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題目 某型錐形蓋沖壓工藝及其模具設(shè)計(jì)
專 業(yè) 名 稱 機(jī)械設(shè)計(jì)制造及其自動化
班 級 學(xué) 號 078105106
學(xué) 生 姓 名 桂瑤堃
指 導(dǎo) 教 師 賀紅林
填 表 日 期 2011 年 03 月 01 日
一、 選題的依據(jù)及意義:
根據(jù)學(xué)生所學(xué)專業(yè)及教學(xué)大綱要求,結(jié)合相關(guān)企業(yè)實(shí)際生產(chǎn)需要及設(shè)計(jì)模式,促使學(xué)生將所學(xué)專業(yè)基礎(chǔ)知識及專業(yè)知識具體應(yīng)用到實(shí)踐中,培養(yǎng)其理論聯(lián)系實(shí)際的能力。
本課題是學(xué)習(xí)模具設(shè)計(jì)的核心內(nèi)容、專業(yè)主干內(nèi)容,在學(xué)習(xí)應(yīng)用模具設(shè)計(jì)中,占有重要地位。模具設(shè)計(jì)的學(xué)生的核心能力主要分為沖壓模具設(shè)計(jì)與制造等能力,而本課題主要學(xué)習(xí)沖壓模具的設(shè)計(jì)能力,在模具技術(shù)更新與企業(yè)的發(fā)展中占據(jù)著舉足輕重的地位。其要求對給定零件錐形蓋進(jìn)行落料、沖孔、翻邊、成形復(fù)合沖壓模設(shè)計(jì),通過對零件進(jìn)行詳細(xì)的工藝分析確定零件的沖壓工藝方案并制定部分零件的制造工藝,如:凸模、凹模、凸凹模、凸模固定板、墊板、凹模固定板、卸料板、導(dǎo)尺、擋料銷、導(dǎo)正銷等。通過該課題能夠讓學(xué)生掌握中等復(fù)雜程度零件沖壓模具設(shè)計(jì)與制造的一般方法,對零件沖壓工藝方案的制定、工藝計(jì)算及模具設(shè)計(jì)有了更深層次的認(rèn)識,并學(xué)會對模具設(shè)計(jì)資料的檢索與整合以及對已有資料的充分合理的使用,該實(shí)踐性課題是對學(xué)生理論學(xué)習(xí)水平的實(shí)踐和檢驗(yàn),可對以后從事類似的工作有一定的指導(dǎo)性與實(shí)踐性意義。
二.國內(nèi)外研究現(xiàn)狀及發(fā)展趨勢(含文獻(xiàn)綜述):
沖壓技術(shù)已經(jīng)有一百多年的歷史,其生產(chǎn)的作業(yè)形式及發(fā)展過程可以概括為:手工——機(jī)械——自動——無人。古代的沖壓加工是依靠手工制作,現(xiàn)代沖壓加工的標(biāo)志是機(jī)械化。如今的沖壓加工已有很大程度的自動化,并已開始向無人化水平發(fā)展。目前,國外沖壓生產(chǎn)的水平及發(fā)展趨勢如下:
1.沖壓生產(chǎn)的自動化、無人化、精密化
(1)?自動化????
a.單機(jī)自動? 比如日本AIDA公司的高速沖床,每分鐘可以進(jìn)行一千多次的沖裁。
b.多機(jī)聯(lián)合生產(chǎn)線? 比如生產(chǎn)汽車門板零件,由5臺大噸位沖床組合,從板料自動送進(jìn)到各道工序的加工到最后產(chǎn)品檢驗(yàn),全由計(jì)算機(jī)控制。
c.沖壓自動線? 不僅有小型薄帶料零件的沖壓自動線,而且有大型厚板料零件的沖壓自動線。有的工廠安裝厚板零件自動沖壓生產(chǎn)線,板料從開卷、反垂、送進(jìn)、沖壓到卷走廢料、取出工件全部自動化。
d.小型沖壓系統(tǒng)? 沖壓設(shè)備不斷推陳出新,比如日本推出的第三次沖床革命的新產(chǎn)品MP210壓力機(jī),可以直列式放置10副模具,并改機(jī)械傳動為液壓驅(qū)動的帶料連續(xù)沖壓設(shè)備,就是一個典型的例子。
(2) 無人化
a.沖壓柔性加工系統(tǒng)? 美國、德國、英國、日本等發(fā)達(dá)國家均有這種系統(tǒng)。比如,日本 TOYOTA公司的柔性加工系統(tǒng)是通過數(shù)控使一組沖壓設(shè)備實(shí)行自動協(xié)調(diào)加工。
b.沖壓加工中心? 日本的AIDA公司很早就開始了沖壓加工中心的研制。不過,對其研制進(jìn)展緩慢,說明難度較大,所需人力,才力投資很大,可能要道1世紀(jì)前期才會開始普遍起來。
(3)? 精密化
