180C柴油機(jī)活塞加工工藝規(guī)程及精鏜銷孔Ф70H6孔工裝夾具設(shè)計(jì)

喜歡這套資料就充值下載吧。。。資源目錄里展示的都可在線預(yù)覽哦。。。下載后都有，，請(qǐng)放心下載，，文件全都包含在內(nèi)，圖紙為CAD格式可編輯，【有疑問咨詢QQ:414951605 或 1304139763】 青島理工大學(xué)本科畢業(yè)設(shè)計(jì)（論文）說(shuō)明書 通過(guò)識(shí)別功能的自動(dòng)分割表面一代注塑模具 K Chung1 ，K Lee2 *和T Kim3 1R&D的研發(fā)團(tuán)隊(duì)， INUS科技，韓國(guó) 2School的機(jī)械航空工程系，漢城國(guó)立大學(xué)，韓國(guó) 3Department的數(shù)字內(nèi)容，世宗大學(xué)，韓國(guó) 摘要 本文提出了一種拓?fù)浣Y(jié)構(gòu)為基礎(chǔ)的識(shí)別算法通道功能使用概念多面孔環(huán)。該多面孔環(huán)是一個(gè)概念是循環(huán)形成幾個(gè)連接面孔和充當(dāng)入口或出口的通道。因此一個(gè)通道功能由兩個(gè)多面孔環(huán)相應(yīng)的入口和出口所確定認(rèn)識(shí)到。至創(chuàng)造的型芯和腔的注塑模具的部分通道的功能，無(wú)論是入口或出口的每個(gè)通道必須涵蓋的面，這面構(gòu)成分型面。該算法，本文提出了檢查連接兩個(gè)多面孔環(huán)承認(rèn)通道特征。在一個(gè)零件上通道特征的數(shù)量是通過(guò)Euler方程計(jì)算的，并且驗(yàn)證程序一直在運(yùn)行直到驗(yàn)證通道特征等于這個(gè)數(shù)字。為了找到某一零件所有多面洞環(huán)，該提出的方法考慮了所有的組合連接的面。凸邊使用用來(lái)判斷多面洞環(huán)的正確性。利用本文所提出的算法，通道特征會(huì)被有效地識(shí)別出來(lái)。提出的方法被很多實(shí)例所驗(yàn)證。 關(guān)鍵詞：通道特征，特征識(shí)別，多面洞環(huán)，注塑模具 一、引言 注塑成型是生產(chǎn)熱塑性聚合物部分最普遍的進(jìn)程。在這過(guò)程中，熱塑性聚合物注入腔所形成的型芯和腔。這模具腔的形狀確定的塑料零件。 一般注塑模具的構(gòu)造如圖1所示。 圖1展現(xiàn)了一個(gè)簡(jiǎn)化的注塑模具和顯示板，型芯和腔。除了上面展示的那些，實(shí)際注塑模具有許多標(biāo)準(zhǔn)件，噴射器，流動(dòng)和冷卻系統(tǒng)。從歷史上看，模具設(shè)計(jì)師使用二維計(jì)算機(jī)輔助設(shè)計(jì)（ CAD ）系統(tǒng)在二維圖紙畫出一個(gè)模具。然而，最近企圖注塑模具的設(shè)計(jì)使用三維CAD系統(tǒng)在個(gè)人電腦上廣泛使用。 利用三維CAD系統(tǒng)進(jìn)行模具設(shè)計(jì)，許多設(shè)計(jì)任務(wù)可以自動(dòng)或便利。 特別是，分型面可以自動(dòng)生成或至少更方便[ 1 - 4 ] 。 分型面是用來(lái)切斷外部塊內(nèi)附部分被塑造成兩塊，即型芯和腔。當(dāng)這部分有通道，無(wú)論其入口或出口都必須被表面所覆蓋。即使零件表面通過(guò)延長(zhǎng)零件到外面而非常容易產(chǎn)生，對(duì)于復(fù)雜零件來(lái)說(shuō)驗(yàn)證所有的通道特征和用恰當(dāng)表面覆蓋它們是有錯(cuò)誤傾向的任務(wù)。在本文中，提出了通過(guò)多面分析通道特征的算法。如圖2所示。 二、背景和動(dòng)機(jī) 圖1 鑄造模型的基本配置 在注塑模具設(shè)計(jì)系統(tǒng)，是基于三維CAD系統(tǒng)，設(shè)計(jì)過(guò)程開始于零件的三維CAD模型。型芯區(qū)塊分為型芯的腔。這個(gè)過(guò)程如圖3所示。型芯和腔的生成如圖4所示。 首先，設(shè)計(jì)師設(shè)計(jì)一個(gè)能包含零件模型的立方塊，在圖 5中表示 。這個(gè)矩形塊被稱為型芯區(qū)塊，這將最終成為型芯的腔。其次，分型面， 而分裂的型芯區(qū)塊的型芯和空腔，會(huì)產(chǎn)生沿外邊界部分模型如圖6a所示。在分型面，如果要求，也可以產(chǎn)生的一端通道特征如圖 6b所示。 圖2 貫穿多面的通道特征 圖3 制作型芯和空腔的流程 型芯塊通過(guò)零件和模型的表面被分離出型芯和空腔。型芯在型芯塊的較低部分，空腔在上部。型芯和空腔的制造過(guò)程如圖7所示。 如圖6b所顯示的，分型面應(yīng)產(chǎn)生的一端每個(gè)通道功能分裂型芯區(qū)塊完全變成兩件，即型芯和腔。范例中所示，對(duì)于一個(gè)簡(jiǎn)單的通道特征，在分型面的通道特征是很容易產(chǎn)生。但是在復(fù)雜通道特征形成多個(gè)面的例子中如圖8所示，識(shí)別環(huán)路包圍的兩端通道特征和表面是非常困難和費(fèi)時(shí)的任務(wù)。 圖9顯示零件表面帶有通行特征的一個(gè)零件模型。以及圖 10 顯示通過(guò)覆蓋通道特征所形成的表面。如圖10所示 ， 這些表面分離通過(guò)區(qū)域包括許多復(fù)雜的面。 圖4，具有一個(gè)通道特征的典型零件上表面和下表面 圖5 型芯快 圖6 產(chǎn)生分型面 圖7 型芯和空腔的形成 圖8 聽力裝置外殼的簡(jiǎn)化圖 大多數(shù)通過(guò)注塑成型的塑料零件在很多面孔上具有通道特征。 這使自動(dòng)識(shí)別通道特征和創(chuàng)建零件表面變得困難。在本文中，一種檢測(cè)通道特征的方法在自動(dòng)生成零件表面的基礎(chǔ)上被提出來(lái)。 2.1相關(guān)工作 自基普里亞努在CAD系統(tǒng)在他的博士論文[ 5 ]指出形狀分類的必要性， 特征識(shí)別中實(shí)體模型一直是熱門研究課題。到現(xiàn)在為止，從CAD數(shù)據(jù)提取加工特征一直是主要研究議題，而且特征識(shí)別技術(shù)已被衍生提取加工功能，如孔， 插槽和口袋特征[ 6 ] 。有四種不同的特征識(shí)別的方法： （a）在圖形模式匹配的方法[ 7 ] ， （b）凸包分解方法[ 8 ， 9 ] ， （c）基于細(xì)胞的分解方法[ 10 ] ， （d）在暗示為基礎(chǔ)的推理方法[ 11 ] 。 Joshi和 Chang所發(fā)現(xiàn)的圖形模式匹配方法在特征識(shí)別領(lǐng)域已被證明是最流行的。這種的做法，在一個(gè)零件的B -Rep數(shù)據(jù)結(jié)構(gòu)的被映射到一個(gè)節(jié)點(diǎn)代表面孔 其分支機(jī)構(gòu)代表邊緣的圖上。該圖被稱為面對(duì)鄰接圖（ FAG ） 。然后，一個(gè)子圖同構(gòu)是用來(lái)搜索匹配的子圖功能模板。然而，在具有交叉功能的例子中，子圖部分的變形，這使特征識(shí)別是不可能的。 Woo[9]提出了凸包分解方法.這種方法確認(rèn)特征之間的布爾運(yùn)算的一部分模型和凸包周邊零件模型。布爾部分之間的運(yùn)作模式和凸包是采用遞歸。當(dāng)輸出布爾操作是空的，行動(dòng)是終止。不幸地是， 分解過(guò)程不一定收斂。為克服這一問題，Kim提出了交替之卷分區(qū)（ ASVP ） 分解[ 9 ] ，其中確認(rèn)功能比較 零件模型面臨的凸包的面。 圖9 構(gòu)成分型面的通道特征所形成表面 圖10 覆蓋通道特征的表面 Sakurai 和 Chin ［?。保啊。萏岢隽嘶诩?xì)胞分解方法， 這種方法確認(rèn) 特征分解三角洲量到最低限度細(xì)胞，然后將這些細(xì)胞結(jié)合。三角洲量同股票和零件模型是不同的。 使用這種方法，由分解三角洲量所產(chǎn)生的細(xì)胞數(shù)量很大。因此，大量的組合必須識(shí)別相結(jié)合的細(xì)胞的特征。 Vandenbrande [ 11 ]提出了暗示推理的方法。這種做法，提出了是為了識(shí)別交叉特征，這是圖形模式匹配的方法主要問題。 這種技術(shù)識(shí)別特征源于傳統(tǒng)的軌跡特征。例如，一個(gè)插槽提示生成，當(dāng)一對(duì)平面平行相交時(shí)， 對(duì)應(yīng)于槽壁。有了這樣的提示， 該算法識(shí)別槽特征通過(guò)搜索槽壁之間的縫隙。 正如所建議的上述情況，研究加工特征識(shí)別目前正在積極進(jìn)行。一些研究也已完成對(duì)特別與模具有關(guān)特征識(shí)別，例如削弱特征[ 13 ] 。然而，就目前作者所知，沒有識(shí)別分型面產(chǎn)生的通道特征數(shù)據(jù)的研究。 三、概述 一個(gè)通道特征由一對(duì)孔環(huán)和連接孔環(huán)的面組成的，從而通道特征識(shí)別是一個(gè)尋找配對(duì)孔環(huán)的程序。由于通道特征可以通過(guò)幾個(gè)連接的面孔，孔環(huán)附著的連接面應(yīng)該首先被識(shí)別出來(lái)。 當(dāng)一個(gè)洞環(huán)被發(fā)現(xiàn)，其配對(duì)孔環(huán)會(huì)被搜查。如果這對(duì)孔環(huán)滿足構(gòu)成一個(gè)通道條件，它將被記為一個(gè)通道特征。 3.1定義 由于通道特征通過(guò)的連接面是被識(shí)別的目標(biāo)特征，一個(gè)特別孔環(huán)，稱為多面孔環(huán)，形成多個(gè)面，在本文中定義如下： 對(duì)于任何一對(duì)連接的面，兩面所有共享的邊緣被消除，擴(kuò)展面生成。如果內(nèi)部環(huán)的擴(kuò)展面邊緣存在，這些內(nèi)部環(huán)被定義為多面孔環(huán)。 一個(gè)說(shuō)明多面孔環(huán)的例子如圖11所示。 圖11 多面孔環(huán)的一個(gè)例子 3.2基本概念 一個(gè)通道特征由兩個(gè)孔環(huán)組成包括多面孔環(huán)和與其相連的面。