撥叉零件的機械加工工藝規(guī)程及銑削86左側(cè)端面工裝夾具設(shè)計,撥叉零件的機械加工工藝規(guī)程及銑削86左側(cè)端面工裝夾具設(shè)計,零件,機械,加工,工藝,規(guī)程,銑削,86,左側(cè),端面,工裝,夾具,設(shè)計 設(shè)計說明書 設(shè)計題目：撥叉零件的機械加工工藝規(guī)程及工藝裝備設(shè)計 所在系部 專 業(yè) 班 級 姓 名 學(xué) 號 指導(dǎo)老師 完成時間：2019年1月7日 目 錄 摘 要 1 Abstract 2 引言 3 1 零件圖的分析 4 1.1 零件作用 4 1.2 零件加工技術(shù)要求分析 4 2 工藝規(guī)程設(shè)計 5 2.1 毛坯的選擇 5 2.2 選擇定位基準 6 2.3 擬定加工工藝路線 7 2.4 切削用量和基本工時 8 3 專用夾具設(shè)計 19 3.1 定位方案的確定 19 3.2 定位誤差的分析 19 3.3 夾緊裝置的要求 19 3.4 銑削力的確定 20 3.5 夾緊力的確定 20 3.6 夾具簡要說明 21 總結(jié)收獲 23 參考文獻 24 致 謝 25 II 摘 要 機械制造業(yè)在中國產(chǎn)業(yè)的地位相當于基石，有這個基石，大到國家重要機械制造產(chǎn)業(yè)，小到平常生活機械產(chǎn)品，可以說現(xiàn)代機械制造業(yè)離不開機械加工過程，隨之而來的是機床的不斷更新和加工技術(shù)不斷優(yōu)化。 撥叉用途廣泛，變速器產(chǎn)品中零部件之一，批量生產(chǎn)撥叉零件，也是間接為國家制造業(yè)提供助力，并進行撥叉夾具設(shè)計，其主要內(nèi)容包括零件的用途和作用，分析零件圖尺寸精度要求等技術(shù)要求；分析零件工藝規(guī)程；設(shè)計零件加工工藝路線，以此為基礎(chǔ)，選擇其中一道工序夾具設(shè)計，批量生產(chǎn)撥叉。 關(guān)鍵詞：撥叉 工藝 工序 夾具 Abstract The position of machinery manufacturing industry in China is equivalent to the cornerstone. With this cornerstone, it can be said that modern machinery manufacturing industry can not be separated from the mechanical processing process, which is accompanied by the continuous updating of machine tools and the continuous optimization of processing technology. The fork is widely used, one of the parts in engine products, mass production of fork parts is also indirect to the national manufacturing industry, and the fork jig design is carried out. Its main contents include the use and function of parts, analysis of the technical requirements such as dimensional accuracy requirements of parts drawings, analysis of parts process regulations, design of parts processing technology route, based on which to select one of them. One process fixture design, batch production fork. Key words: fork; technology; process; fixture 引言 機床的夾具是加工的支柱。