傳動軸突緣叉機械加工工藝規(guī)程及夾具設(shè)計【鉆4-φ16孔】【說明書+CAD】,鉆4-φ16孔,說明書+CAD,傳動軸突緣叉機械加工工藝規(guī)程及夾具設(shè)計【鉆4-φ16孔】【說明書+CAD】,傳動,軸突,機械,加工,工藝,規(guī)程,夾具,設(shè)計,16,說明書,CAD 課程設(shè)計說明書 題目：傳動軸突緣叉(A10B解放牌汽車) 專用夾具設(shè)計 專　　業(yè)： 機械制造與設(shè)計及其自動化 班　　級： 05機制 42 班 姓　　名： 葛麗華 學　　號： 05281095 指導老師： 徐州師范大學 機械加工工藝過程卡片 產(chǎn)品型號 零件圖號 產(chǎn)品名稱 傳動軸突緣叉 零件名稱 傳動軸突緣叉 共 1 頁 第 1 頁 材 料 牌 號 HT200 毛 坯 種 類 鑄鐵 毛坯外形尺寸 每毛坯件數(shù) 每 臺 件 數(shù) 備 注 工 序 號 工 名 序 稱 工 序 內(nèi) 容 車 間 工 段 設(shè) 備 工 藝 裝 備 備注 1 鑄造 鑄造，清理 2 熱處理 時效 3 銑 粗,精銑底平面 X62W 游標卡尺、硬質(zhì)合金銑刀 4 銑 粗,精銑φ95端上頂面 X62W 游標卡尺、硬質(zhì)合金銑刀 5 銑 粗,精銑φ39孔端兩平面 X62W 游標卡尺、硬質(zhì)合金銑刀 6 銑 銑三角槽 X62W 游標卡尺、硬質(zhì)合金銑刀 7 鉆 鉆孔,攻絲4×M８按裝孔 Z4012 專用夾具、φ7鉆頭、M8絲攻 8 鉆 鉆4×φ16孔 Z4012 專用夾具、φ16鉆頭 9 鏜 粗鏜、精鏜側(cè)面φ39內(nèi)孔 T618 游標卡尺、開式自鎖夾緊鏜刀 10 去毛刺 去各部分銳邊毛刺 鉗工臺 平板銼 11 終檢 終檢 檢驗臺上 12 13 14 15 16 設(shè) 計（日 期） 校 對（日期） 審 核（日期） 標準化（日期） 會 簽（日期） 葛麗華 標記 處數(shù) 更改文件號 簽 字 日 期 標記 處數(shù) 更改文件號 簽 字 日 期 徐州師范大學 機械加工工序卡片 產(chǎn)品型號 零件圖號 產(chǎn)品名稱 傳動軸突緣叉 零件名稱 傳動軸突緣叉 共 1 頁 第 1 頁 車間 工序號 工序名稱 材 料 牌 號 8 鉆孔 HT200 毛 坯 種 類 毛坯外形尺寸 每毛坯可制件數(shù) 每 臺 件 數(shù) 鑄造 設(shè)備名稱 設(shè)備型號 設(shè)備編號 同時加工件數(shù) 立式鉆床 Z4120 夾具編號 夾具名稱 切削液 工位器具編號 工位器具名稱 工序工時 (分) 準終 單件 工步號 工 步 內(nèi) 容 工 藝 裝 備 主軸轉(zhuǎn)速 切削速度 進給量 切削深度 進給次數(shù) 工步工時 r/min m/min mm/r mm 機動 輔助 1 安裝 0 0 0 0 2 鉆4-φ16孔 專用夾具、φ16鉆頭 681.4 15 0.27 1 0.4 1.34 3 設(shè) 計（日 期） 校 對（日期） 審 核（日期） 標準化（日期） 會 簽（日期） 葛麗華 2 目 錄 序 言 ……………………………………………………… 2 第一節(jié) 專用夾具設(shè)計的基本要求 …………………………… 2 第二節(jié) 專用夾具設(shè)計的規(guī)范化程序 ………………………… 3 第三節(jié) 零件分析 ……………………………………………9 3.1零件結(jié)構(gòu)功用分析 ………………………………10 3.2零件圖紙分析 …………………………………10 3.3主要技術(shù)條件 …………………………………10 第四節(jié) 鉆4χφ16孔夾具設(shè)計 …………………………… 10 第五節(jié)　設(shè)計體會 ……………………………………………13 參考資料 ……………………………………………………15 序言: 夾具設(shè)計一般是在零件的機械加工工藝過程制訂之后按照某一工序的具體要求進行的。制訂工藝過程，應(yīng)充分考慮夾具實現(xiàn)的可能性，而設(shè)計夾具時，如確有必要也可以對工藝過程提出修改意見。夾具的設(shè)計質(zhì)量的高低，應(yīng)以能否穩(wěn)定地保證工件的加工質(zhì)量，生產(chǎn)效率高，成本低，排屑方便，操作安全、省力和制造、維護容易等為其衡量指標。 第一節(jié) 專用夾具設(shè)計的基本要求 一個優(yōu)良的機床夾具必須滿足下列基本要求： （1）保證工件的加工精度 保證加工精度的關(guān)鍵，首先在于正確地選定定位基準、定位方法和定位元件，必要時還需進行定位誤差分析，還要注意夾具中其他零部件的結(jié)構(gòu)對加工精度的影響，確保夾具能滿足工件的加工精度要求。 （2）提高生產(chǎn)效率 專用夾具的復雜程度應(yīng)與生產(chǎn)綱領(lǐng)相適應(yīng)，應(yīng)盡量采用各種快速高效的裝夾機構(gòu)，保證操作方便，縮短輔助時間，提高生產(chǎn)效率。 （3）工藝性能好 專用夾具的結(jié)構(gòu)應(yīng)力求簡單、合理，便于制造、裝配、調(diào)整、檢驗、維修等。 專用夾具的制造屬于單件生產(chǎn)，當最終精度由調(diào)整或修配保證時，夾具上應(yīng)設(shè)置調(diào)整和修配結(jié)構(gòu)。 （4）使用性能好 專用夾具的操作應(yīng)簡便、省力、安全可靠。在客觀條件允許且又經(jīng)濟適用的前提下，應(yīng)盡可能采用氣動、液壓等機械化夾緊裝置，以減輕操作者的勞動強度。專用夾具還應(yīng)排屑方便。必要時可設(shè)置排屑結(jié)構(gòu)，防止切屑破壞工件的定位和損壞刀具，防止切屑的積聚帶來大量的熱量而引起工藝系統(tǒng)變形。 （5）經(jīng)濟性好 專用夾具應(yīng)盡可能采用標準元件和標準結(jié)構(gòu)，力求結(jié)構(gòu)簡單、制造容易，以降低夾具的制造成本。因此，設(shè)計時應(yīng)根據(jù)生產(chǎn)綱領(lǐng)對夾具方案進行必要的技術(shù)經(jīng)濟分析，以提高夾具在生產(chǎn)中的經(jīng)濟效益。 第二節(jié) 專用夾具設(shè)計的規(guī)范化程序 一、夾具設(shè)計規(guī)范化概述 1．夾具設(shè)計規(guī)范化的意義 研究夾具設(shè)計規(guī)范化程序的主要目的在于： （1）保證設(shè)計質(zhì)量，提高設(shè)計效率 夾具設(shè)計質(zhì)量主要表現(xiàn)在： 1）設(shè)計方案與生產(chǎn)綱領(lǐng)的適應(yīng)性； 2）高位設(shè)計與定位副設(shè)置的相容性； 3）夾緊設(shè)計技術(shù)經(jīng)濟指標的先進性； 4）精度控制項目的完備性以及各控制項目公差數(shù)值規(guī)定的合理性； 5）夾具結(jié)構(gòu)設(shè)計的工藝性； 6）夾具制造成本的經(jīng)濟性。 有了規(guī)范的設(shè)計程序，可以指導設(shè)計人員有步驟、有計劃、有條理地進行工作，提高設(shè)計效率，縮短設(shè)計周期。 （2）有利于計算機輔助設(shè)計 有了規(guī)范化的設(shè)計程序，就可以利用計算機進行輔助設(shè)計，實現(xiàn)優(yōu)化設(shè)計，減輕設(shè)計人員的負擔。利用計算機進行輔助設(shè)計，除了進行精度設(shè)計之外，還可以尋找最佳夾緊狀態(tài)，利用有限元法對零件的強度、剛度進行設(shè)計計算，實現(xiàn)包括繪圖在內(nèi)的設(shè)計過程的全部計算機控制。 （3）有利于初學者盡快掌握夾具設(shè)計的方法 近年來，關(guān)于夾具設(shè)計的理論研究和實踐經(jīng)驗總結(jié)已日見完備，在此基礎(chǔ)上總結(jié)出來的夾具規(guī)范化設(shè)計程序，使初級夾具設(shè)計人員的設(shè)計工作提高到了一個新的科學化水平。 2．夾具設(shè)計精度的設(shè)計原則 要保證設(shè)計的夾具制造成本低，規(guī)定零件的精度要求時應(yīng)遵循以下原則： （1）對一般精度的夾具 1）應(yīng)使主要組成零件具有相應(yīng)終加工方法的平均經(jīng)濟精度； 2）應(yīng)按獲得夾具精度的工藝方法所達到的平均經(jīng)濟精度，規(guī)定基礎(chǔ)件夾具體加工孔的形位公差。 對一般精度或精度要求低的夾具，組成零件的加工精度按此規(guī)定，既達到了制造成本低，又使夾具具有較大精度裕度，能使設(shè)計的夾具獲得最佳的經(jīng)濟效果。 （2）對精密夾具 除遵循一般精度夾具的兩項原則外，對某個關(guān)鍵零件，還應(yīng)規(guī)定與偶件配作或配研等，以達到無間隙滑動等。 二、夾具設(shè)計的規(guī)范程序 工藝人員在編制零件的工藝規(guī)程時，便會提出相應(yīng)的夾具設(shè)計任務(wù)書，經(jīng)有關(guān)負責人批準后下達給夾具設(shè)計人員。夾具設(shè)計人員根據(jù)任務(wù)書提出的任務(wù)進行夾具結(jié)構(gòu)設(shè)計?，F(xiàn)將夾具結(jié)構(gòu)設(shè)計的規(guī)范化程序具體分述如下。 　　1．明確設(shè)計要求，認真調(diào)查研究，收集設(shè)計資料 （1）仔細研究零件工作圖、毛坯圖及其技術(shù)條件。 （2）了解零件的生產(chǎn)綱領(lǐng)、投產(chǎn)批量以及生產(chǎn)組織等有關(guān)信息。 （3）了解工件的工藝規(guī)程和本工序的具體技術(shù)要求，了解工件的定位、夾緊方案，了解本工序的加工余量和切削用量的選擇。 （4）了解所使用量具的精度等級、刀具和輔助工具等的型號、規(guī)格。 （5）了解本企業(yè)制造和使用夾具的生產(chǎn)條件和技術(shù)現(xiàn)狀。 （6）了解所使用機床的主要技術(shù)參數(shù)、性能、規(guī)格、精度以及與夾具連接部分結(jié)構(gòu)的聯(lián)系尺寸等。 （7）準備好設(shè)計夾具用的各種標準、工藝規(guī)定、典型夾具圖冊和有關(guān)夾具的設(shè)計指導資料等。 （8）收集國內(nèi)外有關(guān)設(shè)計、制造同類型夾具的資料，吸取其中先進而又能結(jié)合本企業(yè)實際情況的合理部分。 　　2．確定夾具的結(jié)構(gòu)方案 　在廣泛收集和研究有關(guān)資料的基礎(chǔ)上，著手擬定夾具的結(jié)構(gòu)方案，主要包括： 　 （1）根據(jù)工藝的定位原理，確定工件的定位方式，選擇定位元件。 （2）確定工件的夾緊方案和設(shè)計夾緊機構(gòu)。 （3）確定夾具的其它組成部分，如分度裝置、對刀塊或引導元件、微調(diào)機構(gòu)等。 （4）協(xié)調(diào)各元件、裝置的布局，確定夾具體的總體結(jié)構(gòu)和尺寸。 　在確定方案的過程中，會有各種方案供選擇，但應(yīng)從保證精度和降低成本的角度出發(fā)，選擇一個與生產(chǎn)綱領(lǐng)相適應(yīng)的最佳方案。 　　3．繪制夾具總圖 　繪制夾具總圖通常按以下步驟進行： （1）遵循國家制圖標準，繪圖比例應(yīng)盡可能選取1﹕1，根據(jù)工件的大小時，也可用較大或較小的比例；通常選取操作位置為主視圖，以便使所繪制的夾具總圖具有良好的直觀性；視圖剖面應(yīng)盡可能少，但必須能夠清楚地表達夾具各部分的結(jié)構(gòu)。 （2）用雙點劃線繪出工件輪廓外形、定位基準和加工表面。將工件輪廓線視為“透明體”，并用網(wǎng)紋線表示出加工余量。 （3）根據(jù)工件定位基準的類型和主次，選擇合適的定位元件，合理布置定位點，以滿足定位設(shè)計的相容性。 （4）根據(jù)定位對夾緊的要求，按照夾緊五原則選擇最佳夾緊狀態(tài)及技術(shù)經(jīng)濟合理的夾緊系統(tǒng)，畫出夾緊工件的狀態(tài)。對空行和較大的夾緊機構(gòu)，還應(yīng)用雙點劃線畫出放松位置，以表示出和其他部分的關(guān)系。 （5）圍繞工件的幾個視圖依次繪出對刀、導向元件以及定向鍵等。 （6）最后繪制出夾具體及連接元件，把夾具的各組成元件和裝置連成一體。 （7）確定并標注有關(guān)尺寸 夾具總圖上應(yīng)標注的有以下五類尺寸： 　1）夾具的輪廓尺寸：即夾具的長、寬、高尺寸。若夾具上有可動部分，應(yīng)包括可動部分極限位置所占的空間尺寸。 　2）工件與定位元件的聯(lián)系尺寸：常指工件以孔在心軸或定位銷上（或工件以外圓在內(nèi)孔中）定位時，工件定位表面與夾具上定位元件間的配合尺寸。 　3）夾具與刀具的聯(lián)系尺寸：用來確定夾具上對刀、導引元件位置的尺寸。對于銑、刨床夾具，是指對刀元件與定位元件的位置尺寸；對于鉆、鏜床夾具，則是指鉆（鏜）套與定位元件間的位置尺寸，鉆（鏜）套之間的位置尺寸，以及鉆（鏜）套與刀具導向部分的配合尺寸等。 4）夾具內(nèi)部的配合尺寸：它們與工件、機床、刀具無關(guān)，主要是為了保證夾具裝置后能滿足規(guī)定的使用要求。 5）夾具與機床的聯(lián)系尺寸：用于確定夾具在機床上正確位置的尺寸。對于車、磨床夾具，主要是指夾具與主軸端的配合尺寸；對于銑、刨床夾具，則是指夾具上的定向鍵與機床工作臺上的T型槽的配合尺寸。標注尺寸時，常以夾具上的定位元件作為相互位置尺寸的基準。 　　上述尺寸公差的確定可分為兩種情況處理：一是夾具上定位元件之間，對刀、導引元件之間的尺寸公差，直接對工件上相應(yīng)的加工尺寸發(fā)生影響，因此可根據(jù)工件的加工尺寸公差確定，一般可取工件加工尺寸公差的1/3~1/5；二是定位元件與夾具體的配合尺寸公差，夾緊裝置各組成零件間的配合尺寸公差等，則應(yīng)根據(jù)其功用和裝配要求，按一般公差與配合原則決定。 （8）規(guī)定總圖上應(yīng)控制的精度項目，標注相關(guān)的技術(shù)條件 夾具的安裝基面、定向鍵側(cè)面以及與其相垂直的平面（稱為三基面體系）是夾具的安裝基準，也是夾具的測量基準，因而應(yīng)該以此作為夾具的精度控制基準來標注技術(shù)條件。在夾具總圖上應(yīng)標注的技術(shù)條件（位置精度要求）有如下幾個方面： 1）定位元件之間或定位元件與夾具體底面間的位置要求，其作用是保證工件加工面與工件定位基準面間的位置精度。 2）定位元件與連接元件（或找正基面）間的位置要求。 3）對刀元件與連接元件（或找正基面）間的位置要求。 4）定位元件與導引元件的位置要求。 5）夾具在機床上安裝時位置精度要求。 上述技術(shù)條件是保證工件相應(yīng)的加工要求所必需的，其數(shù)量應(yīng)取工件相應(yīng)技術(shù)要求所規(guī)定數(shù)值的1/3~1/5。當工件沒注明要求時，夾具上的那些主要元件間的位置公差，可以按經(jīng)驗取為（100﹕0.02）~（100﹕0.05）mm，或在全長上不大于0.03~0.05mm。 （9）編制零件明細表 夾具總圖上還應(yīng)畫出零件明細表和標題欄，寫明夾具名稱及零件明細表上所規(guī)定的內(nèi)容。 4．夾具精度校核 在夾具設(shè)計中，當結(jié)構(gòu)方案擬定之后，應(yīng)該對夾具的方案進行精度分析和估算；在夾具總圖設(shè)計完成后，還應(yīng)該根據(jù)夾具有關(guān)元件的配合性質(zhì)及技術(shù)要求，再進行一次復核。這是確保產(chǎn)品加工質(zhì)量而必須進行的誤差分析。 5．繪制夾具零件工作圖 夾具總圖繪制完畢后，對夾具上的非標準件要繪制零件工作圖，并規(guī)定相應(yīng)在的技術(shù)要求。零件工作圖應(yīng)嚴格遵照所規(guī)定的比例繪制。視圖、投影應(yīng)完整，尺寸要標注齊全，所標注的公差及技術(shù)條件應(yīng)符合總圖要求，加工精度及表面光潔度應(yīng)選擇合理。 在夾具設(shè)計圖紙全部完畢后，還有待于精心制造和實踐和使用來驗證設(shè)計的科學性。經(jīng)試用后，有時還可能要對原設(shè)計作必要的修改。因此，要獲得一項完善的優(yōu)秀的夾具設(shè)計，設(shè)計人員通常應(yīng)參與夾具的制造、裝配，鑒定和使用的全過程。 6．設(shè)計質(zhì)量評估 夾具設(shè)計質(zhì)量評估，就是對夾具的磨損公差的大小和過程誤差的留量這兩項指標進行考核，以確保夾具的加工質(zhì)量穩(wěn)定和使用壽命。 第三節(jié) 零件分析 3.1零件結(jié)構(gòu)功用分析： 題目所給的零件是常見零件的一種——拔叉類零件，它的應(yīng)用范圍很廣。由于它們功用的不同，該類零件的結(jié)構(gòu)和尺寸有著很大的差異，但結(jié)構(gòu)上仍有共同特點：零件的主要表面為精度要求較高的孔及其平面，零件由內(nèi)孔、外圓、端面等表面構(gòu)成。 3.2零件圖紙分析： 由零件圖可知，該零件形狀較為復雜、外形尺寸不大，可以采用鑄造毛坯。由于該零件的兩個φ39孔要求較高，它的表面質(zhì)量直接影響工作狀態(tài)，通常對其尺寸要求較高。