這些面被稱為內(nèi)面。因此，尋找通行特征的過(guò)程，可以在概念上 簡(jiǎn)化尋找兩個(gè)相連接孔環(huán)。詳細(xì)過(guò)程的解釋請(qǐng)看第4節(jié)。 四、算法 在本節(jié)中提出的算法將詳細(xì)說(shuō)明解釋 。識(shí)別簡(jiǎn)單的通道特征詳細(xì)的算法將首先被解釋，然后識(shí)別多連接面孔環(huán)所采用的辦法將被敘述。一個(gè)通道特征被簡(jiǎn)單定義如果其入口和出口位于在單一的面。最后，多面孔環(huán)組成通道必要的條件以及找到結(jié)合的連接面方法，將加以解釋。 4.1通過(guò)特征識(shí)別算法 如前所述，一個(gè)通道特征由兩個(gè)孔環(huán)通過(guò)連接面互相結(jié)合組成。 將使用下面的例子描述通道特征識(shí)別詳細(xì)的程序。 在圖12中顯示的樣本零件擁有一個(gè)通道特征，每個(gè)對(duì)象定義如下： 圖12 應(yīng)用簡(jiǎn)單通道特征的例子 a=樣本的上表面 b=連接上下表面的面 c=樣本的下表面 e1=a、b面共有的邊 e2=b、c面共有的邊 L1=a面上的孔環(huán) L2=b面上的孔環(huán) 在這個(gè)樣本零件中，由環(huán)組成通道特征是L1和L2 ，和面，如b面 ，連接這些環(huán)。一般來(lái)說(shuō)，面（面b）組成一個(gè)擁有相鄰面（a面和c面）共同邊的通道特征，而且這些邊在相鄰面（a面和c面）上形成了孔環(huán)。也就是說(shuō)，b面是組成通道特征的面并命名為側(cè)面。a面和c面分別被命名為入口面和出口面。尋找通道特征的程序如下： 1 ．在一個(gè)面內(nèi)搜索孔環(huán)（通道入口面） 。 2 ．搜索組成孔環(huán)的邊，在第1步中搜索。 3 ．搜索分享的邊緣面（側(cè)面），在第2步中搜索。 4 ．如果在第3步中所尋找面（側(cè)面）的邊緣形成了一個(gè)孔環(huán)內(nèi)另一面（出口面），這孔環(huán)和在第1步中的孔環(huán)形成一個(gè)通道特征。 上面對(duì)算法的解釋是在一個(gè)單獨(dú)的面上識(shí)別通道特征。 為了在多個(gè)面上識(shí)別通道特征，就必須用到多面孔環(huán)的概念。 4.2多連接面孔環(huán)的識(shí)別 如前所述，一個(gè)多面孔環(huán)形成一個(gè)通過(guò)消除連接面共同邊緣形成擴(kuò)展的面。在多個(gè)連接面識(shí)別孔環(huán)需要三個(gè)步驟： （a）消除連接面共有的邊 （b ）用余下的邊建造環(huán) （c ）驗(yàn)證內(nèi)部環(huán)。 識(shí)別多面孔環(huán)的程序描述如下。用于多面孔環(huán)的樣本零件如圖13，灰色面的連接面在調(diào)查中?；疑婀蚕磉卐1和e2 。如果兩面共享邊被刪除并且兩面被認(rèn)為是一個(gè)面對(duì)如圖 13b所示，兩個(gè)環(huán)形成，即L1和L2 。環(huán)L1對(duì)應(yīng)內(nèi)環(huán)和環(huán)L2對(duì)應(yīng)于外環(huán)。因此，在這個(gè)例子中多面孔是環(huán)L1。同樣，內(nèi)部環(huán)形成多個(gè)隨意連接面被定義為多面孔環(huán)如果當(dāng)連接面共享邊被消除后內(nèi)環(huán)存在。一旦多面孔環(huán)被驗(yàn)證，先前已描述的尋找簡(jiǎn)單通道的程序就能用來(lái)識(shí)別多面中的通道特征。 4.3．多面孔環(huán)形成通道的必要條件 多面孔環(huán)形成通道特征有兩個(gè)必需條件。首先，組成多面孔環(huán)所有的邊必須是凸的。例如，對(duì)于零件如圖 14 說(shuō)明，在面F1中環(huán)L1是一個(gè)孔環(huán)，但組成的邊孔環(huán)L1并不是通道特征，因?yàn)樗鼈兪前?。這可能是一個(gè)自然的結(jié)論考慮到多面孔環(huán)的邊成為無(wú)論是入口或出口的通道，唯有凸邊可以形成入口或出口。因此，一個(gè)程序來(lái)判斷凸邊是必要的。Kyprianou對(duì)邊的分類如圖15 [ 14 ]所示 。邊通過(guò)兩個(gè)面共享邊所組成的夾角分類，例如， 如果測(cè)量?jī)?nèi)部角度小于180 ，邊是凸的。同樣，如果大于180 ，邊是凹的。如果兩面連接順利如圖中c或d ，邊通過(guò)實(shí)際的曲率來(lái)分類[ 14 ] 。通過(guò)判斷邊的凹凸，組成多面孔環(huán)的凹面或順利凹邊緣在程序識(shí)別通道特征中被排除。 圖13 識(shí)別通道特征的例子 圖14 不能構(gòu)成通道特征的孔環(huán) 圖15 Kyprianou角的分類 即使所有的邊滿足第一條件，有的情況下，通道特征因?yàn)榻M成模型的多面孔環(huán)和其他面的關(guān)系而不能組成。在這里，第二條件下發(fā)揮作用。該多面孔環(huán)可以被看作是一個(gè)邊的集合，將約束后來(lái)的分型面的相應(yīng)通道特征。由于表面生成臨別不得重疊的面的一部分，其多面孔環(huán)內(nèi)部重疊區(qū)域表面必須考慮排除。 一個(gè)多面孔環(huán)滿足這樣的條件如圖16，圖17所顯示多面孔環(huán)違反條件。換言之，多面孔環(huán)L2生成的零件表面如圖16b所示， 這是從復(fù)合面衍化出來(lái)如圖16a，組成零件的面沒有任何重疊的。 圖16 可用多面孔環(huán)舉例 圖17 不可用多面孔環(huán)舉例 在復(fù)合面是一組連接的面孔，其中多面孔環(huán)被搜查。但是， 多面孔環(huán)L2生成的零件表面如圖17b，這是在復(fù)合面尋找圖17a，重疊的部分面孔。 因此，圖17這種情況必須在尋找通道特征中排除考慮。不可用的多面體環(huán)具有詳細(xì)條件如下。讀者可能會(huì)問為什么考慮這樣奇怪的例子。所有可能的多面孔環(huán)必須考慮，因?yàn)樗鼈兪怯蓮?fù)合連接的面自動(dòng)生成的。 共邊的面組成了多面孔環(huán)和不參加的復(fù)合過(guò)程的是側(cè)面。如果邊的起點(diǎn)和終點(diǎn) 被多面孔環(huán)中兩個(gè)側(cè)面共有，這條邊可以和多面孔環(huán)的其他邊組成環(huán)。使用此環(huán)生成的分型面應(yīng)該是側(cè)面中的一個(gè)，這使分型面的重疊零件表面。 圖18b代表18a零件二維布局圖。面F1、F2、F3和F4對(duì)應(yīng)復(fù)合面，面S1、S2、S3、S4、S5對(duì)應(yīng)側(cè)面。多面孔環(huán)的邊界邊用粗線表示。 圖18b所示邊a一條是側(cè)面所共有的邊，a的起點(diǎn)和終點(diǎn)都在多面孔環(huán)上。因此，邊a 形成一個(gè)回路連同其他邊S5，也屬于多面孔環(huán)。由這一回路產(chǎn)生成的分型面因?yàn)镾5的存在也屬于多面孔環(huán)。因此，分型面重疊S5。通過(guò)這種方式，識(shí)別多面孔環(huán)屈服無(wú)效分型面，可避免調(diào)查多面孔環(huán)與側(cè)面共有邊的終點(diǎn)的關(guān)系。 4.4找到所有連接面組合的程序 為了在一個(gè)零件中尋找多面孔環(huán)，驗(yàn)證并復(fù)合連接面是需要。有二種方法可用于生成一組連接面。 第一種方法涉及到通過(guò)判斷面組中面的連接性選取一組用來(lái)復(fù)合的面。然而，這一做法，當(dāng)總數(shù)是很大的隨意生成的組合面數(shù)量增加了可能性。 在此 X=結(jié)合的數(shù)量 n=面的總數(shù) r=將要復(fù)合的面的數(shù)量 例如，如果面的總數(shù)是200 ， 當(dāng)四個(gè)面被復(fù)合時(shí)待定面組合數(shù)量是64 684 950 因此，這種做法在一組連接面復(fù)合時(shí)是低效的。 圖8 Planar組成面展示 第二種方法涉及產(chǎn)生通過(guò)已經(jīng)驗(yàn)證過(guò)設(shè)定一個(gè)可行的面組的連接面面組。 在此方法中，已記錄的面組中各成員面都存儲(chǔ)在堆棧。然后，它搜索能連接最新登記面的面。如果沒有面連接到最新記錄面，那么最后記錄的面將被從堆棧中移除和繼續(xù)搜索與移除面下面的記錄面。這種方法可以有效地縮短生成僅僅通過(guò)結(jié)合面找面組時(shí)間，而第一辦法搜尋所有可能的組合和檢查連接性。 所產(chǎn)生用來(lái)復(fù)合的面組被用于尋找模型中的多面孔環(huán)。 五、執(zhí)行 5.1程序結(jié)構(gòu) 提出算法的基本概念如下。到現(xiàn)在被搜索到的通道特征等于一個(gè)模型中通道特征的數(shù)量，用于復(fù)合的面增加到表2.用Euler方程得到通道特征的總數(shù)。每一步，通過(guò)搜索相連接的多面孔環(huán)，多面孔環(huán)和通道特征被找到并識(shí)別。因此，執(zhí)行程序有四個(gè)子程序，即找到通道特征總數(shù)的路徑 ， 尋找所有組合面的結(jié)合，識(shí)別多面孔環(huán)和通道特征。這個(gè)項(xiàng)目是在Windows NT上用Unigraphics V15.0 API開發(fā)的。 5.2運(yùn)行時(shí)間分析 本文中提出的算法搜索擁有越來(lái)越多的結(jié)合面通道特征。因此，模型中識(shí)別通道特征運(yùn)行時(shí)間由連接面最大數(shù)量確定。因此，運(yùn)行時(shí)間可由最大復(fù)合面數(shù)表示。 如前所述，產(chǎn)生用于復(fù)合的面組程序涉及到多面與一面和再次進(jìn)行搜尋面與已搜查面，直至連接面組所有成員等于給定連接的面數(shù)。如果在一個(gè)零件中的面數(shù)是n，平均連接面的數(shù)量是m,用于復(fù)合的面數(shù)是r，那么隨意組合的面組是數(shù)列n ￠mr?1: X ≈O(n ￠mr?1) 一般而言，一個(gè)零件中平均連接面數(shù)到遠(yuǎn)小于面的總數(shù)。 