?? 精密化是針對沖壓產(chǎn)品特別是小型零件精密化要求而發(fā)展的相應(yīng)生產(chǎn)技術(shù)。例如彩色顯像管電子槍用膜片零件,僅從上面三個直徑為0.57mm小孔的孔徑、孔的不圓度、孔間距精度均小于±0.10mm來看,足見其精度要求之高,日立公司用14道沖壓工序、22個工步的級進(jìn)模加工出來。顯然該產(chǎn)品的精度是由模具的精度來保證的。
(4)塑性成形的基礎(chǔ)理論已基本形成
沖壓成形工藝近年來有很多新的發(fā)展,在精密沖裁、精密成形、精密剪切、復(fù)合材料成形、超塑性成形、軟模成形以及電磁成形等方面取得很大的進(jìn)展。沖壓件的成形精度、生產(chǎn)率越來越高。精密沖壓的范圍越來廣,由平板零件精密沖裁拓寬到精密彎曲、精密拉深及立方體精密成形等??杉庸さ墓ぜ暮穸纫膊粩嗵岣?,并可對高強(qiáng)度合金材料進(jìn)行精密沖裁。
計(jì)算機(jī)輔助工程在沖壓領(lǐng)域得到較好的應(yīng)用,可進(jìn)行應(yīng)力、應(yīng)變等的分析,排樣、毛坯的優(yōu)化設(shè)計(jì)及工藝過程的模擬與分析等,實(shí)現(xiàn)沖壓過程的優(yōu)化設(shè)計(jì)。
此外,沖壓成形性能和成形極限的研究,沖壓件成形難度的判定以及成形預(yù)報(bào)等技術(shù)的發(fā)展,均標(biāo)志著沖壓成形已從原來的經(jīng)驗(yàn)、實(shí)驗(yàn)分析開始走上由沖壓理論指導(dǎo)的科學(xué)聯(lián)系使沖壓成形趲計(jì)算機(jī)輔助工程化和智能化的發(fā)展道路。
2.開發(fā)和發(fā)展沖壓新理論、新工藝
具體表現(xiàn)在以下8個方面:
1).集成化技術(shù)
現(xiàn)代模具設(shè)計(jì)制造系統(tǒng)不僅應(yīng)強(qiáng)調(diào)信息的集成,更應(yīng)強(qiáng)調(diào)技術(shù)、人和管理的集成。在開發(fā)模具制造系統(tǒng)時強(qiáng)調(diào)“多集成”的概念,即信息集成、智能集成、串并行工作機(jī)制集成及人員集成,這更適合未來制造系統(tǒng)的需求。
2).智能化技術(shù)
應(yīng)用人工智能技術(shù)實(shí)現(xiàn)產(chǎn)品生命周期各環(huán)節(jié)的智能化,實(shí)現(xiàn)生產(chǎn)過程各個環(huán)節(jié)的智能化,以及模具設(shè)備的智能化,也要實(shí)現(xiàn)人與系統(tǒng)的融合及人在其中智能的充分發(fā)揮。
3).網(wǎng)絡(luò)技術(shù)的應(yīng)用
網(wǎng)絡(luò)技術(shù)包括硬件和軟件的集成實(shí)現(xiàn)。各種通訊協(xié)議及制造自動化協(xié)議,信息通訊接口系統(tǒng)操作控制策略等,是實(shí)現(xiàn)跨國模具的成功例子。
4).多學(xué)科多功能綜合產(chǎn)品設(shè)計(jì)技術(shù)
未來產(chǎn)品的開發(fā)設(shè)計(jì)不僅用網(wǎng)絡(luò)技術(shù)的應(yīng)用為我國模具企業(yè)實(shí)現(xiàn)敏捷制造和動態(tài)聯(lián)盟奠定了技術(shù)基礎(chǔ)。到機(jī)械科學(xué)的理論知識,還用到電磁學(xué)、光學(xué)、控制理論等。甚至需考慮到經(jīng)濟(jì)、心理、環(huán)境、衛(wèi)生及社會等各方面的因素。產(chǎn)品的開發(fā)要進(jìn)行多目標(biāo)、全性能的優(yōu)化設(shè)計(jì),以求模具產(chǎn)品動態(tài)特性、效率、精度、使用壽命、可靠性、制造成本與制造周期的最佳組合。
5).虛擬現(xiàn)實(shí)與多媒體技術(shù)的應(yīng)用
虛擬現(xiàn)實(shí)UR是人造的計(jì)算機(jī)環(huán)境,人處在這種環(huán)境中有身臨其境的感覺,并強(qiáng)調(diào)人的介入與操作。這項(xiàng)技術(shù)在21世紀(jì)整個制造中都將有廣泛的應(yīng)用,可以用于培訓(xùn)、制造系統(tǒng)仿真、實(shí)現(xiàn)基于制造仿真的設(shè)計(jì)與制造、實(shí)現(xiàn)集成人的設(shè)計(jì)等。美國已于1999年借助此項(xiàng)技術(shù)成功修復(fù)太空望遠(yuǎn)鏡。而多媒體技術(shù)主要是采用多種介質(zhì)來存儲、表達(dá)處理多種信息,融文學(xué)、語言、圖像于一體,給人一種真實(shí)感。