一般為IT7-IT9。加工時兩φ39孔的與其平面的垂直度要求較高.應(yīng)該控制在0.05mm以內(nèi)。 3.3主要技術(shù)條件： ⑴ 孔徑精度：兩φ39孔的孔徑的尺寸誤差和形狀誤差會影響到工作狀態(tài)，因此對孔的要求較高，其孔的尺寸公差為IT7 ⑵ 主要平面的精度：由于φ39端面加工過程中常作為定位基面，則會影響孔的加工精度，因此須規(guī)定其加工要求。 ⑶ 4χφ16四孔對B,C面均有位置度要求. 第四節(jié) 鉆4χφ16孔夾具. 設(shè)計任務(wù) 設(shè)計在成批生產(chǎn)條件下,在通用立式鉆床上鉆φ16孔的鉆床夾具. 1、φ16可一次鉆削保證.該孔在軸線方向的設(shè)計基準是以鉆套的中心線的，設(shè)計基準是以φ95外圓與另一橫孔φ39軸線.. 2、定位基準的選擇 工序結(jié)合面是已加工過的平面，且又是本工序要加工的孔的設(shè)計基準，按照基準重合原則,選擇它作為定位基準是比較恰當?shù)?。因此，選擇結(jié)合面與外圓作為定位比較合理。 3、切削力及夾緊力的計算 刀具：麻花鉆，dw=16mm, 則F=9.81×54.5 ap0.9af0.74ae1.0Zd0-1.0δFz (《切削手冊》) 查表得：d0=16mm,ae=195, af =0.2, ap =9.5mm, δFz =1.06所以： F=(9.81×54.5×2.50.9×0.20.74×192×16×1.06) ÷20=79401N 查表可得，鉆削水平分力，垂直分力，軸向力與圓周分力的比值： FL/ FE=0.8, FV / FE =0.6, FX / Fe =0.53 故FL=0.8 FE =0.8×79401=63521N FV=0.6 FE=0.6×79401=47640N FX =0.53 FE=0.53×79401=42082N 在計算切削力時，必須考慮安全系數(shù)，安全系數(shù) K=K1K2K3K4 式中：K1 —基本安全系數(shù)，2.5 K2—加工性質(zhì)系數(shù)，1.1 K3—刀具鈍化系數(shù)，1.1 K2—斷續(xù)切削系數(shù)，1.1 則F/=K FH=2.5×1.1×1.1×1.1×63521 =211366N 選用螺旋—板夾緊機構(gòu)，故夾緊力 fN=1/2 F/ f為夾具定位面及夾緊面上的摩擦系數(shù)，f=0.25 則 N=0.5×211366÷0.25=52841N 4、操作的簡要說明 在設(shè)計夾具時，為降低成本，可選用手動螺桿夾緊，本道工序的鉆床夾具就是選擇了手動螺旋—壓板夾緊機構(gòu)。由于本工序是粗加工，切削力比較大，為夾緊工件，勢必要求工人在夾緊工件時更加吃力，增加了勞動強度，因此應(yīng)設(shè)法降低切削力?？梢圆扇〉拇胧┦翘岣呙鞯闹圃炀?，使最大切削深度降低，以降低切削力。下圖為本序的夾緊裝配圖. 5、工序精度分析 在夾具設(shè)計中，當結(jié)構(gòu)方案確定后，應(yīng)對所設(shè)計的夾具進行精度分析和誤差計算。影響設(shè)計尺寸的各項誤差分析 1、重合,故產(chǎn)生定位誤差。定位尺寸公差=02mm，在加工尺寸方向上的投影，的方向與加工方向是一致的，所以=0.2mm,因為平面定位。所以 故 2、垂直度所引起的夾具安裝誤差，對工序尺寸的影響均小，既可以忽略不計。面到鉆套座孔之間的距離公差，按工件相應(yīng)尺寸公差的五分之一，。 通常不超過0.005mm.。偏移 用概率法相加總誤差為： 098137mm<0.2mm 從以上的分析可見，所設(shè)計的夾具能滿足零件的加工精度要求。當上述各種元件的結(jié)構(gòu)和布置確定之后，也就基本上決定了夾具體和夾具整體結(jié)構(gòu)的型式。 繪圖時先用雙點劃線（細線）繪出工件，然后在各個定位面繪制出定位元件和夾緊機構(gòu)，就形成了夾具體。并按要求標注夾具有關(guān)的尺寸、公差和技術(shù)要求。 第五節(jié)　設(shè)計體會 課程設(shè)計是對我們所學課程知識的總結(jié)。通過課程設(shè)計可以體現(xiàn)出我們在校期間的學習程度。從而對我們所學專業(yè)知識做出有力判斷。從我們拿到零件圖紙的第一天開始，我們的老師就詳細給我們講了設(shè)計的步驟，還安排了輔導時間。為我們圓滿的完成任務(wù)奠定了良好的基礎(chǔ)。我們以前所接觸的只是課本上的知識，對機械加工工藝只有側(cè)面的了解。但是同過這次設(shè)計，我們才全方位的懂得了什么是機械設(shè)計，從而更加了解了我們的專業(yè)。 剛開始設(shè)計的時候，總覺的難度很大，不知道從什么地方下手，對一些設(shè)計的步驟根本不知道怎么安排，怎么設(shè)計。老師給我們詳細講解了機械設(shè)計應(yīng)注意的條件，讓我們先從分析零件圖開始。 在設(shè)計期間，我們第一次接觸了機械加工工藝的設(shè)計，對我有了很大提高。遇到不懂的問題時，指導老師們都能細心的幫助我。同學之間雖然每個人的設(shè)計課題不一樣，但我們之間還是會經(jīng)常討論，互相幫助，不緊學會了知識，而且還鍛煉了我們的團隊精神。在這次設(shè)計中，要感謝我們的指導老師，他們在設(shè)計期間為我們的解決了很多難題。相信我們通過這次設(shè)計，一定會在以后的工作崗位中更好的發(fā)揮。 參 考 資 料 1.《機械制圖》 教材 2.《機械設(shè)計》 教材 3.《金屬切削原理》 教材 4.<<機械工程材料>> 教材 5.<<金屬工藝學>> 教材 6.<<機械制造工藝學>> 教材 7.<<機床夾具設(shè)計>> 教材 8.<<機床夾具設(shè)計手冊>> 機械工業(yè)出版社 9.<<機械制造工藝學課程設(shè)計指導書>> 哈工大出版社 10.<<切削用量手冊 >> 機械工業(yè)出版社 11.<<機械制造工藝及專用夾具設(shè)計指導>> 冶金工業(yè)出版社 15 ORIGINAL ARTICLEFast collision detection approach to facilitate interactivemodular fixture assembly design in a virtual environmentGaoliang Peng&Xin Hou&Chong Wu&Tianguo Jin&Xutang ZhangReceived: 27 May 2008 /Accepted: 21 April 2009 /Published online: 9 May 2009#Springer-Verlag London Limited 2009Abstract Collision detection is a fundamental componentto simulate realistic and natural object behaviors in virtualreality-based system. In this paper, a hybrid method ofspace decomposition and bounding volume approach ispresented to assist modular fixture assembly design in avirtual environment. Based on characteristics of modularfixture, a novel space decomposition methodology at objectlevel is proposed, which is achieved by automaticallypartitioning the checking space into cells according to theoriented bounding boxes of assembled elements after theinitial approximate collision detection using the intersectionchecking method based on separation plane-based bound-ing box. Then the pairs of candidate objects are determinedfor narrow phase exact polygons overlap tests. Results fromseveral performance tests on modular fixture design systemshow that an important