合。
1.2.2 工藝方案確定
根據(jù)工藝方案的比較:
方案一:落料拉深復(fù)合
方案二:落料→拉深
方案三:落料、拉深級(jí)進(jìn)模
綜合所有因素,此零件選用方案一。
1.3 畫工序圖
1.工序1:落料拉深
(3)排樣圖
a.計(jì)算開料寬度及步距
由參考文獻(xiàn)[1]表2.5.2 取搭邊值=1.5mm =1.2mm
由表2.5.3得 減料公差=0.4mm 導(dǎo)料間隙C=0.1mm
考慮落料后需自然卸下條料 單惻需沖開0.6mm深缺口
1.4 初選沖壓設(shè)備
(1)計(jì)算拉深工藝力,相對(duì)厚度=1.25%<1.5%
t=0.6mm 根據(jù)參考文獻(xiàn)[1]表4.5.2 拉深時(shí)需采用壓邊圈。在該模具中可利用凸凹模與成型頂塊進(jìn)行壓邊。
由于該零件只一次拉深 因此拉深時(shí)需兼整形。拉深工藝力應(yīng)按整形力計(jì)算。參考彎曲校力進(jìn)行計(jì)算。查參考文獻(xiàn)[1]表3.3.3。取單位校力q=40MPa
則
(2)計(jì)算沖裁工藝力
F沖=Ltb=×40×0.6×440=27632N
由參考文獻(xiàn)[1]取頂件力系數(shù)K頂=0.08
則 F頂=K頂F沖=0.08×27632=2210.6N
F總2=F沖+F頂=27632+2210.6=29842.6N
(3)計(jì)算沖壓工藝力
F總=F總1+F總2=47759.4+29842.6=77602N
按F總=77602N,以及F總≤(0.7~0.8)F公
得 F公≥97002.5~110860N
查參考文獻(xiàn)[2]表8-10 初選壓力機(jī)為J23-16
第2章 沖壓模具設(shè)計(jì)
2.1 沖模類型及結(jié)構(gòu)形式
此零件形狀為階梯圓筒形件,分為落料拉深模具,即落料拉深復(fù)合模,采用裝式。利用擋料釘定距,模具本身利用M8螺釘固定及Ф8銷釘定位,本模具采用彈頂器以及打桿作為卸料裝置。
2.2 模具設(shè)計(jì)計(jì)算
1.壓力中心
此零件為階梯圓筒形件,即屬于旋轉(zhuǎn)體件,結(jié)構(gòu)對(duì)稱,所以壓力中心應(yīng)該在其幾何中心。
2.各主要零件外形尺寸
(1)落料凹模外形尺寸
由參考文獻(xiàn)[1]式(2.8.8) H=Kb
查表2.8.2 K取0.3 b=40mm
H1=Kb=0.3×40=12mm 按要求需滿足H1≥15mm
因?yàn)槭菑?fù)合模,另有拉深工序,零件高度為6mm,材料厚度為0.6mm,加之有凸模進(jìn)入凹模的深度,綜上所述,查參考文獻(xiàn)[2],H=25mm
由式(2.8.9)凹模壁厚C=(1.5-2)H1=(1.5~2)×15=22.5~30mm
按要求需滿足C≥30~40mm 故取 C=30mm
為便于加工模板取圓形
則D=2×30+40=100
(2)固定板外形尺寸
直徑D與凹模相同 為100mm
厚度H2=(0.6~0.8)H1(0.6~0.8)×25
=(15~20)mm
取H2=20mm
(3)墊板外形尺寸
直徑D=100mm
厚度H3=(6~12)mm
取H3=8mm
各模板采用Φ8與M8螺釘定位與連接
根據(jù)參考文獻(xiàn)[4] 孔距取76mm
(4)凸凹模、凸凹模型芯、成形頂塊、拉深凸模外形尺寸
根據(jù)成型要求凸凹模、凸凹模型芯、成形頂塊以及拉深凸凹模長(zhǎng)度分別為41mm、35.5mm、18.5和42.5mm。