6).反求技術(shù)的應(yīng)用
常規(guī)的模具設(shè)計(jì)常以產(chǎn)品的已有設(shè)計(jì)信息為依據(jù),這些設(shè)計(jì)信息通過工程圖或者一些模型來表達(dá),然后制定出加工工藝規(guī)劃,最終通過模具和設(shè)備制造出產(chǎn)品。但是在許多情況下,一些產(chǎn)品并非來自設(shè)計(jì)概念,而是起源于另一些產(chǎn)品或?qū)嵨铩H绻胍谥挥挟a(chǎn)品原型或者實(shí)物模型而無產(chǎn)品圖樣的條件下,進(jìn)行模具的設(shè)計(jì)和制造以便制造出產(chǎn)品;那么首先要對實(shí)物進(jìn)行測量,然后利用測量數(shù)據(jù)進(jìn)行實(shí)物的CAD幾何模型的重新構(gòu)造,這個過程就是反求工程。一旦建立了CAD幾何模型,就可以依據(jù)這種數(shù)字化的幾何模型進(jìn)行后續(xù)的許多操作。例如,實(shí)物CAD模型的修改,零件的重新設(shè)計(jì)、有限元分析、誤差分析、數(shù)控加工指令生成及模具的設(shè)計(jì)和制造等。
7).快速成型制造技術(shù)
快速成型制造技術(shù)RPM的基本原理是層制造原理,它是一種能夠迅速制造出產(chǎn)品原型的新技術(shù)。這項(xiàng)技術(shù)與零件的幾何復(fù)雜程度無關(guān),具有復(fù)雜曲面形狀的產(chǎn)品制造更能顯示其優(yōu)越性。這種技術(shù)不僅能夠迅速制造出產(chǎn)品原型,還可以通過形狀復(fù)制,快速經(jīng)濟(jì)地制造出產(chǎn)品模具;從而避免了傳統(tǒng)制造的費(fèi)時和耗成本,因而它在模具制造中發(fā)揮著重要作用。
8).全面質(zhì)量管理技術(shù)
全面質(zhì)量管理技術(shù)的核心思想是:企業(yè)的一切活動都圍繞著質(zhì)量進(jìn)行。不僅要求質(zhì)量管理部門進(jìn)行質(zhì)量管理,還要求從企業(yè)最高決策者到一般員工均應(yīng)參加到質(zhì)量管理過程中。并且強(qiáng)調(diào)質(zhì)量控制活動應(yīng)包括從市場調(diào)研、產(chǎn)品規(guī)劃、產(chǎn)品開發(fā)、制造、檢測到售后服務(wù)等產(chǎn)品生命周期。
而隨著工業(yè)技術(shù)和科學(xué)技術(shù)的發(fā)展,產(chǎn)品對模具的要求越來越高,傳統(tǒng)的模具設(shè)計(jì)與制造方法已不能適應(yīng)工業(yè)產(chǎn)品快速更新?lián)Q代和提高質(zhì)量的要求,因此,發(fā)達(dá)國家從20世紀(jì)50年代就開始了模具CAD/CAM的技術(shù)研究。而且,CAD/CAM技術(shù)最早在冷沖模的設(shè)計(jì)中應(yīng)用[3]。而 UG是當(dāng)前世界上最先進(jìn)和緊密集成的、面向制造行業(yè)的CAD/CAM/CAE高端軟件,也是目前國際、國內(nèi)應(yīng)用最為廣泛的大型CAD/CAM/CAE集成化軟件之一。作為一個集成的全面產(chǎn)品工程解決方案,UG軟件家族使得用戶能夠數(shù)字化地創(chuàng)建和獲取三維產(chǎn)品定義。UG軟件被當(dāng)今許多世界領(lǐng)先地制造商用來從事概念設(shè)計(jì)、工業(yè)設(shè)計(jì)、詳細(xì)的機(jī)械設(shè)計(jì)以及工程仿真和數(shù)字化制造等領(lǐng)域 。UG除了具有通用模塊之外,還提供各種專用模塊如計(jì)算機(jī)輔助設(shè)計(jì)模塊、板金設(shè)計(jì)加工模塊,模具設(shè)計(jì)加工模塊、管路設(shè)計(jì)布局模塊等。它的領(lǐng)先技術(shù)始終位于先進(jìn)制造技術(shù)領(lǐng)域的前沿,反映了當(dāng)前領(lǐng)域發(fā)展的最新成果。
三.本課題研究內(nèi)容