advantage of this proposed methodcompared with other universal algorithms is its simpleinformation representation and low preprocessing cost.Keywords Collisiondetection.Virtualassembly.Modularfixture.Spacedecomposition.Boundingvolume1 IntroductionVirtual reality (VR) became a very common mean duringthe development of the industrial products. The aidprovided by VR is noticeable, since the user can interactwith the virtual prototype in a very natural way 13. VRholds great potential in manufacturing applications to solveproblems before fatal mistakes occur in practical manufac-turing so that great costs are prevented. VR applicationshave gained increasing attention internationally.Fixture design takes a significant part of the total time(cost) necessary for technical and technological productionpreparation. The design of a fixture is a highly complex andintuitive process, which requires knowledge and experience4. Modular fixtures are one of the important aspects ofmanufacturing. Proper fixture design is crucial to productquality with regard to the precision, accuracy, and finish ofthe machined part. Modular fixture is a system ofinterchangeable and highly standardized componentsdesigned to securely and accurately position, hold, andsupport the workpiece throughout the machining process5. Traditionally, fixture designers rely on experiences oruse trial-and-error methods to determine an appropriatefixture scheme.Since the potentially high degree of “reality” experi-enced in a virtual environment (VE), the VR-based modularfixture design has the advantages of designing a fixture in anatural and instructive manner, providing better match tothe working conditions, reducing lead-time, and generallyproviding a significant enhancement to fixture productivityand economy 6. In order to achieve this goal, the VRsystem must be able to simulate realistic and natural objectbehaviors. First of all, as a basic requirement of fixturedesign, there should be no collision between fixture,component and machine tool 7, 8; the objects notInt J Adv Manuf Technol (2010) 46:315328DOI 10.1007/s00170-009-2073-0G. Peng (*):X. Hou:T. Jin:X. ZhangSchool of Mechanical and Electrical Engineering,Harbin Institute of Technology,Harbin, Chinae-mail: C. WuSchool of Management, Harbin Institute of Technology,Harbin, Chinapenetrating into others must be guaranteed. Therefore, a fastinteractive collision detection (CD) algorithm is fundamen-tal in such a VR system.However, collision checking for a complex VE iscomputationally intensive. Researchers have addressedsome “universal” algorithms to reduce the computationalcosts. But these algorithms often need auxiliary datastructures and require intensive preprocessing time cost.In addition, the implementation of such algorithm is verycomplicated. Therefore, based on the well study of modularfixture characteristics and practical requirements, wedevelop a “special” CD algorithm to keep the associatedcosts as low as possible for VR-based modular fixtureassembly design.The paper is organized as follows. A review of relatedwork of the existing CD algorithms is presented inSection 2. Section 3 gives an overview of our proposedalgorithm. In Section 4, we describe the space subdivisionmodel used in our algorithm. Section 5 provides the detailsabout the broad phase of our proposed algorithm, in whichirrelevant objects are discarded and a set of objects that canpossibly collide are determined. The narrow phase for exactpolygon based overlap tests is described in Section 6.Section 7 presents some experimental results of ouralgorithm, and finally, in Section 8, we give concludingremarks and outline directions for future extensions of thiswork.2 Related workDuring the past few years, a great deal of effort