活動塊零件的機械加工工藝及鉆孔夾具設(shè)計【鉆φ20孔】【說明書+CAD】,鉆φ20孔,說明書+CAD,活動塊零件的機械加工工藝及鉆孔夾具設(shè)計【鉆φ20孔】【說明書+CAD】,活動,零件,機械,加工,工藝,鉆孔,夾具,設(shè)計,20,說明書,CAD 機械制造技術(shù)基礎(chǔ) 課程設(shè)計說明書 設(shè) 計 者： 指導教師： 學 號： 0405110076 班 級： 04級機制3班 機械制造技術(shù)基礎(chǔ)課程設(shè)計任務(wù)書 設(shè)計題目 活動塊 活動塊鉆孔的夾具 內(nèi)容： 1.零件圖 1張 2.毛坯圖 1張 3. 機械加工工藝過程綜合卡片 1張 4. 鉆床夾具裝配圖 1張 5. 鉆床夾具零件圖 1張 6. 課程設(shè)計說明書 1份 機械制造課程設(shè)計 目 錄 一、零件的分析………………………………………………2 零件的工藝分析……………………………………………………2 二、工藝規(guī)程設(shè)計……………………………………………2 （一)確定毛坯的制造形式…………………………………………………2 （二）基面的選擇…………………………………………………………2 （三）制定工藝路線………………………………………………………3 （四）機械加工余量、工序尺寸及毛皮尺寸的確定 …………………4 三、夾具設(shè)計…………………………………………………11 （一）問題的提出 …………………………………………………………11 （二）卡具設(shè)計………………………………………………………………11 （三）夾具零件………………………………………………………………12 四、設(shè)計體會………………………………………………13 五、參考文獻…………………………………………………14 序 言 機械制造技術(shù)基礎(chǔ)課程設(shè)計是在學完了大學的全部基礎(chǔ)課、技術(shù)基礎(chǔ)課以及大部分專業(yè)課之后進行的.是進行畢業(yè)設(shè)計之前對所學各課程的一次深入的綜合性的總復習,也是一次理論聯(lián)系實際的訓練,因此,它在我們四年的大學生活中占有重要的地位。 希望能通過這次課程設(shè)計對我們未來將從事的工作進行一次適應(yīng)性訓練，從中鍛煉我們的分析問題、解決問題的能力，為今后參加工作打下一個良好的基礎(chǔ)。 一、 零件的分析 (一)零件的工藝分析 活動塊共有三組加工表面,它們這間有一定的位置要求.現(xiàn)分析如下: 1. 以左端面為基面的加工表面 這一組加工表面包括:右端面,前后端面,前后端面上的槽,及和22 30的方孔其中這個孔為主要加工面. 2. 以右端面為基面的加工表面 這一組加工表面包括:左端面,寬為15的槽, 的孔,下端半圓柱面,及車M6螺紋孔 這這兩組加工表面之間有著一定位置要求,主要是: (1) 與左端面的垂直度公差為0.05mm, (2) 與左端面的平行度公差為0.1mm (3)左端面與右端面的公平度公差0.12mm 由以上分析可知,對于這兩組加工表面而言,可以先加工其中一組表成,然后借助于專用夾具加工另一組表面,并且保證它們之間的位置精度要求. 二、工藝規(guī)程設(shè)計 (一)確定毛坯的制造形式 零件材料為HT200，零件為活動塊, 屬于大批量生產(chǎn)，零件結(jié)構(gòu)又比較簡單，故選擇鑄件毛坯。 （二）基面的選擇 基面選擇是工藝規(guī)程設(shè)計中的重要工作之一?；孢x擇得正確與合理可以使加工質(zhì)量得到保證，生產(chǎn)率得以提高。否則，加工工藝過程中回問題百出，更有甚者，還會造成零件的大批報廢，使生產(chǎn)無法正常進行。 （1）粗基準的選擇。對于零件而言，盡可能選擇不加工表面為粗基準。而對有若干個不加工表面的工件，則應(yīng)以與加工表面要求相對位置精度較高的不加工表面作粗基準。根據(jù)這個基準選擇原則，現(xiàn)選取工件左端面作為粗基準。因為這個零件是長方體類的零件,可以用通用夾具來定位（如臺虎鉗），實現(xiàn)了完全定位，然后進行銑削。 （2）精基準的選擇。主要應(yīng)該考慮基準重合的問題。當設(shè)計基準與工序基準不重合時，應(yīng)該進行尺寸換算，這在以后還要專門計算，此處不再重復。 (三） 制定工藝路線 制定工藝路線得出發(fā)點,應(yīng)當是使零件的幾何形狀、尺寸精度及位置精度等技術(shù)要求能得到合理的保證,在生產(chǎn)綱領(lǐng)已確定的情況下,可以考慮采用萬能性機床配以專用工卡具,并盡量使工序集中來提高生產(chǎn)率。除此之外，還應(yīng)當考慮經(jīng)濟效果，以便使生產(chǎn)成本盡量下降。 1.工藝路線方案一 工序一銑左端面,右端面,銑前后端面,銑前后面的槽,銑下半圓 工序二 插的孔 工序三 鉆的孔 工序四 鏜的孔 工序五 銑15的槽 工序六 鉆M6的孔 工序七 鏜的孔 工序八 鉆的孔 工序九 車M6的螺紋. 工序十 檢查 上面工序加工效率較高，但同時鉆三個孔，對設(shè)備有一定要求。且看另一個方案。 2.工藝路線方案二 工序一 銑左端面,右端面,銑前后端面,銑前后面的槽,銑下半圓銑15的槽 工序二 銑15的槽 工序三 鉆20的孔鏜的孔 工序四 鏜的孔 工序五 鉆M6的孔 工序六 車M6的螺紋 工序七 鉆的孔 工序八 鉸的孔插30 22的孔 工序九 插30 22的孔 工序十 檢查 上面工序可以適合大多數(shù)生產(chǎn)，但效率較低。 綜合考慮以上步驟，得到我的工藝路線。 3.工藝路線方案三 工序一 以右端面為精基準，銑左端面。以后端面粗基準,銑前端面，以前端面為精基準，銑后端面，分別以前后端面為精基準銑前后端面的槽及下半圓 工序二 以左端面為精基準，插30 22的孔 工序三 以30 22為精基準，鉆的孔 工序四 以左端面為精基準，鉆的孔。 工序五 以左端面為精基準，鉆M6的孔。 工序六 以左端面為精基準，車M6的螺紋.. 工序七 以30 22為精基準，鉸的孔. 工序八 以左端面為精基準，鏜的孔 工序九 以30 22為精基準，銑15的槽 工序十 檢查 雖然工序仍然是十步，但是效率大大提高了。工序一和工序二比起工藝路線方案二快了一倍（實際銑削只有兩次，而且刀具不用調(diào)整）。多次加工φ20孔是精度要求所致。 以上工藝過程詳見工藝卡。 （四）機械加工余量、工序尺寸及毛皮尺寸的確定 “活動塊”；零件材料為HT200，硬度190～210HB，毛皮重量2.2kg，生產(chǎn)類型大批量，鑄造毛坯。 據(jù)以上原始資料及加工路線，分別確定各家工表面的機械加工余量、工序尺寸及毛坯尺寸如下： 1. 銑左端面,右端面,銑前后端面,銑前后面的槽,銑下半圓。 工件材料：HT200,σb =0.16GPa HB=190~241,鑄造 加工要求：銑左端面,右端面,銑前后端面,銑前后面的槽,銑下半圓。 機床：X6140臥式銑床。 刀具：W18Cr4V硬質(zhì)合金鋼端銑刀,牌號YG8。銑削寬度ae<=60,深度ap<=4,齒數(shù)z=10,故據(jù)《切削用量簡明手冊》（后簡稱《切削手冊》）取刀具直徑do=80mm。選擇刀具前角γo＝＋5°后角αo＝8°，副后角αo’=8°，刀齒斜角λs=－10°,主刃Kr=60°,過渡刃Krε=30°,副刃Kr’=5°過渡刃寬bε=1mm。 2. 切削用量 1） 銑削深度 因為切削量較小，故可以選擇ap=1.0mm，一次走刀即可完成所需長度。 2） 每齒進給量 機床功率為7.5kw。查《切削手冊》f=0.14~0.24mm/z。選進給量f=0.2mm/z。 3） 查后刀面最大磨損及壽命 查《切削手冊》表3.7，后刀面最大磨損為1.0~1.5mm。 查《切削手冊》表3.8，壽命T=180min 4） 計算切削速度 按《切削手冊》，查得 Vc＝98mm/s，n=439r/min,Vf=490mm/s 據(jù)XA6132銑床參數(shù)，選擇nc=475r/min,Vfc=475mm/s,則實際切削速度V c=3.14*80*475/1000=119.3m/min,實際進給量為f zc=V fc/ncz=475/(300*10)=0.16mm/z。 5)校驗機床功率 查《切削手冊》Pcc=1.1kw,而機床所能提供功率為Pcm>Pcc。故校驗合格。 