氣壓瓶蓋注塑模具設計（全套含CAD圖紙）,氣壓,瓶蓋,注塑,模具設計,全套,cad,圖紙 注射模設計的三維模型發(fā)展 如今，為了使注塑工藝變得更簡單，很多嵌入式軟件都在高級3D 注塑平臺的基礎上開發(fā)出來的，諸如有限元分析，計算機輔助制造，注射模設計，模擬以及形象化設計。這些軟件都是很有利的。然而，它關非沒有缺點。事實上，這些嵌入式軟件也可以通過低級的3D更靈活和更輕便性開發(fā)出來。這篇文章查閱了各種各樣基于3D應用發(fā)展的期刊和方法，主要是關于軟件方面。首先，提出了一種基于3D的應用發(fā)展的方法，這種觀點通過使用Parasolid模型的注射模實現(xiàn)的。基于在已建立的模具設計中的模具設計概念，文中說明了一種被叫做IMOLD的模件。在一個Windows NT 平臺上，面向?qū)ο蟮木幊陶Z言被用來開發(fā)這種軟件。 關鍵字： 3D 模型； 計算機輔助設計; 注射模設計； 1. 介紹 三維計算機輔助設計系統(tǒng)已經(jīng)越來越被用來加速產(chǎn)品的實現(xiàn)過程。涉及產(chǎn)品自動化設計過程的第一步是3D建模應用中的組件部件的建立，在建模過程中，這種3D 模型的建立稱為數(shù)字化建模，這種數(shù)字化建模得到的3D的關鍵一步是生產(chǎn)過程自動化。 組件部件的3D數(shù)字化建模僅僅是第一步。還有許多的其他輔助任務必須在零件被生產(chǎn)之前完成。這些任務包括有限元分析、夾具和固定裝置的設計、注射模設計、計算機輔助制造、模擬和形象化設計。當今很多在高級3D建模平臺上發(fā)展起來的嵌入式軟件來促進這些輔助任務。這種3D建模站臺提供了一個具有編程的用戶界面和風格的嵌入式軟件。結(jié)果，這種嵌入式軟件的開發(fā)時間大幅度地減少。 這種方法在很多方面都是有利的，但是，它也有它的缺點，特別是從長遠的角度考慮。為了為現(xiàn)有的軟件開發(fā)另外一種嵌入式軟件，那些開發(fā)者必須兼顧很多現(xiàn)有的限制條件，必需與源軟件的風格一致。那些開發(fā)者必須利用系統(tǒng)所提供的各種庫函數(shù)來實現(xiàn)各種功能性操作， 大多數(shù)的終端用戶需要源軟件和嵌入式軟件。不過，在很多情況，他們可能對使用只有嵌入式的軟件更感興趣。 在注射模設計過程中就有這種情況的例子，不過，這些用戶必須購買包括很多他們不需要的特征和功能的整個軟件包， 這么大的程序通常是硬件上所必需的，同時這也意味著會費用更高。這嵌入式軟件也很大程度上依賴源軟件的發(fā)展。一旦源軟件版本被更新，那些嵌入式軟件的開發(fā)者必須采取相應的行動， 如果這些應用在一個低級的平臺上發(fā)展，這些缺點可能會不存在。事實上，這些嵌入式軟件可以使用低級的3D 模型更靈活和更輕便性發(fā)展。在很多情況下，這樣的操作既可行又有利。傳統(tǒng)上，注射模設計可以直接在計算機輔助設計系統(tǒng)執(zhí)行，整個注射模，可能由數(shù)百個組件部件組成，在計算機輔助設計系統(tǒng)(例如 AutoCAD，PRO/工程師和Unigraphics)上建模和裝配，因為注射 模設計過程是反復的，所以重新建模和裝配是相當費時，在這個方面，像這些基于特征的PRO/工程師以及Unigraphics那樣的3D. 計算機輔助設計系統(tǒng)比像AutoCAD那樣的2D 計算機輔助設計系統(tǒng)的更有優(yōu)勢， 為加速注射模設計工藝的發(fā)展，這種嵌入式軟件在3D系統(tǒng)上自動發(fā)展一些注射工藝 ，這種附加應用的例子包括在國立新加坡大學發(fā)展，基于Unigraphics上發(fā)展的IMOLD(智能模型設計和裝配系統(tǒng))、專家模具設計者(基于CADKEY)及模型制作者(基于EUCLID) . 因為以上每一個都基于特定的計算機輔助設計系統(tǒng)，所以都沒有嵌入兼容性。在1994年，Mok和張 [1]基于Unigraphics的注射模設計應用上做了研究。在1997年，Shah [2] 在幾何建模之間的聯(lián)系標準化之間提出了互訪結(jié)構(gòu)模型，他的目標是在基于Parasolid的3D 應用以及ACIS之間獲得嵌入兼容性，只不過它包括三維建模 。 在這篇文章里，作者試圖直接發(fā)展一種質(zhì)量輕的使用低級的3D模型注射模設計應用，并把重點放在軟件開發(fā)的靈活性和速度上。設計概念和程序來自IMOLD [4,5 ]、模具設計和3D 裝配中應用。盡管這些討論僅僅局限于注射模設計，這種方法學能很容易地被應用在其他基于3D的應用中，并且有相似的作用，開發(fā)者工具的結(jié)合就是為了這個目的而選擇的。在方法學被討論之前，對于其中的一些先提出的工具作一個簡短的介紹，他們分別是IMOLD、Parasolid 10.1 版本、VC6.0 版本和微軟公司基礎種類。 2.IMOLD 用作模具設計應用 IMOLD(智能模型設計和裝配) 是在基于3D的應用致力發(fā)展的注射模設計。它在一個叫做Unigraphics的高級計算機輔助設計系統(tǒng)之上發(fā)展起來的。該發(fā)展正在通過使用系統(tǒng)所提供的編程接口(API)來實現(xiàn)。該軟件通過提供常用的設計工具促使模具設計者能夠迅速進行設計。在設計中所需的常用的標準組件部件，可以在軟件里預先創(chuàng)建并且可能被容易被設計者調(diào)用。這很大程度上降低了設計時間。模具設計過程可分成幾個階段，以一種固定的方式給設計者們提供模具設計方法。 它們便是： 1. 數(shù)據(jù)準備。 2. 填充系統(tǒng)設計。 3. 模具基礎設計。 4. 插件與零件設計。 5. 冷卻系統(tǒng)設計。 6. 滑板和提升設計。 7. 注射系統(tǒng)設計。 8. 標準零件庫。 每個階段都可以被認為是一個獨立的模件設計過程?；?D的每個模件的要求變化甚微。成功地建立模型基礎模件意味著在發(fā)展其它模件過程中也是可行的。 3．用作3D模型設計的Parasolid Parasolid被用設計為基于3D 模型數(shù)據(jù)系統(tǒng)的核心。實體建模有必要被用作。 1．建造并且操作實體。 2. 計算質(zhì)量和慣性矩，并且進行干涉檢測。 3. 以多種方式輸出實體。 4. 在特定的數(shù)據(jù)庫或者檔案內(nèi)儲存實體并且可以稍后提取出來。 在計算機輔助設計中，Parasolid是最先進的3D 模型設計軟件。它是Unigraphics和Solid- Works的3D核心。它獨特的公差模擬運作功能使得它能以其它格式接收和存儲數(shù)據(jù)。因此Parasolid模型文件是十分方便的而且它也是獨立應用發(fā)展的高級平臺?；?D的應用與Parasolid之間通過它的3個界面中的一個相連接。 這些被稱這之為Parasolid 核心界面、模型界面以及底端界面。PK界面和模型界面位于建模系統(tǒng)的頂部，通過這些方法來建模和對實體進行操作以及控制建模的功能。底端界面位于建模窗口的底部。當需要執(zhí)行集中數(shù)據(jù)或系統(tǒng)類型操作時建模者便需要它。它由3個部分組成：函數(shù)、圖形輸出和外形幾何 ，以下分別對其作出簡短的介紹。 3.1 KI 和PK界面 KI 和PK是供程序員進入Parasolid模型里進行建模的接口 他們是建模功能的標準庫。程序員在他們的程序里稱之為建模功能。因為KI不久將被淘汰，所以我們選擇使用PK界面。 3.2 函數(shù) 函數(shù)是一必須由應用程序員編寫的功能，當數(shù)據(jù)必須被存儲或者提取時需要使用該功能。當使用Parasolid時，應用程序員必須首先決定怎樣管理數(shù)據(jù)的存儲，通過該功能Parasolid輸出該數(shù)據(jù)。通過該功能轉(zhuǎn)存數(shù)據(jù)通常與寫入文件或?qū)С鑫募嘘P。文件的形式和及存儲位置在寫該功能時被確定。 3.3圖形的輸出 對圖形輸出功能是由應用程序員所編寫的另一種功能。對需要PK給予功能的設計者來說，圖形數(shù)據(jù)是由GO界面輸出的， 然后3D數(shù)據(jù)被傳給3D圖像包。OpenGL，是圖形卡片的一個軟件接口可以為我們提供我們所需的數(shù)據(jù)包。 3.4 外形幾何 外形幾何學可以為用戶幾何類型的發(fā)展(例如機構(gòu)內(nèi)部及表面的曲線)提供功能操作。它通常與在Parasolid內(nèi)的建模標準幾何類型一起使用。 4. 