C6150車床主軸箱箱體加工工藝及夾具設(shè)計畢業(yè)資料含CAD圖紙
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計算機(jī)輔助夾具設(shè)計技術(shù)回顧與發(fā)展趨勢綜述
計算機(jī)輔助夾具設(shè)計(Computer-aided fixture design，CAFD)技術(shù)從20世紀(jì)70年代發(fā)展至今，已經(jīng)成為CAD/CAM集成技術(shù)的一個重要組成部分。文中從CAFD技術(shù)所包含的4個研究方面(安裝規(guī)劃，裝夾規(guī)劃，夾具構(gòu)形設(shè)計，夾具性能評價)入手，對國內(nèi)外CAFD技術(shù)的發(fā)展(主要對近10幾年內(nèi)的發(fā)展成果)進(jìn)行了回顧，并對CAFD的未來發(fā)展趨勢進(jìn)行了分析。
隨著制造技術(shù)的發(fā)展，產(chǎn)品的設(shè)計周期縮短，更新?lián)Q代增快。傳統(tǒng)的大批量生產(chǎn)模式逐步被中小批量生產(chǎn)模式所取代。機(jī)械制造業(yè)欲適應(yīng)這種變化須具備較高的柔性，國外已把柔性制造系統(tǒng)作為開發(fā)新產(chǎn)品的有效手段，并將其作為機(jī)械制造業(yè)的主要發(fā)展方向。柔性化的著眼點主要在機(jī)床和工裝兩個方面，而夾具又是工裝柔性化的重點。組合夾具的平均設(shè)計和組裝時間是專用夾具所花時間的5%—20%，可以認(rèn)為組合夾具就是柔性夾具的代名詞。由于組合夾具應(yīng)變能力強(qiáng)、設(shè)計和制造周期短、成本低、適應(yīng)產(chǎn)品更新?lián)Q代的要求，提高了企業(yè)的競爭力，所以日益受到廠家的青睞。應(yīng)用組合夾具的一項關(guān)鍵技術(shù)就是CAFD技術(shù)。我國從20世紀(jì)80年代中期就已經(jīng)開始研究這項技術(shù)，并對如何將人工智能的理論應(yīng)用到組合夾具計算機(jī)輔助設(shè)計(CAD)過程進(jìn)行了探索。但由于組合夾具設(shè)計取決于被加工工件，而被加工工件又千變?nèi)f化，造成組合夾具CAD難以實現(xiàn)智能化。經(jīng)過30多年國內(nèi)外眾多學(xué)者的不懈努力，工作雖有進(jìn)展，但離生產(chǎn)實際應(yīng)用還有很大距離。
1 CAFD技術(shù)概述
從20世紀(jì)70年代開始夾具CAD研究至今，CAFD技術(shù)已經(jīng)發(fā)展成為CAD/CAM集成技術(shù)的一個重要組成部分。目前，圍繞CAFD技術(shù)所展開的研究主要包括4方面內(nèi)容：安裝規(guī)劃，裝央規(guī)劃，夾具構(gòu)形設(shè)計和夾具性能評價：
(1) 安裝規(guī)劃。
安裝規(guī)劃的任務(wù)是確定加工時所需的安裝次數(shù)，每次安裝中工件的方位及加工面。這部分也可以是CAPP(Computer-aided process planning)的一個子集，也是CAFD和CAPP集成的交互接口。安裝規(guī)劃的框架包括制造特征描述和特征庫的開發(fā)、裝夾特征的定義和定位表面的選擇、安裝規(guī)劃算法、以及夾具設(shè)計和驗證。安裝規(guī)劃由于與CAPP聯(lián)系更為緊密，大多數(shù)CAFD領(lǐng)域內(nèi)的研究都集中在裝夾規(guī)劃，夾具構(gòu)形設(shè)計和夾具性能評價3方面，但目前在夾具構(gòu)形設(shè)計中對夾具自動構(gòu)形設(shè)計的研究仍然較少。
(2) 裝夾規(guī)劃。
裝夾規(guī)劃主要用來決定在某一特定安裝條件下工件上的定位支撐面，支撐點以及夾緊點。裝夾規(guī)劃所考慮的主要問題包括：工件上可以選作為裝夾表面的表面類型;裝夾表面相對于刀具軸線的方位;候選裝夾表面的精度要求;候選裝夾表面的組合情況;裝夾穩(wěn)定性和裝夾表面的可及性等。
(3) 夾具構(gòu)形設(shè)計。
