附錄附錄 1：外文翻譯集成和信息輔助夾具設(shè)計與制造F. MERVYN, A. SENTHIL KUMAR* and A. Y. C NEE雖然大量的研究已應(yīng)用于開發(fā)計算機(jī)輔助夾具設(shè)計系統(tǒng)，但夾具設(shè)計制造領(lǐng)域和其他領(lǐng)域之間的信息交換并沒有徹底處理。本文針對這一差距，在夾具設(shè)計中通過應(yīng)用適當(dāng)?shù)男畔⒛Ｐ脱芯坑嬎銠C(jī)輔助夾具設(shè)計系統(tǒng)和集成支持制造業(yè)。夾具設(shè)計的模型主要是介紹有關(guān)夾具設(shè)計，以及其他設(shè)計和制造活動。對應(yīng)用在 XML 的信息模型和信息交流中的一個基于 XML 的消息傳遞模型的方法進(jìn)行了討論。關(guān)鍵詞：夾具設(shè)計，綜合設(shè)計和制造;信息建模;1.介紹在一個旨在降低產(chǎn)品交貨時間和成本以及提高產(chǎn)品質(zhì)量的過程中，企業(yè)尋求各種工程所涉及的一體化進(jìn)程設(shè)計和制造產(chǎn)品。適當(dāng)?shù)恼蠈⒃试S在一個產(chǎn)品實現(xiàn)涉及領(lǐng)域作出的決定適用于其他領(lǐng)域的需要，導(dǎo)致整體的最優(yōu)解設(shè)計和制造產(chǎn)品。計算機(jī)輔助系統(tǒng)發(fā)揮了關(guān)鍵作用在于協(xié)助不同領(lǐng)域開展工作。開發(fā)集成設(shè)計和制造系統(tǒng)的一個關(guān)鍵成功因素在于能在各種電腦輔助系統(tǒng)的信息進(jìn)行交流。夾具設(shè)計領(lǐng)域的發(fā)展已出現(xiàn)大量的電腦輔助系統(tǒng)的應(yīng)用。在制造過程設(shè)備服務(wù)于持有目的工件和保持一個安全方面的一致關(guān)系的工具。已通過各種辦法發(fā)展半自動化，自動化夾具設(shè)計系統(tǒng)。張畢（2001）努力提出的這些最新成果。盡管通過大量的研究，適應(yīng)各域之間的信息和其他制造業(yè)領(lǐng)域的交流，但是需求并沒有得到徹底處理。適當(dāng)?shù)膴A具設(shè)計信息模型描述知識和技術(shù)規(guī)格將有助于大大提高產(chǎn)品質(zhì)量和縮短產(chǎn)品交貨時間。本文的目的是要為解決通過對相應(yīng)的信息化輔助模式的夾具設(shè)計系統(tǒng)，并支持集成設(shè)計和制造。該這項工作的范圍只限于加工裝置本文組織如下：第 2 條的有關(guān)研究進(jìn)行討論在發(fā)展生產(chǎn)的信息模型;第 3 條提出了一個活動模型夾具設(shè)計;第 4 給出了不同的夾具設(shè)計信息模式，以支持集成設(shè)計和制造，而第 5條提出了一個使用 XML 的例子，實現(xiàn)了信息模型。第 6 節(jié)介紹交流信息的夾具設(shè)計方法為基礎(chǔ)上的信息模型和第 7 條最后的文件。2.相關(guān)研究制造業(yè)的信息交流的重要性已經(jīng)發(fā)展了發(fā)展各種信息模型為代表的加工過程。國際標(biāo)準(zhǔn)化組織 10303 部分（國際標(biāo)準(zhǔn)化組織，1997）是一個應(yīng)用協(xié)議的存儲和交換（美聯(lián)社）進(jìn)程之間的數(shù)控加工零件計劃的資料不同的計算機(jī)輔助工藝規(guī)劃（CAPP 系統(tǒng)）系統(tǒng)。對 AP 213 的范圍包括規(guī)劃信息的數(shù)控加工計劃，生產(chǎn)任務(wù)的指示利用數(shù)控機(jī)床的一部分，數(shù)控編程和過程檢驗資料。Wysk 等。 （1995 年）制定了工藝方案和正式代表模式聯(lián)營工廠資源模型。他們的工作范圍是就如何處理計劃可以用在車間控制環(huán)境，從而提供整合工藝規(guī)劃和生產(chǎn)之間的執(zhí)行。性等。 （1998）開發(fā)了一個信息模型的 CAPP 系統(tǒng)。采用面向?qū)ο蟮慕：推⒎址匠贪l(fā)展數(shù)據(jù)技術(shù)。該模型包括零件信息模型，計劃信息模型的過程和生產(chǎn)資源信息模型。該工藝方案模型包含制造業(yè)活動的資料，例如程序，設(shè)置和制造業(yè)務(wù)。在制造工程工具包（METK）項目，標(biāo)準(zhǔn)和技術(shù)研究所（NIST）的在美國開發(fā)的一個過程計劃（李 1999 年）作為信息模型在整合過程中的規(guī)劃和 NC 驗證的應(yīng)用程序的手段，這個過程計劃規(guī)定對每個產(chǎn)品的流程順序指示。 Ryou 和 Jerard（2001）最近開發(fā)的基于 XML 的一個代表性數(shù)值稱為控制標(biāo)記語言（NCML 之）作為一個有利的技術(shù)，允許買家和自定義加工零件賣方通過互聯(lián)網(wǎng)進(jìn)行電子商貿(mào)。在代表性，資料工件，設(shè)置，工具和信息寬容是提供讓用戶判斷一個零件的可制造。很明顯從文獻(xiàn)回顧，信息的加工過程發(fā)展模式要么不提供或只提供信息裝置固定裝置的信息作為車間執(zhí)行系統(tǒng)資源。原因這是因為在集成設(shè)計和制造設(shè)備的作用已被忽視，不經(jīng)過深入的探討。通過模式的發(fā)展，活動模型通常是先發(fā)展。活動模式設(shè)置在其中的作用是不同的域之間的交換方面設(shè)計和制造，從而確定捕獲的信息類型在信息模型。這些活動的模型的一些審查中可以找到（1996） ?；顒幽Ｊ桨l(fā)展至今，裝置只能被視為一個制造系統(tǒng)的資源。對裝置的影響一個產(chǎn)品的設(shè)計仍沒有得到處理。在確定一個產(chǎn)品的關(guān)鍵作用，準(zhǔn)確度也高，一個制造系統(tǒng)的靈活性、夾具的能力，有效的產(chǎn)品，因此應(yīng)在設(shè)計關(guān)注一個產(chǎn)品。本文針對這在當(dāng)前制造業(yè)信息化差距模型提出一個模型，夾具設(shè)計活動的需要考慮作用在產(chǎn)品設(shè)計和制造設(shè)備。適當(dāng)?shù)膴A具設(shè)計信息模型，然后發(fā)展到支持集成的設(shè)計和制造業(yè)。該信息模型的開發(fā)利用作為一個 XML 的文件格式和交換信息的基礎(chǔ)上的做法。3.夾具設(shè)計活動模型擬議的夾具設(shè)計活動的模型如圖 1 所示。該活動已使用 IDEF0 方法描述，并且只有在一個描述抽象的層面，使信息模型是獨立的執(zhí)行這些活動的。在圖 1 可以看出，一為綜合設(shè)計夾具設(shè)計系統(tǒng)與制造執(zhí)行兩個主要活動，格 A1 -夾具概念設(shè)計和 A2 -詳細(xì)夾具設(shè)計。夾具設(shè)計活動的概念是一個規(guī)劃過程的一部分活動，在那里他們討論了需要概念工藝規(guī)劃的活動，支持產(chǎn)品設(shè)計的概念確定生產(chǎn)過程，選擇資源和設(shè)備，從制造成本估算的概念活動輸出發(fā)送反饋到產(chǎn)品概念設(shè)計活動。