綜上所述,歸納所得 (單位:mm)
落料凹模Ф100×25 GB2858.4-81
上、下固定板Ф100×20 GB2858.5-81
上、下墊板Ф100×8 GB2858.5-81
凸凹模: Ф46×40
凸凹模型芯:Ф9×35.5
成形頂塊:Ф40×18.5
拉深凸模:Ф14×42.5
聯(lián)接螺釘:M8 GB70-85
定位銷釘:Ф8 GB119-86
孔距Ф76
4.選用模架
因?yàn)榘寄V芙鐬椐?00,根據(jù)參考文獻(xiàn)[3],采用冷沖模滑動(dòng)導(dǎo)向中間導(dǎo)柱模架,根據(jù)各項(xiàng)指標(biāo),選用模架為:模架100×130~150 GB2851.6-81.HT20-40
上、下模板厚度分別為H=25mm. H=30mm
5.校核壓力機(jī)
(1)閉合高度校核
模具閉合高度H=H+ H+HtH+H+H
=25+8+35.5+0.6+42.5+8+30=149.5mm
由[2]表8-10得 壓力機(jī)最大裝模高度H=220-40=180mm
由[2]表8-10得 壓力機(jī)最小裝模高度H=180-45=135mm
滿足H-5≥H≥H+10
(2)公稱壓力F校核
F=160KN>F=77.6KN
所以F合格。
(3)滑塊行程校核
根據(jù)參考文獻(xiàn)[2]表8-10得滑塊行程H=55㎜
模具工作行程H=(2~2.5)H=(2~2.5)×6=(12~15)mm
H>H 滿足使用要求
(4)工作臺(tái)尺寸校核
由參考文獻(xiàn)[2]. 工作臺(tái)前后尺寸為300mm,左右為450㎜
模架型號(hào)100×130~150
由參考文獻(xiàn)[3]. 模架左右為260㎜,前后為170㎜,滿足工作臺(tái)尺寸每邊大于模具50~70mm的要求
因?yàn)楣ぷ髋_(tái)孔尺寸直徑為210㎜,能容納下彈頂器,所以滿足要求。
第3章 選用模架、確定閉合高度
3.1 模架的選用
由凹模外形尺寸,選擇中間導(dǎo)柱模架(GB/T2851.5—1990)在按其標(biāo)準(zhǔn)選擇具體結(jié)構(gòu)尺寸如下
上模板 HT250
下模板 ZG450
導(dǎo) 柱 20鋼
導(dǎo) 套 20鋼
凸緣模柄 Q235
模具閉合高度 MAX 350mm MIN 305mm
該副模具沒有漏料問題,故不必考慮漏料孔尺寸。
3.2 模具的閉合高度
所謂的模具的閉合高度H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)。
模具的實(shí)際閉合高度,一般為:
……………5.1
該副模具使用上墊板厚度為8mm,凹模固定板厚度為8mm。如果沖頭(凸凹模)的長(zhǎng)度設(shè)計(jì)為140mm,凹模(落料凹模)設(shè)計(jì)為130mm,則閉合高度為:
查開式壓力機(jī)設(shè)備參數(shù)表知,1600KN壓力機(jī)最大閉合高度為450mm(封閉調(diào)節(jié)高度為130mm)。因?yàn)槟>叩拈]合高度絕對(duì)不能大于所選的壓力機(jī),所以初選的1250KN噸位的壓力機(jī)裝模高度過小,這里我們采用1600KN的開式壓力機(jī)。
故實(shí)際設(shè)計(jì)模具的閉合高度為
壓力機(jī)的裝模高度必須符合模具閉合高度的要求。其關(guān)系式為
…………………………………5.2
式中