材料:08 厚度:0.5mm
通過對錐形蓋進(jìn)行工藝分析,零件的生產(chǎn)包括落料、拉深、切邊、沖孔等工序,其總體工藝過程有以下幾種:
方案一:先落料,然后拉深,再沖孔,最后切邊。采用單工序模生產(chǎn)。
方案二:先落料拉深復(fù)合,后沖孔切邊復(fù)合。采用復(fù)合模生產(chǎn)。
方案三:采用級進(jìn)?;蚨喙の蛔詣訅毫C(jī)上生產(chǎn)。
其中,方案一模具結(jié)構(gòu)簡單,但需要四副單工序模,成本高而生產(chǎn)效率低,難以滿足大批量生產(chǎn)要求。方案二需要兩副復(fù)合模,結(jié)構(gòu)復(fù)雜,制造難度加大,成本高,但工件的相對位置精度及生產(chǎn)效率都較高,滿足大批量生產(chǎn)要求,工件精度也能滿足要求,操作方便。方案三中的級進(jìn)模比單工序模生產(chǎn)率高,減少了模具和設(shè)備的數(shù)量,工件精度較高,便于操作和實(shí)現(xiàn)生產(chǎn)自動化。對于特別復(fù)雜或孔邊距較小的沖壓件,用簡單模或復(fù)合模沖制有困難時,可用級進(jìn)模逐步?jīng)_出。但級進(jìn)模輪廓尺寸較大,制造較復(fù)雜,成本較高,一般適用于大批量生產(chǎn)小型沖壓件。
通過對上述三種方案的分析比較,該零件的沖壓生產(chǎn)采用方案二為佳。
然后再計(jì)算參數(shù)與確定毛坯尺寸,制定沖壓工藝過程,用AutoCAD軟件設(shè)計(jì)并繪制模具結(jié)構(gòu)圖及其中的部分零件圖。
四.本課題研究方案
通過對錐形蓋零件圖的初步工藝性分析,確定采用落料、沖孔、拉深、彎曲等沖壓成形工藝,按照設(shè)計(jì)任務(wù)書的要求,為達(dá)到縮短生產(chǎn)周期,提高經(jīng)濟(jì)效益的目的,將盡量采用復(fù)合模來完成操作。
五.研究目標(biāo)、主要特色及工作進(jìn)度:
目標(biāo):本課題主要是經(jīng)過分析錐形蓋確定具體的工藝流程,制定先落料拉深復(fù)合,后沖孔切邊復(fù)合。采用復(fù)合模生產(chǎn)為最佳的工藝方案,并對其進(jìn)行模具設(shè)計(jì),以達(dá)到縮短生產(chǎn)周期,降低模具成本,提高經(jīng)濟(jì)效益,以增強(qiáng)企業(yè)的市場競爭力。
主要特色:在設(shè)計(jì)中將以AutoCAD為輔助工具完成模具的圖形制作為。
工作進(jìn)度大致安排如下:
2月20日——3月27日?? 查閱文獻(xiàn)、熟悉相關(guān)軟件使用,撰寫開題報(bào)告
2月27日——3月05日?? 翻譯外文資料,完成開題報(bào)告
3月05日——3月14日?? 錐形蓋沖壓工藝分析及沖壓工藝方案確定
3月14日——3月20日?? 計(jì)算工藝參數(shù)
3月20日——4月03日 沖模的結(jié)構(gòu)型式及其主要零部件結(jié)構(gòu)尺寸確定
4月04日——5月11日? 沖模的總裝圖設(shè)計(jì)
5月11日——5月24日 沖模的主要零件的工作圖設(shè)計(jì)
5月25日——6月02日 準(zhǔn)備答辯
六、參考文獻(xiàn):
[1] 郝濱海. 沖壓模具簡明設(shè)計(jì)手冊[S]. 北京:化學(xué)工業(yè)出版社,2004.11.
[2] 王嘉. 冷沖模設(shè)計(jì)與制造實(shí)例[C]. 北京:機(jī)械工業(yè)出版社,2009.7.
[3] 翁其金. 冷沖壓技術(shù)[M]. 北京:機(jī)械工業(yè)出版社,2000.11.
[4] 翁其金,徐新成. 沖壓工藝及沖模設(shè)計(jì)[M]. 北京:機(jī)械工業(yè)出版社,2004.7.
[5] 王伯平. 互換性與測量技術(shù)基礎(chǔ)[S]. 北京:機(jī)械工業(yè)出版社,2004.4。
[6] 沖模設(shè)計(jì)手冊編寫組. 沖模設(shè)計(jì)手冊[S]. 北京:機(jī)械工業(yè)出版社,2000.
[7] 王孝培. 實(shí)用沖壓技術(shù)手冊[S]. 北京:機(jī)械工業(yè)出版社,2001.3.
[8] 周大雋. 沖模結(jié)構(gòu)設(shè)計(jì)要領(lǐng)與規(guī)范[M]. 北京:機(jī)械工業(yè)出版社,2006.