機床夾具的設(shè)計和使用對今后的發(fā)展起著至關(guān)重要的作用。隨著我國機械工業(yè)的不斷發(fā)展，機床夾具的創(chuàng)新與制造已成為機械工人和技術(shù)人員在技術(shù)創(chuàng)新中的主要作用。 設(shè)計對我們每個大學(xué)生來說都非常重要，因為它可以幫助我們將來去工作。但是，對于我們的機械專業(yè)，在以后的工作中會有一些機械設(shè)計和夾具設(shè)計的工作，在這里，在我的設(shè)計身體部分，例如，在它的工藝過程和夾具設(shè)計。通過在畢業(yè)設(shè)計前進行設(shè)計可以很好地獲得更好的綜合運用知識，同時加強學(xué)習(xí)和學(xué)習(xí)知識的早期階段，從而提高判斷、分析和解決問題的能力。因此，做好課程設(shè)計是必要的。 本次設(shè)計主要撥叉工藝規(guī)程及夾具設(shè)計，其具體設(shè)計流程主要包括以下幾個方面： 1，對撥叉零件的主要技術(shù)要求進行分析 2，完成撥叉零件的加工工藝設(shè)計 3，完成撥叉零件的機械加工工藝過程卡片的編制 4，根據(jù)撥叉零件的結(jié)構(gòu)合理設(shè)計夾具。 1 零件圖的分析 1.1 零件作用 汽車變速箱上的部件，與變速手柄相連，位于手柄下端，撥動中間變速輪，使輸入/輸出轉(zhuǎn)速比改變。如果是機床上的撥叉是用于變速的，主要用在操縱機構(gòu)中，就是把2個咬合的齒輪撥開來再把其中一個可以在軸上滑動的齒輪撥到另外一個齒輪上以獲得另一個速度。即改變車床滑移齒輪的位置，實現(xiàn)變速?；蛘邞?yīng)用于控制離合器的嚙合、斷開的機構(gòu)中，從而控制橫向或縱向進給。零件如下圖1.1： 圖1-1 撥叉的零件圖 1.2 零件加工技術(shù)要求分析 撥叉零件一共有兩個加工基準面，要求如下： 1.以內(nèi)孔φ25為基準面，銑各端面及內(nèi)孔； 2.以底面和端面為基準面，鉆擴鉸內(nèi)孔φ25； 撥叉零件的在加工時，既然考慮他的尺寸精度及形位公差，又要看清圖紙，各個尺寸所在的位置，由于此零件屬于復(fù)雜性的加工件，在選擇加工面及定位基準時，都要按照圖紙的得要求，保證其要求。 2 工藝規(guī)程設(shè)計 2.1 毛坯的選擇 確定毛坯的制造形式 包括以下2個方面 1、選擇毛坯類型 2、確定其制造方法 1.常見的毛坯類型有鑄造、鍛造、壓制、沖壓、焊接型材和板材等7大類根據(jù)加工零件的不同，確定毛坯采用什么類型時 要考慮以下幾個因素： （1）加工零件的材料：其承受的力。當選好零件材料后，就基本定了毛坯的類型。比如，材料是是HT200、毛坯類型就為鑄造， （2）材料如果是鋼材的比如HT200，其塑性較強，就選鑄造； （3）力學(xué)性能要求非常高，或者較高時，我們可以選擇鑄造，。 2.壁厚較薄的零件，不宜用砂型鑄造；形狀復(fù)雜，尺寸有比較大的鑄件，宜用砂型鑄造；中、小型零件可用較先進的熔模鑄造及其他鑄造方法。 3.生產(chǎn)類型。大批量生產(chǎn)應(yīng)根據(jù)零件的精度不同，選者不同的加工方法 如果精度較高，鑄件應(yīng)采用金屬模機器造型精密鑄造；鍛件應(yīng)采用模鍛冷軋冷拉型材等。 如果精度較低就可以采用成本更低的砂型鑄造，以滿足生產(chǎn)需求，同時又降低成本。單件或者小批量生產(chǎn)的毛坯，則應(yīng)采用木模手工造型，自由鍛。 4.生產(chǎn)條件。確定毛坯類型必須與具體的生產(chǎn)條件相結(jié)合，如現(xiàn)場毛坯制造的實際水平和能力、外協(xié)的可能性等，外協(xié)工廠的制作能力，制作設(shè)備的新舊程度等等。 