圖8所示這個(gè)零件，總面數(shù)是286平均連接面數(shù)是5 。在這種情況下，預(yù)計(jì)用于復(fù)合的面數(shù)在表1中顯示 。 六、舉例 6.1樣本部分 樣本零件如圖19a條有很多凹臺(tái)面， 孔和通道特征邊界的孔環(huán)形成一個(gè)面。圖19b顯示6個(gè)通道特征識(shí)別。 圖19 擁有環(huán)槽和通孔的典型零件 6.2 L形部分 圖20a顯示的樣本零件中是L形，有一個(gè)通過(guò)特征組成孔環(huán)形成多面加上樣本特征通道。在這種情況下，形成多面孔環(huán)的面數(shù)是4 。被識(shí)別的通道特征如圖20b。 圖20 L型零件 6.3套管的手機(jī) 圖21a顯示樣本零件是一個(gè)手機(jī)封面并擁有14個(gè)通道特征。識(shí)別的通道特征如圖21b。 圖21 典型手機(jī)表面 6.4 小型組成封面 樣本零件如圖 22a的是一個(gè)小型部分封面 ，并擁有多面通道特征。這部分有15個(gè)通道特征。識(shí)別的通道特征如圖22b。 上述4例的運(yùn)行時(shí)間在表2中列出。 圖22 聽力裝置表面 七、結(jié)論 本文提出了一種算法，使用多面孔環(huán)概念自動(dòng)識(shí)別通道特征。分型面的自動(dòng)產(chǎn)生是用三維CAD系統(tǒng)設(shè)計(jì)模具最自然的目標(biāo)任務(wù)。當(dāng)零件的邊界產(chǎn)生之后分型面很容易生成。但是，如果被制造零件具有通道特征，其入口和出口應(yīng)該被分型面覆蓋。有時(shí)，當(dāng)零件有一個(gè)復(fù)雜的形狀時(shí)驗(yàn)證所有通道特征是一個(gè)乏味和容易出錯(cuò)的任務(wù)。在本文該算法通過(guò)自動(dòng)識(shí)別多面的通道特征縮短設(shè)計(jì)時(shí)間。 本文中該算法提出了識(shí)別通道特征，增加可復(fù)合面數(shù)量。因此，識(shí)別通道特征時(shí)間受多面孔環(huán)形成通道特征的面的最大數(shù)量影響。隨著復(fù)合面的增多，選擇用于復(fù)合面的時(shí)間也因?yàn)槊娼M數(shù)量的增加隨之增加。因此，該算法生成復(fù)合的面組需要首先通過(guò)排除不實(shí)際的情況。此外，基于通道特征自動(dòng)生成分型面算法需要開發(fā)。分型面位于入口和出口的通道時(shí)生成分型面會(huì)更加困難。當(dāng)通道的側(cè)面有一個(gè)凸曲率這種情況就會(huì)發(fā)生。 21 畢業(yè)設(shè)計(jì)（論文）任務(wù)書 專業(yè) 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 班級(jí) 機(jī)械051 姓名 湯啟峰 下發(fā)日期 2009-3-10 題目 180C柴油機(jī)活塞加工工藝規(guī)程及工裝設(shè)計(jì) 專題 柴油機(jī)活塞工藝規(guī)程及鏜夾具設(shè)計(jì) 主 要 內(nèi) 容 及 要 求 設(shè)計(jì)內(nèi)容：首先仔細(xì)分析所加工零件的主要表面、技術(shù)要求、生產(chǎn)綱領(lǐng)，制定一套以上的本零件的加工工藝規(guī)程，認(rèn)真分析各規(guī)程的優(yōu)缺點(diǎn)，從中選擇最優(yōu)的，根據(jù)這一規(guī)程，繪制出各個(gè)主要工序的工序卡片，設(shè)計(jì)主要工序的機(jī)床夾具，分析計(jì)算定位誤差，設(shè)計(jì)機(jī)床夾具的主要零件。 要求：根據(jù)給定的180C活塞零件圖，制定出符合加工要求的工藝規(guī)程，并對(duì)所制定的各種規(guī)程進(jìn)行可得性和優(yōu)化性比較，從中選出最好的工藝設(shè)計(jì)，設(shè)計(jì)其中重要工序的工藝裝備，要求的圖紙量折合為零號(hào)圖后不少于三張，設(shè)計(jì)說(shuō)明書不少于二萬(wàn)字。 主要技術(shù)參數(shù) 主要數(shù)據(jù)： 180C柴油機(jī)活塞為組合式活塞，活塞頭材料為42CrMoA，活塞裙的材料為鑄造鋁；規(guī)定活塞為中小批量生產(chǎn)；銷孔精度為H6；重量為12240±20g。 進(jìn) 度 及 完 成 日 期 3月16日至3月27日（2周）:工廠實(shí)習(xí),熟悉了解柴油機(jī)基本結(jié)構(gòu)及其加工工藝。同時(shí)熟悉AUTOCAD或UG等設(shè)計(jì)軟件的使用方法。 3月27日至4月6日（2周）: 根據(jù)設(shè)計(jì)任務(wù)書要求查閱資料，完成外文翻譯工作。 4月6日至4月12日（1周）：工藝方案設(shè)計(jì)的擬定及技術(shù)分析、可行性分析，確定出最佳方案。 4月 13日至4 月 26日（2周）：編制工藝卡片，計(jì)算主要工序的切削用量和基本時(shí)間，設(shè)計(jì)其中某一重要工序的夾具。 4月 27日至5 月 31日（4周）：繪制主要零件圖及活塞裝配圖和夾具總裝圖。 6月 1日至6 月14日（2周）：編寫畢業(yè)設(shè)計(jì)說(shuō)明書。 6月15日至6月21日（1周）: 修改、整理資料,打印資料。 6月22日至6月23日（2天）: 答辯。 教學(xué)院長(zhǎng)簽字 日 期 教研室主任簽字 日 期 指導(dǎo)教師簽字 日 期 摘 要 在柴油機(jī)氣缸內(nèi)，活塞在一部分工作循環(huán)壓縮氣體，而在另一部分工作循環(huán)氣缸內(nèi)混合氣體燃燒膨脹使活塞頂面承受高溫（約569°C）高壓（約116～120Kgf/cm2）氣體的作用，并把壓力通過(guò)活塞銷、連桿傳給曲軸?？梢?，活塞是在高溫高壓下作長(zhǎng)時(shí)間連續(xù)變負(fù)荷的往復(fù)運(yùn)動(dòng)，它的負(fù)荷和工作環(huán)境很惡劣。在本設(shè)計(jì)中將對(duì)活塞的加工工藝進(jìn)行設(shè)計(jì)，以保證活塞長(zhǎng)久穩(wěn)定工作。現(xiàn)將設(shè)計(jì)中所做的工作簡(jiǎn)要介紹如下： 180C柴油機(jī)活塞加工工藝合理性是很重要的，通過(guò)對(duì)零件的作用及工藝方案分析，擬定毛坯的制造形式及工藝路線，通過(guò)分析、比較，采用了相對(duì)集中加工工藝方案，最終確定比較合理的機(jī)械加工工藝路線。制定工藝路線時(shí)主要考慮粗、精加工安排、加工方法選擇、工序集中與分散、加工順序等方面的要求。接著確定加工余量、工序尺寸，經(jīng)過(guò)對(duì)工序特點(diǎn)的分析，恰當(dāng)選擇相應(yīng)加工設(shè)備和工藝裝備。接下來(lái)經(jīng)過(guò)計(jì)算查表確定活塞各主要工序的切削用量并繪制工序卡片，最后設(shè)計(jì)夾具。設(shè)計(jì)夾具時(shí)，要多方面考慮，嚴(yán)格要求，機(jī)床夾具的好壞直接影響工件加工表面的位置精度。所以，機(jī)床夾具設(shè)計(jì)是裝備設(shè)計(jì)中的一項(xiàng)重要的工作，是加工過(guò)程中最活躍的因素之一。在本畢業(yè)設(shè)計(jì)中特別設(shè)計(jì)了定位準(zhǔn)確、結(jié)構(gòu)簡(jiǎn)單和使用方便的精鏜銷孔夾具。 關(guān)鍵字：活塞；工藝路線；加工設(shè)備；切削用量；夾具 Abstract In diesel engine cylinder, the piston part of the cycle in the compressed gases, and in another part of the work cycle of the combustion gas mixture within the cylinder so the piston top surface expansion high pressure (about 116 ~ 120Kgf/cm2)°under high temperature (about 569°C) gas role, and the pressure through the piston pin, connecting rod to the crankshaft. Can be seen that the piston is a long time under high temperature and high pressure in continuous reciprocating motion of the load, its load and working conditions were appalling. During the design process of the piston will be designed to ensure long-term stability of the work piston. The design of the work done by a brief introduction as follows: Diesel Engine Piston 180C reasonable processing technology is important, the role of parts and technology program analysis, preparation of rough form and process manufacturing line, through the analysis, comparison, use of the relative concentration of processing programs, and ultimately more reasonable to determine the mechanical line processing. The development process of