、—壓力機(jī)的最大和最小裝模高度
H—模具的閉合高度
所以有
故閉合高度設(shè)計(jì)合理。
3.3 壓力中心
由于該零件落料、拉深均為軸對(duì)稱形狀,故不必進(jìn)行壓力中心的計(jì)算。
第4章 模具的主要零部件結(jié)構(gòu)設(shè)計(jì)
4.1落料凹模
落料凹模的內(nèi)外形尺寸和厚度在前面的計(jì)算中已算出,這里需要有三個(gè)的螺紋孔,以便與下模板固定,而且還需要有兩個(gè)與下模板同時(shí)加工的銷釘孔,在其內(nèi)圈設(shè)計(jì)了限位倒角,以限制壓邊圈的行程。在落料凹模上還有一個(gè)銷孔,用來安裝擋料銷。在圖中標(biāo)注尺寸精度、形位公差及粗糙度。落料凹模的零件圖如圖6.1所示。
4.2 凸凹模
凸凹模的工作部分尺寸在前面的設(shè)計(jì)計(jì)算中已經(jīng)算出,這里根據(jù)零件的加工深度設(shè)計(jì)出凸凹模的內(nèi)外形尺寸。在凸凹模上設(shè)計(jì)了四個(gè)螺紋孔,以便與上模板固定,而且同時(shí)配作兩個(gè)銷釘孔。在其內(nèi)部設(shè)計(jì)了限位倒角,以限制壓邊圈的行程,在上圓口設(shè)計(jì)了安裝拉深凸模的沉槽。在圖中標(biāo)注尺寸精度、形位公差及粗糙度。凸凹模的零件圖如圖6.2所示。
4.3拉深凸模
拉深凸模的工作部分尺寸在前面的設(shè)計(jì)計(jì)算中已經(jīng)算出,這里根據(jù)零件拉深的拉伸深度設(shè)計(jì)出凸模的內(nèi)外形尺寸。在拉深凸模上設(shè)計(jì)了三個(gè)推桿孔,以便安裝推桿。在其內(nèi)部設(shè)計(jì)了透氣孔,以使拉深后的沖壓件不受空氣的壓力而緊緊地包住在凸模上能順利脫下。在頂端設(shè)計(jì)了圓凸緣結(jié)構(gòu),以便裝配在凸凹模上與上模板固定。在圖中標(biāo)注尺寸精度、形位公差及粗糙度。
4.4彈性卸料板
彈性卸料板的尺寸可以根據(jù)彈簧的數(shù)目以及外徑來計(jì)算。
作為沖模卸料或推件用的彈簧,是屬于標(biāo)準(zhǔn)零件。標(biāo)準(zhǔn)中給出了彈簧的有關(guān)數(shù)據(jù)和特性曲線,我們可以按需要選取。一般選用彈簧(材料為65Mn彈簧鋼)的原則,應(yīng)該是在滿足模具結(jié)構(gòu)要求的前提下,保證所選用的彈簧能夠給出要求的作用力和行程。
為了保證沖模的常工作,在沖模不工作的時(shí)候,彈簧也應(yīng)該在預(yù)緊力的作用下產(chǎn)生一定的預(yù)壓緊量,這時(shí)預(yù)緊力應(yīng)為
………………………………………6.1
為了保證沖模常工作所必需的彈簧最大壓緊量為:
………………………………………6.2
式中 —彈簧最大許用壓縮量
—彈簧預(yù)緊量
—工藝行程
—余量,主要考慮模具的刃磨量和調(diào)整量,一般取5~10mm
由于卸料力為14825N,初定彈簧的根數(shù)為8根,則每根彈簧上的卸料力為
根據(jù)所需的預(yù)緊力和彈簧的總壓縮量,參照彈簧的選取表,初選彈簧的規(guī)格,彈簧的直徑D=60mm,彈簧絲的直徑d=10mm,序號(hào)為85號(hào)。
在拉深凹模上設(shè)計(jì)了三個(gè)螺紋孔,以便與下模板固定。在其內(nèi)部設(shè)計(jì)了一個(gè)螺紋大孔,用以安裝碟型彈簧。在圖中標(biāo)注尺寸精度、形位公差及粗糙度。拉深凹模的零件圖如圖6.5所示。