使用VC以及微軟公司基金類型的面向?qū)ο蟮某绦蛟O計 面向?qū)ο蟮某绦蛟O計(OOP)已無可爭議地成為軟件開發(fā)者的選擇。它是在目前所存在的軟件中最高級的開發(fā)軟件。微軟公司Visual Studio就是這樣的一個軟件包。它刻劃了許多基于因特網(wǎng)和基于Windows編程用的開發(fā)工具。在這些工具中包含有VC以及微軟公司基金種類(MFC)。VC是面向?qū)ο蟮某绦蛟O計的強有力的開發(fā)工具，而MFC是一種基于Windows編程的框架。它以強大的開發(fā)特性和功能性，例如自動編碼基于wizard操作，為應用程序員提供開發(fā)工具。這大大改進了生產(chǎn)效率。我們使用的程序的整個用戶界面是使用VC以及MFC開發(fā)出來的。 5. 系統(tǒng)設計 基于3D的使用3D模型的附加應用的直接發(fā)展的問題正待解決。在最高的水平上它由3個主要階段組成。 首先，必要特征和嵌入式應用軟件功能的識別： 第二，應用框架的設計與開發(fā)； 最后，具有合適的開發(fā)工具的框架中個別模件的設計與開發(fā)。 5.1 必要軟件的識別 Parasolid作為一種3D建模方法，只提供許多庫函數(shù)以及3D應用開發(fā)的基本框架。因此，那些開發(fā)者有必要識別和開發(fā)3D計算機輔助設計系統(tǒng)中其他的必要設施。為了識別所需的設施，理解兩者之間的差異是很重要。 表格1 總結(jié)了3D模型和3D計算機輔助設計系統(tǒng)所提供的主要設備的差別。其中的一些設備，例如特征和參數(shù)建模，在耗時與技術上都要求有發(fā)展。因為大多數(shù)的嵌入式軟件不使用源程序中的所有設備，只通過開發(fā)這些使用低級3D模型所需要的嵌入式軟件生產(chǎn)單獨的版本是很有可能的。 表格1從第7條到第9是使用基于3D的應用發(fā)展Parasolid的必要條件。 通過研究嵌入式的應用的必要條件，其他必要的設備的要求也可以被鑒定。然后提出了該應用程序的一個框架，該框架是基于由Parasolid建模所提供的設備。 5.2 基于3D應用的框架 對于由開發(fā)的工具和.應用的要求所提供的設備，開發(fā)了一種框架。它專門被設計以使單個編程模件之間的差異最小化。這將導致編程代碼發(fā)生小程度的變化。事實上，程序代碼使用起來更加的輕便各更有助于維修，而且將來的發(fā)展前景也是相當好的。這個框架的概述在圖2里得以說明，各種各樣的模件的詳細情況被在以后的章節(jié)里討論。 5.2.1個基于Windows的用戶界面(A) Parasolid不為程序員提供用戶界面。因此，在每一個階段基于3D應用的發(fā)展將涉及到從頭開始設計用戶界面。相關的必要開發(fā)內(nèi)容包含： 1. 基于3D的應用的環(huán)境設置和顯示。 2. 交互式圖表的接口和全部應用功能操作的執(zhí)行程序。 5.2.2 3D 開發(fā)者(B)圖層的設置 因為不同的基于3D的應用在不同程度上需要不同的3D設備，該框架必須為用戶提供這些變量的設置。一個3D開發(fā)者圖層的設置(參閱圖2)被概念化來解決這些變化。這是基于Parasolid模型已經(jīng)開發(fā)出來的對象的庫函數(shù)或者類別。開發(fā)的程度取決于建模的要求情況。 圖表一由3D模型和計算機輔助設計系統(tǒng)所提供的設施的摘要 3D模型和3D計算機輔助設計系統(tǒng)設施： 1. 基本3D低級建模和通用功能以及高級功能和特殊功能； 2. 由整個系統(tǒng)提供的裝配多種庫函數(shù)； 3. 基于特征的建模； 4. 不經(jīng)常被提供的參數(shù)建模； 5. 系統(tǒng)常提供的低級建模功能； 6. 系統(tǒng)提供的不完全草圖； 7. 系統(tǒng)不常提供的交互式用戶界面； 8. 系統(tǒng)所提供的三維物體基本概念框架功能和庫函數(shù)的可視化； 9. 系統(tǒng)所提供文件管理系統(tǒng)的基本概念和多個信息庫功能的完全發(fā)展。 除了要滿足應用條件中的變量要求外，3D開發(fā)者設置層也要為非Parasolid開發(fā)者提供一個編程接口。這樣的一個接口能也其他基于3D的應用的開發(fā)者重新使用。3D開發(fā)者設置層基本上由3 個主要部分組成。他們可分別被用于3D建模和裝配，3D可視化以及3D 數(shù)據(jù)管理。 I . 3D建模和裝配 3D建模和裝配模件是所有這3個部分中最重要和最精心制作的部分。它與由大多數(shù)計算機輔助設計系統(tǒng)提供應用編程接口(API)相似。該模件由一基于3D對象或類別的庫函數(shù)組成，它可用于核心應用模件的發(fā)展。大多數(shù)3D應用所需要的3D基本的功能的操作性能必須被首先開發(fā)出來?；趩蝹€基于3D的應用所需的條件，其他更多的高級特性后來也被增加進來了。 II. 3D的可視化。 在三維物體的顯示窗口用戶范圍需要一個團體軟件圖表接口。圖表的輸出以及所選擇的圖表的接口經(jīng)常被在基于3D的應用里以及視圖對象管理和轉(zhuǎn)變之中。為這個目的而開發(fā)了一個類別庫函數(shù)。 III. 3D 數(shù)據(jù)管理。 3D數(shù)據(jù)管理模件是在函數(shù)之上被開發(fā)出來的。函數(shù)是存在于使存檔以及3D零件文件的進入變得容易的Parasolid的模件之中。為此開發(fā)了一種使用函數(shù)來處理的類型選擇器。 1. 3D目標文件形式； 2. 諸如打開和保存3D目標文件這樣的文件管理操作。 5.2.3 應用模塊(C) 這些是位于3D開發(fā)者設置層和應用用戶界面之間存在的基于3D的應用模塊。這些模塊的設計的主要取決于應用的屬性并且相互之間的差別很大。在這個領域已經(jīng)正在進行很多有研發(fā)工作主要發(fā)展的工作的大部分被進行。然而，研發(fā)的難易主要取決于3D開發(fā)者設置層的能力。 5.2.4個其他軟件模塊(D) 通常，基于3D的應用可能需要來自于其他已存軟件模塊或應用模塊的功能性操作。因此，諸如此類的連接是可能存在的。在這篇文章的應用部分就為這樣的一個例子加以說明了。 5．3 單個模塊的發(fā)展 在進行一個合適設計之前，對每個模塊都得進行研究和分析，它的開發(fā)難易很大程度上取決于所選的框架和開發(fā)者設置層。下一部分說明了注射模設計的3D模型開發(fā)的實施情況。 6. 實施情況 應用系統(tǒng)設計，開發(fā)了基于3D的注射模設計。這被通過使用前面章節(jié)所述的開發(fā)者工具獲得的。因為模型基礎需要更大范圍的3D功能性操作，包括裝配的生成，所以選用它來加以說明。 6.1每個模塊的要求應用框架和所需要的條件 對于識別開發(fā)工作，專門設定了了一個應用框架。發(fā)展的工作鑒定。圖3說明了基于Windows用戶的模型基礎模塊的詳細情況。在每個模件里的詳細要求在討論如下： 6.1.1 Windows NT的用戶界面(A) 模型基礎設計是一個反復的過程。模型設計者首先從目錄中選擇了一個標準模型，然后對模型的尺寸進行修改直到所有的條件都得以滿足。因此，為了這個目的有必要考慮使用交互式用戶界面。 使用VC和MFC來開發(fā)基于Windows的界面，它包括： 1. 菜單條欄目、菜單項和工具條按鈕的創(chuàng)建、顯示和管理，以便更方便地進行應用的功能性操作。 2. 引導用戶或獲得用戶輸入的對話框的創(chuàng)建、顯示和管理 3. 顯示區(qū)域內(nèi)各種視角的創(chuàng)建、顯示和管理。 4. 拖動的鼠標的作用。 5.對每個功能的順序操作設計。 應用之后的結(jié)果如圖4中所示，它是一個典型的其于Windows應用的用戶界面。 6.1.2 3D 開發(fā)者(B)設置層 對基于3D模型基礎設計的要求進行分析，然后識別一下即將開發(fā)的模塊。 基于3D模型基礎設計的要求如下： 1. 創(chuàng)建初始模型(例如矩形，圓柱，圓錐)； 2. 創(chuàng)建圓角和倒角； 3. 進行布爾運算：并集和差集； 4. 變換操作：變換和旋轉(zhuǎn)； 5. 對象屬性的管理，諸如名字和顏色； 6. 創(chuàng)建引用特征； 7. 創(chuàng)建總裝配和子裝配； 因為以上這些應用不是那么的廣泛，所以可以開了一個基礎建模集。有了單個模塊的詳細開發(fā)情況，就可以給開發(fā)者設置層添加更多的功能。每個模塊的全部要求條件將在以后的章節(jié)加以說明。 I . 3D建模和裝配 一個模型基礎基本上是許多組件部件的集合，諸如鍵和螺絲。 