鉆套零件的工藝夾具設(shè)計(jì)

資源目錄里展示的全都有，所見(jiàn)即所得。下載后全都有,請(qǐng)放心下載。原稿可自行編輯修改=【QQ：401339828 或11970985 有疑問(wèn)可加】 河南工業(yè)職業(yè)技術(shù)學(xué)院 機(jī)床夾具設(shè)計(jì) 課程設(shè)計(jì)說(shuō)明書(shū) 設(shè)計(jì)題目：設(shè)計(jì)“鉆套夾具設(shè)計(jì)”鉆孔 班 級(jí) 設(shè) 計(jì) 者 指導(dǎo)教師 設(shè)計(jì)日期 目錄 序言 1 1夾具設(shè)計(jì)任務(wù)書(shū) 2 1.1零件 2 1.2技術(shù)要求分析 2 2確定夾具設(shè)計(jì)方案 2 2.1 基準(zhǔn)面選擇 2 2.2 定位方式 3 2.3夾緊方案、夾緊力計(jì)算 3 2.4分度方案 4 3夾具設(shè)計(jì) 4 3.1夾具圖上的尺寸、公差和技術(shù)要求 4 3.1.1夾具圖上技術(shù)要求標(biāo)注 4 3.1.2夾具圖上公差值的確定 4 3.2對(duì)刀方案確定 5 4誤差分析與計(jì)算 5 5主要零件的設(shè)計(jì)說(shuō)明 5 5.1夾具體 5 5.2其他元件 6 6夾具裝配要求 7 7夾具的使用維護(hù)要求 7 7.1夾具的使用 7 7.2夾具的使用維護(hù)要求 7 總結(jié) 8 參考文獻(xiàn) 9 夾具圖 10 夾具裝配圖 11 課程設(shè)計(jì)心得體會(huì) 12 序???言 機(jī)械制造業(yè)是制造具有一定形狀位置和尺寸的零件和產(chǎn)品，并把它們裝備成機(jī)械裝備的行業(yè)。機(jī)械制造業(yè)的產(chǎn)品既可以直接供人們使用，也可以為其它行業(yè)的生產(chǎn)提供裝備，社會(huì)上有著各種各樣的機(jī)械或機(jī)械制造業(yè)的產(chǎn)品。我們的生活離不開(kāi)制造業(yè)，因此制造業(yè)是國(guó)民經(jīng)濟(jì)發(fā)展的重要行業(yè)，是一個(gè)國(guó)家或地區(qū)發(fā)展的重要基礎(chǔ)及有力支柱。從某中意義上講，機(jī)械制造水平的高低是衡量一個(gè)國(guó)家國(guó)民經(jīng)濟(jì)綜合實(shí)力和科學(xué)技術(shù)水平的重要指標(biāo)。 鉆模的加工工藝規(guī)程及其，鉆孔的夾具設(shè)計(jì)是在學(xué)完了機(jī)械制圖、機(jī)械制造技術(shù)基礎(chǔ)、機(jī)械設(shè)計(jì)、機(jī)械工程材料等進(jìn)行課程設(shè)計(jì)之后的下一個(gè)教學(xué)環(huán)節(jié)。正確地解決一個(gè)零件在加工中的定位，夾緊以及工藝路線安排，工藝尺寸確定等問(wèn)題，并設(shè)計(jì)出專(zhuān)用夾具，保證零件的加工質(zhì)量。本次設(shè)計(jì)也要培養(yǎng)自己的自學(xué)與創(chuàng)新能力。因此本次設(shè)計(jì)綜合性和實(shí)踐性強(qiáng)、涉及知識(shí)面廣。所以在設(shè)計(jì)中既要注意基本概念、基本理論，又要注意生產(chǎn)實(shí)踐的需要，只有將各種理論與生產(chǎn)實(shí)踐相結(jié)合，才能很好的完成本次設(shè)計(jì)。本次設(shè)計(jì)水平有限，其中難免有缺點(diǎn)錯(cuò)誤，敬請(qǐng)老師們批評(píng)指正。 12 1 夾具設(shè)計(jì)任務(wù)書(shū) 1.1 零件圖 1.2 技術(shù)要求分析 零件的技術(shù)要求主要包括尺寸精度、形狀精度、位置精度、表面粗糙度要求等，這些技術(shù)要求應(yīng)當(dāng)是能夠保證零件使用性能前提下的極限值。進(jìn)行零件技術(shù)要求分析，主要是分析這些技術(shù)要求的合理性，以及實(shí)現(xiàn)的可能性，重點(diǎn)分析重要表面和部位的加工精度和技術(shù)要求，為制定合理的加工方案做好準(zhǔn)備。同時(shí)通過(guò)分析以確定技術(shù)要求是否過(guò)于嚴(yán)格，因?yàn)檫^(guò)高的精度和過(guò)小的表面粗糙度要求會(huì)使工藝過(guò)程變得復(fù)雜，加工難度大，增加不必要的成本。 從圖得知，該零件的部分尺寸精度要求較高，最高公差為0.06mm，在加工中可以達(dá)到此要求；該零件無(wú)形位公差要求，按照IT10—11進(jìn)行控制均可；零件的表面粗糙度要求不高，最高處才Ra3.2，在加工中很容易保證。 2 確定夾具設(shè)計(jì)方案 2.1 基準(zhǔn)面的選擇 由于零件有一個(gè)較大的中心孔，所以可以采用定位元件進(jìn)行定位,而又零件的下表面是設(shè)計(jì)基準(zhǔn),且已經(jīng)加工完,所以決定采用短銷(xiāo)和一平面進(jìn)行定位,短銷(xiāo)限制2個(gè)自由度分別為X方向和Y方向的自由度,而一平面限制3個(gè)自由度，分別為繞X轉(zhuǎn),繞Y轉(zhuǎn)和Z方向，而由于零件比較復(fù)雜所以用三個(gè)支撐釘來(lái)充當(dāng)一個(gè)平面，限制3個(gè)自由度，零件為Z方向加工孔，但不是中心孔，需要限制5個(gè)自由度，所以還需選擇一個(gè)繞Z方向旋轉(zhuǎn)的定位，而可以同過(guò)一個(gè)一個(gè)活動(dòng)型塊來(lái)通過(guò)來(lái)限制此自由度，選用的具體定位裝置見(jiàn)裝配圖。 加工一開(kāi)始，總是把用作精加工基準(zhǔn)的表面加工出來(lái)，因?yàn)槎ㄎ换鶞?zhǔn)的表面精確，裝夾誤差就小，所以任何零件的加工過(guò)程，總是先對(duì)定位基準(zhǔn)面進(jìn)行粗加工和半精加工，必要時(shí)還要進(jìn)行精加工，例如，軸類(lèi)零件總是對(duì)定位基準(zhǔn)面進(jìn)行粗加工和半精加工，再進(jìn)行精加工。例如軸類(lèi)零件總是先加工中心孔，再以中心孔面和定位孔為精基準(zhǔn)加工孔系和其他表面。如果精基準(zhǔn)面不止一個(gè)，則應(yīng)該按照基準(zhǔn)轉(zhuǎn)換的順序和逐步提高加工精度的原則來(lái)安排基準(zhǔn)面的加工。 2.2 定位方式 根據(jù)零件鉆孔的尺寸、形狀和位置嫉精度要求，工件定位時(shí)需限制5個(gè)自由度。工件的定位基準(zhǔn)和夾緊位置雖然在工序圖上已經(jīng)規(guī)定，但在擬定夾緊方案時(shí)，扔需要對(duì)其進(jìn)行分析研究，主要是考察定位基準(zhǔn)的選擇能否滿足工件位置精度的要求，夾具的結(jié)構(gòu)能否實(shí)現(xiàn)。 在鉆削的工序中，工件在鉆孔方向的工序基準(zhǔn)是和孔平行的面，若以此端面為定位基準(zhǔn)，可以達(dá)到與工序基準(zhǔn)想重合。但是，由于要在次面上鉆孔，那么夾具的定位面就要設(shè)計(jì)成另外一個(gè)面，這樣會(huì)給定位和夾緊帶來(lái)麻煩，夾具架構(gòu)也比較復(fù)雜。如果選擇與所加工孔的相對(duì)另一端面為定位基準(zhǔn)，則會(huì)引起基準(zhǔn)不重合誤差，其大小等于工件面端面之間的公差，考慮到孔的公差稍微大些，因此完全可以保證加工精度的要求。同時(shí)，這樣可以使定位夾緊可靠，操作方便，所以應(yīng)選擇工件底面為定位基準(zhǔn)，采用定位銷(xiāo)作為定位元件。 2.3 夾緊方案、夾緊力計(jì)算 根據(jù)夾緊力的方向應(yīng)朝向主要限位面以及作用點(diǎn)應(yīng)落在應(yīng)落在定位元件的支撐范圍內(nèi)的原則，夾緊力的作用線應(yīng)落在中間范圍內(nèi)，夾緊力與垂直的夾角應(yīng)盡量小，以保證夾緊穩(wěn)定可靠。 由于鉆套不是很長(zhǎng)，所以用一塊壓板夾緊。如果采用手動(dòng)夾緊，工件裝卸所花的時(shí)間較長(zhǎng)，不能適應(yīng)大批生產(chǎn)的要求。夾緊元件主要是定位銷(xiāo)，由于該工件較小，批量又不大，為使夾具結(jié)構(gòu)簡(jiǎn)單，采用了手動(dòng)的螺旋壓板夾緊機(jī)構(gòu)。 