最終確定 ap=1.0mm，nc=475r/min,Vfc=475mm/s，V c=119.3m/min，f z=0.16mm/z。 6）計算基本工時 tm＝L/ Vf=(32+80)/475=0.09min。 工序二 工序三 以左端面為精基準，鉆、鉸φ30孔，保證垂直度誤差不超過0.05mm,孔的精度達到IT9。 1. 選擇鉆頭 選擇高速鋼麻花鉆鉆頭，粗鉆時do=28mm，鉆頭采用雙頭刃磨法，后角αo＝12°，二重刃長度bε=2.5mm,橫刀長b=1.5mm,寬l=3mm,棱帶長度 ° ° ° 2.選擇切削用量 （1）決定進給量 查《切》 所以， 按鉆頭強度選擇 按機床強度選擇 最終決定選擇機床已有的進給量 經(jīng)校驗 校驗成功。 （2）鉆頭磨鈍標準及壽命　 后刀面最大磨損限度（查《切》）為0.5～０.８mm，壽命． ?。?）切削速度 查《切》 修正系數(shù) 故。 查《切》機床實際轉(zhuǎn)速為 故實際的切削速度 （4）校驗扭矩功率 所以 故滿足條件，校驗成立。 ３.計算工時 由于所有工步所用工時很短，所以使得切削用量一致，以減少輔助時間。 擴鉸和精鉸的切削用量如下： 擴鉆： 鉸孔： 工序四 鉆的孔 選擇高速鋼麻花鉆鉆頭，粗鉆時do=4mm，后角αo＝16°，二重刃長度 ° ° ° 2.選擇切削用量 （1）決定進給量 查《切》 按鉆頭強度選擇 按機床強度選擇 最終決定選擇機床已有的進給量 經(jīng)校驗校驗成功。 （2）鉆頭磨鈍標準及壽命　 后刀面最大磨損限度（查《切》）為0.5～0.8mm，壽命． ?。?）切削速度 查《切》 修正系數(shù) 故。 查《切》機床實際轉(zhuǎn)速為 故實際的切削速度 （4）校驗扭矩功率 故滿足條件，校驗成立。 ３.計算工時 3. 其他尺寸直接鑄造得到 由于本設(shè)計規(guī)定的零件為大批量生產(chǎn)，應(yīng)該采用調(diào)整加工。因此在計算最大、最小加工余量時應(yīng)按調(diào)整法加工方式予以確認。 工序五 鉆M6的孔。 選擇高速鋼麻花鉆鉆頭，粗鉆時do=4mm，后角αo＝16°，二重刃長度 ° ° ° 2.選擇切削用量 （1）決定進給量 查《切》 按鉆頭強度選擇 按機床強度選擇 最終決定選擇機床已有的進給量 經(jīng)校驗校驗成功。 （2）鉆頭磨鈍標準及壽命　 后刀面最大磨損限度（查《切》）為0.5～0.8mm，壽命． ?。?）切削速度 查《切》 修正系數(shù) 故。 查《切》機床實際轉(zhuǎn)速為 故實際的切削速度 （4）校驗扭矩功率 故滿足條件，校驗成立。 ３.計算工時 3. 其他尺寸直接鑄造得到 由于本設(shè)計規(guī)定的零件為大批量生產(chǎn)，應(yīng)該采用調(diào)整加工。因此在計算最大、最小加工余量時應(yīng)按調(diào)整法加工方式予以確認。 工序六 車M6的螺紋 1. 選擇鉆頭 選擇高速鋼麻花鉆鉆頭，粗鉆時do=4mm，后角αo＝16°，二重刃長度 ° ° ° 2.選擇切削用量 （1）決定進給量 查《切》 按鉆頭強度選擇 按機床強度選擇 最終決定選擇機床已有的進給量 經(jīng)校驗校驗成功。 （2）鉆頭磨鈍標準及壽命　 后刀面最大磨損限度（查《切》）為0.5～0.8mm，壽命． 　（3）切削速度 查《切》 修正系數(shù) 故。 查《切》機床實際轉(zhuǎn)速為 故實際的切削速度 （4）校驗扭矩功率 故滿足條件，校驗成立。 ３.計算工時 螺紋鉆削由于沒有手冊可查，故以鉆削切削用量及其他鉆螺紋工序估算。祥見工藝卡片。 工序七 鉸的孔. 查《工藝手冊》表2.2～2.5，取φ30已鑄成孔長度余量為3，即鑄成孔半徑為26mm。 工序八 鏜的孔、以底平面為精基準. 1、 加工要求：精鏜20mm孔，以底面為定位基準，根據(jù)《機械制造技術(shù)基礎(chǔ)》表5.8內(nèi)孔表面加工方案及其經(jīng)濟精度可得到：粗鏜時其加工經(jīng)濟精度可達到IT6~IT7,表面粗糙度Ra為3.2—1.6。具體余量如下： 20-19.5=0.5mm 2Z=1mm 單邊余量Z=0.5mm 由以上精度查《公差配合實用手冊》表2—3可以知道其孔加工的上下偏差為： 19.5mm+1mm=20mm 2、選用機床：查《機械工藝師手冊》表10—2臥式鏜床型號及技術(shù)參數(shù)選用TX618臥式銑鏜床 p輸=5.5kw 3、選用刀具：因為主軸Ⅰ上有階梯孔，查《機械工藝師手冊》選用900單刃鏜刀即可，這種鏜刀適合鏜階梯孔還能鏜削圓柱端面。 4、選擇切削用量 ①決定切削深度 由切削余量可知道 ap=0.5mm （單邊） 查《機械工藝師手冊》表29—14可知道精鏜時ap=0.3--0.8mm，所以采用一次切削。 ②決定切削進給量 查《機械工藝師手冊》表30—26 工件是鑄鐵時，刀頭是刀頭時 af=1mm 因為粗鏜所以采用較大進給量 ③、決定切削速度 查《機械工藝師手冊》表30-26工件是鑄鐵時，刀頭是刀頭時 v=40m/min因為粗鏜所以采用較小速度 計算主軸轉(zhuǎn)速 159r/min 按機床說明書見《機械加工工藝師》手冊表11—3可知道機床分18級8~1000r/min選主軸轉(zhuǎn)速為173r/min 所以實際速度為： 計算各孔加工工時 =0.242min 工序九 銑15的槽 工序十 檢查 其余幾步數(shù)據(jù)見工藝卡片 三、 卡具設(shè)計 經(jīng)過與老師協(xié)商，決定設(shè)計第五道工序——鉆20孔的夾具。本夾具將用于搖臂鉆床Z3025，刀具D=19mm的麻花鉆，使用高速剛刀具。 為了提高生產(chǎn)率，保證加工質(zhì)量，降低勞動強度，需設(shè)計作用夾具。 （一） 問題的提出 在給定的零件中，對本步加工的定位并未提出具體的要求，因為20的孔要精加工,所以對鉆孔的公差較低，定位要求較低，而且表面粗糙度要求也不高。因此，本步的重點應(yīng)在卡緊的方便與快速性上，以提高生產(chǎn)率、降低勞動強度方面著重考慮。 （二） 夾具設(shè)計 1． 定位基準的選擇 由零件圖可知，該工序加工簡單，一次鉆削即可完成加工，而且也沒其它的要求。出于定位簡單和快速的考慮，選擇工件底平面基準，（自由度限制數(shù)：3），再配合機座上的短定位銷（自由度限制數(shù)：2）,共限制個自由度,由于垂直方向上不需要限制，所以可以不用考慮該方向上的定位。而且鉆孔的力與夾緊力的方向一致，所以需要的夾緊力不太大，使用螺旋壓緊壓板進行卡緊。這樣一來夾具的結(jié)構(gòu)也簡單，所夾持部位也不會變形，工人安裝也比較方便快捷。 2. 定位誤差分析 本工序采用基面定位和壓板壓緊會產(chǎn)生一定的定位誤差，但是由于加工是自由公差，故能滿足定位要求。 3. 夾具設(shè)計及操作的簡要說明 夾具的卡緊力不大，故使用手動卡緊。為了提高生產(chǎn)力，使用快速螺旋卡緊機構(gòu)。 （三）夾具零件 1.夾緊螺母 采用M9的螺母與雙頭螺柱來控制壓板來施加加緊力. 2.墊片 與夾緊螺母配合來防松 3.壓板 來傳遞夾緊螺母對工件的夾緊力 4.加強肋 由于壓板比較長,用加強肋來提高壓板的剛度. 5.銷釘 壓板和擺動壓板用銷釘來連接 6.擺動壓板 為了減小夾緊力與定位元件對工件的誤差采用擺動壓板 7.快換鉆套 采用快換鉆頭為了防止鉆頭把鉆模板磨損 8.鉆模板 對鉆頭導向. 9.螺釘 用來固定快換鉆套與鉆模板 10.定位銷 來限制工件X方向與Y方向上的自由度 11.彈簧 來自動彈起壓板. 12.雙頭螺柱 與夾緊螺母來控制壓板. 13.騎縫螺釘 來夾緊雙頭螺柱 14.機座 對壓板導向 15.固定螺釘 來固定機座 16.底版 與鉆床連接,同時來限制工件的XY方向的轉(zhuǎn)動與Z方向的移動. 四、設(shè)計體會 課程設(shè)計是培養(yǎng)學生綜合運用所學知識,發(fā)現(xiàn),提出,分析和解決實際問題,鍛煉實踐能力的重要環(huán)節(jié),是對學生實際工作能力的具體訓練和考察過程.此次課程設(shè)計是在學完《機械制造技術(shù)基礎(chǔ)》和《機械裝備》等課程后的一次對專業(yè)知識的綜合性的實際運用；更是在學完大學四年來所學的所有專業(yè)課及生產(chǎn)實習的一次理論與實踐相結(jié)合的綜合訓練。 