沖壓成形與板材沖壓
1. 概述
通過模具使板材產(chǎn)生塑性變形而獲得成品零件的一次成形工藝方法叫做沖壓。由于沖壓通常在冷態(tài)下進(jìn)行,因此也稱為冷沖壓。只有當(dāng)板材厚度超過8~100mm時,才采用熱沖壓。沖壓加工的原材料一般為板材或帶材,故也稱板材沖壓。某些非金屬板材(如膠木板、云母片、石棉、皮革等)亦可采用沖壓成形工藝進(jìn)行加工。
沖壓廣泛應(yīng)用于金屬制品各行業(yè)中,尤其在汽車、儀表、軍工、家用電器等工業(yè)中占有極其重要的地位。沖壓成形需研究工藝設(shè)備和模具三類基本問題。
? 板材沖壓具有下列特點(diǎn):
(1).高的材料利用率。
(2).可加工薄壁、形狀復(fù)雜的零件。
(3).沖壓件在形狀和尺寸方面的互換性好。
(4).能獲得質(zhì)量輕而強(qiáng)度高、剛性好的零件。
(5).生產(chǎn)率高,操作簡單,容易實(shí)現(xiàn)機(jī)械化和自動化。
沖壓模具制作成本高,因此適合大批量生產(chǎn)。對于小批量、多品種生產(chǎn),常采用簡易沖模,同時引進(jìn)沖壓加工中心等新型設(shè)備,以滿足市場求新求變的需求。板材沖壓常用的金屬材料有低碳鋼、銅、鋁、鎂合金及高塑性的合金剛等。如前所述,材料形狀有板材和帶材。
沖壓生產(chǎn)設(shè)備有剪床和沖床。剪床是用來將板材剪切成具有一定寬度的條料,以供后續(xù)沖壓工序使用,沖床可用于剪切及成形。
2. 沖壓成形的特點(diǎn)
生產(chǎn)時間中所采用的沖壓成形工藝方法有很多,具有多種形式餓名稱,但塑性變形本質(zhì)是相同的。沖壓成形具有如下幾個非常突出的特點(diǎn)。
(1).垂直于板面方向的單位面積上的壓力,其數(shù)值不大便足以在板面方向上使??板材產(chǎn)生塑性變形。由于垂直于板面方向上的單位面積上壓力的素質(zhì)遠(yuǎn)小于板面方向上的內(nèi)應(yīng)力,所以大多數(shù)的沖壓變形都可以近似地當(dāng)作平面應(yīng)力狀態(tài)來處理,使其變形力學(xué)的分析和工藝參數(shù)的計(jì)算大呢感工作都得到很大的簡化。
(2).由于沖壓成形用的板材毛胚的相對厚度很小,在壓應(yīng)力作用下的抗失穩(wěn)能力也很差,所以在沒有抗失穩(wěn)裝置(如壓邊圈等)的條件下,很難在自由狀態(tài)下順利地完成沖壓成形過程。因此,以拉應(yīng)力作用為主的伸長類沖壓成形過程多于以壓應(yīng)力作用為主的壓縮類成形過程。
(3).沖壓成形時,板材毛胚內(nèi)應(yīng)力的數(shù)值等于或小于材料的屈服應(yīng)力。在這一點(diǎn)上,沖壓成形與體積成形的差別很大。因此,在沖壓成形時變形區(qū)應(yīng)力狀態(tài)中的靜水壓力成分對成形極限與變形抗力的影響,已失去其在體積成形時的重要程度,有些情況下,甚至可以完全不予考慮,即使有必要考慮時,其處理方法也不相同。
(4).在沖壓成形時,模具對板材毛胚作用力所形成的約束作用較輕,不像體積成形(如模鍛)是靠與制件形狀完全相同的型腔對毛胚進(jìn)行全面接觸而實(shí)現(xiàn)的強(qiáng)制成形。在沖壓成形中,大多數(shù)情況下,板材毛胚都有某種程度的自由度,常常是只有一個表面與模具接觸,甚至有時存在板材兩側(cè)表面都有于模具接觸的變形部分。在這種情況下,這部分毛胚的變形是靠模具對其相鄰部分施加的外力實(shí)現(xiàn)其控制作用的。例如,球面和錐面零件成形時的懸空部分和管胚端部的卷邊成形都屬這種情況。
? ?由于沖壓成形具有上述一些在變形與力學(xué)方面的特點(diǎn),致使沖壓技術(shù)也形成了一些與體積成形不同的特點(diǎn)。由于不需要在板材毛的表面施加很大的單位壓力即可使其成形,所以在沖壓技術(shù)中關(guān)于模具強(qiáng)度與剛度的研究并不十分重要,相反卻發(fā)展了學(xué)多簡易模具技術(shù)。
由于相同原因,也促使靠氣體或液體壓力成形的工藝方法得以發(fā)展。因沖壓成形時的平面應(yīng)力狀態(tài)或更為單純的應(yīng)變狀態(tài)(與體積成形相比),當(dāng)前對沖壓成形匯中毛胚的變形與 力能參數(shù)方面的研究較為深入,有條件運(yùn)用合理的科學(xué)方法進(jìn)行沖壓加工。借助于電子計(jì)算機(jī)與先進(jìn)的測試手段,在對板材性能與沖壓變形參數(shù)進(jìn)行實(shí)時測量與分析基礎(chǔ)上,實(shí)現(xiàn)沖壓過程智能化控制的研究工作也在開展。人們在對沖壓成形過程有離開較為深入的了解后,已經(jīng)認(rèn)識到?jīng)_壓成型與原材料有十分密切的關(guān)系。所以,對板材沖壓性能即成形性與形狀穩(wěn)定性的研究,目前已成為沖壓技術(shù)的一個重要內(nèi)容。對板材沖壓性能的研究工作不僅是沖壓技術(shù)發(fā)展的需要,而且也促進(jìn)了鋼鐵工業(yè)生產(chǎn)技術(shù)的發(fā)展,為其提高板材的質(zhì)量提供了一個可靠的基礎(chǔ)與依據(jù)。
3.沖壓變形的分類
? ?沖壓變形工藝可完成多種工序,其基本工序可分為分離工序和變形工序兩大類。分離工序是使胚料的一部分與另一部分相互分離的工藝方法,主要有落料、沖孔、切邊、剖切、修整等。其中又以沖孔、落料應(yīng)用最廣。變形工序是使胚料的一部分相對于另一部分產(chǎn)生位移而不破裂的工藝方法,主要有拉深、彎曲、局部成形、脹形、翻邊、縮徑、校形、旋壓等。
從本質(zhì)上看,沖壓成形就是毛胚的變形區(qū)在外力的作用下產(chǎn)生相應(yīng)的塑性變形,所以變形區(qū)內(nèi)的應(yīng)力狀態(tài)和變形特點(diǎn)景象的沖壓成形分類,可以把成形性質(zhì)相同的成形方法概括成同一個類型并進(jìn)行體系化的研究。
絕大多數(shù)沖壓成形時毛胚變形區(qū)均處于平面應(yīng)力狀態(tài)。通常認(rèn)為在板材表面上不受外力的作用,即使有外力作用,其數(shù)值也是較小的,所以可以認(rèn)為垂直于板面方向上的應(yīng)力為零,使板材毛胚產(chǎn)生塑性變形的是作用于板面方向上相互的兩個主應(yīng)力。由于板厚較小,通常都近似地認(rèn)為這兩個主應(yīng)力在厚度方向上是均勻分布的?;谶@樣的分析,可以把各種形式?jīng)_壓成型中的毛陪變形區(qū)的受力狀態(tài)與變形特點(diǎn),在平面應(yīng)力的應(yīng)力坐標(biāo)系中與相應(yīng)的兩向應(yīng)變坐標(biāo)系中以應(yīng)力與應(yīng)變坐標(biāo)決定的位置來表示。
4.沖壓用原材料