螺紋公稱(chēng)直徑d =10mm 螺紋中徑d2=9mm 手柄長(zhǎng)度L=120mm 作用力FQ=50N 計(jì)算的FW=9379N 2.4分度方案 由于4個(gè)通孔的對(duì)稱(chēng)度要求不高(未標(biāo)注公差)，設(shè)計(jì)一般精度的分度裝置即可。分度盤(pán)與定位心軸做成一體，在夾具體的回轉(zhuǎn)套中回轉(zhuǎn)，采用對(duì)定銷(xiāo)對(duì)定，鎖緊螺母鎖緊，結(jié)構(gòu)簡(jiǎn)單，動(dòng)作迅速可靠。 3 夾具設(shè)計(jì) 3.1夾具圖上的尺寸、公差和技術(shù)要求 3.1.1夾具圖上技術(shù)要求標(biāo)注 ?為了保證夾具制造和裝配后達(dá)到設(shè)計(jì)規(guī)定的精度要求，在設(shè)計(jì)圖上除了直接標(biāo)注尺寸公差和形位公差外，夾具總圖上無(wú)法用符合標(biāo)準(zhǔn)而又必須說(shuō)明的問(wèn)題，可作為技術(shù)要求用文字寫(xiě)在總圖上，習(xí)慣上把用文字說(shuō)明的夾具精度要求統(tǒng)稱(chēng)為技術(shù)條件。主要內(nèi)容有：? 1）夾具的裝配、調(diào)整方法。? 2）某些零件的重要表面應(yīng)一起加工。3）夾具表面上的裝飾要求。 4）夾具使用時(shí)的操作順序。 3.1.2夾具圖上公差值的確定 夾具總圖上標(biāo)注公差值的原則： 在滿足工件加工要求的前提下，盡量降低夾具的制造精度。直接影響工件加工精度的夾具公差δJ。取夾具總圖上的尺寸公差或δJ?=(1/2~1/5)?，式中δk一與δJ相應(yīng)的工件尺寸公差或位置公差。當(dāng)工件批量大、精度低時(shí)，δJ取小值，反之取最大。? 對(duì)于直接影響工件加工精度的配合尺寸，在確定了配合性質(zhì)后，應(yīng)盡量選用優(yōu)先配合。 ?工件的加工尺寸未注公差時(shí)，工件公差δk視為IT12~IT14，夾具上相應(yīng)的尺寸公差按IT9~IT11標(biāo)注；工件上的位置要求未注公差10，工件位置公差δk視為9~11級(jí)，夾具上的相應(yīng)位置公差按7~9級(jí)標(biāo)注；工件上加工角度未注公差時(shí)，工件公差δk視為±30~±10，夾具上相應(yīng)的角度公差標(biāo)為10~±3（相應(yīng)邊長(zhǎng)為10~400mm，邊長(zhǎng)短時(shí)取最大值）。??夾具上其他重要尺寸的公差與配合。以上各尺寸和公差、技術(shù)要求、公差值都在夾具體中和夾具裝備總圖中進(jìn)行了具體的標(biāo)注，詳見(jiàn)附錄中的夾具體圖樣和夾具裝配總圖。 3.2對(duì)刀方案的確定 本工序被加工的孔精度一般，主要保證孔和空的中心線通過(guò)大孔 Φ22h7中心等要求。夾具中采用對(duì)刀塊及塞尺的對(duì)刀裝置來(lái)調(diào)整鉆刀相對(duì)夾具的位置。其中，利用對(duì)刀塊的鉛垂對(duì)刀面級(jí)塞尺調(diào)整鉆刀，使其寬度方向的對(duì)稱(chēng)面通過(guò)圓柱銷(xiāo)的中心，從而保證該零件加工后能達(dá)到滿足要求。加工孔的鉆刀需要兩個(gè)方向?qū)Φ?，故采用直角?duì)刀塊。 4 誤差分析與計(jì)算 △D=△B+△Y,式中△D-定位誤差； △B-基準(zhǔn)不重合誤差； △Y-基準(zhǔn)位移誤差。 由于軸套孔的工序基準(zhǔn)是15和定位基準(zhǔn)是軸線，基準(zhǔn)不重合，△B=0.025；夾具中定位基準(zhǔn)面是Φ22軸線，所以存在基準(zhǔn)位移誤差：△Y=0.013mm 定位誤差：△B=0.025mm △D=△Y+△B=0.038mm 工件尺寸25mm公差按自由公差，取ITl2級(jí)，查表IT=0.21mm，所以加工公差=0.21mm,△D<／3,此定位方案可行。 因?yàn)槲覀兾覀円庸さ拿鏇](méi)有位置度要求，同時(shí)也沒(méi)有公差要求，因此一般的定位都能滿足要求，需要考慮如何提高生產(chǎn)效率。 5 主要零件的設(shè)計(jì)說(shuō)明 5.1 夾具體 選用鑄造夾具體，夾具體是夾具中的基礎(chǔ)元件，它所有的元件的支撐面，分度盤(pán)的鎖緊裝置在夾具體的下方，因此夾具體下方要挖出槽來(lái)。 夾緊力分析：夾緊力是保證定位穩(wěn)定,夾具可行的因素.夾緊力不能太小，否則加工時(shí)容易發(fā)生工件位移而破壞定位。夾緊力也不太過(guò)大，否則工件易變形，增大結(jié)構(gòu)尺寸。本次鉆孔孔徑較小，所需夾緊力較??；綜合考慮加工因素，選用M10的夾緊螺母，能夠滿足夾緊要求。 5.2 其他元件 6 夾具裝配要求 (1)總裝配圖應(yīng)按國(guó)家標(biāo)準(zhǔn)盡可能1:1的繪制，這樣圖樣有良好的直觀性。主視圖應(yīng)按操作實(shí)際位置布置，三制圖要能完整清出表示出夾具的工作原理和結(jié)構(gòu)。 (2)視工件為透明體，用雙點(diǎn)畫(huà)線畫(huà)出主要部件。畫(huà)出定位元件、夾緊機(jī)構(gòu)、導(dǎo)向裝置的位置。 （3）按照夾緊狀態(tài)畫(huà)出夾緊元件和夾緊機(jī)構(gòu)。 （4）標(biāo)注主要的尺寸、配合、公差等。 7 夾具的使用維護(hù)要求 7.1夾具的使用要求 （1）使用前對(duì)限位尺寸檢查是否還保持正確位置； （2）如果擋銷(xiāo)磨損超差，可以進(jìn)行打磨修復(fù)；如果擋板、插銷(xiāo)、定位錐頭銷(xiāo)磨損超差，可以重新組裝，錯(cuò)開(kāi)磨損部位后繼續(xù)使用； （3）使用后需要涂防銹油 （4）夾具應(yīng)清潔定位面，不許積聚污垢和其他銹蝕物，夾緊時(shí)要求平穩(wěn)，不使工件移位 7.2夾具的維護(hù)要求 常用的夾具，要保護(hù)定位面不被劃傷，兩件夾具可定期放到平面磨床上磨平修整，使二者保持等高。對(duì)于夾具絕緣性的測(cè)定也應(yīng)注意，尤其是絕緣夾層用吸水性較大的材料制成的夾具. 總 結(jié) 一周的課程設(shè)計(jì)結(jié)束了，時(shí)間雖然短暫但是它對(duì)我們來(lái)說(shuō)受益菲淺的，通過(guò)這次的設(shè)計(jì)使我們不再是只知道書(shū)本上的空理論，不再是紙上談兵，而是將理論和實(shí)踐相結(jié)合進(jìn)行實(shí)實(shí)在在的設(shè)計(jì)，使我們不但鞏固了理論知識(shí)而且掌握了設(shè)計(jì)的步驟和要領(lǐng)，使我們更好的利用圖書(shū)館的資料，更好的更熟練的利用我們手中的各種設(shè)計(jì)手冊(cè)和AUTOCAD等制圖軟件，為我們踏入設(shè)計(jì)打下了好的基礎(chǔ)。 在這次的課程設(shè)計(jì)中不僅檢驗(yàn)了我所學(xué)習(xí)的知識(shí)，也培養(yǎng)了我如何去把握一件事情，如何去做一件事情，又如何完成一件事情。在設(shè)計(jì)過(guò)程中，與同學(xué)商量分析，和同學(xué)相互探討，相互學(xué)習(xí)，相互監(jiān)督。學(xué)會(huì)了合作，學(xué)會(huì)了寬容，學(xué)會(huì)了理解。 課程設(shè)計(jì)是我們專(zhuān)業(yè)課程知識(shí)綜合應(yīng)用的實(shí)踐訓(xùn)練，這是我們邁向社會(huì)，從事職業(yè)工作前一個(gè)必不少的過(guò)程。我今天認(rèn)真的進(jìn)行課程設(shè)計(jì)，學(xué)會(huì)腳踏實(shí)地邁開(kāi)這一步，就是為明天穩(wěn)健地在社會(huì)大潮中奔跑打下堅(jiān)實(shí)的基礎(chǔ)。通過(guò)這次夾具設(shè)計(jì)，本人在多方面有所提高。