此次課程設(shè)計涉及到的知識面很廣，涉及到了《材料力學》、《機械工程材料》、《機械制造技術(shù)基礎(chǔ)》、《機械制造裝備設(shè)計》、《公差配合與技術(shù)測量》、《機械設(shè)計》、《工程材料與熱處理》等課程的相關(guān)知識，同時還聯(lián)系到了生產(chǎn)實習中的一些經(jīng)驗，應(yīng)用到的知識廣、全面。 隨著社會的快速發(fā)展，制造業(yè)的不斷更新，制造能力和質(zhì)量的飛速發(fā)展與更加高精、高速、高能。而對與一個走機械制造專業(yè)方向的人來說，社會對他們的要求已愈來愈高，搞工藝不但要會搞工藝，更要能搞設(shè)計、搞開發(fā)、搞創(chuàng)新，懂得材料、設(shè)備、控制……所以，搞自己的專業(yè)，要在自己專業(yè)的道路上搞出成就，就應(yīng)該時時充實自己，更新自己，增加自己的專業(yè)知識及其它綜合能力；更新自己的思維方式和思想觀念。更加明確自己的人生觀，價值觀，世界觀。力爭將自己培養(yǎng)成有志向、有道德、懂科學、愛國家，能適應(yīng)不同社會環(huán)境的優(yōu)秀社會主義青年。 回顧起此次課程設(shè)計，至今我仍感慨頗多，的確，從選題到定稿，從理論到實踐，在整整三星期的日子里，可以說得是苦多于甜，但是可以學到很多很多的的東西，同時不僅可以鞏固了以前所學過的知識，而且學到了很多在書本上所沒有學到過的知識。通過這次課程設(shè)計使我懂得了理論與實際相結(jié)合是很重要的，只有理論知識是遠遠不夠的，只有把所學的理論知識與實踐相結(jié)合起來，從理論中得出結(jié)論，才能真正為社會服務(wù)，從而提高自己的實際動手能力和獨立思考的能力。在設(shè)計的過程中遇到問題，可以說得是困難重重，難免會遇到過各種各樣的問題，同時在設(shè)計的過程中發(fā)現(xiàn)了自己的不足之處，對以前所學過的知識理解得不夠深刻，掌握得不夠牢固，通過這次課程設(shè)計之后，一定把以前所學過的知識重新溫。 這次課程設(shè)計終于順利完成了，在設(shè)計中遇到了很多編程問題，最后在姜明老師的辛勤指導下，終于游逆而解。同時，在姜明老師的身上我學得到很多實用的知識，在次我表示感謝！同時，對給過我?guī)椭乃型瑢W和各位指導老師再次表示忠心的感謝！ 五、參考文獻 序號 書名 出版社 主編 1. 《機械制造技術(shù)基礎(chǔ)》 武漢理工大學出版社 曾志辛 呂明 2. 《金屬切學機床夾具設(shè)計手冊》 機械工業(yè)出版社 上海柴油機工藝設(shè)備研究所 3. 《機床夾具設(shè)計手冊》 上?？茖W技術(shù)出版社 東北重型機械學院洛陽分院 4. 《機械制造工藝及專用夾具設(shè)計指導》冶余工業(yè)出版社 孫麗媛 雒運強 張嘉鈺 5. 《機械制造工藝設(shè)計手冊》 哈爾濱工業(yè)出版社 王紹俊 6. 《機械設(shè)計課程設(shè)計手冊》 高等教育出版社 吳宗澤 羅圣國 7. 《鉗工工藝與技能訓練》 高等教育出版社 徐冬元 8. 《機械制造工技術(shù)基礎(chǔ)》 西南交通大學出版社 張捷 李先民 趙虎 9. 《機床夾具設(shè)計》 哈爾濱工業(yè)大學、上海工業(yè)大學出版社 10. 《材料力學》 高等教育出版社 劉碧文 11. 《機械制造裝備》 機械工業(yè)出版社 黃鶴汀 王芙蓉 劉建明 12. 《機械設(shè)計》 高等教育出版社 邱宣懷 13. 《機械制造工藝設(shè)計簡明手冊》 機械工業(yè)出版社 李益民 14. 《切削用量簡明手冊手冊》 機械工業(yè)出版社 艾興 肖詩剛 15 A functional approach for the formalization of the fixture design processR. Huntera, J. Riosb,*, J.M. Pereza, A. VizanaaDepartment of Mechanical and Manufacturing Engineering, Escuela Tecnica Superior de Ingenieros Industriales, Universidad Politecnica de Madrid,Jose Gutierrez Abascal, 2, 28006 Madrid, SpainbCurrently in Enterprise Integration (Bldg 53), Cranfield University, Cranfield, MK43 0AL, UKReceived 14 January 2005; accepted 14 April 2005Available online 26 August 2005AbstractThe design of machining fixtures is a highly complex process that relies on designer experience and his/her implicit knowledge to achievea good design. In order to facilitate its automation by the development of a knowledge-based application, the explicit definition of the fixturedesign process and the knowledge involved is a prior and a fundamental task to undertake. Additionally, a fundamental and well-knownengineering principle shouldbe considered: the functional requirements and their associated constraints should be the first input toany designprocess. Considering these two main ideas, this paper presents the development undertaken to facilitate the automation of the fixture designprocess based on a functional approach.In this context, the MOKA methodology has been used to elicit fixtures knowledge. IDEF0 and UML have been used to represent thefixture design process. A methodology based on the function concept and aiming to formalize such design process is proposed. Fixturefunctional requirements have beendefined and formalized. Functional fixtures elements havebeen used tocreate a functionaldesign solution,the link of these elements with the functional requirements and with typical commercial fixture components has been defined via tables andrules mapping. And finally, a prototype knowledge-based application has been developed in order to make an initial validation of theproposed methodology.q 2005 Elsevier Ltd. All rights reserved.Keywords: Fixture design process; Fixture knowledge modelling, Fixture functional