has beenmade to solve the CD problem for various types ofinteractive 3D graphics and scenarios. For a workspacefilled with n objects, the most obvious problem is the O(n2)problem of detecting collisions between all objects, whichis time consuming and not bearable if the number n is large.Thus, some necessary techniques are needed to reduce thecomputational costs. Generally, a CD algorithm consists oftwo main steps, namely broad phase and narrow phase 9.The first phase aims to filter out pairs of objects which areimpossible to interact and determine which objects in theentire workspace potentially interact. The second phase isto perform a more accurate test to identify collisionbetween those selected object parts in the first phase,moreover if necessary, to find the pairs of contactingprimitive geometric elements (polygons), and to calculatethe overlapping distance.For a CD algorithm, it is critical to reduce the number ofpairs of objects or primitives that need to be checked.Therefore, a number of different techniques have been usedto make coarse grain detection, among which spacedecomposition and bounding volumes is most popular.In space decomposition methods, the environment issubdivided into space grids using hierarchical spacesubdivision. Objects in the environment are clusteredhierarchically according to the regions that they fall into.These objects are then checked for intersection by testingfor overlapping grid cells exploiting spatial partitioningmethods like Octrees 10, 11, BSP-trees 12, k-d trees13, etc. Using such decompositions in a hierarchicalmanner can further speed up the collision detection processbut leads to extremely high storage requirements.Bounding volume (BV) approach is used in previouscomputer graphics algorithms to speed up computation andrendering process. The BVof a geometric object is a simplevolume enclosing the object. Typically, BV types are axis-aligned boxes (AABBs) 14, spheres 15, and orientedbounding boxes (OBB) 16.Since AABBs method is simple to compute and allowsefficient overlap queries, it is often used in hierarchy, but italso may be a particularly poor approximation of the setthat they bound, leaving large “empty corners.” Thesystems utilizing AABBS include I-COLLIDE 17, Q-COLLIDE 18, and SOLID 19, etc.Bounding sphere is another natural choice to approxi-mate an object as it is particularly simple to test pairs foroverlap, and the update for a moving object is trivial.However, spheres are similar to AABBs as they can be poorapproximations to the convex hull of contained objects.In comparison, an OBB is a rectangular bounding box atarbitrary orientations in 3D space. In an ideal case, theOBB can be repositioned such that it is able to enclose anobject as tightly as possible. In other words, the OBB is thesmallest possible bounding box of arbitrary orientation thatcan enclose the geometry in question. This approach is verygood at performing fast rejection tests. A system calledRAPID 20 for interference detection based on OBB hasbeen built, which approximates geometry better thanAABBs. The shortcomings of OBB-tree against sphere treelie in its slowness to update and orientation sensitive 9.Most CD-related researches are involved in “universal”algorithms, and few literatures are found to develop CDapproach in a special application like virtual assembly.Actually, a fast and interactive collision detection algorithmis fundamental to a virtual assembly environment, whichallows designers to move parts or components to performassembly and disassembly operations.Figueiredo 21 presented a faster algorithm for thebroad and narrow phases of the collision detectionalgorithm of determining precise collisions between surfa-ces of 3D assembly models in virtual prototype