? ?沖壓加工用原材料有很多種,它們的性能也有很大的差別,所以必須根據(jù)原材料的性能與特點(diǎn),采用不同的沖壓成形方法、工藝參數(shù)和模具結(jié)構(gòu),才能達(dá)到?jīng)_壓加工的目的。由于人們對沖壓成形過程板材毛胚的變形行為有了較為深入的認(rèn)識,已經(jīng)相當(dāng)清楚的建立了由原材料的化學(xué)成分、組織等因素所決定的材料性能與沖壓成形之間的關(guān)系,這就使原材料生產(chǎn)部門不但按照沖壓件的工作條件與使用要求進(jìn)行原材料的設(shè)計(jì)工作,而且也根據(jù)沖壓件加工過程對板材性能的要求進(jìn)行新型材料的開發(fā)工作,這是沖壓技術(shù)在原材料研究方面的一個重要方向。對沖壓用原材料沖壓性能方面的研究工作有
(1)原材料沖壓性能的含義。
(2)判斷原材料沖壓性能的科學(xué)方法,確定可以確切反映材料沖壓性能的參數(shù),建立沖壓性能的參數(shù)與實(shí)際沖壓成形間的關(guān)系,以及沖壓性能參數(shù)的測試方法等。
(3)建立原材料的化學(xué)成分、組織和制造過程與沖壓性能之間的關(guān)系。沖壓用原材料主要是各種金屬與非金屬板材。金屬板材包括各種黑色技術(shù)和有色金屬板材。雖然在沖壓生產(chǎn)中所用金屬板材的種類很多,但最多的原材料蛀牙是鋼板、不銹鋼板、鋁合金板及各種復(fù)合金屬板。
5.板材沖壓性能及其鑒定方法
? ? 板材是指對沖壓加工的適應(yīng)能力。對板材沖壓性能的研究具有飛行重要的意義。為了能夠運(yùn)用最科學(xué)與最經(jīng)濟(jì)合理的沖壓工藝過程與工藝參數(shù)制造出沖壓零件,必須對作為加工對象的板材的性能具有十分清楚的了解,這樣才有可能充分地利用板材在加工方面的潛在能力。另一方面,為了能夠依據(jù)沖壓件的形狀與尺寸特點(diǎn)及其所需的成形工藝等基本因素,正確、合理地選用板材,也必須對板材的沖壓性能有一個科學(xué)的認(rèn)識與正確的判斷。評定板材沖壓性能的方法有直接試驗(yàn)法與間接試驗(yàn)法。
? ?實(shí)物沖壓試驗(yàn)是最直接的板材沖壓性能的評定方法。利用實(shí)際生產(chǎn)設(shè)備與模具,在與生產(chǎn)完全相同的條件下進(jìn)行實(shí)際沖壓零件的性能評定,當(dāng)然能夠的最可靠的結(jié)果。但是,這種評定方法不具有普遍意義,不能作為行業(yè)之間的通用標(biāo)準(zhǔn)進(jìn)行信息的交流。
? ?模擬試驗(yàn)是把生產(chǎn)中實(shí)際存在的沖壓成形方法進(jìn)行歸納與簡單化處理,消除許多過于復(fù)雜的因素,利用軸對稱的簡化了的成形方法,在保證試驗(yàn)中板材的變形性質(zhì)與應(yīng)力狀態(tài)都與實(shí)際沖壓成形相同的條件下進(jìn)行的沖壓性能的評定工作。為了保證模擬試驗(yàn)結(jié)果的可靠性與通用性,規(guī)定了私分具體的關(guān)于試驗(yàn)用工具的幾何形狀與尺寸、毛胚的尺寸、試驗(yàn)條件(沖壓速度、潤滑方法、壓邊力等)。
? ?間接試驗(yàn)法也叫做基礎(chǔ)試驗(yàn)法。間接試驗(yàn)法的特點(diǎn)是:在對板材在塑性變形過程中所表現(xiàn)出的基本性質(zhì)與規(guī)律進(jìn)行分析與研究的基礎(chǔ)上,進(jìn)一步把它和具體的沖壓成形中板材的塑性變形參數(shù)聯(lián)系起來,建立間接試驗(yàn)結(jié)果(間接試驗(yàn)值)與具體的沖壓成形性能(工藝參數(shù))之間的相關(guān)性。由于間接試驗(yàn)時所用試件的形狀與尺寸以及加載的方式等都不同于具體的沖壓成形過程,所以它的變形性質(zhì)和應(yīng)力狀態(tài)也不同于沖壓變形。因此間接試驗(yàn)所得的結(jié)果(試驗(yàn)值)并不是沖壓成形的工藝參數(shù),而是可以用來表示板材沖壓性能的基礎(chǔ)性參數(shù)。
Characteristics and Sheet Metal Forming
1. The article overview
Stamping is a kind of plastic forming process in which a part is produced by means of the plastic forming the material under the action of a die. Stamping is usually carried out under cold state, so it is also called stamping. Heat stamping is used only when the blank thickness is greater than 8~100mm. The blank material for stamping is usually in the form of sheet or strip, and therefore it is also called sheet metal forming. Some non-metal sheets (such as plywood, mica sheet, asbestos, leather)can also be formed by stamping.
?? Stamping is widely used in various fields of the metalworking industry, and it plays a crucial role in the industries for manufacturing automobiles, instruments, military parts and household electrical appliances, etc.
? ?The process, equipment and die are the three foundational problems that needed to be studied in stamping.
? ?The characteristics of the sheet metal forming are as follows:
(1)? ? High material utilization
(2)? ? Capacity to produce thin-walled parts of complex shape.
(3)? ? Good interchangeability between stamping parts due to precision in shape??
and dimension.
(4)? ? Parts with lightweight, high-strength and fine rigidity can be obtained.
(5)? ? High productivity, easy to operate and to realize mechanization and? ? automatization.