requirements1. IntroductionThe main objective of any design theory is to provide asuitable framework and methodology for the definition ofa sequence of activities that conform the design process of aproduct or system 1. In general, all of them identifyrequirements as the starting point in the design process. Infact, the engineering discipline dealing with product designcan be defined as the one that considers scientific andengineering knowledge to create product definitions anddesign solutions based on ideas and concepts derived fromrequirements and constraints 24.For this research, a relevant issue when consideringrequirements, taking this as a general concept, is to makeexplicit the meaning of two main terms: FunctionalRequirement (FR) and Constraint (C). A functionalrequirement, as it stated by different authors, representswhat the product has to or must do independently of anypossible solution, 2,4. A FR is a kind of requirement, andconsidering some basic principles widely recognized in thefield of Requirements Engineering, we could add it is aunique and unambiguous statement in natural language of asingle functionality, written in a way that it can be ranked,traced, measured, verified, and validated. A constraintcan be defined as a restriction that in general affects somekind of requirement, and it limits the range of possiblesolutions while satisfying the requirements. So, a constraintshould be always linked to a requirement, and its purpose isto narrow the design outcome to acceptable solutions.Considering the Theory of Axiomatic Design 4,functional requirements should be defined in the functionaldomain, which brings on the scene the issue of how to defineand represent the functionality of a product. The way used torepresent it will affect the reasoning process of the designer,and in that sense, the mapping between the functionalInternational Journal of Machine Tools & Manufacture 46 (2006) - see front matter q 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.ijmachtools.2005.04.018*Corresponding author. Tel.: C44 1234 754936; fax.: C44 1234750852.E-mail address: j.rioscranfield.ac.uk (J. Rios).and the physical domains, being the later the one where thedesign solutions are developed. Several authors haveinvestigated the concept of functionality and functionalrepresentation 2,58. Their design approach provides aview based on the Function-Behaviour-Structure frame-work, where function is defined using structure andbehaviour 6. The objective is to fill the gap that allowsa designer to progress from FRs to physical designsolutions. The approach is that product functions areachieved by means of its structure, which seems to lead toan iterative causal approach, where solutions are soughtuntil the selected structure causes the intended functionality.The approach adopted in the research presented in this paperis based on the definition of Fixture Functional Components(FFC), which can satisfy the fixture functionality, and on themapping between such FFC and fixture commercialelements.An advanced approach to the definition of requirementsand functions comes from the creation of ontologies. Theontological approach pursues the definition of the meaningof terms making use of some kind of logic, and the definitionof axioms to enable automatic deduction and reasoning 9.The ontological approach has got a higher relevance sincethe representation of knowledge is considered the key factorin whatever engineering process, and it has been recognizedas a way to facilitate the integration of engineeringapplications 10, to describe functional design