environ-ments. The algorithm used the overlapping AABB and theR-tree data structure to improve performance in both thebroad and narrow phases of the collision detection. Thisapproach is for such a VE with objects dispersed in the316Int J Adv Manuf Technol (2010) 46:315328space. In addition, the R-tree data structure is very memoryintensive.Stephane 22 worked on continuous collision detectionmethods and constraints to deal with rigid polyhedralobjects for desktop virtual prototyping. Whereas such a4D method is only useful for handling the path of knownmoving objects. Especially, the algorithm is so computa-tionally intensive that it has to run on high-end computers.Collision detection is a critical problem in multi-axisnumerical control (NC) machining with complex machiningenvironments. There has been much previous work oninterference detection and avoidance in NC machiningsimulation. Wang 23 developed a graphics-assistedcollision detection approach for multi-axis NC machining.In this method, a combination of machining environmentculling and a two-phase collision detection strategy wasused.Researches surveyed above provided various efficienttechniques to carry out collision detection for polygonalmodels. However, these popular algorithms aimed atgeneral polygonal models, most of which need expensivepretreatments or large system memory or both of them inorder to improve the performance and meet real-timerequirements. Therefore, when these algorithms are utilizedin desktop VR application system such as modular fixturedesign, the requirement of real time cannot be wellguaranteed.Few CD researches can be found in the area ofcomputer-aided fixture design. Hu 24 presented analgorithm of fast interference checking between themachining tool and fixture units, as well as between fixtureunits, to replace the visually checked method. Moreover, inKumars work 25, in order to automate interference-freemodular fixture assembly design, the machining interferencedetection is accomplished through the use of cutter-sweptsolid based on cutter-swept volume approach. However,these algorithms are only capable of static interferencechecking and applied in CAD software packages.The research presented in this paper makes a solution tothese issues by addressing a “special” collision detectionalgorithm for VR-based modular fixture design. Theproposed algorithm uses the hybrid approach of spacedecomposition and bounding volume method to get highperformance.3 Algorithm overview3.1 Requirements for proposed algorithmWe aimed to develop a desktop VR-based modular fixtureassembly design system, in which the designer can selectsuitable fixture elements and put them together to generatea fixture structure, like “building blocks.” Without physicalfixture elements, he/she can test different structure schemesand finally design a feasible fixture configuration that meetsthe fixturing function requirements. In order to retain highdegree of “reality” in engineering application, there arethree main requirements for a CD algorithm to performmodular fixture configuration design:1.Precise and fast: During the simulation of assemblyand disassembly operations, finding precise collisionsis an important task for achieving realistic behavior26. When the user interactively assembles a part or acomponent, the “flying” object may collide with staticmodels, thus the system must find out the “colliding”event immediately. The interval between two checkingpoints should be near enough to achieve betterperformance. Otherwise, when objects move very fast,they may appear before checking, which will reduce theimmersive feelings. Therefore, the proposed systemcarries out a CD checking task in each rendering loopof VE. In addition, in modular fixture assembly