通過(guò)這次夾具設(shè)計(jì)，綜合運(yùn)用本專(zhuān)業(yè)所學(xué)課程的理論和提高學(xué)生獨(dú)立工作能力，鞏固與擴(kuò)充了鉆模夾具設(shè)計(jì)等課程所學(xué)內(nèi)容，掌握了鉆模夾具設(shè)計(jì)的方法和步驟，掌握了鉆模夾具設(shè)計(jì)的基本的夾具技能懂得了怎樣分析零件的工藝性，怎樣確定工藝方案，了解了夾具的基本結(jié)構(gòu)，提高了計(jì)算能力，繪圖能力，熟悉了規(guī)范和標(biāo)準(zhǔn)，同時(shí)各科相關(guān)的課程都有了全面的復(fù)習(xí)，獨(dú)立思考的能力也有了提高。 課程設(shè)計(jì)使我們認(rèn)識(shí)到了努力的學(xué)好書(shū)本上的知識(shí)是不夠的，還應(yīng)該更好的做到理論和實(shí)踐的結(jié)合。因此同學(xué)們非常感謝老師給我們的辛勤指導(dǎo)，使我們學(xué)到了好多，也非常珍惜學(xué)院給我們的這次設(shè)計(jì)的機(jī)會(huì)，它將是我們將來(lái)走向工作崗位的更出色的關(guān)鍵一步。 參考資料 1.切削用量簡(jiǎn)明手冊(cè),艾興、肖詩(shī)綱主編,機(jī)械工業(yè)出版社出版，1994年 2.機(jī)械制造工藝設(shè)計(jì)簡(jiǎn)明手冊(cè)，李益民主編，機(jī)械工業(yè)出版社出版，1994年 3.機(jī)床夾具設(shè)計(jì)，機(jī)械工業(yè)大學(xué)、上海工業(yè)大學(xué)主編、上?；瘜W(xué)工業(yè)出版社、上?？茖W(xué)技術(shù)出版社出版，1983年 4.機(jī)床夾具設(shè)計(jì)手冊(cè)，東北重型機(jī)械學(xué)院、洛陽(yáng)工學(xué)院、一汽制造廠職工大學(xué)編，上海科學(xué)技術(shù)出版社出版，1990年 5.金屬機(jī)械加工工藝人員手冊(cè)，上?？茖W(xué)技術(shù)出版社，1981年10月 6.機(jī)械制造工藝學(xué)，郭宗連、秦寶榮主編，中國(guó)建材工業(yè)出版社出版，1997年 7.趙家奇,機(jī)械制造工藝學(xué)課程設(shè)計(jì)指導(dǎo)書(shū)(2版),機(jī)械工業(yè)出版社,2006年.? 8.曾志新,呂明主編,機(jī)械制造技術(shù)基礎(chǔ),:武漢理工大學(xué)出版社,2001年.? 9.李益明主編,機(jī)械制造工藝設(shè)計(jì)簡(jiǎn)明手冊(cè)機(jī)械工業(yè)出版社,1993年.? 9.肖詩(shī)綱主編,切削用量手冊(cè),機(jī)械工業(yè)出版社,1993年.? 10.金屬切削機(jī)床夾具設(shè)計(jì)手冊(cè).上海柴油機(jī)廠工藝設(shè)備研究所編,機(jī)械工業(yè)出版社， 1987年 3課程設(shè)計(jì)心得體會(huì) 我所選課程設(shè)計(jì)題題目是“鉆模夾具鉆孔”，對(duì)于我自己來(lái)說(shuō)，它是很具有的挑戰(zhàn)性的，總覺(jué)得自己所學(xué)到的知識(shí)很欠缺，但是越是自己薄弱的環(huán)節(jié)越要有勇氣去嘗試。在課程設(shè)計(jì)的工藝設(shè)計(jì)的過(guò)程中，因?yàn)闆](méi)有真正的工作經(jīng)驗(yàn)，在做夾具設(shè)計(jì)的工程中總覺(jué)得很辛苦，有時(shí)還會(huì)產(chǎn)生放棄的念頭，但是最終堅(jiān)持了下來(lái)，完成了我的課程設(shè)計(jì)，為了自己的目標(biāo)，更為了自己的選擇。在指導(dǎo)老師的指點(diǎn)下，我開(kāi)始通過(guò)各種渠道翻閱資料。接下來(lái)，我開(kāi)始對(duì)所搜集的資料進(jìn)行整理、分析研究，解決設(shè)計(jì)中的問(wèn)題，最終在短暫的一周時(shí)間內(nèi)順利完成任務(wù)。 通過(guò)這次的課程設(shè)計(jì)，使我深深體會(huì)到，干任何事情都必須認(rèn)真、耐心、細(xì)致。課程設(shè)計(jì)過(guò)程中，許多計(jì)算有時(shí)候令我感到有些心煩意亂，有幾次因?yàn)槭韬?，?shù)據(jù)算錯(cuò)，只能毫不留情地重新來(lái)。但一想起老師平時(shí)對(duì)我們耐心的教導(dǎo)，想到不久的將來(lái)自己就要承擔(dān)社會(huì)責(zé)任，想到世界上有好多因?yàn)楹苄〉募?xì)節(jié)失誤而出現(xiàn)的令人無(wú)比震驚的事故，無(wú)時(shí)不在提醒著自己，一定要養(yǎng)成一種高度負(fù)責(zé)、一絲不茍的良好習(xí)慣。 至此，我衷心的感謝老師。是你的嚴(yán)厲批評(píng)喚醒了我，是您的諄諄教誨啟發(fā)了我，我感謝老師您今天又為我增添了一副堅(jiān)強(qiáng)的翅膀。 Robotics and Computer-Integrated Manufacturing 21 (2005) 368378Locating completeness evaluation and revision in fixture planH. Song?, Y. RongCAM Lab, Department of Mechanical Engineering, Worcester Polytechnic Institute, 100 Institute Rd, Worcester, MA 01609, USAReceived 14 September 2004; received in revised form 9 November 2004; accepted 10 November 2004AbstractGeometry constraint is one of the most important considerations in fixture design. Analytical formulation of deterministiclocation has been well developed. However, how to analyze and revise a non-deterministic locating scheme during the process ofactual fixture design practice has not been thoroughly studied. In this paper, a methodology to characterize fixturing systemsgeometry constraint status with focus on under-constraint is proposed. An under-constraint status, if it exists, can be recognizedwith given locating scheme. All un-constrained motions of a workpiece in an under-constraint status can be automatically identified.This assists the designer to improve deficit locating scheme and provides guidelines for revision to eventually achieve deterministiclocating.r 2005 Elsevier Ltd. All rights reserved.Keywords: Fixture design; Geometry constraint; Deterministic locating; Under-constrained; Over-constrained1. IntroductionA fixture is a mechanism used in manufacturing operations to hold a workpiece firmly in position. Being a crucialstep in process planning for machining parts, fixture design needs to ensure the positional accuracy and dimensionalaccuracy of a workpiece. In general, 3-2-1 principle is