作為活動的一部分概念工藝規(guī)劃，通過對活動支持的困難分析概念產(chǎn)品設(shè)計夾具設(shè)計的概念夾具在該產(chǎn)品的特點，估計該產(chǎn)品的加工成本所采取的固定裝置和夾具的制造時間。到投入活動是概念產(chǎn)品設(shè)計，產(chǎn)品的數(shù)量的估計是生產(chǎn)和當(dāng)前夾具清單。該任務(wù)的概念夾具設(shè)計活動有：1.確定要使用夾具的類型為基礎(chǔ)的估計量該產(chǎn)品被制造。2.在加工過程中的部分限制的基礎(chǔ)上確定的困難概念產(chǎn)品的幾何形狀。3.估計的時間和新設(shè)備的設(shè)計和制造成本如果目前的庫存設(shè)備不能使用。夾具的概念設(shè)計活動的關(guān)鍵是信息模型和概念設(shè)計的反饋。這將提供產(chǎn)品信息模型與問題反饋設(shè)計，并提供了夾具上一個度量產(chǎn)品設(shè)計人員比較關(guān)注的不同的初始設(shè)計。圖 1.夾具設(shè)計活動模型。夾具的概念設(shè)計活動的輸出是信息模型與概念設(shè)計反饋。這將提供產(chǎn)品信息模型與問題的反饋設(shè)計，并提供了一個度量產(chǎn)品設(shè)計人員比較關(guān)注的夾具上有不同的初始設(shè)計。該夾具的詳細(xì)設(shè)計活動的投入是固定的類型從概念夾具設(shè)計活動的信息，中間部分模型將被加工和夾具庫存信息。中間部分模型零件的幾何關(guān)系設(shè)置。作為一個例子，圖2 顯示了一個部分，需要 3 設(shè)置機(jī)器的特點。中間部分是固定式模式，在每個安裝圖中顯示。中間部分模型可以得出一旦制造業(yè)序列測定。應(yīng)當(dāng)指出，該夾具設(shè)計活動作為輸入接收信息控制整個零件模型。該圖提供了對現(xiàn)有夾具元件所需資料，以便夾具設(shè)計中使用。圖 2.例如部分，中間部分的模型。夾具的詳細(xì)設(shè)計活動的任務(wù)是：1.設(shè)計為每個安裝夾具。這包括進(jìn)行夾具布局夾具的設(shè)計和配置設(shè)計。2.評估所設(shè)計的夾具以及如何履行其職能的準(zhǔn)確定位，限制和支持工件3. 生成的鋪地板的固定裝置處理必要的指示。這包括在夾緊工件和正確的到達(dá)的每個夾緊力應(yīng)驅(qū)動。順序夾具的詳細(xì)設(shè)計活動的輸出是信息模型，中間部分模型反饋，夾具配置和組裝工件裝載指示。中間部分模型提供反饋信息反饋的過程以及如何規(guī)劃師每個零件模型之間的中間可以設(shè)置固定式。反饋將使這個進(jìn)程規(guī)劃達(dá)到夾具最佳工藝方案。夾具裝配模型的配置信息有兩個目的。首先，它提供有關(guān)的信息工具的夾具裝配路徑規(guī)劃配置。這些信息可以被用來生成夾具裝配的檢查刀具路徑之間的干擾和夾具元件。其次，它使車間人員構(gòu)建基于組件的夾具提供信息。工件裝載指示信息模型提供車間工件如何適用于于人員的指示和信號燈。4.夾具設(shè)計信息模型本節(jié)描述了各種夾具設(shè)計信息模型的細(xì)節(jié)將要生成的夾具設(shè)計活動。該信息模型已使用 XML 實現(xiàn)。兩種方法可以用來表示數(shù)據(jù)時使用 XML，第一是使用一個文檔類型定義（DTD） ，第二個是使用一個 XML 架構(gòu)。在這項工作中，我們代表的數(shù)據(jù)使用一個 DTD。一個 DTD 定義該元素可以出現(xiàn)在一個 XML 文件和辦法，使他們能夠出現(xiàn)。對每個 DTD 的結(jié)構(gòu)信息模型解釋了部分。這些文件是由一個開發(fā)計算機(jī)輔助夾具設(shè)計產(chǎn)生系統(tǒng)（默文等，2003） 。4.1 概念設(shè)計和反饋該概念設(shè)計反饋 XML 文件的 DTD 列于圖 3 是由四個組的信息了：（一）產(chǎn)品設(shè)計的評價是進(jìn)行了身份，（二）固定式的使用，（三）該概念設(shè)計的幾何評價，并（四）預(yù)計成本和時間，制造燈具。圖 3.概念設(shè)計反饋 DTD 的 XML 文件。在該夾具類型的基礎(chǔ)上加以確定的估計量產(chǎn)品被生產(chǎn)。該夾具類型要么是'專用'或'彈性'。一般來說，一個專一個靈活的夾具用于小批量的生產(chǎn)。用夾具用于大批量的生產(chǎn)和幾何直觀的評價應(yīng)該是對產(chǎn)品設(shè)計人員認(rèn)識上的夾具設(shè)計產(chǎn)品的幾何效應(yīng)。有關(guān)資料也應(yīng)可解釋為電腦自動化環(huán)境中使用。為了要做到這一點，幾何評價已經(jīng)被映射到該產(chǎn)品的特點設(shè)計。每個產(chǎn)品的功能，被加工有三個屬性，'定位'，克制'和'支持'。這些屬性是一個代表的職責(zé)夾具。因此，他們描述的能力，夾具加工過程中的一部分功能。雖然有幾個功能可以在一次裝夾加工，這個映射已經(jīng)被采納，使產(chǎn)品設(shè)計師能夠輕松地認(rèn)識到這一問題的該產(chǎn)品的幾何形狀。三個屬性的每個有兩個子屬性，'存在人臉'和'臉'獲取。這兩個屬性的集體描述能否完成特定功能的燈具。面對存在的屬性指的是尋找緩解面臨的定位，夾緊工件和支持在加工的功能。此屬性將一個整數(shù)的數(shù)值范圍從 1 至5，1 個非常容易和非常困難的 5。輔助功能屬性的臉指的是在公司目前的庫存夾具能夠訪問夾具的臉。這可能是一兩個值，'標(biāo)準(zhǔn)'或'特殊'。如果臉難以進(jìn)入，一個可能需要特殊的夾具和值將是'特殊'。標(biāo)準(zhǔn)裝置是可以買現(xiàn)成的，現(xiàn)成的或現(xiàn)有的裝置元素在可用于裝夾部分用于公司。這個屬性允許產(chǎn)品設(shè)計人員了解有關(guān)產(chǎn)品的成本影響幾何夾具及采取的制造夾具的時間。例如，如果類型的夾具'是一個靈活的夾具，但面臨的無障礙特殊，它意味著由于該產(chǎn)品幾何，專用夾具需要一個靈活的，雖然夾具的基礎(chǔ)上更適合需要的產(chǎn)品數(shù)量。這將使產(chǎn)品設(shè)計師，了解了產(chǎn)品的增加導(dǎo)致時間和成本。在成本和時間估算屬性有三個子屬性，估計費用制造夾具，預(yù)計需時多久制造的，可以在一夾具加工工件夾具蔚，數(shù)量。這些屬性使產(chǎn)品設(shè)計師 1 夾具的成本和效果的估計的夾具在產(chǎn)品交貨時間?？傮w而言，這一信息模型提供了難易程度反饋夾具概念設(shè)計。該 fixturability 據(jù)分析映射以該產(chǎn)品的模型功能允許直觀地了解產(chǎn)品設(shè)計師其特點將構(gòu)成裝夾加工過程中的問題。產(chǎn)品設(shè)計人員可以使用這些信息來作出評估的概念設(shè)計或改變之間關(guān)于 fixturability 關(guān)注的幾個概念設(shè)計。4.2 中間部分模型 fixturability 反饋該模型的中間部分的 XML 文件的 DTD fixturability 反饋需要的 結(jié)構(gòu)如圖 4 所示。