designprocess, the designer selects elements and assemblesthem to right position or disassembles them to changethe fixture configuration. Once an element is assembledor disassembled, the “static” environment models areupdated. Accordingly, the CD checking model needsrestructure. So the preprocess should not take too long;otherwise, the performance of proposed system will beimpaired severely for certain “smooth feel” cannot beachieved.2.Low system requirements: Finding collisions in a 3Denvironment is time-consuming. In some cases, it caneasily consume up to 50% of the total run time 21.However, in modular fixture design workspace, thereare some other time-consuming tasks, such as designprocess control and reasoning, automatic geometricconstraints recognition and solving, etc. In spite of thecomplexity of the 3D virtual prototypes due tothousands of polygons, the designed CD checkingprocedure must be done in real time with relativelylow system resource demands.3.Low hardware cost: In order to achieve wider engi-neering applications, the proposed modular fixtureassembly system is designed to run on common PClike popular CAD commercial software. Althoughmuch research has engaged in developing hardware-accelerated CD algorithms, which utilize special graph-ic hardware, like graphics processing unit, to deal withthe computing collisions, thus the systems CPU can befreed. Nevertheless, we did not plan to adopt this kindof method and optimize performance only fromsoftware implementation. The objective of this researchis to develop a CD algorithmInt J Adv Manuf Technol (2010) 46:315328317Taking into account all above requirements, unfortunate-ly, these objectives usually are in conflict. To meet theprecise demand, we must increase checking frequencywhich will enormously increase the computational com-plexity and the memory bandwidth requirement. So, howcan a balance be reached with regard to these? In otherwords, how can the utilization of system resources beminimized yet the performance optimized without the helpof extra hardware? It is the start point of our algorithm.3.2 Modular fixture analysisThe objective of this research is to develop a CD algorithmfor assisting in modular fixture assembly design operationsin VE. To simplify the algorithm and to gain highperformance, the characteristics of modular fixture shouldbe well studied.1.Process of modular fixture assembly design: The tasksof modular fixture assembly design are to select theproper fixture elements and assemble them to aconfiguration one by one according to the designedfixturing plan. Thus, the CD problem in VR-basedmodular fixture assembly design can be stated as: theintersection checking between one moving object(assembling element or unit) with the static environ-ment objects (assembled elements) at discrete time.2.Fixture element shape: Modular fixture elements withregular shape can be classified into three types, namely,block, cylinder, and block-cylinder 27. Other compli-cated assembly units can be regarded as compositionsof these three meta-elements. It is well known that theOBB is tighter than the AABB and sphere. Moreover,when an object changes its position and orientation inVE, its OBB does not need to rebuild. Therefore, wecan construct OBBs of modular fixture elements off-line and store them as attributes of element models.During the assembly design process, such attributes canbe retrieved directly; thus, complex work for construct-ing bounding volume in run time can be avoided.3.Fixture element layout: A modular fixture system oftenconsists of supporting units, locating units, and clamp-ing units. These units lie out on the base plate andprovide corresponding functions at certain positions. AsFig. 