? ? The manufacture of the stamping die is costly, and therefore it only fits to mass production. For the manufacture of products in small batch and rich variety, the simple stamping die and the new equipment such as a stamping machining center, are usually adopted to meet the market demands. The materials for sheet metal stamping include mild steel, copper, aluminum, magnesium alloy and high-plasticity alloy-steel, etc.??
Stamping equipment includes plate shear punching press. The former shears plate into strips with a definite width, which would be pressed later. The later can be used both in shearing and forming.
2.Characteristics of stamping forming
There are various processes of stamping forming with different working patterns and names. But these processes are similar to each other in plastic deformation. There are following conspicuous characteristics in stamping:
(1).The force per unit area perpendicular to the blank surface is not large but is enough to cause the material plastic deformation. It is much less than the inner stresses on the plate plane directions. In most cases stamping forming can be treated approximately as that of the plane stress state to simplify vastly the theoretical analysis and the calculation of the process parameters.
(2).Due to the small relative thickness, the anti-instability capability of the blank is weak under compressive stress. As a result, the stamping process is difficult to proceed successfully without using the anti-instability device (such as blank holder). Therefore the varieties of the stamping processes dominated by tensile stress are more than dominated by compressive stress.
(3).During stamping forming, the inner stress of the blank is equal to or sometimes less than the yield stress of the material. In this point, the stamping is different from the bulk forming. During stamping forming, the influence of the hydrostatic pressure of the stress state in the deformation zone to the forming limit and the deformation resistance is not so important as to the bulk forming. In some circumstances, such influence may be neglected. Even in the case when this influence should be considered, the treating method is also different from that of bulk forming.
(4).In stamping forming, the restrain action of the die to the blank is not severs as in the case of the bulk forming (such as die forging). In bulk forming, the constraint forming is proceeded by the die with exactly the same shape of the part. Whereas in stamping, in most cases, the blank has a certain degree of freedom, only one surface of the blank contacts with the die. In some extra cases, such as the forming of the blank on the deforming zone contact with the die. The deformation in these regions are caused and controlled by the die applying an external force to its adjacent area.
Due to the characteristics of stamping deformation and mechanics mentioned above, the stamping technique is different form the bulk metal forming: The importance or the strength and rigidity of the die in stamping forming is less than that in bulk forming because the blank can be formed without applying large pressure per unit area on its surface. Instead, the techniques of the simple die and the pneumatic and hydraulic forming are developed.