夾具構(gòu)形設(shè)計的任務(wù)是選擇夾具元件，構(gòu)造夾具結(jié)構(gòu)，并把它們裝配成最終的夾具構(gòu)形來夾持工件。CAFD中夾具構(gòu)形設(shè)計的主要問題包括：夾具元件的選擇如與工件直接接觸的定位支承與壓板等的選擇;確定夾具組件的高度;夾具組件在基礎(chǔ)板上的擺放;夾具元件之間的連接;夾具、工件及加工面之問的干涉檢查等。
(4) 夾具性能評價。
夾具性能評價是對已經(jīng)設(shè)計完成的夾具的有關(guān)性能進(jìn)行評價和分析，定義、測量并對夾具設(shè)計進(jìn)行優(yōu)化處理，用以保證夾具設(shè)計的質(zhì)量。性能評價的內(nèi)容包括定位精度，加工表面精度，夾緊和加工穩(wěn)定性，抵抗夾具元件變形的剛度，刀具路徑的干涉檢查，表面可及性等。
2 國內(nèi)外CAFD技術(shù)研究現(xiàn)狀和成果
文獻(xiàn)[5]對CAFD從最初的起步到20世紀(jì)后的發(fā)展趨勢作了回顧，這其中既包括最初的Latombe，Ingrand(1980)對于自動夾具推理的努力，也包括Markus(1984)和Miller(1985)開發(fā)一種半自動化的方法對給定的工件產(chǎn)生一種夾具設(shè)計的嘗試，這種方法雖非自動，但提供了交互選擇夾緊點，定位點和支撐點等功能，Chou等人(1989)基于工件穩(wěn)定性和全約束要求的雙重標(biāo)準(zhǔn)，重點研究了夾具設(shè)計中的夾緊過程。隨著開發(fā)CAFD的剪要性被越來越多的學(xué)者所認(rèn)可，人工智能和專家系統(tǒng)在夾具設(shè)計當(dāng)中的應(yīng)用也越來越多地被提出來，包括Davishi等人(1988)的開發(fā)專家系統(tǒng)的知識庫表示，Nee等人(1992)基于特征的夾具分類模式，以及Pham等人(1990)的夾具CAD系統(tǒng)的開發(fā)等。
縱觀CAFD發(fā)展歷程，其歷經(jīng)交互式計算機(jī)輔助夾具設(shè)計系統(tǒng)(I—CAFD)，基于成組技術(shù)和知識的CAFD系統(tǒng)及20世紀(jì)90年代后的第3代CAFD系統(tǒng)3個階段。而按照自動化程度劃分，夾具設(shè)計系統(tǒng)又可分為交互，半自動和自動系統(tǒng)。20世紀(jì)90年代后，總結(jié)經(jīng)驗后認(rèn)為，CAFD最終必須要生成夾具結(jié)構(gòu)，而過去的系統(tǒng)只解決安裝、定位、夾緊等問題或檢索類似的結(jié)構(gòu)，不能獲得合乎工件實際應(yīng)用的結(jié)構(gòu)圖，而且分析也不全面。所以，必須開發(fā)出以產(chǎn)生夾具結(jié)構(gòu)為目的，實際生產(chǎn)為導(dǎo)向的商品化夾具設(shè)計軟件上。
下面著重對最近10幾年來CAFD方面較新的研究進(jìn)展和存在問題給予關(guān)注和總結(jié)。
2.1 國外CAFD技術(shù)研究現(xiàn)狀和成果
國外CAFD研究內(nèi)容在裝夾規(guī)劃，夾具構(gòu)形設(shè)計及夾具性能評價等方面的研究如下：
裝央規(guī)劃方面：Rong等人基于快速夾具構(gòu)形設(shè)計系統(tǒng)研究了定位方法在自動組合裝夾規(guī)劃系統(tǒng)中對夾具元件和工件的幾何關(guān)系進(jìn)行了分析，對自動組合裝夾規(guī)劃中的夾裝精度，夾緊規(guī)劃，夾具可及性及夾緊穩(wěn)定性進(jìn)行了研究，一旦裝夾規(guī)劃確定了，分析結(jié)果會應(yīng)用到夾具設(shè)計的性能評價中;除了機(jī)械加工用的組合夾具外，Wang等人將基于案例推理的方法(CBR)應(yīng)用到了焊接夾具的研究中，提出了一種用于夾具設(shè)計信息表示的數(shù)據(jù)提取方法，在此方法基礎(chǔ)上，提出了用于焊接夾具設(shè)計的多級CBR方法;Perremans開發(fā)了可以進(jìn)行裝夾規(guī)劃如輸入定位，夾緊，支撐表面等的專家系統(tǒng)，并可通過專家系統(tǒng)實現(xiàn)組合夾具元件的組裝;Mervyn等人利用進(jìn)化搜索算法提出了一種自動組合夾具分析方法;Varadarajan等人到為六軸定位和裝夾精度設(shè)計了動力學(xué)模型和硬度模型。