the most widely used guiding principle for developing a locationscheme. V-block and pin-hole locating principles are also commonly used.A location scheme for a machining fixture must satisfy a number of requirements. The most basic requirement is thatit must provide deterministic location for the workpiece 1. This notion states that a locator scheme producesdeterministic location when the workpiece cannot move without losing contact with at least one locator. This has beenone of the most fundamental guidelines for fixture design and studied by many researchers. Concerning geometryconstraint status, a workpiece under any locating scheme falls into one of the following three categories:1. Well-constrained (deterministic): The workpiece is mated at a unique position when six locators are made to contactthe workpiece surface.2. Under-constrained: The six degrees of freedom of workpiece are not fully constrained.3. Over-constrained: The six degrees of freedom of workpiece are constrained by more than six locators.In 1985, Asada and By 1 proposed full rank Jacobian matrix of constraint equations as a criterion and formed thebasis of analytical investigations for deterministic locating that followed. Chou et al. 2 formulated the deterministiclocating problem using screw theory in 1989. It is concluded that the locating wrenches matrix needs to be full rank toachieve deterministic location. This method has been adopted by numerous studies as well. Wang et al. 3 consideredARTICLE IN PRESS front matter r 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.rcim.2004.11.012?Corresponding author. Tel.: +15088316092; fax: +15088316412.E-mail address: hsongwpi.edu (H. Song).locatorworkpiece contact area effects instead of applying point contact. They introduced a contact matrix andpointed out that two contact bodies should not have equal but opposite curvature at contacting point. Carlson 4suggested that a linear approximation may not be sufficient for some applications such as non-prismatic surfaces ornon-small relative errors. He proposed a second-order Taylor expansion which also takes locator error interaction intoaccount. Marin and Ferreira 5 applied Chous formulation on 3-2-1 location and formulated several easy-to-followplanning rules. Despite the numerous analytical studies on deterministic location, less attention was paid to analyzenon-deterministic location.In the Asada and Bys formulation, they assumed frictionless and point contact between fixturing elements andworkpiece. The desired location is q*, at which a workpiece is to be positioned and piecewisely differentiable surfacefunction is gi(as shown in Fig. 1).The surface function is defined as giq? 0: To be deterministic, there should be a unique solution for the followingequation set for all locators.giq 0;i 1;2;.;n,(1)where n is the number of locators and q x0;y0;z0;y0;f0;c0? represents the position and orientation of theworkpiece.Only considering the vicinity of desired location q?; where q q? Dq; Asada and By showed thatgiq giq? hiDq,(2)where hiis the Jacobian matrix of geometry functions, as shown by the matrix in Eq. (3). The deterministic locatingrequirement can be satisfied if the Jacobian matrix has full rank, which makes the Eq. (2) to have only one solutionq q?:rankqg1qx0qg1qy0qg1qz0qg1qy0qg1qf0qg1qc0:qgiqx0qgiqy0qgiqz0qgiqy0qgiqf0qgiqc0:qgnqx0qgnqy0qgnqz0qgnqy0qgnqf0qgnqc026666666664377777777758:9=; 6.