5.在控制好成本，保證質(zhì)量的前提下，可以考慮采用新工藝新技術(shù) 新材料的可能性。目前新技術(shù) 新材料的發(fā)展很快。毛坯制造方面的新工藝，采用這些新的方法，可大大減少機械加工量，降低機床的磨損，減少工人的勞動強度，同時也降低了整個公司的成本，其經(jīng)濟效果非常顯著，并且采用新方法后 有時甚至可不再進行機械加工。零件材料為HT200?？紤]零件在機床運行過程中所受沖擊不穩(wěn)定，零件結(jié)構(gòu)又比較簡單一些，在加工過程中，加工斜度面，有難度，故選擇鑄造毛坯。 6.毛坯的形狀和大小的影響因素主要包括幾個加工等因素的測定毛坯的形狀大小表面結(jié)構(gòu)尺寸部分,盡可能,為了減少勞動過程,并努力實現(xiàn)很少或沒有處理。然而,由于現(xiàn)有毛坯的制造成本限制,需求和產(chǎn)品精密機械加工表面質(zhì)量越來越高,因此,需要有一些粗糙表面加工,零件加工技術(shù)。模式之間的差異的大小的大小稱為一個毛坯的邊緣。之間的差異最大尺寸和最小尺寸允許的公稱尺寸鍛造毛坯的尺寸公差。毛坯的邊緣毛坯的大小和形狀。 綜上說述，撥叉的材料為HT200，毛坯類型為鑄造。 毛坯圖如下： 圖2-1 撥叉的毛坯圖 2.2 選擇定位基準 正確地選擇定位基準是設(shè)計工藝過程的一項重要內(nèi)容，也是保證零件加工精度的關(guān)鍵。定位基準分為精基準、粗基準。 1.粗基準選擇應(yīng)當滿足以下要求： （1）不管如何選擇；都要考慮到產(chǎn)品表面平整、光潔等因素；所以在粗基準的選擇當中包括這方面的要求。 （2）由于粗糙和不規(guī)則的基準面沒有重復(fù)使用；所以對粗基準的選擇應(yīng)該考慮較多；保證了加工精度。 粗基準選擇撥叉內(nèi)孔φ25。 2.精基準的選擇應(yīng)滿足以下原則： （1）“基準重合”原則 應(yīng)盡量選擇加工表面的設(shè)計基準為定位基準，避免基準不重合引起的誤差。 （2）“基準統(tǒng)一”原則 盡可能在多數(shù)工序中采用同一組精基準定位，以保證各表面的位置精度，避免因基準變換產(chǎn)生的誤差，簡化夾具設(shè)計與制造。 （3）“自為基準”原則 某些精加工和光整加工工序要求加工余量小而均勻，應(yīng)選擇該加工表面本身為精基準，該表面與其他表面之間的位置精度由先行工序保證。 （4）“互為基準”原則 當兩個表面相互位置精度及自身尺寸、形狀精度都要求較高時，可采用“互為基準”方法，反復(fù)加工。 綜合考慮采用加工好的86左側(cè)端面為精基準，之后加工其他工序的尺寸。 2.3 擬定加工工藝路線 制訂工藝路線的出發(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)為成批生產(chǎn)的條件下，可以考慮采用機床配以專用夾具，并盡量使工序集中在提高生產(chǎn)率。除此以外，還應(yīng)當考慮經(jīng)濟效果，以便使生產(chǎn)成本盡量降下來。 表2-1 加工路線表 01 銑 粗銑86左側(cè)端面 02 鉆 鉆孔23 03 銑 粗銑86右側(cè)端面 04 銑 粗銑右側(cè)II端面 05 銑 粗銑左側(cè)II端面 06 銑 粗銑右側(cè)I端面 07 銑 粗銑左側(cè)I端面 08 銑 粗銑B向端面 09 鉆 鉆孔18 10 鉸 鉸孔φ15.5 10 攻 攻絲18H6 10 銑 銑平臺 11 銑 粗銑三面凹槽 12 銑 粗銑上平面 13 鉸 擴孔24.8 14 鉸 粗鉸孔24.94 15 銑 半精銑右側(cè)II平面 16 銑 半精銑左側(cè)II平面 2.4 切削用量和基本工時 加工切削用量包括主軸轉(zhuǎn)速n（切削速度Vc）、背吃刀量ap和進給量f（或進給速度Vf）其確定原則與普通機械加工相似，對于不同的加工方法，需要選擇不同的切削用量，合理選擇切削用量的原則是：粗加工時，一般以提高生產(chǎn)率為主，但也應(yīng)考慮經(jīng)濟性和加工成本；半精加工和精加工時，應(yīng)在保證質(zhì)量的前提下，兼顧切削效率、經(jīng)濟性和加工成本。