夾具構(gòu)形設(shè)計方面：Rong等人從裝夾規(guī)劃到夾具構(gòu)形設(shè)計，對CAFD進(jìn)行了深入而廣泛的研究，開發(fā)了基于孔系的自動組合夾具構(gòu)形設(shè)計系統(tǒng)。在快速反應(yīng)制造中開發(fā)了自動定制夾具構(gòu)形設(shè)計系統(tǒng);在夾具可重構(gòu)方面，Kong等人將基于夾具工作區(qū)的結(jié)構(gòu)合成及快速夾具校驗的可視化分析應(yīng)用于快速可重構(gòu)組裝夾具系統(tǒng)中;Shen等人糾以滑動副作為可重構(gòu)夾具的基本結(jié)構(gòu)，提出了用于可重構(gòu)夾具系統(tǒng)的4種類型的機(jī)構(gòu);Ryll等人提出了一種快速可重構(gòu)方法以及工件一夾具在智能裝夾系統(tǒng)中的定位，可重構(gòu)中應(yīng)用了面向?qū)ο蟮姆椒▉泶_保無需改變控制軟件而保證夾具在不同的安裝下工作;Culpepper，Varadarajan等人基于壓力激勵和彎曲軸承提出了一種雙重目的的定位夾具(DPF)和偏心的球一軸夾具，用以彌補(bǔ)夾具元件的公差和軸承磨損，但并未涉及到工件公差對相關(guān)工件定位的影響;Ibrahim等人在綜合考慮工件材料，工件表面粗糙度，夾具元件粗糙度，法向載荷等影響條件，通過實驗方法確定工件、夾具元件接觸表面之間的摩擦系數(shù)，通過靜態(tài)方法來減少實驗誤差，以確保實驗結(jié)果的可信度。結(jié)果對夾具構(gòu)形設(shè)計至關(guān)重要;Martin等人針對夾具設(shè)計中應(yīng)用專家知識所引起的不精確及不確定性等缺點，提出了模糊推理(fuzzy reasoning)的方法來支持來源于不同知識語義的造型;Surendra等人Ⅲo開發(fā)了用于棱柱形工件的自動夾具生成系統(tǒng)，該自動夾具構(gòu)形設(shè)計系統(tǒng)可以自動選擇夾具元件并按照符合需要的組裝關(guān)系放置在合適的位置;Hunter等人利用知識模板的重用，可以實現(xiàn)不同知識族中所定義知識的重用，并與模型結(jié)合起來，基于IDEFO和UML的功能方法表示夾具設(shè)計過程。
夾具性能評價方面：Kulankara等人對工件尺寸和精度有較大影響的夾具布局過程進(jìn)行了研究，提出了一種基于遺傳算法(GA)的夾具布局優(yōu)化技術(shù)，可以減少由于夾緊力和切削力所引起的加工表面的變形;Pelinescu等人基于多質(zhì)量標(biāo)準(zhǔn)確定夾具布局設(shè)計并對所接受的夾具設(shè)計方案進(jìn)行評估，選擇一個最優(yōu)的夾具設(shè)計方案來平衡多性能需求，文中給出了3個性能目標(biāo)，即定位工件的精度，定位接觸力的降低和定位接觸力的平衡;Siebenaler等人重點研究了利用有限元方法分析預(yù)測工件變形的影響因素，仿真結(jié)果表明，基于表面對表面的工件一夾具接觸模型可以對工件和反應(yīng)力做出預(yù)測;Satyanarayana等人用有限元方法對不同邊界條件導(dǎo)致的工件彈性變形和反作用力的預(yù)測進(jìn)行了分析，并通過實驗進(jìn)行了性能評價;Amaral等人同樣用有限元方法在夾具設(shè)計系統(tǒng)中對夾具設(shè)計進(jìn)行了性能評價和優(yōu)化;Song等人在確定定位狀態(tài)的基礎(chǔ)上，進(jìn)一步分析和研究了非確定定位方案，用一種算法來檢測幾何約束狀態(tài)，該算法可以識別欠約束狀態(tài)并指出工件的非約束運動，也可以識別過約束狀態(tài)及不必要的定位，這種信息可以幫助設(shè)計者分析和改善已有的定位方案;Subranmanian提出了一種基于遺傳算法(GA)的優(yōu)化方法，利用空間坐標(biāo)來表示夾具元件的位置，集成了遺傳算法中很多諸如實數(shù)編碼，突變及共享等重要概念;Kaya也將GAs應(yīng)用于夾具結(jié)構(gòu)優