(3)Upon given a 3-2-1 locating scheme, the rank of a Jacobian matrix for constraint equations tells the constraint statusas shown in Table 1. If the rank is less than six, the workpiece is under-constrained, i.e., there exists at least one freemotion of the workpiece that is not constrained by locators. If the matrix has full rank but the locating scheme hasmore than six locators, the workpiece is over-constrained, which indicates there exists at least one locator such that itcan be removed without affecting the geometry constrain status of the workpiece.For locating a model other than 3-2-1, datum frame can be established to extract equivalent locating points. Hu 6has developed a systematic approach for this purpose. Hence, this criterion can be applied to all locating schemes.ARTICLE IN PRESSX Y Z O X Y Z O (x0,y0,z0) gi UCS WCS Workpiece Fig. 1. Fixturing system model.H. Song, Y. Rong / Robotics and Computer-Integrated Manufacturing 21 (2005) 368378369Kang et al. 7 followed these methods and implemented them to develop a geometry constraint analysis module intheir automated computer-aided fixture design verification system. Their CAFDV system can calculate the Jacobianmatrix and its rank to determine locating completeness. It can also analyze the workpiece displacement and sensitivityto locating error.Xiong et al. 8 presented an approach to check the rank of locating matrix WL(see Appendix). They also intro-duced left/right generalized inverse of the locating matrix to analyze the geometric errors of workpiece. It hasbeen shown that the position and orientation errors DX of the workpiece and the position errors Dr of locators arerelated as follows:Well-constrained :DX WLDr,(4)Over-constrained :DX WTLWL?1WTLDr,(5)Under-constrained :DX WTLWLWTL?1Dr I6?6? WTLWLWTL?1WLl,(6)where l is an arbitrary vector.They further introduced several indexes derived from those matrixes to evaluate locator configurations, followed byoptimization through constrained nonlinear programming. Their analytical study, however, does not concern therevision of non-deterministic locating. Currently, there is no systematic study on how to deal with a fixture design thatfailed to provide deterministic location.2. Locating completeness evaluationIf deterministic location is not achieved by designed fixturing system, it is as important for designers to knowwhat the constraint status is and how to improve the design. If the fixturing system is over-constrained, informa-tion about the unnecessary locators is desired. While under-constrained occurs, the knowledge about all the un-constrained motions of a workpiece may guide designers to select additional locators and/or revise the locatingscheme more efficiently. A general strategy to characterize geometry constraint status of a locating scheme is describedin Fig. 2.In this paper, the rank of locating matrix is exerted to evaluate geometry constraint status (see Appendixfor derivation of locating matrix). The deterministic locating requires six locators that provide full rank locatingmatrix WL:As shown in Fig. 3, for given locator number n; locating normal vector ai;bi;ci? and locating position xi;yi;zi? foreach locator, i 1;2;.;n; the n ? 6 locating matrix can be determined as follows:WLa1b1c1c1y1? b1z1a1z1? c1x1b1x1? a1y1:aibiciciyi? biziaizi? cixibixi? aiyi:anbncncnyn? bnznanzn? cnxnbnxn? anyn2666666437777775.(7)When rankWL 6 and n 6; the workpiece is well-constrained.When rankWL 6 and n46; the workpiece is over-constrained. This means there are n ? 6 unnecessary locatorsin the locating scheme. The workpiece will be well-constrained without the presence of those n ? 6 locators. Themathematical representation for this status is that there are n ? 