為了使模型基礎設計變得容易，設計者必須提供一個事先已經(jīng)準備好的模型基礎庫。通過選擇特別的尺寸，可以生成一個標準的模型基礎件。為了使這些變得容易，識別和開發(fā)了基于3D的功能庫，該功能與前面6.1.2所提及到的要求條件相對應。正因為該編碼是面向?qū)ο蟮?，在需要的時候，它們很容易被延伸以適應其他模型設計模塊。 II. 3D視圖的可視化 使用圖表的輸出和作為圖表界面的OpenGL所提供的功能共同作用來為3D的實體操作開發(fā)投影和視圖變換等諸多功能。它們包括： 1.用所選擇的顏色給3D堆零部件著色； 2. 用所選擇的顏色給3D裝配體著色(圖7和圖8分別用陰影和線框的模式給3D裝配體加以顯示)； 3. 用所選擇的顏色在屏幕上給其他3D實體著色； 4. 在模型基礎裝配中用不同的顏色分別給單個組件著色； 5. 交互式視圖變換(諸如旋轉(zhuǎn)，變換和縮放)； 6. 裝配樹顯示和操作。 III. 3D 數(shù)據(jù)管理。 開發(fā)獨立應用程序的好處之一就是它的輕便性，所以采用最大的輕便性打開的形式是很重要的。因此以原先的Parasolid文件形式(.xmtFtxt)來替代新的文件形式。一個模型基礎件的數(shù)據(jù)管理要求包括如下內(nèi)容： 1. 打開，保存，另存為和關閉Parasolid零件文件。 2. 打開，保存，另存為和關閉Parasolid裝配文件。 3. 輸入和輸出零件文件。 6.1.3個模型基礎模件(C) 為了促進標準模型基礎組件的自動生成，系統(tǒng)必須提供一個模型基礎零部件庫, 其尺寸大小取決于目錄中的標準值。為使設計容易進行，需對這些尺寸進行順序修改，這個模件詳細情況將在第6.2部分進行討論。 6.1.4 數(shù)據(jù)庫支持(D) 一個標準模型基礎件需要用將近100個參數(shù)來對單個組件的尺寸和位置進行完全描述。這些參數(shù)的大部分都是相互聯(lián)系的并且可以從其它數(shù)據(jù)庫中獲得。因此，一個數(shù)據(jù)庫文件需要被用來存儲基于目錄的標準模型基礎件的參數(shù)。Microsoft Access 數(shù)據(jù)庫形式被使用在MFC里進行直接存儲數(shù)據(jù)庫文件。在MFC里使用數(shù)據(jù)存取對象(DAO)，一套被用作抽取和管理數(shù)據(jù)庫城相關參數(shù)的功能。 6.2模型基礎設計的發(fā)展 模型基礎模件由3個主要部分組成，即，模型基礎組件生成、模型基礎裝配生成、模型基礎類選擇和自定義模件。第4個部分被稱作為模型基礎參數(shù)管理，也是被用來開發(fā)為應用提供數(shù)據(jù)支持。這些已經(jīng)圖表中5中說明了。注注射模設計的開發(fā)部分的細節(jié)內(nèi)容討論如下： I . 零部件庫的生成 有了3D開發(fā)者設置層的支持，為模型基礎的標準組件部件被創(chuàng)建和存儲在組件庫中。通過規(guī)定合適的尺寸，這些組件部件可以被生成而且可以被模型基礎裝配生成器所使用。 II.裝配生成器 使用3D 圖層設置并將組件庫生成器各標準模型基礎集中并存儲在裝配庫中。當提供從數(shù)據(jù)庫中提取特定參數(shù)集時，由于它得到了特別的參數(shù)支持，所以特定的標準模具基礎裝配可以自動地 III. 參數(shù)管理者 參數(shù)管理者將模型基礎應用模件和數(shù)據(jù)庫支持連接起來。當一個特定的標準模型基礎被選擇后，它的為模型基礎裝配的相應參數(shù)已經(jīng)從數(shù)據(jù)庫中提取出來并且發(fā)送到組件庫生成器和裝配生成器中。除此以外，參數(shù)管理者也允許用戶為了設計的目的而對參數(shù)進行修改。 IV. 模型基礎設計者。 模型基礎設計者為兩個主要目的服務。首先，允許用戶選擇來自裝配生成器的標準模型基礎。其次，通過允許模型基礎設計者修改所選擇的模型基礎的尺寸來使模型基礎設計變得容易。該樣品代碼給那些模型基礎來生成功能。從圖9中我們可以注意到使用了許多代表模型基礎的參數(shù)的變量的功能， 這是用于裝入那些零部件生成各種各樣的模型基礎零部件的創(chuàng)造。裝配生成器然后使用那些零部件和那些參數(shù)集來確定模型裝配基礎的創(chuàng)建，正如在3D開發(fā)者層設置外一樣，在樣本程序中沒有直接被叫作 Parasolid功能的當今的模型基礎設計應用能意識到在工廠要求設計的注射?；A設計的全部功能性設計情況。因為模型基礎是IMOLD模件中的最廣泛應用的3D模型，所以它的成功開發(fā)意味著開發(fā)了一完全基于3D注射模設計和裝配應用的可行性。 7. 結(jié)論 高級編程語言的發(fā)展已經(jīng)允許程序員用參數(shù)來重新使用編程代碼，該編程代碼存在于象微軟公司基金類型那樣的對象里。 這些強大的特征已經(jīng)使程序員從更多的編程標準函數(shù)的程序和建立用戶界面中分離出來了。他們現(xiàn)在能夠把精力集中在軟件的核心組成部分，從而增加生產(chǎn)效率。這導致發(fā)展獨立版本的軟件諸如CAE、計算機輔助設計和計算機輔助制造可行性提高。不過目前，這種方法是既耗時的而且技術要求高。盡管如此，它還是可行的而且前景是非常好的。通過把幾種高級的開發(fā)者工具結(jié)合起來，我們已經(jīng)設法增加了這些工具開發(fā)注射模設計的應用能力。迄今為止，只有模具設計工藝的前三個階段得以編碼。這給隨后的模型設計模件的開發(fā)奠定了基礎。該方法也可以很容易地在包含標準組件設計的其他軟件中實施。這些包括夾具和固定設備設計、冷鑄、和生產(chǎn)產(chǎn)品自動化。 Int J Adv Manuf Technol (2001) 17:453–461 2001 Springer-Verlag London Limited Three-Dimensional Kernel Development for Injection Mould Design T. L. Neo and K. S. Lee Department of Mechanical and Production Engineering, National University of Singapore, Singapore Today, many software “plug-ins” have been developed on high-level 3D modelling platforms to facilitate processes such as FEM analysis, CAM, injection mould design, simulation and visualisation. Such an arrangement is advantageous in many ways. However, it is not without shortcomings. Ideally, these “plug-ins” could also be developed using low-level 3D kernels for higher flexibility and better portability. This paper examines the various issues and methodologies related to the development of such 3D-based applications. The emphasis is placed on the software aspect. First, a methodology for the development of 3D-based applications is proposed. The idea is then implemented by developing an injection mould design application using a low-level 3D kernel called Parasolid. Based on design concepts used in an established mould design application, IMOLD, the development of a mould base design module is illustrated. An object-oriented programming language has been chosen for the development of the