knowledge7, and to define requirements 11. Considering a puristapproach, if an ontology does not include axioms to enablereasoning then it could be considered more like aninformation model, and in this sense, this is the approachdeveloped in the work presented in this paper.When considering the methodologies developed for thedesign of fixtures, it can be stated that in general they arerational and propose a series of steps to follow. For example,the methodologies proposed by Scallan and Henriksen 12,13, make use of this approach to describe in general termsthe information needed in each stage of the fixture designprocess. Basically, the importance of modelling in detailsuch information, which mainly is related to fixturerequirements, fixture functionality, fixture components,manufacturing resources, manufacturing processes, anddesign rules; resides on the possibility to automate thedesign process through the development of a knowledge-based application or system. It is relevant to mention thatseveral authors have already aimed to develop knowledge-based applications for fixture design, none of them based ona functional approach, some of the most recently publishedworks can be found in the Refs. 1419.Inthefollowingsections,thispaperpresentsamethodology to formalize the design process of machin-ingfixturesbasedontheengineeringconceptsoffunctional requirements and fixture functions 20. Theformalization of the functional requirements is achievedthrough the application of a structured way of specifica-tion via natural language. Additionally, IDEF0, MOKAmethodology, and UML diagrams are used to capture,represent and formalize knowledge, being the ultimategoal to facilitate the automation of the fixture designprocess.The IDEF0 method is used to create an activity model ofthe fixture design process, allowing the identification of theinformation used in each one of the different tasks itcomprises. UML has been used to complement the IDEF0model by representing the interaction between the activitiesof the process. The MOKA methodology together withUML, are used to capture and represent knowledge involvedin the fixture design process. Finally, to validate theproposed methodology, partial results obtained from thedevelopment of a prototype knowledge-based applicationare presented.2. Analysis of machining fixtures requirementsIn Section 1, two terms have been defined: functionalrequirement and constraint. Requirements have alwaysexisted, the way in which they are expressed, and howthey are integrated in the product design process, are aspectsthat are addressed from different disciplines, for example:product design engineering and requirements engineeringamong others. In general, Requirements Engineering refersto the discipline dealing with the capture, formalization,representation, analysis, management and verification ofrequirements fulfilment. However, all these aspects need tobe integrated in the product design process, and require-ments should lead to the definition of the possible productdesign solutions, which in general demands an integratedview of the requirements issue. It is important to keep inmind that the development of such discipline is stronglyrelated to Software Engineering and Systems Engineering,and in fact much of the research related to requirementscome from authors from these engineering areas 2123.When considering the analysis of requirements, prob-ably, the first aspect to think about is how the requirementsare represented or declared. As it has been previouslymentioned, the way of expressing requirements