Due to the plane stress or simple strain state in comparison with bulk forming, more research on deformation or force and power parameters has been done. Stamping forming can be performed by more reasonable scientific methods. Based on the real time measurement and analysis on the sheet metal properties and stamping parameters, by means of computer and some modern testing apparatus, research on the intellectualized control of stamping process is also in proceeding. It is shown that there is a close relationship between stamping forming and raw material. The research on the properties of the stamping forming, that is, forming ability and shape stability, has become a key point in stamping technology development, but also enhances the manufacturing technique of iron and steel industry, and provides a reliable foundation for increasing sheet metal quality.
3.Categories of stamping forming
? ? Many deformation processes can be done by stamping, the basic processes of the stamping can be divided into two kinds: cutting and forming.Cutting is a shearing process that one part of the blank is cut from the other. It mainly includes blanking, punching, trimming, parting and shaving, where punching and blanking are the most widely used. Forming is a process that one part of the blank has some displacement from the other. It mainly includes deep drawing, bending, local forming, bulging, flanging, necking, sizing and spinning.
In substance, stamping forming is such that the plastic deformation occurs in the deformation zone of the stamping blank caused by the external force. The stress state and deformation characteristic of the deformation zone are the basic factors to decide the properties of the stamping forming. Based on the stress state and deformation characteristics of the deformation zone, the forming methods can be divided into several categories with the same forming properties and be studied systematically.
??The deformation zone in almost all types of stamping forming is in the plane stress state. Usually there is no force or only small force applied on the blank surface. When is assumed that the stress perpendicular to the blank surface equals to zero, two principal stresses perpendicular to each other and act on the blank surface produce the plastic deformation of the material. Due to the small thickness of the blank, it is assumed approximately the two principal stresses distribute uniformly along the thickness direction. Based on this analysis, the stress state and the deformation characteristics of the deformation zone in all kinds of stamping forming can be denoted by the points in the coordinates of the plane principal stresses and the coordinates of the corresponding plane principal strains.
4.Raw materials for stamping forming
There are a lot of raw materials used in stamping forming, and the properties of these materials may have large difference. The stamping forming can be succeeded only by determining the stamping method, the forming parameters and the die structures according to the properties and characteristics of the raw materials. The deformation of the blank during stamping forming has been investigated quite thoroughly. The relationships between the material properties decided by the chemistry component and structure of the material and the stamping forming has been established clearly. Not only the proper material can be selected based on the working condition and usage demand, but also the new material can be developed according to the demands of the blank properties during processing the stamping part. This is an important domain in stamping forming research. The research on the material properties for stamping forming is as follows:
(1).Definition of the stamping property of the material.
(2).Method to judge the stamping property of the material, find parameters to express the definitely material property of the stamping forming, establish the relationship between the property parameters and the practical stamping forming, and investigate the testing methods of the property parameters.
(3).Establish the relationship among the chemical component, structure, manufacturing process and stamping property.
?? The raw materials for stamping forming mainly include various metals and nonmetal plate. Sheet metal includes both ferrous and nonferrous metals. Although a lot of sheet metals are used in stamping forming, the most widely used materials are steel, stainless steel, aluminum alloy and various composite metal plates.
5.Stamping forming property of sheet metal and its assessing method
The stamping forming property of the sheet metal is the adaptation capability of the sheet metal to stamping forming. It has crucial meaning to the investigation of the stamping forming property of the sheet metal. In order to produce stamping forming parts with most scientific, economic and rational stamping forming process and forming parameters, it is necessary to understand clearly the properties of the sheet metal, so as to utilize the potential of the sheet metal fully in the production. On the other hand, to select plate material accurately and rationally in accordance with the characteristics of the shape and dimension of the stamping forming part and its forming technique is also necessary so that a scientific understanding and accurate judgment to the stamping forming properties of the sheet metal may be achieved.
There are direct and indirect testing methods to assess the stamping property of the sheet metal?.Practicality stamping test is the most direct method to assess stamping forming property of the sheet metal. This test is done exactly in the same condition as actual production by using the practical equipment and dies. Surely, this test result is most reliable. But this kind of assessing method is not comprehensively applicable, and cannot be shared as a commonly used standard between factories.
? ? The simulation test is a kind of assessing method that after simplifying and summing up actual stamping forming methods, as well as eliminating many trivial factors, the stamping properties of the sheet metal are assessed, based on simplified axial-symmetric forming method under the same deformation and stress states between the testing plate and the actual forming states. In order to guarantee the reliability and generality of simulation results, a lot of factors are regulated in detail, such as the shape and dimension of tools for test, blank dimension and testing conditions(stamping velocity, lubrication method and blank holding force, etc).???Indirect testing method is also called basic testing method its characteristic is to connect analysis and research on fundamental property and principle of the sheet metal during plastic deformation, and with the plastic deformation parameters of the sheet metal in actual stamping forming, and then to establish the relationship between the indirect testing results(indirect testing value) and the actual stamping forming property (forming parameters). Because the shape and dimension of the specimen and the loading pattern of the indirect testing are different from the actual stamping forming, the deformation characteristics and stress states of the indirect test are different from those of the actual one. So, the results obtained form the indirect test are not the stamping forming parameters, but are the fundamental parameters that can be used to represent the stamping forming property of the sheet metal.