具體數(shù)值應(yīng)根據(jù)機床說明書，參考的切削用量手冊，并結(jié)合經(jīng)驗而定。 1.粗銑86左側(cè)端面 專用夾具、φ40高速鋼立銑刀、游標卡尺、立式銑床X51 粗銑時，確定背吃刀量（ap）：ap=0.5mm 確定切削速度：由實用金屬切削計算手冊v＝15~21m/min，選擇v=15m/min 相近的轉(zhuǎn)速為160r/min。 確定每齒進給量fz：f=0.07~0.18mm/z，取f=0.15mm/z 所以實際切削速度 確定進給量 基本工時：式中，，取，則有： 。 則 2.鉆孔23 專用夾具、φ23硬質(zhì)合金麻花鉆、游標卡尺、立式鉆床Z525 確定背吃刀量（ap）：ap=11.5mm 確定切削速度：v＝45~60m/min，選擇v=46m/min 相近的轉(zhuǎn)速為680r/min。 確定進給量f：f=0.3~0.5mm/r，取f=0.48mm/r 所以實際切削速度 基本工時：式中，，取，則有： 則 3.粗銑86右側(cè)端面 專用夾具、φ40高速鋼立銑刀、游標卡尺、立式銑床X51 確定切削速度：由實用金屬切削計算手冊v＝15~21m/min，選擇v=15m/min 相近的轉(zhuǎn)速為160r/min。 確定每齒進給量fz：f=0.07~0.18mm/z，取f=0.15mm/z 所以實際切削速度 確定進給量 基本工時：式中，，取，則有： 。 則 4.粗銑右側(cè)II平面 專用夾具、φ10高速鋼立銑刀、游標卡尺、立式銑床X51 粗銑時，確定背吃刀量（ap）：ap=0.25mm 確定切削速度：由實用金屬切削計算手冊v＝15~21m/min，選擇v=15m/min 相近的轉(zhuǎn)速為490r/min。 確定每齒進給量fz：f=0.07~0.18mm/z，取f=0.15mm/z 所以實際切削速度 確定進給量 基本工時：式中，，取，則有： 。 則 5.粗銑左側(cè)II平面 專用夾具、φ10高速鋼立銑刀、游標卡尺、立式銑床X51 粗銑時，確定背吃刀量（ap）：ap=0.25mm 確定切削速度：由實用金屬切削計算手冊v＝15~21m/min，選擇v=15m/min 相近的轉(zhuǎn)速為490r/min。 確定每齒進給量fz：f=0.07~0.18mm/z，取f=0.15mm/z 所以實際切削速度 確定進給量 基本工時：式中，，取，則有： 。 則 6.粗銑右側(cè)I平面 專用夾具、φ15高速鋼立銑刀、游標卡尺、立式銑床X51 粗銑時，確定背吃刀量（ap）：ap=0.5mm 確定切削速度：由實用金屬切削計算手冊v＝15~21m/min，選擇v=15m/min 相近的轉(zhuǎn)速為490r/min。 確定每齒進給量fz：f=0.07~0.18mm/z，取f=0.15mm/z 所以實際切削速度 確定進給量 基本工時：式中，，取，則有： 。 則 7.粗銑左側(cè)I平面 專用夾具、φ15高速鋼立銑刀、游標卡尺、立式銑床X51 粗銑時，確定背吃刀量（ap）：ap=0.5mm 確定切削速度：由實用金屬切削計算手冊v＝15~21m/min，選擇v=15m/min 相近的轉(zhuǎn)速為490r/min。 確定每齒進給量fz：f=0.07~0.18mm/z，取f=0.15mm/z 所以實際切削速度 確定進給量 基本工時：式中，，取，則有： 。 則 8.粗銑B向端面 專用夾具、φ30高速鋼立銑刀、游標卡尺、立式銑床X51 粗銑時，確定背吃刀量（ap）：ap=0.5mm 確定切削速度：由實用金屬切削計算手冊v＝15~21m/min，選擇v=15m/min 相近的轉(zhuǎn)速為160r/min。 