圖 4.中間部分模型 fixturability 反饋 DTD 的 XML 文件。在這個信息模型中，模型的中間部分評價是基于三個屬性，'定位'，'克制'和'支持'。如前面提到的，這些屬性是一個固定的職能的代表。不過，相對的概念產(chǎn)品設(shè)計評價，中間部分模型的詳細(xì)信息可在這個階段。因此，在履行職能的能力上更徹底的代表性在此提供的信息模型。對位置屬性的孔來定位和信息的一部分建立一個基準(zhǔn)誤差估計。每個定位孔上有定位元素限制?；鶞?zhǔn)誤差估計屬性從工件位置的理想位置提供的信息可能偏差。這一信息是提供 6 個自由度，翻譯從 X -，y 軸和 z 軸和旋轉(zhuǎn)攻方的 X，Y 型和 Z -軸。屬性的限制和支持也包含的信息用于工件夾緊和支持。屬性的限制有進(jìn)一步的約束分析屬性。此屬性描述的能力夾具以制止在加工過程中工件的議案。這可能需要一兩個值，限制或無限制。類似屬性的約束分析，支持屬性具有變形分析子屬性。此屬性介紹了夾具在機(jī)械加工能力，以支持和工件防止變形。此屬性將一個整數(shù)的值從 1 至 5，1 對應(yīng)非常差和 5 對應(yīng)非常好?；鶞?zhǔn)誤差估計，約束分析和變形分析屬性提供反饋的進(jìn)程以及如何規(guī)劃每個可以是固定的中間部分模型。附錄 2：英文原文Fixture design information support for integrated designand manufacturingF. MERVYN, A. SENTHIL KUMAR* and A. Y. C NEEAlthough a vast amount of research has been conducted on developingcomputer-aided fixture design systems, the need for information exchangebetween the fixture design domain and other manufacturing domains hasnot been thoroughly dealt with. This paper addresses this gap in fixture designresearch through the development of appropriate information models forcomputer-aided fixture design systems to support integrated design andmanufacturing. A fixture design activity model is presented that relatesfixture design to other design and manufacturing activities. The implementationof the information models in XML and the exchange of the informationmodels based on an XML messaging approach are also discussed.Keywords: Fixture design; Integrated design and manufacturing; Informationmodelling; XML1. IntroductionIn an aim to reduce product lead-time and cost as well as improve product quality,enterprises seek the integration of the various engineering processes involved in thedesign and manufacture of a product. Proper integration will allow the differentdomains involved in the realization of a product to make decisions taking intoaccount the requirements of other domains, resulting in overall optimal solutions forthe design and manufacture of a product. Computer-aided systems play a key roletoday in aiding the different domains carry out their tasks. A crucial factor in thesuccess of developing integrated design and manufacturing systems lies in the abilityto exchange information among the various computer-aided systems.The fixture design domain has seen a vast amount of research in developingcomputer-aided systems. Fixtures are devices that serve the purpose of holding aworkpiece securely and maintaining a consistent relationship with respect to the toolsduring a manufacturing process (Nee et al. 1995). Various approaches have beenadopted in developing interactive, semi-automated and automated fixture designsystems. Bi and Zhang (2001) present a recent review of these efforts. Despite thevast amount of research, the need for information exchange between the fixture*Corresponding author. Email: mpeask@nus.edu.sgInternational Journal of Production ResearchISSN 0020–7543 print/ISSN 1366–588X online 2006 Taylor section 3 presents an activitymodel for fixture design; section 4 presents the different fixture design informationmodels to support integrated design and manufacturing, while