6 row vectors in locating matrix that can be expressedas linear combinations of the other six row vectors. The locators corresponding to that six row vectors consist oneARTICLE IN PRESSTable 1RankNumber of locatorsStatuso 6Under-constrained 6 6Well-constrained 646Over-constrainedH. Song, Y. Rong / Robotics and Computer-Integrated Manufacturing 21 (2005) 368378370locating scheme that provides deterministic location. The developed algorithm uses the following approach todetermine the unnecessary locators:1. Find all the combination of n ? 6 locators.2. For each combination, remove that n ? 6 locators from locating scheme.3. Recalculate the rank of locating matrix for the left six locators.4. If the rank remains unchanged, the removed n ? 6 locators are responsible for over-constrained status.This method may yield multi-solutions and require designer to determine which set of unnecessary locators shouldbe removed for the best locating performance.When rankWLo6; the workpiece is under-constrained.3. Algorithm development and implementationThe algorithm to be developed here will dedicate to provide information on un-constrained motions of theworkpiece in under-constrained status. Suppose there are n locators, the relationship between a workpieces position/ARTICLE IN PRESSFig. 2. Geometry constraint status characterization.X Z Y (a1,b1,c1) 2,b2,c2) (x1,y1,z1) (x2,y2,z2) (ai,bi,ci) (xi,yi,zi) (aFig. 3. A simplified locating scheme.H. Song, Y. Rong / Robotics and Computer-Integrated Manufacturing 21 (2005) 368378371orientation errors and locator errors can be expressed as follows:DX DxDyDzaxayaz2666666666437777777775w11:w1i:w1nw21:w2i:w2nw31:w3i:w3nw41:w4i:w4nw51:w5i:w5nw61:w6i:w6n2666666666437777777775?Dr1:Dri:Drn2666666437777775,(8)where Dx;Dy;Dz;ax;ay;azare displacement along x, y, z axis and rotation about x, y, z axis, respectively. Driisgeometric error of the ith locator. wijis defined by right generalized inverse of the locating matrix Wr WTLWLWTL?15.To identify all the un-constrained motions of the workpiece, V dxi;dyi;dzi;daxi;dayi;dazi? is introduced such thatV DX 0.(9)Since rankDXo6; there must exist non-zero V that satisfies Eq. (9). Each non-zero solution of V represents an un-constrained motion. Each term of V represents a component of that motion. For example, 0;0;0;3;0;0? says that therotation about x-axis is not constrained. 0;1;1;0;0;0? means that the workpiece can move along the direction given byvector 0;1;1?: There could be infinite solutions. The solution space, however, can be constructed by 6 ? rankWLbasic solutions. Following analysis is dedicated to find out the basic solutions.From Eqs. (8) and (9)VX dxDx dyDy dzDz daxDax dayDay dazDaz dxXni1w1iDri dyXni1w2iDri dzXni1w3iDri daxXni1w4iDri dayXni1w5iDri dazXni1w6iDriXni1Vw1i;w2i;w3i;w4i;w5i;w6i?TDri 0.10Eq. (10) holds for 8Driif and only if Eq. (11) is true for 8i1pipn:Vw1i;w2i;w3i;w4i;w5i;w6i?T 0.(11)Eq. (11) illustrates the dependency relationships among row vectors of Wr: In special cases, say, all w1jequal to zero,V has an obvious solution 1, 0, 0, 0, 0, 0, indicating displacement along the x-axis is not constrained. This is easy tounderstand because Dx 0 in this case, implying that the corresponding position error of the workpiece is notdependent of any locator errors. Hence, the associated motion is not constrained by locators. Moreover, a combinedmotion is not constrained if one of the elements in DX can be expressed as linear combination of other elements. Forinstance, 9w1ja0;w2ja0; w1j ?w2jfor 8j: In this scenario, the workpiece cannot move along x- or y-axis. However, itcan move along the diagonal line between x- and y-axis defined by vector 1, 1, 0.To find solutions for general cases, the following strategy was developed:1. Eliminate dependent row(s) from locating matrix. Let r rank WL; n number of locator. If ron; create a vectorin n ? r dimension space U u1:uj:un?rhi1pjpn ? r; 1pujpn: Select ujin the way that rankWL r still holds after setting all the terms of all the ujth row(s) equal to zero. Set r ? 