(yōu)化設(shè)計中，并利用有限元方法進(jìn)行目標(biāo)函數(shù)值的計算;Varadarajan等人對六軸定位原理和裝夾精度進(jìn)行了特性分析和評價;Kang提出了對夾具的定位性能、加工表面精度，穩(wěn)定性及表面可及性等方面進(jìn)行驗證;Hurtado等人提出了一種用于優(yōu)化柔性夾具設(shè)計的模型，該模型用于發(fā)現(xiàn)最優(yōu)活動銷的數(shù)目，所用算法目的在于獲得夾具一工件的一致性和保持工件剛體運動穩(wěn)定平衡，使夾具彈性變形保持在或低于用戶指定的值;Ratchev等人基于FEA方法，提出了一種有效的性能評價方法，即用一種創(chuàng)新的仿真方法來預(yù)測夾具一工件系統(tǒng)中的動態(tài)行為，并兼容于任何商業(yè)化FEA平臺;Wang和Kayaml提出了基于約束和遺傳算法的定位和夾緊布局優(yōu)化。
2.2 國內(nèi)CAFD技術(shù)研究現(xiàn)狀和成果
國內(nèi)夾具CAD的研究起源于20世紀(jì)80年代中期，中國航空技術(shù)進(jìn)出口公司應(yīng)歐洲客戶要求，設(shè)計了一套二維計算機(jī)輔助組裝軟件，拉開了我國開發(fā)夾具CAD系統(tǒng)的帷幕。從20世紀(jì)80年代中期開始，我國先后有l(wèi)O余所高校對組合夾具CAD系統(tǒng)作了探索，但能長期堅持研究開發(fā)的有北京機(jī)械工業(yè)學(xué)院、河北工業(yè)大學(xué)、南京航空航天大學(xué)、西北工業(yè)大學(xué)和哈爾濱工業(yè)大學(xué)等。目前，對夾具CAD研究的內(nèi)容越來越深入和具體，參與研究的學(xué)術(shù)單位和團(tuán)體也越來越多，除上述單位外，四川大學(xué)、大連理工大學(xué)、天津大學(xué)、河海大學(xué)等眾多的高校與研究機(jī)構(gòu)參與到了夾具CAD的研究當(dāng)中來，包括一些高校在ACIS。，Solid·work，Pro—E，UG等不同CAD平臺上進(jìn)行的夾具CAD系統(tǒng)的研發(fā)和不同平臺下的夾具元件建庫工作。
近年來，國內(nèi)夾具CAD研究的主要內(nèi)容大部分集中在裝夾規(guī)劃和夾具構(gòu)形設(shè)計(包括計算機(jī)輔助夾具系統(tǒng)的研究和開發(fā))方面，部分對夾具性能評價的研究穿插于上述兩方面。
裝夾規(guī)劃方面：唐東等人將ANN算法(即Hopfield algorithm)用于自動裝夾規(guī)劃(automatic fixtureplanning)中，同時通過利用定位夾緊面的選擇規(guī)則和確定工件定位的評估矩陣對定位和夾緊表面的選擇進(jìn)行了研究，并開發(fā)了從數(shù)據(jù)庫中選擇定位和夾緊元件進(jìn)行夾具的組裝方法;吳玉光，張坤明舊叫。針對孔系組合夾具采用了工件外輪廓規(guī)約化方法，確定工件可行夾緊點方案集合，對夾緊方案的自動規(guī)劃方法進(jìn)行了研究;吳玉光等人還就最優(yōu)夾緊方案評價及定位方案的自動確定方法進(jìn)行了研究，并利用關(guān)聯(lián)(Linkage)機(jī)制進(jìn)行工件定位候選點的識別，在評估可及性和裝夾性的算法中采用了諸如IRC(instantaneousrotational center)三角形及定位可見圓錐等新概念;Zheng等人”副針對以往組合夾具裝夾研究重點集中在2D和3D規(guī)則幾何形狀的對象方面，為3D復(fù)雜對象或者以任意位置放置的需要定位的對象夾具建立了數(shù)學(xué)模型，對3D組合夾具進(jìn)行了系統(tǒng)研究。