section 5 presents anexample of the information models implemented using XML. Section 6 describes theexchange of the fixture design information models based on a messaging approachand section 7 concludes the paper.2. Related researchThe importance of information exchange in manufacturing has seen the developmentof various information models for representing the machining process. ISO 10303Part 213 (ISO, 1997) is a STEP application protocol (AP) for storing and exchangingprocess plan information for numerically controlled machined parts betweendissimilar computer-aided process planning (CAPP) systems. The scope of AP 213includes planning information of NC process plans, task instructions to manufacturea part using NC machines, NC programming and in-process inspection information.Wysk et al. (1995) developed a formal representation schema for process plans andan associated factory resource model. The scope of their work was on how processplans can be used in a shop floor control environment, thus providing integrationbetween process planning and production execution. Xing et al. (1998) developed aninformation model for CAPP by using object-oriented modelling and the PDES/STEP data techniques. The model consists of the part information model, theprocess plan information model and the production resource information model.The process plan model contains information on manufacturing activities such asprocesses, setups and manufacturing operations. The manufacturing engineeringtoolkit (METK) project at the National Institute of Standards and Technology(NIST) in the USA developed an information model for a process plan (Lee 1999) asa means of integrating process planning and NC validation applications. The processplan provides instructions on the sequence of processes for each product. Ryou andJerard (2001) recently developed a representation based on XML called numericalcontrol markup language (NCML) as an enabling technology to permit buyers andsellers of custom machined parts to conduct e-commerce via the Internet. In therepresentation, information regarding workpiece, setups, tool information andtolerance is provided to allow users to judge the manufacturability of a part.From the literature review, it was evident that the machining process informationmodels developed either do not provide information on fixtures or only provideinformation on fixtures as a resource for shop floor execution systems. The reasonfor this is that the role of fixtures in integrated design and manufacturing has beenoverlooked and not thoroughly explored. In the development of standard2 F. Mervyn et al.information models, an activity model is normally developed first. Activity modelsset the context in which information is exchanged between the different domains indesign and manufacturing, and thus determine the type of information capturedin information models. A review of some of these activity models can be found inFeng (1996). In the activity models developed thus far, fixtures have only beenconsidered as a resource for manufacturing systems. The effect of fixtures on thedesign of a product has not been dealt with. Fixtures