4.5上墊板
墊板的作用是直接承受和擴(kuò)散凸模傳遞的壓力,以降低模座所受的單位壓力,防止模座被壓出陷痕而損壞。在設(shè)計(jì)中我們把墊板的外形尺寸與凸凹模的外形尺寸相匹配,其厚度我們?cè)O(shè)計(jì)為8mm。在上墊板上設(shè)計(jì)了三個(gè)推桿孔,以便安裝推桿,還有四個(gè)螺釘孔以及兩個(gè)銷孔,這些都是為了與凸凹模和拉深凸模上的各種固定零件的安裝相匹配的。在圖中標(biāo)注尺寸精度、形位公差及粗糙度。上墊板的零件圖如圖6.6所示。
4.6凹模固定板
凹模固定板的作用是對(duì)凹模進(jìn)行限位止動(dòng),以求得位置保持一定和可靠的方向性。在設(shè)計(jì)中我們把凹模固定板的外形尺寸與落料凹模和拉深凹模的外形尺寸相匹配,其總厚度我們?cè)O(shè)計(jì)為24mm。在凹模固定板中間設(shè)計(jì)了一個(gè)高16mm的凹模固定塊,是為了固定拉深凹模。在固定板上設(shè)計(jì)了三個(gè)頂桿孔,以便安裝頂桿,還有七個(gè)螺釘孔以及兩個(gè)銷孔,這些都是為了與落料凹模和拉深凹模上的各種固定零件的安裝相匹配的。在圖中標(biāo)注尺寸精度、形位公差及粗糙度。凹模固定板的零件圖如圖6.7所示。
第5章 模具的整體安裝
5.1模具的總裝配
由以上的設(shè)計(jì)計(jì)算,并經(jīng)繪圖設(shè)計(jì),該落料拉深復(fù)合模裝配圖如圖7.1所示。
圖7.1 落料拉深復(fù)合模裝配圖
5.2模具零件
該復(fù)合模的主要零部件在模具的結(jié)構(gòu)設(shè)計(jì)中已經(jīng)進(jìn)行了仔細(xì)的設(shè)計(jì),其余的非標(biāo)準(zhǔn)的零件可以根據(jù)需要按國(guó)標(biāo)選取使用。
第6章 選定沖壓設(shè)備
6.1壓力機(jī)的規(guī)格
沖壓設(shè)備選擇是沖壓工藝過程設(shè)計(jì)的一項(xiàng)重要內(nèi)容,它直接關(guān)系到設(shè)備的安全和使用的合理,同時(shí)也關(guān)系到?jīng)_壓工藝過程的順利完成及產(chǎn)品質(zhì)量、零件精度、生產(chǎn)效率、模具壽命、板料的性能與規(guī)格、成本的高低等一系列重要問題。
在前面的設(shè)計(jì)中,我們已經(jīng)對(duì)沖壓設(shè)備的噸位以及閉合高度等參數(shù)進(jìn)行了確定。這里根據(jù)前面所算出來的各項(xiàng)數(shù)據(jù)。查表選擇壓力機(jī),其主要具體參數(shù)如下
公稱壓力 1600KN
滑塊行程 160mm
行程次數(shù) 40/次·
最大封閉高度 450mm
封閉高度調(diào)節(jié)量 130mm
工作臺(tái)尺寸 1120710mm
柄孔尺寸 70×80mm
工作臺(tái)板厚 130mm
電動(dòng)機(jī)功率 15KW
6.2電動(dòng)機(jī)功率的校核
對(duì)于本次設(shè)計(jì)由于行程比較長(zhǎng),設(shè)備的噸位雖然足夠,但設(shè)備具備的功不一定能滿足拉深的要求。遇到這種情況,可能出現(xiàn)拉深時(shí)壓力機(jī)行程速度減緩,甚至?xí)p壞設(shè)備的電動(dòng)機(jī)。為此,還需要對(duì)拉深功進(jìn)行核算。
因?yàn)?