確定每齒進給量fz：f=0.07~0.18mm/z，取f=0.15mm/z 所以實際切削速度 確定進給量 基本工時：式中，，取，則有： 。 則 9.鉆孔18 專用夾具、φ18高速鋼麻花鉆、游標卡尺、立式鉆床Z525 確定背吃刀量（ap）：ap=9mm 確定切削速度：v＝16~24m/min，選擇v=18m/min 相近的轉(zhuǎn)速為380r/min。 確定進給量f：f=0.2~0.4mm/r，取f=0.36mm/r 所以實際切削速度 基本工時：式中，，取，則有： 則 10.鉸孔15.5、攻絲M18H6、銑平臺 （1）專用夾具、φ15.5硬質(zhì)合金鉸刀偏角45°、游標卡尺、立式銑床X51 確定背吃刀量（ap）：ap=7.75mm 確定切削速度：v＝8~15m/min，選擇v=15m/min 相近的轉(zhuǎn)速為300r/min。 確定進給量f：f=0.12~0.15mm/r，取f=0.13mm/r 所以實際切削速度 基本工時：式中，則有： 則 （2）攻18 專用夾具、M18絲錐、游標卡尺、立式銑床X51 確定切削速度：v＝5~10m/min，選擇v=8m/min 相近的轉(zhuǎn)速為160r/min。 確定進給量f：f=P=1.5mm/r 所以實際切削速度 基本工時：其中，，取。是螺距，所以，??；取；進給次數(shù) 則： （3）銑平臺 專用夾具、φ5高速鋼立銑刀、游標卡尺、立式銑床X51 粗銑時，確定背吃刀量（ap）：ap=2.5mm 確定切削速度：由實用金屬切削計算手冊v＝15~21m/min，選擇v=15m/min 相近的轉(zhuǎn)速為1225r/min。 確定每齒進給量fz：f=0.07~0.18mm/z，取f=0.15mm/z 所以實際切削速度 確定進給量 基本工時：式中，，取，則有： 。 則 11.粗銑三面凹槽 專用夾具、φ15高速鋼立銑刀、游標卡尺、立式銑床X51 粗銑時，確定背吃刀量（ap）：ap=7.5mm 確定切削速度：由實用金屬切削計算手冊v＝15~21m/min，選擇v=15m/min 相近的轉(zhuǎn)速為380r/min。 確定每齒進給量fz：f=0.07~0.18mm/z，取f=0.15mm/z 所以實際切削速度 確定進給量 基本工時：式中，，取，則有： 。 則 12.粗銑上平面 專用夾具、φ36高速鋼立銑刀、游標卡尺、立式銑床X51 粗銑時，確定背吃刀量（ap）：ap=0.5mm 確定切削速度：由實用金屬切削計算手冊v＝15~21m/min，選擇v=18m/min 相近的轉(zhuǎn)速為160r/min。 確定每齒進給量fz：f=0.07~0.18mm/z，取f=0.15mm/z 所以實際切削速度 確定進給量 基本工時：式中，，取，則有： 。 則 13.擴孔24.8 專用夾具、φ24.8硬質(zhì)合金麻花鉆、游標卡尺、立式鉆床Z525 確定背吃刀量（ap）：ap=0.9mm 確定切削速度：v=46m/min 相近的轉(zhuǎn)速為680r/min。 確定進給量f：f=0.3~0.5mm/r，取f=0.48mm/r 所以實際切削速度 基本工時：式中，，取，則有： 則 14.粗鉸孔24.94 專用夾具、φ24.94硬質(zhì)合金鉸刀偏角45°、游標卡尺、立式鉆床Z525 確定背吃刀量（ap）：ap=0.07mm 確定切削速度：v＝8~15m/min，選擇v=15m/min 相近的轉(zhuǎn)速為195r/min。 確定進給量f：f=0.12~0.15mm/r，取f=0.13mm/r 所以實際切削速度 基本工時：式中，則有： 則 15.半精銑右側(cè)II平面 專用夾具、φ10高速鋼立銑刀、游標卡尺、立式銑床X51 半精銑時，確定背吃刀量（ap）：ap=0.25mm 確定切削速度：由實用金屬切削計算手冊v＝15~21m/min，選擇v=20m/min 相近的轉(zhuǎn)速為590r/min。 確定每齒進給量fz：f=0.07~0.18mm/z，取f=0.8mm/z 所以實際切削速度 確定進給量 基本工時：式中，，取，則有： 。 