夾具構(gòu)形設(shè)計方面：陳慰芳等人。提出了夾具裝配模型分層的思想，實現(xiàn)了夾具元件的快速裝配。融亦鳴等人設(shè)計的準(zhǔn)商品化軟件Fix-Des夾具自動結(jié)構(gòu)設(shè)計系統(tǒng);李劍峰等人將分解與重構(gòu)原理和功能映射關(guān)系在組合夾具CAD系統(tǒng)中的應(yīng)用做了介紹;徐雷將知識工程與夾具設(shè)計過程結(jié)合起來，對夾具知識描述、分類、發(fā)現(xiàn)及重用的基本原理和智能化夾具設(shè)計中的知識求解技術(shù)進(jìn)行了重點研究并開發(fā)了基于集成知識資源的計算機(jī)輔助夾具設(shè)計支持系統(tǒng);金天國等人針對組合夾具裝配中順序裝配法的缺點，提出了自動求解裝配體中零部件尺寸或位置的啟發(fā)式算法;謝曉文等人以槽系組合夾具為例，利用人工智能的夾具設(shè)計方法和參數(shù)化的組合夾具建模技術(shù)結(jié)合粗糙集理論與夾具設(shè)計原理建立了計算機(jī)輔助組合夾具設(shè)計系統(tǒng);劉惠英，劉瓊等人利用PowerBuilder和Oracle研制了計算機(jī)輔助組合夾具管理系統(tǒng);胡瑞飛等人將夾具元件庫，典型組件庫和典型結(jié)構(gòu)庫組成多層夾具實例庫，提出了一種自頂向下的分層組合夾具智能輔助裝配系統(tǒng)。
河北工業(yè)大學(xué)是國內(nèi)進(jìn)行組合夾具CAD研究較早的單位之一，在20世紀(jì)80年代末與航天工業(yè)部保定向陽精密機(jī)械廠聯(lián)合開發(fā)了組合夾具軟件組裝CAD系統(tǒng)，并在該系統(tǒng)基礎(chǔ)上不斷發(fā)展。段國林、齊紅威等人將人工智能模塊及基于案例推理(Case—based Reasoning，CBR)的方法加入到了組合夾具計算機(jī)三維軟件組裝及構(gòu)形設(shè)計系統(tǒng)中。多年來對組合夾具計算機(jī)輔助構(gòu)形設(shè)計系統(tǒng)的研究與開發(fā)經(jīng)歷了從最早的R14到AutoCAIY2002，歷經(jīng)了多次版本更新和軟件架構(gòu)的改善，已開發(fā)的組合夾具輔助設(shè)計軟件包MFS CAD5.0版已在實際中得到了很好的應(yīng)用，目前該CAFD軟件已升級為6.0版本，并對軟件功能進(jìn)一步完善，開發(fā)了三維組合夾具CAD系統(tǒng)的圖庫管理系統(tǒng)，系統(tǒng)還進(jìn)一步推廣到了ACIS平臺下，目的在于開發(fā)自主平臺下的夾具CAD軟件拼裝系統(tǒng)并推廣應(yīng)用。并在以上研究基礎(chǔ)上，對組合夾具元件庫系統(tǒng)的異構(gòu)平臺應(yīng)用展開了研究，目的在于提供可供不同CAD平臺應(yīng)用的組合夾具元件庫系統(tǒng)。
3 CAFD發(fā)展面臨的問題和趨勢
以上按照CAFD的研究內(nèi)容分別對CAFD近幾年在裝夾規(guī)劃，夾具構(gòu)形設(shè)計及夾具性能評價等幾方面國內(nèi)外的研究進(jìn)展進(jìn)行了回顧，可以看到，在CAFD發(fā)展過程中，針對不同的側(cè)重點展開了多方位多角度運用多種方法(造型，模型分析等軟件的應(yīng)用，基于人工智能包括知識和專家系統(tǒng)的應(yīng)用，算法，推理及功能分析方法等的應(yīng)用)的計算機(jī)輔助夾具設(shè)計研究，為夾具CAD的研究提供了更多的借鑒和參考，也使夾具設(shè)計系統(tǒng)的自動化程度大大提高，但是至今仍然沒有成熟的夾具CAD商品化軟件?，F(xiàn)有CAFD系統(tǒng)研究存在的主要問題有：夾具設(shè)計和裝配手段仍未從計算機(jī)輔助工程中得到更多的受益，它仍是現(xiàn)代制造系統(tǒng)的瓶頸之一。對于CAFD的研究多，應(yīng)用少，同CAD，CAM，PDM，MIS等相關(guān)計算機(jī)輔助技術(shù)相比，差距很大，CAFD應(yīng)向著集成化，知識化，智能化和實用化方向發(fā)展。