definitivelyaffects their interpretation and the creation of a designsolution. In this sense, it is widely accepted, that the use ofnatural language is the most common way of expressingrequirements and in consequence, their writing becomes animportant issue. The anatomy proposed by Alexander et al.24 to write requirements in a semi-structured way is usedas basis to declare the functional requirements andconstraints of fixtures 20.In machining, work holding is a key aspect, and fixturesare the elements responsible to satisfy this general goal. Intheir design process, the starting point is the definition of themachining fixtures functional requirements and constraints.Usually, a fixture solution is made of one or several physicalelements, as a whole the designed fixture solution mustsatisfy all the FRs and the associated Cs. Centring, locating,R. Hunter et al. / International Journal of Machine Tools & Manufacture 46 (2006) 683697684orientating, clamping, and supporting, can be considered thefunctional requirements of fixtures, what a fixture must doindependently of any particular solution. In terms ofconstraints, what limits the range of possible solutions,there are many factors to be considered, mainly dealingwith: shape and dimensions of the part to be machined,tolerances, sequence of operations, machining strategies,cutting forces, number of set-ups, set-up times, volume ofmaterial to be removed, batch size, production rate, machinemorphology, machine capacity, cost, etc. At the end, thesolution can be characterized by its: simplicity, rigidity,accuracy, reliability, and economy.2.1. Functional requirementsFrom the literature review 2527, and from theinterview with designers of machining fixtures 28, it canbe concluded that basic functional requirements that anyfixture solution must satisfy are related to: centring,locating, orientating, clamping, and supporting.However, the way that designers deal with these FRs isfar from being independent of the solution they areconsidering, and in general the FRs are not explicit butimplicit in the design process. Chakrabarti et al. 29 pointout some of the problems that appear in relation torequirements during the design process, for examplerequirements during conceptual and embodiment designsresult mainly from analysis of proposed designs, which infact it is in contradiction with the basic principle, presentedby different authors, of functional definition prior to anydesign solution identification. Adopting the ideas ofToyotas Set-based Concurrent Engineering 30 andAxiomatic Design Theory 4, it seems logical to statethat the FRs should be clearly identified and defined prior toselecting any possible design solution and as the designprogresses the different constraints linked to the FRs shouldbe refined to narrow the set of possible solutions.Chakrabarti et al. 29 also conclude that in order forrequirements to be adequately fulfilled by the final design,they must be identified, understood, remembered and used.Thisconclusion is not new, and in this sense, it demonstrateshow actual and relevant this issue is. It also reinforces acouple of ideas widely recognized in engineering design,one is the need to capture, formalize and documentknowledge, and the second is to make use of it in thedevelopment of Knowledge-Based Engineering (KBE)applications that could help the designers to carry outtheir job and make use in an automatic way of as muchscientific knowledge as possible 31. In this particular caseapplied to the design of machining fixtures.When addressing the development of a KBE application,there are two different sorts of FRs that need to be identifiedand documented. One kind is the functional requirements ofthe application itself; in this case a KBE application forthe design of machining fixtures; and the second one is thefunctional requirements of the components subject of theapplication; in this case machining fixtures. An example ofthe former ones for an application developed in collabor-ation with an industrial partner is presented by Rios et al.28. For this kind of FRs specification, UML seems to beFig. 