rough line the main consideration, finishing arrangements, choice of processing methods, centralized and decentralized processes, such as processing the order requirements. Then determine the allowance, process size, after the analysis of the characteristics of the process, select the appropriate processing equipment and technical equipment. Calculated look-up table to determine the next major piston cutting process and the mapping of processes card, the design of the final fixture. Fixture design, it is necessary to take various aspects into account, the strict requirements of the fixture a direct impact on the surface of the workpiece processing position accuracy. Therefore, the machine tool design fixture design is an important task is the processing of one of the most active. During the graduation project in a specially designed positioning accuracy, simple structure and easy-to-use precision pin hole boring jig. Keywords: Piston; Technology; processing equipment; cutting; Fixture 目錄 摘要……………………………………………………………………Ⅰ Abstract………………………………………………………………Ⅱ 目錄………………………………………………………………………Ⅲ 第1章 序論………………………………………………………… 1 1.1?180 C柴油機(jī)活塞的由來(lái) ……………………………………………………1 1.2 機(jī)械加工工藝規(guī)程………………………………………………………………7 第2章 180C柴油機(jī)活塞零件圖的分析 ………………………………8 2.1 活塞的功用……………………………………………………………………8 2.2 活塞的結(jié)構(gòu)特點(diǎn)和技術(shù)要求 …………………………………………………8 2.3 180C活塞的工作情況 …………………………………………………………9 2.4 180C組合活塞結(jié)構(gòu) ……………………………………………………………10 第3章 活塞加工工藝制定 …………………………………………12 3.1 計(jì)算生產(chǎn)綱領(lǐng)確定生產(chǎn)類型 …………………………………………………12 3.2 審查零件圖圖樣工藝性 ……………………………………………………12 3.3 選擇毛坯 ………………………………………………………………………12 3.4 工藝過(guò)程設(shè)計(jì) ………………………………………………………………13 3.5 確定加工余量及毛坯尺寸、設(shè)計(jì)毛坯圖 …………………………………25 3.6 部分重要工序設(shè)計(jì) ……………………………………………………………29 3.7 確定切削用量及基本用時(shí) …………………………………………………33 第4章 夾具設(shè)計(jì)……………………………………………………50 4.1 機(jī)床夾具概述 ………………………………………………………………50 4.2 機(jī)床專用夾具設(shè)計(jì)的基本要求 ……………………………………………50 4.3 活塞夾具的設(shè)計(jì)思路 …………………………………………………………51 4.4 活塞裙精鏜銷孔夾具設(shè)計(jì) ……………………………………………………51 結(jié)論…………………………………………………………………56 參考文獻(xiàn)…………………………………………………………57 致謝…………………………………………………………………58 附件 1…………………………………………………………59 附件 2…………………………………………………………81 青島理工大學(xué) 畢業(yè)設(shè)計(jì)實(shí)習(xí)報(bào)告 題目 180C柴油機(jī)活塞加工工藝規(guī)程及工裝設(shè)計(jì) 學(xué)生姓名： 湯啟峰 學(xué)生學(xué)號(hào)： 200506024 指導(dǎo)教師： 趙 娟 機(jī)械工程 學(xué)院 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 專業(yè) 051 班 2009年6月15日 Recognition of pass features for automatic partingsurface generation in injection mouldsK Chung1, K Lee2* and T Kim31R&D Team, INUS Technology, Korea2School of Mechanical and Aerospace Engineering, Seoul National University, Korea3Department of Digital Contents, Sejong University, KoreaAbstract: This paper proposes a topology-based algorithm for recognizing passage features using theconcept of a multiface hole loop. The multiface hole loop is a conceptual hole loop that is formed overseveral connected faces and serves as an entrance or an exit of a passage. A passage feature is thusrecognized by identifying two multiface hole loops corresponding to its entrance and exit. Togenerate the core and the cavity of an injection mould for a part with passage features, either theentrance or the exit of each passage must be covered by a surface, and this surface constitutes theparting surfaces. The algorithm proposed in this paper checks the connectivity of the two multifacehole loops to recognize passage features. The total number of passage features in a part iscalculated from the Euler equation, and the identication procedure continues until the number ofidentied passage features equals this number. To nd all of the multiface hole loops in a part, theproposed approach considers all of the combinations of connected faces. The edge convexity is usedto judge the validity of multiface hole loops. By using the algorithm proposed in this paper, thepassage features could be recognized eVectively. The approach proposed is illustrated with severalexample cases.Keywords: passage feature, feature recognition, multiface hole loop, injection mould1INTRODUCTIONInjection moulding is the most prevalent process for theproduction of thermoplastic polymer parts. In thisprocess, a thermoplastic polymer is injected into thecavity formed by the core and the cavity. This mouldcavity determines the shape of the plastic part. Thegeneral conguration of an injection mould is shown inFig. 