play a key role in determiningthe accuracy of a product and also, the flexibility of a manufacturing system.The ability to effectively fixture a product should therefore be a concern in the designof a product. This paper addresses this gap in current manufacturing informationmodels by presenting a fixture design activity model that takes into account therole of fixtures in product design and manufacturing. Appropriate fixture designinformation models are then developed to support integrated design andmanufacturing. The information models are developed using XML as a file formatand exchanged based on a messaging approach.3. Fixture design activity modelThe proposed fixture design activity model is as shown in figure 1.The activities have been described using IDEF0 and are only described at anabstract level so that the information models are independent of the implementationof these activities. As seen in figure 1, a fixture design system for integrated designand manufacturing performs two main activities, A1—Conceptual Fixture Designand A2—Detailed Fixture Design.The conceptual fixture design activity is part of a conceptual process planningactivity, described in Feng and Zhang (1999), where they discuss the need for aconceptual process planning activity that supports conceptual product design bydetermining the manufacturing processes, selecting resources and equipment, andestimating manufacturing costs roughly. The output from the conceptual processFigure 1. Fixture design activity model.planning activity is sent as feedback to the conceptual product design activity.As part of the conceptual process planning activity, the conceptual fixture designactivity supports conceptual product design through an analysis of the difficulties infixturing the product during the machining of the product features, estimation of thecost of the fixtures and the time taken to manufacture the fixture. The inputs to theactivity are the conceptual product design, the estimated quantity of the product tobe manufactured and the current fixture inventory. The tasks of the conceptualfixture design activity are:. Determine the type of fixture to be used based on the estimated quantity ofthe product to be manufactured.. Determine difficulties in restraining a part during machining based on theconceptual product geometry.. Estimate the time and cost of designing and manufacturing new fixturesif the current inventory of fixtures cannot be used.The output of the conceptual fixture design activity is the information model,conceptual design fixturability feedback. This information model will provide productdesigners with feedback on fixturability problems and also provides a metric forproduct designers to compare different initial designs in terms of fixturing concerns.The inputs to the detailed fixture design activity are the type of fixtureinformation from the conceptual fixture design activity, the intermediate part model,the faces of the intermediate part model that will be machined and the fixtureinventory information. The intermediate part model is the geometry of the partin between setups. As an example, figure 2 shows