對于夾具構(gòu)形設(shè)計當(dāng)中針對不同CAD平臺問夾具系統(tǒng)的信息傳輸和數(shù)據(jù)共享方面研究則更加缺乏，CAFD的網(wǎng)絡(luò)化和異構(gòu)平臺應(yīng)用作為夾具構(gòu)形設(shè)計中一個很重要的發(fā)展和研究方向，應(yīng)以能夠滿足網(wǎng)絡(luò)時代下的信息交互和CAD系統(tǒng)間的數(shù)據(jù)共享為發(fā)展目標(biāo)。某一特定平臺下夾具設(shè)計系統(tǒng)的缺陷在于將用戶局限于特定的CAD系統(tǒng)中，當(dāng)CAD系統(tǒng)或者操作系統(tǒng)變化時，很難再重新利用該夾具系統(tǒng)，為了解決這種矛盾，克服單一平臺的缺陷，亟需進(jìn)行夾具設(shè)計系統(tǒng)如何獨立于單一CAD平臺的研究。一個有效的夾具設(shè)計系統(tǒng)應(yīng)該便于在不同操作平臺上進(jìn)行數(shù)據(jù)傳輸，能夠與其它制造系統(tǒng)交互并且為了達(dá)到最優(yōu)設(shè)計應(yīng)具備一定的柔性。使夾具設(shè)計及拼裝系統(tǒng)的應(yīng)用不再依附于某一特定平臺，最終實現(xiàn)異構(gòu)平臺之間的數(shù)據(jù)轉(zhuǎn)換和夾具CAD系統(tǒng)的重用。
所以，CAFD技術(shù)目前仍然處于自動化和智能化程度不高，缺乏智能反饋應(yīng)用功能，構(gòu)形設(shè)計仍然對手工依賴較大，自動構(gòu)形技術(shù)還非常缺乏，夾具設(shè)計和夾具組裝系統(tǒng)大部分局限于某一特定平臺而難以實現(xiàn)異構(gòu)平臺應(yīng)用的這樣一種現(xiàn)狀。夾具構(gòu)形中針對典型結(jié)構(gòu)這種模塊化夾具的研究，以及夾具元件庫異構(gòu)平臺應(yīng)用都相對較少，眾多的研究重點集中在某特定平臺下的夾具設(shè)計及夾具組裝等研發(fā)工作中，而異構(gòu)平臺之間的數(shù)據(jù)共享和交瓦無疑是網(wǎng)絡(luò)化制造和應(yīng)用的研究重點，未來科技的發(fā)展更重視信息交流，沒有信息交互的過程，協(xié)同將只是一種假設(shè)，而沒有協(xié)同的設(shè)計環(huán)境，企業(yè)及行業(yè)在未來信息化的發(fā)展中將變得寸步難行，更無從談競爭和發(fā)展。
隨著CAFD技術(shù)的進(jìn)一步發(fā)展和現(xiàn)代生產(chǎn)的需求，對組合夾具的設(shè)計和構(gòu)形自動化，智能化提出了更高的要求。在當(dāng)今面向制造環(huán)境的虛擬企業(yè)中，規(guī)劃和過程設(shè)計資源分布在全球各地，軟件工具和其他虛擬企業(yè)資源來自于異構(gòu)CAD平臺，難以實現(xiàn)彼此間的無縫交互，在這種急劇變化的國際制造背景下，應(yīng)發(fā)展創(chuàng)新夾具設(shè)計方法，實現(xiàn)遠(yuǎn)程分布合作伙伴在無縫協(xié)同方式下的交互，根據(jù)產(chǎn)品需求變化快速開發(fā)裝夾規(guī)劃，隨著信息技術(shù)驅(qū)動下的制造環(huán)境已經(jīng)發(fā)生了很大的變化，新的CAFD方法須矚目于無縫數(shù)據(jù)交換，分布協(xié)同和集成規(guī)劃等方面。
Computer Aided Fixture Design Technology Review and Trends Summary
Computer-aided fixture design (Computer-aided fixture design, CAFD) technology from the 1970s to now, has become an important part of integrated CAD / CAM technology. Article from the four research areas ( installation planning, fixture planning , fixture configuration design , fixture performance evaluation ) CAFD technology included start CAFD technology development at home and abroad (mainly for development results within the past 10 years ) were review , and future trends CAFD analyzed .