software on a Windows NT platform. Keywords: 3D kernel; Computer-aided design (CAD); Injection mould design; Parasolid 1. Introduction Three-dimensional CAD systems have increasingly been used to speed up the product realisation process. One of the first steps involved in the automation of the product design process is the creation of the component parts in a 3D modelling application. The 3D model, upon creation, is called the digital master copy. This 3D digital model forms the key to a wide spectrum of process automation. Creating the 3D digital model of component parts is only the very first step. There are several other secondary tasks that must to be done before the part can be manufactured. Such tasks include finite-element analysis, jigs and fixtures design, injection mould design, computer-aided manufacturing, simul Correspondence and ofprint requests to: K.-S. Lee, Department of Mechanical and Production Engineering, National University of Singapore, 119260 Singapore. E-mail: mpeleeksKnus.edu.sg ation, and visualisation. Today, many application Plug-ins have been developed on high-level 3D modelling platforms to facilitate these secondary tasks. The 3D-modelling platform provides the plug-in software with a library of functions as well as an established user interface and style of programming. As a result, the development times for these plug-ins are significantly reduced. Such an arrangement is advantageous in many ways. However, it has its shortcomings, especially in the long run. In order to develop a plug-in for established software, the developers must adhere to the many constraints imposed. There is a need to be consistent with the style of the parent software. The developers must be able to achieve any functionality they need with only the set of library functions provided. Most end-users need both the parent software and the plug-in. In many cases, however, they may be more interested in using only the plug-in software. An example of such a situation is in injection mould design. These users, however, must purchase the entire software package which includes many features and functions that they do not need. Such a large program is often very demanding on the hardware, which also means higher cost. The plug-in software is also very dependent on developments in the parent software. Whenever a new version is updated for the parent software, the plug-in developers have to follow-up on the changes. These shortcomings may not exist if these applications were developed on a low-level platform. Ideally, these plug-ins could be developed using low-level 3D kernels for higher flexibility and better portability. In many instances, such a move is both feasible and advantageous. Traditionally, injection mould design is carried out directly on a CAD system. The entire injection mould, consisting of perhaps hundreds of components, is modelled and assembled on CAD systems such as AutoCAD, Pro/Engineer, and Unigraphics. As the injection mould design process is recursive, it is very time-consuming to re-model and re-assemble the design. In this aspect, 3D CAD systems such as Pro/Engineer and Unigraphics, which are feature-based, have a significant advantage over 2D CAD systems such as AutoCAD. To further speed up the injection mould design process, plug-ins were developed on these 3D systems to automate certain stages of the design process. Examples of such add-on applications include IMOLD (Intelligent Mold Design and Assembly Sys- 454 T. L. Neo and K. S. Lee tem, developed at the National University of Singapore, based on Unigraphics), Expert Mold Designer (based on CADKEY) and Moldmaker (based on EUCLID). As each is based on