6 modified locating matrixWLMa1b1c1c1y1? b1z1a1z1? c1x1b1x1? a1y1:aibiciciyi? biziaizi? cixibixi? aiyi:anbncncnyn? bnznanzn? cnxnbnxn? anyn2666666437777775r?6,where i 1;2;:;niauj:ARTICLE IN PRESSH. Song, Y. Rong / Robotics and Computer-Integrated Manufacturing 21 (2005) 3683783722. Compute the 6 ? n right generalized inverse of the modified locating matrixWr WTLMWLMWTLM?1w11:w1i:w1rw21:w2i:w2rw31:w3i:w3rw41:w4i:w4rw51:w5i:w5rw61:w6i:w6r26666666664377777777756?r3. Trim Wrdown to a r ? rfull rank matrix Wrm: r rankWLo6: Construct a 6 ? r dimension vector Q q1:qj:q6?rhi1pjp6 ? r; 1pqjpn: Select qjin the way that rankWr r still holds after setting all theterms of all the qjth row(s) equal to zero. Set r ? r modified inverse matrixWrmw11:w1i:w1r:wl1:wli:wlr:w61:w6i:w6r26666664377777756?6,where l 1;2;:;6 laqj:4. Normalize the free motion space. Suppose V V1;V2;V3;V4;V5;V6? is one of the basic solutions of Eq. (10) withall six terms undetermined. Select a term qkfrom vector Q1pkp6 ? r: SetVqk ?1;Vqj 0 j 1;2;:;6 ? r;jak;(5. Calculated undetermined terms of V: V is also a solution of Eq. (11). The r undetermined terms can be found asfollows.v1:vs:v62666666437777775wqk1:wqki:wqkr2666666437777775?w11:w1i:w1r:wl1:wli:wlr:w61:w6i:w6r2666666437777775?1,where s 1;2;:;6saqj;saqk;l 1;2;:;6 laqj:6. Repeat step 4 (select another term from Q) and step 5 until all 6 ? r basic solutions have been determined.Based on this algorithm, a C+ program was developed to identify the under-constrained status and un-constrained motions.Example 1. In a surface grinding operation, a workpiece is located on a fixture system as shown in Fig. 4. The normalvector and position of each locator are as follows:L1:0, 0, 10, 1, 3, 00,L2:0, 0, 10, 3, 3, 00,L3:0, 0, 10, 2, 1, 00,L4:0, 1, 00, 3, 0, 20,L5:0, 1, 00, 1, 0, 20.Consequently, the locating matrix is determined.WL0013?100013?300011?20010?203010?2012666666437777775.ARTICLE IN PRESSH. Song, Y. Rong / Robotics and Computer-Integrated Manufacturing 21 (2005) 368378373This locating system provides under-constrained positioning since rankWL 5o6: The program then calculatesthe right generalized inverse of the locating matrix.Wr000000:50:5?1?0:51:50:75?1:251:5000:250:25?0:5000:5?0:50000000:5?0:526666666643777777775.The first row is recognized as a dependent row because removal of this row does not affect rank of the matrix. Theother five rows are independent rows. A linear combination of the independent rows is found according therequirement in step 5 of the procedure for under-constrained status. The solution for this special case is obvious that allthe coefficients are zero. Hence, the un-constrained motion of workpiece can be determined as V ?1; 0; 0; 0; 0; 0?:This indicates that the workpiece can move along x direction. Based on this result, an additional locator should beemployed to constraint displacement of workpiece along x-axis.Example 2. Fig. 5 shows a knuckle with 3-2-1 locating system. The normal vector and position of each locator in thisinitial design are as follows:L1:0, 1, 00, 896, ?877, ?5150,L2:0, 1, 00, 1060, ?875, ?3780,L3:0, 1, 00, 1010, ?959, ?6120,L4:0.9955, ?0.0349, 0.0880, 977, ?902, ?6240,L5:0.9955, ?0.0349, 0.0880, 977, ?866, ?6240,L6:0.088, 0.017, ?0.9960, 1034, ?864, ?3590.The locating matrix of this configuration isWL010515:000:8960010378:001:0600010612:001:01000:9955?0:03490:0880?101:2445?707:26640:86380:9955?0:03490:0880?98:0728?707:26640:82800:08800:0170?0:9960866:6257998:24660:093626666666643777777775,rankWL 