1. MOKA Entity form for fixture FRs.R. Hunter et al. / International Journal of Machine Tools & Manufacture 46 (2006) 683697685a good methodology: activity, component, and use casediagrams help to specify and give a view of the system.However, when getting into the logical view where classand interaction diagrams have to be defined, it is needed tohave a complete understanding of the object of theapplication: machining fixtures. With this objective, andconsidering that the design of machining fixtures based onfunctional requirements would be the aim of a KBEapplication, the capture and documentation of the machin-ing fixtures FRs is part of the subject of the work developed20, and it is commented next.In this context, the approach adopted was to use part ofthe tools provided by the MOKA methodology 31, thenamed: Illustrations, Constraints, Activities, Rules andEntities forms, to elicit knowledge about machiningfixtures as a first step in the formalization of the FRs andCs. Based on these forms, it is possible to represent themain components linked with the fixture design process:non-functional requirements, functional requirements,constraints, design rules, fixture functional elements,fixture commercial components, etc. 20. Figs. 1 and 2present an example of application to the definition offixture FRs and Cs.After this first phase, the requirements capture iscompleted with the formalization of the functionalrequirements syntax. At this point, it is important toremember that the declaration of a FR is a sentence writtenin a way that allows the FR to be measured, verified, andvalidated. The structure proposed is based on Alexandersanatomy 24, and it has similarities with the functionrepresentation presented by Takeda et al. 6, where it isstated that a function is a combination of a function body(verb), an objective entity (on which the function occurs onor to), and functional modifiers (adverb). The structureproposed in this research is made up of four maincomponents: action, object, resource, and qualifiers(Fig. 3). And unlike with the Takeda approach, all themodal adverbs (i.e.: firmly, precisely, in general allInside the working area of the table:X = 200 mmY = 400 mmZ = 400 mmTolerance for all the dimensions: 1 mmObjectResourcePart A in vertical ma chining center DM T50 ActionQualifierSupport Fig. 3. Functional requirement structure.MOKA ICARE: ENTITYNameReferenceEntity TypeFunctionBehaviourContext, Information,ValidityDescriptionManagementAuthorDateVersionStatusConstraints Functional Requirements for the FixtureConstraints Functional Requirements (CFR)StructureDefine constrains to Functional Requirements for the fixtureNot ApplicableDefine constraints that support the functional requirementsThe constraints will be structured thinking on the functional requirements structureWith this target it has been defined a group of constraints associated with eachfunctional requirement of the fixture, such as:OrientationSupportLocateClampMachiningResourcesRenato Hunter03-07-041.0In progressFig. 