N·m…………………………7.1
因而,壓力機(jī)的電動(dòng)機(jī)功率可按下式進(jìn)行核算
……………………………7.2
式中 W—拉深功(N·m)
n—壓力機(jī)行程次數(shù)(次/min)
N—電動(dòng)機(jī)功率(KW)
—壓力機(jī)效率,
—電動(dòng)機(jī)效率,
K—不均衡系數(shù),
所以有
經(jīng)核算后拉深所需要的功率小于壓力機(jī)的電機(jī)功率15KW,符合要求。
總結(jié)
數(shù)月的課程設(shè)計(jì)即將結(jié)束,希望老師對(duì)我的設(shè)計(jì)過程作最后的審閱,最全面的指。
在這次課程設(shè)計(jì)中我通過參考及查閱各種有關(guān)模具設(shè)計(jì)方面的資料,請(qǐng)蔡昀老師指導(dǎo)有關(guān)模具方面的問題,特別是采用標(biāo)準(zhǔn)件時(shí)所遇到的困擾,老師給予我們想要的解答,使我在著短短的時(shí)間里對(duì)模具結(jié)構(gòu)及動(dòng)作過程等有了更深一步的了解。其中在設(shè)計(jì)過程中,起初設(shè)計(jì)目標(biāo)與最終所想有些矛盾,但通過查閱相關(guān)書籍都得到了解決,從開始的無從下手到現(xiàn)在的得心應(yīng)手,至少了解了簡(jiǎn)單模具設(shè)計(jì)。這些都是通過自己的努力與老師的指導(dǎo)才得到了現(xiàn)在的水準(zhǔn)。
經(jīng)過這幾個(gè)月的設(shè)計(jì),我深信這次課程設(shè)計(jì)能為我以后的課程設(shè)計(jì)做一個(gè)很好的基礎(chǔ),甚至對(duì)以后的踏上社會(huì)也有許多幫助。
致謝
這次我的課程設(shè)計(jì)課題能夠成功完成,首先要感謝我的課程設(shè)計(jì)指導(dǎo)老師模具教研室的主任,老師不僅借給我?guī)妆娟P(guān)于本次轉(zhuǎn)子片課程設(shè)計(jì)非常好的資料,而且還幫我把控整個(gè)課程設(shè)計(jì)的方向。
在我遇到瓶頸時(shí)也耐心的輔導(dǎo)我,幫助我順利的完成我的轉(zhuǎn)子片課題設(shè)計(jì)。同時(shí)也感謝我們學(xué)院教過我的老師,在我AutuCAD工程繪圖時(shí)遇到不會(huì)時(shí)她耐心的教我如何用AutuCAD繪圖,這才使我的設(shè)計(jì)圖能夠順利的用繪圖軟件畫出來,并在設(shè)計(jì)說明書中插入部分圖紙,還有教我們模具設(shè)計(jì)在我的設(shè)計(jì)出現(xiàn)于實(shí)際生產(chǎn)不相符的時(shí)候及時(shí)的指導(dǎo)我,
但是由于老師時(shí)間比較緊,不可能完全的將所有的問題都找出了,加之我對(duì)于模具設(shè)計(jì)的各方面知識(shí)學(xué)得還不到位,有很多的東西還沒學(xué)好,無法避免的會(huì)出現(xiàn)一些不足之處,這點(diǎn)將在以后的工作中會(huì)進(jìn)一步完善。
這次保溫瓶?jī)?nèi)膽底課題的課程設(shè)計(jì)的設(shè)計(jì)過程中參考了很多書籍還有一些網(wǎng)站,并且我們宿舍的舍友和班級(jí)里面的同學(xué)都給與我了我很大的幫助,在此表示衷心的感謝。
參考文獻(xiàn)
[1]成虹,沖壓工藝與模具設(shè)計(jì),北京,高等教育出版社,2002
[2]郭鐵良,模具制造工藝學(xué),高等教育出版社,1999
[3]陳于萍,高曉康編著,互換性與測(cè)量技術(shù),北京高等教育出版社,2002
[4]吳宗澤,機(jī)械零件設(shè)計(jì)手冊(cè),北京,機(jī)械工業(yè)出版社,1992
[5]許發(fā)越,實(shí)用模具設(shè)計(jì)與制造手冊(cè),北京,機(jī)械工業(yè)出版社,1992
[6]王芳,冷沖壓模具設(shè)計(jì)指導(dǎo),北京,機(jī)械工業(yè)出版社,1999
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.