a specific CAD system, there is no plug compatibility. In 1994, Mok and Cheung [1] presented work on the development of an injection mould design application based on Unigraphics. In 1997, Shah [2] proposed a 3-tier architecture for standardising communications between geometric modelling kernels and applications that require geometric modelling services. His objective is to achieve plug compatibility between 3D applications that are based on Parasolid [3] (a 3D kernel, developed at the University of Cambridge) and ACIS. This, however, involved an extensively developed 3-tier modelling husk. In this paper, the author attempts to develop a lightweight injection mould design application using a low-level 3D kernel directly. The focus is on the flexibility and speed of the software development. Design concepts and procedures were taken from IMOLD [4,5], a complete mould design and assembly 3D application. Although the discussion is limited to injection mould design only, the methodology applied can easily be applied in other 3D-based applications that are of a similar nature. A combination of developer tools was chosen for this purpose. Before the methodology is discussed, brief introductions to some of these tools are first presented. They are, IMOLD, Parasolid version 10.1, Visual Cversion 6.0, and the Microsoft Foundation Classes. 2. IMOLD as a Mould Design Application IMOLD (Intelligent Mold Design and Assembly) is an established 3D-based application that is dedicated to injection mould design. It is developed on top of an advanced CAD system called Unigraphics. The development is carried out using the applications programming interface (API) provided. The software enables mould designers to create a design rapidly by providing the tools that are commonly needed. Standard components parts, that are often required in the design, have been pre-created in the software and can be readily used by the designer. This reduces the design time significantly. The mould design process is divided into several stages, providing the designer with a consistent method of creating the mould design. They are, namely: 1. Data preparation. 2. Filling system design. 3. Mould base design. 4. Inserts and parting design. 5. Cooling system design. 6. Slider and lifter design. 7. Ejection system design. 8. Standard parts library. Each stage can be considered as an independent module of the program. The 3D-based requirements for each module vary only slightly. The success in developing the mould base module implies feasibility in developing all the other modules. 3. Parasolid as a 3D Kernel Parasolid is designed to be the centre or “kernel” of any system that is based on 3D model data. It is essentially a solid modeller, which can be used to: 1. Build and manipulate solid objects. 2. Calculate mass and moments of inertia, and perform clash detection. 3. Output the objects in various ways, including pictorially. 4. Store the objects in some sort of database or archive, and retrieve them later. Parasolid is one of the most advanced 3D kernels among CAD applications. It is the 3D kernel of Unigraphics and Solid-Works. Its unique tolerant modelling functionality enables it to accept data stored in other modeller formats. Parasolid model files are thus very potable. It is, therefore, a superior platform for the development of stand-alone applications. The 3D-based application interacts with Parasolid through one of its three interfaces (see Fig. 1). These are called the Parasolid kernel (PK) interface, the kernel interface (KI) and the downward interface. The PK interface and the kernel interface sit “on top” of the modeller (side-by-side), and are the means by which the application models and manipulates the objects, as well as controls the functioning of the modeller. The downward interface lies “beneath” the modeller, and is called by the modeller when it needs to perform data-intensive or system type operations. It consists of three parts: frustrum; graphical output (GO); and foreign geometry. These are briefly explained below. 