1.Figure 1 represents a simplied conguration of aninjection mould and illustrates the plates, the core andthe cavity. The actual injection mould has manystandard parts, ejectors, a slide system and a coolingsystem, in addition to those shown. Historically, moulddesigners have generated the two-dimensional drawingsof a mould using a two-dimensional computer aideddesign (CAD) system. Recently, however, attempts todesign injection moulds using three-dimensional CADsystems have been made as three-dimensional CADsystems running on personal computers have becomewidely available.By using a three-dimensional CAD system for moulddesign, many design tasks can be automated or facili-tated. In particular, the parting surfaces can be generatedautomatically or at least much more conveniently 14.Parting surfaces are used to cut the external block enclos-ing the part to be moulded into two pieces, i.e. the coreand the cavity. When the part has passages, either theirentrances or exits have to be covered by the partingsurfaces. Even though the parting surfaces are generatedfairly easily by extending the parting lines towards theoutside of the part, identifying all the passage featuresand covering them with proper surfaces are error-pronetasks when the shape of the part is complicated. In thispaper, an algorithm for nding such passage featurespassing through multiple faces, as shown in Fig. 2, isproposed.2BACKGROUND AND MOTIVATIONIn injection mould design systems that are based onthree-dimensional CAD systems, the design process783B05601IMechE 2002Proc Instn Mech Engrs Vol 216 Part B: J Engineering ManufactureThe MS was received on 21 May 2001 and was accepted after revisionfor publication on 21 December 2001.*Corresponding author: Department of Mechanical and AerospaceEngineering, Seoul National University, San56-1, Shillim-Dong,Kwanak-Gu, Seoul 151-742, Korea.starts from the three-dimensional CAD model of a part.Then, the core and the cavity are created from the partmodel. The procedure is shown in Fig. 3. The core andthe cavity of the part modelshown inFig. 4 aregeneratedas follows.Firstly, a designer creates a cubic block enclosing thepart model, as illustrated in Fig. 5. The rectangularblock is called the core block, which will eventuallybecome the core and the cavity. Next, the parting sur-faces, which split the core block into the core and thecavity, are generated along the outer boundaries of thepart model as shown in Fig. 6a. The parting surfaces, ifrequired, are also generated on one end of the passagefeature as shown in Fig. 6b.The core block is split into the core and the cavity bythe parting surfaces and the faces of the part model. Thecore is the lower portion of the core block, and the cavityis its upper portion. The created core and cavity areillustrated in Fig. 7.As illustrated in Fig. 6b, the parting surfaces should begenerated on one end of each passage feature to split thecore block completely into two pieces, i.e. the core andthe cavity. In the case of a simple passage feature, asshown in the example, the parting surface of the passagefeature is easily generated. However, in the case ofcomplicatedpassagefeaturesformedoverseveralfaces as illustrated in Fig. 8, the recognition of theloops bounding the ends of the passage feature and theFig. 1General conguration of an injection mouldFig. 2Passage feature passing through multiple facesFig. 3Procedure for generating the core and the cavity784K CHUNG, K LEE AND T KIMProc Instn Mech Engrs Vol 216 Part B: J Engineering ManufactureB05601IMechE 2002generation of the parting surfaces on them are verydi?cult and time consuming tasks.Figure 9 shows a part model with the parting surfaceswith the corresponding passage features, and Fig. 10shows the surfaces that will form the parting surface bycovering the passage features. As shown in Fig. 10,these surfaces for separating the passage region consistof many complicated faces.Most plastic parts fabricated by injection mouldinghave passage features passing through multiple faces.This makes it di?cult to recognize passage featuresand to generate the parting surfaces automatically. Inthis paper, an algorithm to detect passage features isproposed as the basis for automatic parting surfacegeneration.Fig. 4Top and bottom views of an example part with one passage featureFig. 5Core blockFig. 6Generation of parting surfacesRECOGNITION OF PASS FEATURES FOR AUTOMATIC PARTING SURFACE GENERATION785B05601IMechE 2002Proc Instn Mech Engrs Vol 216 Part B: J Engineering ManufactureFig. 