則 16.半精銑左側(cè)II平面 專用夾具、φ10高速鋼立銑刀、游標卡尺、立式銑床X51 半精銑時，確定背吃刀量（ap）：ap=0.25mm 確定切削速度：由實用金屬切削計算手冊v＝15~21m/min，選擇v=20m/min 相近的轉(zhuǎn)速為590r/min。 確定每齒進給量fz：f=0.07~0.18mm/z，取f=0.8mm/z 所以實際切削速度 確定進給量 基本工時：式中，，取，則有： 。 則 3 專用夾具設(shè)計 3.1 定位方案的確定 此零件需要銑削夾具設(shè)計，由于此工件的形狀和加工位置，不好加工，于是確定定位方案將工件固定好機床上，之后加工此零件。 該設(shè)計為了滿足銑削86左側(cè)端面的需要選擇以下定位 銑86左側(cè)端面時，在定位過程中需要保證零件自由度限制達到要求，故選用圓柱銷以及支承板進行定位，加上移動壓板，同時一個圓柱銷防止工件旋轉(zhuǎn)。滿足定位要求。 3.2 定位誤差的分析 銑86左側(cè)端面時，此夾具的主要定位是兩銷，于是這里計算定位誤差分析。 式中——第一定位基準孔與圓柱定位銷間的最小間隙； ——第二定位基準孔與圓柱定位銷間的最小間隙； 注：為工件中心線的偏轉(zhuǎn)角度誤差。 經(jīng)計算分析，定位合格。 3.3 夾緊裝置的要求 對夾緊裝置的基本要求： 1）在夾緊過程中，不得改變其夾緊固定的位置。 2）夾緊力的大小適當，夾緊力誤差越小對定位誤差影響也越小。 本設(shè)計是銑削平面夾具，加工工件的86的左側(cè)端面，由于撥叉分別以內(nèi)孔和右側(cè)端面定位，為必須保證在銑削過程中零件位置保持不動，所以必須設(shè)計夾緊裝置。銑削左側(cè)夾具設(shè)計的夾緊方式為移動壓板夾緊機構(gòu)進行夾緊，采用螺旋壓緊壓板機構(gòu)。 3.4 銑削力的確定 1.銑左側(cè)端面的銑削力 式中 F ——銑削力（N） CP——高速鋼立銑刀銑削系數(shù) ap ——銑削深度（mm） fz ——每齒進給量（mm） D ——銑刀直徑（mm） B ——銑削寬度（mm） n ——銑刀每分鐘轉(zhuǎn)數(shù) z ——銑刀齒數(shù) KP ——修正系數(shù) 根據(jù)工序得出， ap =0.5mm，fz =0.15mm，D =40mm，B =40mm，z=2，查表確定KP =0.6，Cp=294。 代入上式得粗銑F=108.263N 3.5 夾緊力的確定 撥叉銑夾具的夾緊力，計算步驟如下： 由《機床夾具設(shè)計手冊》得： 可知圖中的六角螺母的夾緊力：M=10mm, P=1.5mm作用力：F=45N，夾緊力：Wk=3550N 定位形式：工件以平面定位 夾緊形式：夾緊力與切削力方向垂直 公式： 參數(shù): K = 1.2 參數(shù): F =108.263 參數(shù):μ1 = 0.16 參數(shù):μ2 = 0.16 計算結(jié)果 =405.986 理論夾緊力大于實際夾緊力405.986N，故此夾緊機構(gòu)合格。 3.6 夾具簡要說明 圖4.1銑左側(cè)端面裝配圖 銑削夾具一般為固定零件對零件進行平面或槽等加工的夾具。它是一種專用夾具，它能跟好的對零件進行定位和加緊，在空間具有唯一確定位置。 1.如圖4.1為夾具裝配圖，夾具體采用的是鑄件。夾具體材料使用灰鑄鐵（HT200）。內(nèi)六角圓柱頭螺釘?shù)淖饔弥饕糜谥苯菍Φ秹K和定位鍵與夾具體連接，為防止其斷裂其材料需要較高的強度和韌性，連接使用螺釘跟方便拆卸。使用短圓柱銷和圓柱銷可以定位工件。 采用移動壓板組合機構(gòu)進行夾緊，其中六角螺母等可以方便拆卸和確保夾緊力。其中定位鍵是為了找準機床定位。對刀裝置選擇直角對刀塊。 圖4.2夾緊圖示 2.