3.1 The KI and PK Interface The KI and the PK are interfaces for the programmer to access the modelling capabilities in the Parasolid kernel. They are standard libraries of modelling functions. The programmer calls these modelling functions in their programs. As the KI is to be phased out soon, we chose to use the PK interface. Fig. 1. Parasolid components. 3D Kernel Development for Injection Mould Design 455 3.2 The Frustrum The frustrum is a set of functions, which must be written by the applications programmer. The kernel calls them when data must be saved or retrieved. When using Parasolid, the applications programmer must first decide how to manage the storage of data, which Parasolid outputs through the frustrum. Transferring data through the frustrum usually involves writing to, or reading from, files. The format and location of the files is determined when writing the frustrum functions. 3.3 The Graphical Output (GO) The graphical output is another set of functions, which is to be written by the applications programmer. When a call is made to the PK rendering functions, the graphical data generated are output through the GO interface. The graphical data are then passed to a 3D rendering package. OpenGL, a software interface to graphic cards, is a rendering package that is used for our purpose. 3.4 The Foreign Geometry The foreign geometry provides functionality for the development of customised geometrical types such as in-house curves and surfaces. These are used together with the standard geometrical types for modelling within Parasolid. 4. Object-Oriented Programming Using Visual Cand the Microsoft Foundation Classes Object-oriented programming (OOP) has been the undisputed option for software developers. It is among the most advanced developmental tools available. The Microsoft Visual Studio is such a software package. It features several developmental tools that are meant for Internet-based and Windows-based programming. Among these tools are the Visual C(VC) and the Microsoft Foundation Classes (MFC). The VCis a powerful development tool for object-oriented programming, whereas the MFC is a framework of Cclasses that are dedicated to Windows-based programming. Together, these provided the applications programmer with powerful development features and functionalities such as auto-code generation, and wizard-based operations. These greatly improved productivity. The entire user-interface for our program is developed using the VCand the MFC. 5. System Design The direct development of a 3D-based add-on application using a 3D kernel requires several issues to be addressed. They consist of 3 main stages at the highest level. First, the identification of the crucial features and functions required for the plug-in application. Secondly, the development of the design for the application framework. Lastly, the design and development of the individual modules in the framework with appropriate developmental tools. 