a part that requires three setupsto machine the features. The intermediate part models to be fixtured at each setupare shown in the figure. The intermediate part model can be derived once themanufacturing sequences are determined. It should be noted that the conceptualfixture design activity receives the entire part model as an input. The fixtureFigure 2. Example part and intermediate part models.inventory provides the necessary information on the available fixture elements to beused in fixture design.The tasks of the detailed fixture design activity are:. Design the fixture for each setup. This includes carrying out fixture layoutdesign and fixture configuration design.. Evaluate how well the designed fixture fulfils its functions of accuratelylocating, restraining and supporting a workpiece.. Generate the necessary instructions for shop floor handling of fixtures. Thisincludes arriving at a proper sequence for clamping the workpiece and theforce that each clamp should be actuated with.The outputs of the detailed fixture design activity are the information models,intermediate part model fixturability feedback, fixture assembly configuration andworkpiece loading instructions.The intermediate part model fixturability feedback information model providesfeedback to the process planner on how well each intermediate part model betweensetups can be fixtured. The feedback will allow the process planner to arrive at theoptimal process plan taking into account fixturing considerations.The fixture assembly configuration information model serves two purposes.Firstly, it provides tool path planners with information on the fixture assemblyconfiguration. This information can then be used to generate the fixture assembly forchecking of interference between the tool path and fixture elements. Secondly, itallows shop floor personnel to construct the fixture assemblies based on the providedinformation.The workpiece loading instructions information model provides shop floorpersonnel instructions on how the workpiece should be located and restrained onthe fixture.4. Fixture design information modelsThis section describes the details of the various fixture design information modelsto be generated by the fixture design activities. The information models have beenimplemented using XML. Two approaches can be used when representing data usingXML; the first is to use a document type definition (DTD) and the second is to usean XML schema. In this work, we represent the data using a DTD. A DTD definesthe elements that can appear in an XML document and the way in which they canappear. The structure of the DTD of each information model is explained in thissection. These files are to be generated by a developed computer-aided fixture designsystem (Mervyn et al. 2003b).4.1 Conceptual design fixturability feedbackThe DTD of the conceptual design fixturability feedback XML file is shown infigure 3 and is made up of four groups of information:(i) the identity of the product design that the evaluation is carried out for,(ii) the type of fixture to be used,(iii) the geometric evaluation of the conceptual design, and(iv) the estimated