2. MOKA Entity form for fixture Cs.R. Hunter et al. / International Journal of Machine Tools & Manufacture 46 (2006) 683697686the adverbs ending with the suffix y) are not considered as amodifier, since they do not have a quantitative value, and inconsequence they cannot be measured neither validated.The Action component is expressed by an active verb thatrefers to the function of the fixture. As named previously,these functions are: centre, position, orientate, clamp, andsupport. A noun expresses the Object component, and refersto the physical object on which the action is performed. Inthe first level of fixture FRs definition, Object will be thepart to be machined. A noun expresses the Resourcecomponent, and it refers to where the action will beperformed. In the first level of fixture FRs definition,part_requirementscost_requirementsprocess_requirementsorientation_requirements-identificacion : char-nombre : char-descripcion : char-accion : char-que : char-recurso : char-calificador : chardocumentation_requirementFixture_requirementslocate_requirementssupport_requirementsclamp_requirements-Requirements1-Documentation1.*accesibility_requirements-Process1.*-Part1formal_representation_requirements-identificador : char-nombre : char-descripcion : char-accion : char-que : char-recurso : char-calificador : charfunctional_requirements-identificador : char-nombre : char-descripcion : char-accion : char-que : char-recurso : char-cualificador : charno_functional_requirements-identificador : char-nombre : char-descripcion : char-accion : char-que : char-recurso : char-calificador : charstructure_requirementscentre_requirementsmachine_tool_requirementsmachining_feature_requirements-Part1-feature1.*-Process1-Feature1.*-Identificator: char-name: char-description: char-action: char-object: char-resource: char-qualifier: char-Identificator: char-name: char-description: char-action: char-object: char-resource: char-qualifier: char-Identificator: char-name: char-description: char-action: char-object: char-resource: char-qualifier: char-Identificator: char-name: char-description: char-action: char-object: char-resource: char-qualifier: charFig. 4. UML model of the fixture functional requirements.Table 1Instances of fixture FRsActionObjectQualifiersQualifier typeOrientatePartIn the machine tool (M0)(Resource)Respect to the coordinated system of thepart (M1)(How)On the orientation part activity (M2)(When/Where)Modifier (M0)Respect to system axis of machine toolModifier (M0)In a vertical milling machineModifier (M1)Respect to the tool pathConstraintsMachine tool type (Vertical or horizontalmill)Work area: lengths in X, Y, ZSupportPartIn machine tool (M0)(Resource)On static equilibrium (M1)(How)On the support part activity (M2)(When/Where)Modifier (M0)In a vertical milling machineModifier (M1)When the sum of forces is equal to zeroModifier (M2.1)Vertical degree of freedom of the partModifier (M2.2)When the orient activity propose a resultConstraintsWork area: lengths in X, Y, Z Shape andsize of the base plateR. Hunter et al. / International Journal of Machine Tools & Manufacture 46 (2006) 683697687Resource will be the machine tool on which the machiningis performed. A quantitative adjective group or noun groupexpresses a Qualifier for the action. The Qualifierscomponents refer to limits of the FRs, and allowrepresenting the constraints (Cs) associated with them.Each quantitative qualifier must have at least a nominalnumerical value, a unit of measure, and a tolerance. Each FRmust have at least one quantitative qualifier. Considering theprevious concept of constraints refinem