5.1 Identification of Essential Modules Parasolid, as a 3D kernel, provides only a number of libraries and a conceptual framework for 3D application development. It is thus necessary for the developers to identify and develop the other essential facilities that are provided in a 3D CAD system. In order to identify the required facilities, it is important to understand the discrepancies between the two. Table 1 summarises the main differences in the facilities provided by a 3D kernel and a 3D CAD system. Some of these facilities, such as features and parametric modelling, are both time-consuming and technically demanding to develop. As most plug-ins do not use all the facilities of the parent software, it is possible to develop only those required by the plug-ins using low-level 3D kernels, producing a standalone version. Items 7 to 9 in Table 1 are prerequisites for the development of 3D-based applications using Parasolid. By studying the requirements of the plug-in application, other essential facilities can be identified. A framework for the application is then proposed, based on the facilities provided by the Parasolid kernel. 5.2 Framework for 3D-Based Applications A framework is developed with reference to the facilities provided by the developmental tools and the requirements of the application. It is designed so that there are minimum dependencies between individual code modules. This may result in a small degree of code duplication. In exchange, there is better portability of the program codes, greater ease of maintenance and a better prospect for future expansion. The overview of this framework is illustrated in Fig. 2. The details of the various modules are discussed in the following sections. 5.2.1 Windows-Based User-Interface (A) Parasolid does not provide the programmer with a userinterface. Thus, the development of the 3D-based application at every single stage will involve designing the user-interface from scratch. The necessary developments involve: 1. Environmental setting and display of the 3D-based application. 2. Interactive graphical interface and execution procedure for all application functionality. 5.2.2 3D Developer Layer (B) Since different 3D-based applications require 3D-facilities to different extent, the framework must provide for these variations. A 3D developer layer (See Fig. 2, Item B) is conceptualised to handle such variations. It is a library of objects or classes that are developed, based on the Parasolid kernel. The extent of development depends on the requirements of the 456 T. L. Neo and K. S. Lee Table 1. Summary of facilities provided by a 3D kernel and a CAD system. Facilities 3D kernel 3D CAD system 1. Basic 3D modelling Low-level and general functions provided High-level and specific functions provided 2. Assemblies Several library functions provided Complete system provided 3. Feature-based modelling Not provided Established feature set provided 4. Parametric modelling Not provided Often provided 5. Free-form modelling Low-level functions provided Often provided 6. Drafting Not provided Complete system provided 7. Interactive user-interface Not provided Always provided 8. Visualisation of 3D objects Conceptual framework and several library Completely developed functions provided 9. File management system Conceptual framework and several library Completely developed functions provided Fig. 2. Overview of 3D-based application. application identified in the previous section. Besides catering for variations in application requirements, the 3D developer layer also acts as a programming interface for non-Parasolid developers. Such an interface can also be re-used for subsequent development of other 3D-based applications. The 3D developer layer essentially consists of three main sections. They are used for 3D modelling and assembly, 3D visualisation and 3D data management, respectively. I. 3D Modeling and Assembly. The 3D modelling and assembly module is the most important and elaborate of all three sections. It is analogous