1 shows, in the projection view parallel to the baseplate, the units are arranged in some kind of “regions.”In addition, to meet the height requirement of fixturingpoint, a unit often utilizes a number of supportingelements severed as blocking up objects. Therefore, atthe direction perpendicular to the baseplate, theelements lay out hierarchically. Accordingly, we candecompose the space with regard to elements layoutfeature.3.3 Algorithm flowchartAccording to the above characteristics of modular fixture,the proposed algorithm is designed to decrease thecomplexity and meet the requirements of VR-basedmodular fixture assembly design. As Fig. 2 shows, at thepreprocessing stage, once an element or component isassembled or disassembled, the Layer-based ProjectionModel (LPM) is established in terms of OBBs of thoseassembled elements. Such an LPM is used for the CDchecking when a new object is assembled.Just like the traditional CD method, proposed algorithmconsists of two steps, namely, broad phase and narrowphase. The broad phase is responsible for filtering pairs ofobjects that cannot intersect. At this stage, it determinespairs of objects in the same subspace, whose silhouettes inLPM overlap and their OBBs intersect. These pairs ofobjects are candidates for exact polygon-based collisiontests in the next narrow phase. During the broad phase, the(a)default view(b)downtown view Fig. 1 Modular fixture structure318Int J Adv Manuf Technol (2010) 46:315328test may cease at any time if no intersection is found, whichhelps to reject many noncollision or trivial collision cases.In the narrow phase, the collision detection algorithm willcalculate detailed intersection between geometrical meshesof the objects. If no intersection polygons are found, thecollide will not occur, and the active object can keep onmoving. Otherwise, whenever overlaps are detected, relatedreactions (for proposed system, it highlights objects anddoes back-tracking) may arise.4 Space decomposition for identifyingneighboring objectsConsidering the fact that most regions of the “universe” areoccupied by only a few objects or left empty, it means thatcollision only happens among objects that are close enough.So we can use this phenomenon to filter out most of “far-away” objects. Space decomposition is the commonapproach to be used for this intention. It first splits the“universe” into cells and then does further collision tests forobjects in the same cell. In order to keep generality, most ofexisting space subdivision approaches are based on a set ofpolygons. Such a “polygon-oriented” approach is socomputationally intensive to deal with large number ofpolygons. Since standard components are almost withrelatively regular shapes, we plan to develop an “object-oriented” space decomposition method.4.1 Space decomposition modelAfter the baseplate is arranged, the remaining work is toassemble the fixture elements or units onto the baseplate.As the assembling elements or units move to the assembledposition, collisions may happen between active object andthe assembled elements that have been fixed in the spacearound the baseplate. Hence, the CD checking processneeds start-up only after the active object enters into thisspace. Firstly, as Fig. 3a shows, we define a valid collisionspace noted as , which is a cuboid whose bottom face isdecided by the baseplate, and its height would change alongwith the assembling operation. The top of is determinedby the vertex coordinates of OBBs. is defined toguarantee that all the assembled elements are inside.After the checking space is identified, we need todecompose the space into a number of cells. How can weorganize these cells into proper structure and represent therelevant information to facilitate interaction checking? Inliterature, some