此夾具為銑86左側(cè)端面的夾具設(shè)計：由裝配圖可以看出，此夾具的定位方式為短圓柱銷和圓柱銷組合機構(gòu)限制了工件的4個自由度，工件底面支承板與限制了工件的1個自由度，移動壓板限制了1個自由度，這樣共限制了工件的6個自由度。首先先把夾具體通過定位鍵向安裝在銑床上，之后T型槽通過螺釘固定，其次安裝短圓柱銷、圓柱銷和支承板以及螺釘?shù)?，直角對刀塊通過螺釘及圓柱銷固定在夾具體上，接著安裝工件，工件定好位后，安裝移動壓板組合夾緊機構(gòu)，之后檢查夾具體是否安裝正確，工件是否安裝在正確的位置等，進行加工。 總結(jié)收獲 通過這次論文，我發(fā)現(xiàn)了自身存在的許多不足，在沒有做畢業(yè)設(shè)計以前覺得畢業(yè)設(shè)計只是對這幾年來所學(xué)知識的單純總結(jié)，但是通過這次做畢業(yè)設(shè)計發(fā)現(xiàn)自己的看法有點太片面。畢業(yè)設(shè)計不僅是對前面所學(xué)知識的一種檢驗，而且也是對自己能力的一種提高。通過這次畢業(yè)設(shè)計使我明白了自己原來知識還比較欠缺。自己要學(xué)習(xí)的東西還太多，以前老是覺得自己什么東西都會，什么東西都懂，有點眼高手低。通過這次畢業(yè)設(shè)計，深深的澆滅我的驕傲之心，我才明白學(xué)習(xí)是一個長期積累的過程，在以后的工作、生活中都應(yīng)該不斷的學(xué)習(xí)，努力提高自己知識和綜合素質(zhì)。 在設(shè)計過程中，我通過上網(wǎng)查閱資料和有關(guān)書籍、文獻等，與同學(xué)交流經(jīng)驗和自學(xué)，并向老師請教等方式，使自己學(xué)到了不少相關(guān)專業(yè)知識，也吃了不少苦，但是回報也是巨大。在整個設(shè)計過程中中我懂得了許多東西，培養(yǎng)了我獨立自主的能力，樹立了對未來即將工作的信心，相信會對今后的學(xué)習(xí)工作生活有非常重要的影響，而且不懼社會艱難。在實踐操作機床等實踐過程中，同時提高了我的動手實踐操作的能力，使我充分體會到了在艱苦奮斗直至成功一刻的成功時的喜悅。腳踏實地，認真嚴謹，實事求是的人生態(tài)度是我在畢業(yè)設(shè)計過程中感悟最深的一種態(tài)度，徜徉在書海中，面對資料和書本，只有這種態(tài)度，才能找出自己需要的資料。也是這種態(tài)度，慢慢培養(yǎng)自己的良好學(xué)習(xí)習(xí)慣和敏捷的思路，可以說這是我在設(shè)計過程中所學(xué)到的東西是這次畢業(yè)設(shè)計的最大收獲和財富，使我終身受益。 參考文獻 [1]王先逵主編，《機械制造技術(shù)基礎(chǔ)》，華中科技大學(xué)出版社，2007 [2]孫麗媛主編，《機械制造工藝及專用夾具設(shè)計指導(dǎo)》，冶金工業(yè)出版社，2003 [3]李益民主編，《機械制造工藝設(shè)計簡明手冊》，機械工業(yè)出版社，1994 [4]劉守勇主編，《機械制造與機床夾具》，機械工業(yè)出版社，1994 [5]楊興駿，莫雨松等編，《互換性與技術(shù)測量》第4版，中國計量出版社，2005 [6]南京市機械研究所主編,《金屬切削機床夾具圖冊》下冊(專用夾具)，機械工藝出版社，1984 致 謝 這次設(shè)計使我收益不小，為我今后的學(xué)習(xí)和工作打下了堅實和良好的基礎(chǔ)。但是，查閱資料尤其是在查閱夾具計算手冊時，由于經(jīng)驗不足，在選取數(shù)據(jù)上存在一些問題，不過我的指導(dǎo)老師每次都很有耐心地幫我提出寶貴的意見，在我遇到難題時給我指明了方向，最終我很順利的完成了畢業(yè)設(shè)計。在此謹向指導(dǎo)老師致以誠摯的謝意。 同時，在這次設(shè)計過程中，本組同學(xué)也給予我很大的幫助。在此，對老師和各位同學(xué)以及幫助過我的人表示由衷的感謝！ 25 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