5o6 reveals that the workpiece is under-constrained. It is found that one of the first five rows can beremoved without varying the rank of locating matrix. Suppose the first row, i.e., locator L1is removed from WL; theARTICLE IN PRESSXZYL3L4L5L2L1Fig. 4. Under-constrained locating scheme.H. Song, Y. Rong / Robotics and Computer-Integrated Manufacturing 21 (2005) 368378374modified locating matrix turns intoWLM010378:001:0600010612:001:01000:9955?0:03490:0880?101:2445?707:26640:86380:9955?0:03490:0880?98:0728?707:26640:82800:08800:0170?0:996866:6257998:24660:09362666666437777775.The right generalized inverse of the modified locating matrix isWr1:8768?1:8607?20:666521:37160:49953:0551?2:0551?32:444832:44480?1:09561:086212:0648?12:4764?0:2916?0:00440:00440:0061?0:006100:0025?0:00250:0065?0:00690:0007?0:00040:00040:0284?0:0284026666666643777777775.The program checked the dependent row and found every row is dependent on other five rows. Without losinggenerality, the first row is regarded as dependent row. The 5 ? 5 modified inverse matrix isWrm3:0551?2:0551?32:444832:44480?1:09561:086212:0648?12:4764?0:2916?0:00440:00440:0061?0:006100:0025?0:00250:0065?0:00690:0007?0:00040:00040:0284?0:028402666666437777775.The undetermined solution is V ?1; v2; v3; v4; v5; v6?:To calculate the five undetermined terms of V according to step 5,1:8768?1:8607?20:666521:37160:499526666666643777777775T?3:0551?2:0551?32:444832:44480?1:09561:086212:0648?12:4764?0:2916?0:00440:00440:0061?0:006100:0025?0:00250:0065?0:00690:0007?0:00040:00040:0284?0:0284026666666643777777775?1 0; ?1:713; ?0:0432; ?0:0706; 0:04?.Substituting this result into the undetermined solution yields V ?1;0; ?1:713; ?0:0432; ?0:0706; 0:04?ARTICLE IN PRESSFig. 5. Knuckle 610 (modified from real design).H. Song, Y. Rong / Robotics and Computer-Integrated Manufacturing 21 (2005) 368378375This vector represents a free motion defined by the combination of a displacement along ?1, 0, ?1.713 directioncombined and a rotation about ?0.0432, ?0.0706, 0.04. To revise this locating configuration, another locator shouldbe added to constrain this free motion of the workpiece, assuming locator L1was removed in step 1. The program canalso calculate the free motions of the workpiece if a locator other than L1was removed in step 1. This provides morerevision options for designer.4. SummaryDeterministic location is an important requirement for fixture locating scheme design. Analytical criterion fordeterministic status has been well established. To further study non-deterministic status, an algorithm for checking thegeometry constraint status has been developed. This algorithm can identify an under-constrained status and indicatethe un-constrained motions of workpiece. It can also recognize an over-constrained status and unnecessary locators.The output information can assist designer to analyze and improve an existing locating scheme.Appendix. Locating matrixConsider a general workpiece as shown in Fig. 6. Choose reference frame fWg fixed to the workpiece. Let fGg andfLig be the global frame and the ith locator frame fixed relative to it. We haveFiXw;Hw;rwi fiXli;Hli;rli,(12)where Xw2 3?1and Hw2 3?1(Xli2 3?1and Hli2 3?1) are the position and orientation of the workpiece(the ith locator) in the global frame fGg; rwi2 3?1(rli2 3?1) is the position of the ith contact point between theworkpiece and the ith locator in the workpiece frame fWg (the ith locator frame fLig).Assume that DXw2 3?1(DHw2 3?1) and Drwi2 3?1are the deviations of the position Xw2 3?1(orientationHw2 3?1) of the workpiece and the position of the ith contact point rwi2 3?1; respectively. Then we have the actualcontact on the wor