?With the development of manufacturing technology , product design cycles, faster replacement . The traditional mass production model gradually being replaced by small batch mode . To adapt to these changes machinery manufacturing industry should have higher flexibility, flexible manufacturing systems have already abroad as an effective means to develop new products , and the main development direction as machinery manufacturing . The main focus of flexibility in both the machine and tooling , tooling and fixtures is flexible focus. Average modular fixture design and assembly time is spent on special fixtures 5% -20 % of the time , can be considered synonymous with flexible modular fixture fixture . Due to a combination of strong adaptability fixture design and manufacturing cycle is short, low cost , to adapt to the requirements of replacement products , improve the competitiveness of enterprises, so growing manufacturers of all ages . A key technology is modular fixture CAFD technology. Our mid-80s from the 20th century had begun to study the technology , and how the theory of artificial intelligence applied to computer-aided modular fixture design (CAD) process are explored . However, due to a combination of fixture design depends on the workpiece , the workpiece has been changing , resulting in modular fixture CAD difficult to achieve intelligent. After 30 years of tireless efforts of many scholars at home and abroad , although the progress of the work , but from the practical application there is a great distance.
1 CAFD Technical Overview
From the 1970s began fixture CAD research to date , CAFD technology has developed into CAD / CAM integration is an important part of technology . Currently, the research commenced around CAFD technology mainly includes four aspects: installation planning, installation of central planning , design and fixtures fixture configuration performance evaluation :
( 1 ) installation plan .
Installation planning task is to determine the processing time required to install the number and orientation of each workpiece machined surface mounting . This part can also be CAPP (Computer-aided process planning) a subset is CAFD interactive interface and integrated CAPP . Installation planning framework , including the development of manufacturing and feature library characterization , definition and positioning choices clamping surface characteristics , installation planning algorithms, and fixture design and verification. Since the installation planning closer links with CAPP , most CAFD field of research has focused on planning clamping jig and fixture design configuration performance evaluation in three areas , but in the fixture configuration design, automatic configuration of the fixture design Research is still small .
( 2 ) clamping planning.
Fixture planning is mainly used to determine the condition of a particular installation support surface of the workpiece positioning , anchor and clamping points . The main problem considered by the planning fixture comprising: a surface can be selected as the type of clamping the workpiece surface ; clamping surface with respect to the tool axis orientation ; candidate precision clamping surface ; candidate combinations of clamping surfaces ; clamping stability and clamping surface can be and so on.
( 3 ) fixture configuration design .
Fixture configuration design task is to select the fixture components, fixture structure constructed and assembled them into a final configuration of the fixture to clamp the workpiece . The main problem CAFD jig design configuration comprising: selecting a fixture element such as selection direct contact with the workpiece supporting and positioning the platen ; determine the height of the clamp assembly; placed in the base plate of the clamp assembly ; between the clamp element connection ; fixture, machined surface of the workpiece and ask interference inspection.
( 4 ) Performance Evaluation fixture .
Performance evaluation is a fixture on performance fixture has been designed to evaluate and analyze , define , measure and optimize fixture design process to ensure the quality of the fixture design. Evaluation of the content includes positioning accuracy , surface precision, clamping and processing stability , resistance to deformation of the clamp element stiffness , the tool path interference check , the surface accessibility and the like.
2 CAFD study abroad technology status and results
[5 ] for CAFD from the initial start-up to the development trend of the 20th century, made ??after a review , which includes both the original Latombe, Ingrand (1980) reasoning for automatic fixture efforts , including Markus (1984) and Miller (1985 ) developed a semi- automated method for a given workpiece try a fixture design , this approach , though not automatically , but provides interactive clamping points, anchor points and support points and other functions , Chou et al ( 1989 ) based on double standards workpiece stability and full restraint requirements , focusing on the design of the clamping fixture process . With the development of CAFD shear to be recognized by a growing number of scholars , artificial intelligence and expert systems applications in the fixture designs are also increasingly being proposed, including Davishi et al ( 1988 ) for the development of expert systems Knowledge Base said , Nee et al ( 1992 ) feature-based fixture classification model, and Pham et al ( 1990 ) developed CAD system and other fixtures .
CAFD Throughout the development process , which experienced an interactive computer-aided fixture design system (I-CAFD), based on a set of skills and knowledge of CAFD systems and in the 1990s after the 3rd generation CAFD system three stages. And according to the degree of automation division, fixture design system can be divided into interactive , semi-automatic and automatic systems. After the 1990s , the experience gained, think , CAFD final fixture structure must be generated , and the system only resolved last installation , positioning, clamping and other issues or similar structure search , can not get in line with the practical application of the structure of the work , and analysis nor comprehensive . Therefore, we must develop a structure for the purpose to produce the fixture , the actual production on the commercialization of fixture design -oriented software .