7Generation of the core and the cavityFig. 8Simplied front cover of an audio system786K CHUNG, K LEE AND T KIMProc Instn Mech Engrs Vol 216 Part B: J Engineering ManufactureB05601IMechE 20022.1Related workSince Kyprianou pointed out the necessity for shapeclassication in CAD systems in his PhD thesis 5,feature recognition in solid models has been a popularresearch topic. Until now, the extraction of machiningfeatures from CAD data has been the main subject ofresearch, and feature recognition techniques have beenderived to extract machining features, such as holes,slots and pocket features 6. There are four distinctapproaches to feature recognition:(a) the graph pattern matching approach 7,(b) the convex hull decomposition approach 8, 9,(c) the cell-based decomposition approach 10,(d) the hint-based reasoning approach 11.The graph pattern matching approach was introduced byJoshi and Chang, and has proven to be the most popularmethod in the feature recognition eld 12. In thisapproach, the B-Rep data structure of a part ismapped onto a graph whose nodes represent faces andwhose branches represent edges. This graph is calledthe face adjacency graph (FAG). Then, a subgraph iso-morphism is used to search subgraphs that match thefeature templates. However, in the case of intersectingfeatures, the subgraphs in the part are deformed, whichmakes feature recognition impossible.The convex hull decomposition approach was pro-posed by Woo 9. This approach recognizes the featuresFig. 9Surfaces generated from passage features that constitute parting surfacesFig. 10Surfaces covering passage featuresRECOGNITION OF PASS FEATURES FOR AUTOMATIC PARTING SURFACE GENERATION787B05601IMechE 2002Proc Instn Mech Engrs Vol 216 Part B: J Engineering Manufactureby Boolean operations between a part model and aconvex hull surrounding the part model. The Booleanoperation between the part model and convex hull isapplied recursively. When the output of the Booleanoperation is empty, the operation is terminated. Unfor-tunately, the decomposition process may not necessarilyconverge. To overcome this problem, Kim proposed thealternating sum of volumes with partitioning (ASVP)decomposition 9, which recognizes features by compar-ing the part model faces with its convex hull faces.The cell-based decomposition approach was proposedby Sakurai and Chin 10. This method recognizesfeatures by decomposing the delta volume into minimalcells and then combining these cells. The delta volumeis the diVerence between a stock and a part model.Using this approach, the number of cells derived fromthe decomposed delta volume is large. Consequently, alarge number of combinations are needed to recognizethe features by combining the cells.The hint-based reasoning approach was proposed byVandenbrande 11. This approach was proposed inorder to recognize intersecting features, which are themain problem of the graph pattern matching approach.The technique recognizes features from the traditionaltraces of features. For example, a slot hint is generatedwhen a pair of parallel opposing planar faces is encoun-tered, which correspond to slot walls. With such hints,the algorithm recognizes the slot feature by searchingthe slot oor between the slot walls.As is suggested by the above, research on machiningfeature recognition is being actively pursued. Someresearch has also been performed on feature recognitionspecically related to moulds, for example upon under-cut features 13. However, as far as the present authorsare aware, no research has been undertaken to date onthe recognition of passage features for parting surfacegeneration.3OVERVIEWA passage featureiscomposed of a pair of hole loops andthe faces connecting the hole loops, and thus passagefeature recognition is a process of nding paired holeloops. Because a passage feature can pass throughseveral connected faces, the hole loops lying over severalconnected faces should be identied at rst.When a hole loop is found, its pair hole loop issearched. If the pair of hole loops satises a certain con-dition to become a passage, it is registered as a passagefeature.3.1DenitionSince the passage features passing through many con-nected faces are the target features to be recognized, aspecial hole loop, called a multiface hole loop, formedover several faces, is dened in this paper as follows:For any pair of connected faces, allthe edges shared bytwo faces in the pair are eliminated and an expandedface is generated. If internal loops of edges inside theexpanded face exist, these internal loops are denedas multiface hole loops.An example of a multiface hole loop is illustrated inFig. 