to the application-programming interface (API) provided by most CAD systems. The module consists of a library of 3D-based objects or classes, which are used for the development of the core application modules. The basic 3D functionality that is required by most 3D applications must be developed first. Depending on the requirements of the individual 3D-based application, other more advance features are subsequently added. II. 3D Visualisation. The display of 3D objects in a Windows client area requires a software graphics interface. The graphical output together with a selected graphical interface, are used for the rendering of 3D objects in the 3D-based application, as well as the management of the viewing projections and transformations. Here, a library of classes is developed for such purposes. III. 3D Data Management. The 3D data management module is developed on top of the frustrum. The frustrum is the module in the Parasolid kernel that facilitates archiving and access of 3D part files. A library of classes are developed using the frustrum for handling: 1. 3D object file format. 2. File management operations such as opening and saving a 3D object file. 5.2.3 Application Modules (C) These are the actual 3D-based application modules that sit between the 3D developer layer and the application userinterface. The design of these modules depends mainly on the nature of the applications and often differs greatly. The main bulk of the developmental work is carried out in this area. The ease of the development, however, depends on the capabilities of the 3D developer layer. 5.2.4 Other Software Modules (D) Very often, the 3D-based application may require functionality from other existing software modules or application modules. Therefore, such a link may exist. An example of such a requirement is illustrated in the implementation section of this paper. 5.3 Development of Individual Modules Each module to be developed is studied and analysed before a suitable design is produced. The ease of development depends greatly on the design of the framework and the developer tools selected. The next section illustrates the implementation of the Fig. 3. Overview of the injection mould base design application. above methodology on a 3D-based injection mould base design and assembly application. 6. Implementations Applying the system design, a 3D-based injection mould design application is developed. This is achieved using the developmental tools mentioned in the earlier sections. The mould base module is chosen for illustration, as it requires the widest range of 3D functionality, including the generation of assemblies. 6.1 Framework of Application and the Requirements of Each Module A framework for the application is designed with reference to the developmental work identified. Figure 3 illustrates the framework for the Mold Base design application. The details of the requirements in each module are discussed as follows: 6.1.1 Windows NT User-Interface (A) Mould base design is an iterative process. The Mould designer first selects a standard mould base from the catalogue, and then repeatedly makes modifications to the dimensions of the mould base until all the design requirements are met. It is, therefore, necessary to consider an interactive user-interface for such purpose. Using the Visual Cand the MFC, a Windows-based interface is developed. These include: 1. Creation, display and management of menu bar items, context menu items and toolbar buttons for easy access to functionality of the application. 2. Creation, display and management of dialogue boxes to guide the user or to obtain user input. 458 T. L. Neo and K. S. Lee Fig. 6. Cavity pla