The following focuses on the last 10 years to a newer CAFD research progress and problems in terms of attention and summary.
2.1 Foreign CAFD technology research status and results
CAFD research study abroad planning in clamping jig and fixture configuration design and other aspects of performance evaluation as follows :
Mounted central planning : Rong et al studied based on fast fixture configuration design system automatically positioning method in combination clamping fixture components of the planning system and the workpiece geometry is analyzed, a combination of automatic clamp fixture planning accuracy clamping planning and sexual and clamping fixtures can conduct stability studies , once established fixture planning , the results will be applied to the performance evaluation of the fixture design ; addition to the combination of mechanical machining fixture outside , Wang et al. methods case based Reasoning (CBR) is applied to the study of welding fixture , the proposed data extraction method for fixture design information representation , in this method , based on a multi -level CBR method for welding fixture design ; Perremans fixture planning can be developed as input positioning, clamping , expert systems and other supporting surface , and to achieve a combination of fixture elements assembled by expert systems ; Mervyn , who use evolutionary search algorithm presents a method for automatic analysis of modular fixture ; Varadarajan and others to the six -axis precision positioning and clamping kinetic model was designed and hardness models.
Fixture configuration design : Rong et al from fixture to fixture configuration design plan for CAFD depth and extensive research and development based on the automatic system configuration design of modular fixture hole system. In the development of rapid response manufacturing automatic configuration of custom fixture design system ; reconfigurable areas in the fixture , Kong et al will rapidly reconfigurable assembly fixture system based on visual analysis is applied to the structure of the fixture workspace synthesis and verification of fast fixture in ; Shen et al correct sliding vice reconfigurable fixture as a basic structure , the proposed four types of institutions for reconfigurable fixture system ; Ryll , who proposed a method for rapid reconfiguration of a fixture and workpiece positioned in the smart clamping system , reconfigurable application of object-oriented approach to ensure that the need to change control software to ensure that work at different fixture installation ; Culpepper, Varadarajan and others bent on incentives and pressures bearing presents a dual purpose of positioning fixture (DPF) and an eccentric shaft ball jig fixture elements to compensate for tolerances and bearing wear , but not related to the impact of the workpiece positioning tolerances of related artifacts ; Ibrahim and others in considering the workpiece material , surface roughness , roughness fixture elements , such as the impact of normal load conditions to determine experimentally the workpiece fixture element contact surface friction coefficient between to reduce experimental error by static methods to ensure the credibility of the experimental results . The results of the configuration is crucial fixture design ; Martin et al imprecise and disadvantages for fixture design uncertainty caused by the application of expert knowledge , a fuzzy reasoning (fuzzy reasoning) approach to support semantic knowledge from different modeling ; Surendra et al Ⅲ o developed a system for automatically generating fixture prismatic workpieces , the automatic fixture configuration design system can automatically select the fixture elements and in accordance with the assembly to meet the needs placed in the right position ; Hunter , who use knowledge templates reuse , you can achieve different knowledge reuse of knowledge as defined by the tribe , and combined with the model , which means that the fixture design process is based on a functional approach IDEFO and UML .
Fixture Performance evaluation : Kulankara fixture layout process , who have a greater impact on the workpiece size and precision were studied, and fixture layout optimization technique based on genetic algorithms (GA) can reduce the clamping force and cutting force machined surface deformation caused ; Pelinescu et al fixture based on multiple criteria to determine the quality of the design and layout of acceptable fixture design to evaluate and select an optimal fixture design scheme to balance multiple performance requirements , the paper gives three performance objectives, namely the positioning accuracy of the workpiece, reducing the balance of the positioning of the contact force and positioning of the contact force ; Siebenaler , who focused on the factors analyzed using the finite element method to predict deformation of the workpiece , the simulation results show that the surface of the workpiece surface based on a fixture models can make contact with the workpiece and the reaction force projections; elastic deformation of the workpiece and reaction Satyanarayana , who predicted using the finite element method leads to different boundary conditions were analyzed through experiments carried out performance evaluation ; Amaral , who also using the finite element method in the fixture design system for fixture design performance evaluation and optimization ; Song et al determine the positioning of the state , based on further analysis and study of the non-deterministic positioning program , with an algorithm to detect geometric constraint condition, the algorithm can recognize that under-constrained state and the non-bindin
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