11.3.2Basic conceptsA passage feature is composed of two hole loops includ-ing multiface hole loops and the faces coupling these holeloops. These faces are called side faces. Thus, the pro-cedure for nding passage features can be conceptuallysimplied to nd two connected hole loops. The detailedprocedure will be explained in Section 4.4ALGORITHMIn this section the proposed algorithm will be explainedin detail. The detailed algorithm for recognizing thesimple passage feature will be explained rst, and thenthe approach used to recognize the hole loops onmultiply connected faces will be described. A passagefeature is dened as simple if its entrance and exit lieover a single face. Finally, the conditions necessary formultiface hole loops to compose a passage, and themethod for nding all the combinations of connectedfaces, will be explained.4.1Algorithm for passage feature recognitionAs explained earlier, a passage feature is composed oftwo hole loops connected to each other by side faces.The detailed procedure for passage feature recognitionis described using the following example.The sample part illustrated in Fig. 12 has one passagefeature and each symbol is dened as follows:Fig. 11Example of a multiface hole loop788K CHUNG, K LEE AND T KIMProc Instn Mech Engrs Vol 216 Part B: J Engineering ManufactureB05601IMechE 2002a top face of the sample partb face connecting the top and bottom surfacesc bottom face of the sample parte1 edge shared by face a and face be2 edge shared by face c and face bL1 hole loop in face aL2 hole loop in face cIn the example part, the loops composing the passagefeature are L1 and L2, and the faces, such as face b, con-nect these loops. Generally, the face (face b) composing apassage feature has edges shared by the neighbouringfaces (face a and face c), and these edges form holeloops in the neighbouring faces (face a and face c).That is, face b is a face composing the passage featureand is named the side face. Faces a and c are namedthe entrance face and the exit face respectively. The pro-cedure for nding the passage features is as follows:1. Search for hole loops in a face (entrance face of apassage).2. Search for edges composing the hole loop searchedfor in step 1.3. Search for faces (side faces) sharing the edgessearched for in step 2.4. If the edges of the face (side face) searched for in step3 form a hole loop inside another face (exit face), thishole loop and the hole loop searched for in step 1form a passage feature.Thealgorithm explained above isfor recognizing passagefeatures composed of hole loops residing on a single face.To recognize the passage features composed of holeloops lying over multiple faces, the concept of the multi-face hole loop must be applied.4.2Recognition of hole loops on multiply connected facesAs described earlier, a multiface hole loop is dened asthe internal loop formed over an expanded face formedby removing edges shared by connected faces. Threesteps are needed in order to recognize the hole loopson multiply connected faces:(a) remove the edges shared by the connected faces,(b) construct loops with the remaining edges,(c) identify the internal loop.The procedure for recognizing a multiface hole loop canbe described as follows. A sample part for explaining themultiface hole loop is shown in Fig. 13, where the greyfaces are the connected faces being investigated. Thegrey faces share edges e1 and e2. If the shared edges inFig. 12Example using a simple passage featureFig. 13Example for recognizing a multiface hole loopRECOGNITION OF PASS FEATURES FOR AUTOMATIC PARTING SURFACE GENERATION789B05601IMechE 2002Proc Instn Mech Engrs Vol 216 Part B: J Engineering Manufacturethe two faces are removed and the two faces are consid-ered as one face, as shown in Fig. 13b, two loops areformed, i.e. L1 and L2. Loop L1 corresponds to theinternal loop and loop L2 corresponds to the peripheralloop. Consequently, the multiface hole loop is loop L1 inthis case. Likewise, the internal loops formed over narbitrary connected faces are dened as multiface holeloops if internal loops exist when the shared edges ofconnected faces are removed. Once the multiface holeloops are identied, the procedure for nding a simplepassage described earlier can be applied in order torecognize the passage features in the multiple faces.4.3Conditions necessary