cost and time to manufacture the fixture.Figure 3. DTD of conceptual design fixturability feedback XML file.The type of fixture is to be determined based on the estimated quantity ofproducts to be manufactured. The type of fixture could either be ‘dedicated’or ‘flexible’. Generally, a dedicated fixture is used for high volume production anda flexible fixture is used for low volume production.The geometric evaluation should be intuitive to the product designer tounderstand the effect of the product geometry on the fixture design. The informationshould also be computer interpretable for use in an automated environment. In orderto do this, the geometric evaluation has been mapped to the features of the productdesign. Each feature of the product to be machined has three attributes, ‘location’,‘restraint’ and ‘support’. These attributes are representative of the functions of afixture. They thus describe the ability to fixture the part during the machining of thefeature. Although several features can be machined in a single setup, this mappinghas been adopted to allow the product designer to easily recognize the problem withthe product geometry. Each of the three attributes has two sub-attributes, ‘presenceof faces’ and ‘a(chǎn)ccessibility of faces’. These two attributes collectively describe theability to fulfil the particular function of the fixture. The presence of faces attributerefers to the ease of finding faces for locating, clamping and supporting the workpieceduring the machining of the feature. This attribute takes an integer value rangingfrom 1 to 5, 1 for very easy and 5 for very difficult. The accessibility of faces attributerefers to the ability of a fixture in the company’s current inventory to access thefixturing face. This could be one of two values, ‘standard’ or ‘special’. If a face isdifficult to access, a special fixture might be required and the value would be ‘special’.Standard fixtures are elements that could be bought off-the-shelf or existing fixturesin the company that can be used for fixturing the part. This attribute allows theproduct designer to understand the effect of the product geometry on the cost of thefixture and the time taken to manufacture the fixture. For example, if the type offixture’ is a flexible fixture, but the accessibility of faces is special, it would mean thatdue to the product geometry, a dedicated fixture is required although a flexiblefixture is more suitable based on the product quantity required. This would allow theproduct designer to understand the increase in the product lead-time and cost.The cost and time estimation attribute has three sub-attributes, the estimated costto manufacture the fixture, the estimated time taken to manufacture the fixture andFigure 4. DTD of intermediate part model fixturability feedback XML file.the number of workpieces that can be machined in one fixture. These attributes givethe product designer an estimate of the cost of the fixture and the effect of the fixtureon the product lead-time.Overall, this information model provides feedback on the ease or difficulty offixturing the conceptual design. The mapping o