for a multiface hole loop toform a passageFor the multiface hole loops to compose passage fea-tures, two conditions are required. First of all, all theedges composing the multiface hole loop must beconvex. For example, for the part illustrated in Fig. 14,loop L1 is a hole loop in face F1, but the edges compos-ing the hole loop L1 do not compose a passage featurebecause they are concave. This may be a natural conclu-sion considering that the edges of the multiface holeloops become either the entrance or exit of the passageand only convex edges may form the boundary of theentrance or the exit. Therefore, a procedure for judgingthe convexity of edges is required. The classication ofedges by Kyprianou is illustrated in Fig. 15 14.Edges are classied by the angle between the two facesthat share the corresponding edge; i.e. if the anglemeasured inside a part is smaller than 180 , the edge isconvex. Likewise, if it is larger than 180 , the edge isconcave. If the two faces are connected smoothly asshown in Figs 15c or d, the edges are classied by thelocal curvature 14. By judging the convexity of theedges, the multiface hole loops composed of concave orsmooth concave edges are excluded during the procedurefor recognizing passage features.Even if all the edges satisfy the rst condition, there arecases where passage features cannot be composed becauseof the relationship between the multiface hole loops andthe faces composing the model. Here,the secondcondition comes into play. The multiface hole loops canbe considered as a collection of edges that will boundthe parting surfaces later for the corresponding passageFig. 14Hole loop that does not constitute a passage featureFig. 15Kyprianous edge classication 14790K CHUNG, K LEE AND T KIMProc Instn Mech Engrs Vol 216 Part B: J Engineering ManufactureB05601IMechE 2002features. Since the generated parting surfaces must notoverlap the faces of a part, multiface hole loops whoseinside region overlaps the part surfaces must be excludedfrom consideration.A multiface hole loop that satises such a condition isshown in Fig. 16, and Fig. 17 shows a multiface hole loopthat violates the condition. In other words, the partingsurface to be generated using multiface hole loop L2shown in Fig. 16b, which is identied from the mergedfaces hatched in Fig. 16a, does not overlap the faces com-posing the part. Merged faces are a set of connected faceswithin which a multiface hole loop is searched for. How-ever, the parting surface to be generated using multifacehole loop L2in Fig. 17b, which issearched for among themerged faces hatched in Fig. 17a, overlaps the part faces.Therefore, the case in Fig. 17 must be excluded from con-sideration in nding the passage features. The detailedcondition for invalid multiface hole loops is as follows.The readers may wonder why an odd situation like thisis considered. All possible cases of multiface hole loopshave to be considered because they are generated auto-matically by merging connected faces.The faces that share the edges composing a multifacehole loop and do not participate in the merging processare side faces. If both the starting point and the end-point of an edge shared by two side faces are on themultiface hole loop, this edge can compose a loop withseveral other edges that belong to the multiface holeloop. A parting surface generated using this loopshould be the same face as one of the side faces, whichmakes the parting surface overlap the part face.Figure 18b represents a two-dimensional layout of thepart in Fig. 18a. Faces F1, F2, F3 and F4 correspond tothe merged faces, and faces S1, S2, S3, S4 and S5correspond to the side faces. The boundary edges ofthe multiface hole loop are indicated by thick lines.Edge a shown in Fig. 18b is an edge shared by the sidefaces, and both the starting point and the end-point ofedge a are on the multiface hole loop. Thus, edge aforms a loop together with other edges of S5 that alsobelong to the multiface hole loop. The parting surfacegenerated from this loop becomes the existing face S5,and thus the parting surface overlaps S5. In this way,Fig. 16Example of a valid multiface hole loopFig. 17Example of an invalid multiface hole loopRECOGNITION OF PASS FEATURES FOR AUTOMATIC PARTING SURFACE GENERATION791B05601IMechE 2002Proc Instn Mech Engrs Vol 216 Part B: J Engineering Manufacturethe recognition of multiface hole loops yielding invalidparting surfaces can be avoided by investigating therelationship between