外文翻譯--集成和信息輔助夾具設計與制造

1、<p><b>　　附錄</b></p><p><b>　　附錄1：外文翻譯</b></p><p>　　集成和信息輔助夾具設計與制造</p><p>　　F. MERVYN, A. SENTHIL KUMAR* and A. Y. C NEE</p><p>　　雖然大量的研究已應用于

2、開發(fā)計算機輔助夾具設計系統(tǒng)，但夾具設計制造領域和其他領域之間的信息交換并沒有徹底處理。本文針對這一差距，在夾具設計中通過應用適當?shù)男畔⒛Ｐ脱芯坑嬎銠C輔助夾具設計系統(tǒng)和集成支持制造業(yè)。夾具設計的模型主要是介紹有關夾具設計，以及其他設計和制造活動。對應用在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行了討論。</p><p>　　關鍵詞：夾具設計，綜合設計和制造;信息建模;1.介紹</p

3、><p>　　在一個旨在降低產(chǎn)品交貨時間和成本以及提高產(chǎn)品質量的過程中，企業(yè)尋求各種工程所涉及的一體化進程設計和制造產(chǎn)品。適當?shù)恼蠈⒃试S在一個產(chǎn)品實現(xiàn)涉及領域作出的決定適用于其他領域的需要，導致整體的最優(yōu)解設計和制造產(chǎn)品。計算機輔助系統(tǒng)發(fā)揮了關鍵作用在于協(xié)助不同領域開展工作。開發(fā)集成設計和制造系統(tǒng)的一個關鍵成功因素在于能在各種電腦輔助系統(tǒng)的信息進行交流。夾具設計領域的發(fā)展已出現(xiàn)大量的電腦輔助系統(tǒng)的應用。在制造過程設

4、備服務于持有目的工件和保持一個安全方面的一致關系的工具。已通過各種辦法發(fā)展半自動化，自動化夾具設計系統(tǒng)。張畢（2001）努力提出的這些最新成果。盡管通過大量的研究，適應各域之間的信息和其他制造業(yè)領域的交流，但是需求并沒有得到徹底處理。適當?shù)膴A具設計信息模型描述知識和技術規(guī)格將有助于大大提高產(chǎn)品質量和縮短產(chǎn)品交貨時間。本文的目的是要為解決通過對相應的信息化輔助模式的夾具設計系統(tǒng)，并支持集成設計和制造。該這項工作的范圍只限于加工裝置本文組

5、織如下：第2條的有關研究進行討論在發(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計;第4給出了不同的夾具設計信息模式，以支持集成設計和制造，而第5條提</p><p><b>　　2.相關研究</b></p><p>　　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。國際標準化組織10303部分（國際標準化組織，1997）是一個應用協(xié)議的存儲

6、和交換（美聯(lián)社）進程之間的數(shù)控加工零件計劃的資料不同的計算機輔助工藝規(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)任務的指示利用數(shù)控機床的一部分，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)。采用面向對象的建模和

7、偏微分方程發(fā)展數(shù)據(jù)技術。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，設置和制造業(yè)務。在制造工程工具包（METK）項目，標準和技術研究所（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</p>

8、<p>　　3.夾具設計活動模型</p><p>　　擬議的夾具設計活動的模型如圖1所示。</p><p>　　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，一為綜合設計夾具設計系統(tǒng)與制造執(zhí)行兩個主要活動，格A1 -夾具概念設計和A2 -詳細夾具設計。</p><p>　　夾具設計活動的概念

9、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)品設計的概念確定生產(chǎn)過程，選擇資源和設備，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)品設計夾具設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)品設計，產(chǎn)品的數(shù)量的估計是生產(chǎn)和當前夾具清單。該任務的概念夾具設計活動有： 1.確定要使用夾具

10、的類型為基礎的估計量該產(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.估計的時間和新設備的設計和制造成本如果目前的庫存設備不能使用。</p><p>　　夾具的概念設計活動的關鍵是信息模型和概念設計的反饋。這將提供產(chǎn)品信息模型與問題反饋設計，并提供了夾具上一個度量產(chǎn)品設計人員比較關注的不同的初始設計。</p><p>　　圖1.夾具設計活動模型

11、。</p><p>　　夾具的概念設計活動的輸出是信息模型與概念設計反饋。這將提供產(chǎn)品信息模型與問題的反饋設計，并提供了一個度量產(chǎn)品設計人員比較關注的夾具上有不同的初始設計。</p><p>　　該夾具的詳細設計活動的投入是固定的類型從概念夾具設計活動的信息，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系設置。作為一個例子，圖2顯示了一個部分，需要3設置機器的特點。中間部分

12、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。應當指出，該夾具設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，以便夾具設計中使用。</p><p>　　圖2.例如部分，中間部分的模型。</p><p>　　夾具的詳細設計活動的任務是： 1.設計為每個安裝夾具。這包括進行夾具布局夾具的設計和配置設計。 2.評估所設計的夾具以

13、及如何履行其職能的準確定位，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的每個夾緊力應驅動。順序夾具的詳細設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。</p><p>　　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置固定式。反饋將使這個進程規(guī)劃達到夾具最佳工藝方案。</p><p&g

14、t;　　夾具裝配模型的配置信息有兩個目的。首先，它提供有關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，它使車間人員構建基于組件的夾具提供信息。</p><p>　　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。</p><p>　　4.夾具設計信息模型</p><p>　　本節(jié)描述了各種

15、夾具設計信息模型的細節(jié)將要生成的夾具設計活動。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。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的結構信息模型解釋了部分。這些文件是由一個開發(fā)計算機輔助夾具設計產(chǎn)生系統(tǒng)（默文等，2003）。4.1概念設計和反饋該概念設計反饋XML

16、文件的DTD列于圖3是由四個組的信息了：（一）產(chǎn)品設計的評價是進行了身份，（二）固定式的使用，（三）該概念設計的幾何評價，并（四）預計成本和時間，制造燈具。</p><p>　　圖3.概念設計反饋DTD的XML文件。</p><p>　　在該夾具類型的基礎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

17、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該是對產(chǎn)品設計人員認識上的夾具設計產(chǎn)品的幾何效應。有關資料也應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

18、納，使產(chǎn)品設計師能夠輕松地認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，'標準'或'特殊

19、'。如果臉難以進入，一個可能需要特殊的夾具和值將是'特殊'。標準裝置是可以買現(xiàn)成的，現(xiàn)成的或現(xiàn)有的裝置元</p><p>　　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。總體而言，這一信息模型提供了難易程度反饋夾具概念設計。該fixturability據(jù)分析映射以

20、該產(chǎn)品的模型功能允許直觀地了解產(chǎn)品設計師其特點將構成裝夾加工過程中的問題。產(chǎn)品設計人員可以使用這些信息來作出評估的概念設計或改變之間關于fixturability關注的幾個概念設計。</p><p>　　4.2中間部分模型fixturability反饋</p><p>　　該模型的中間部分的XML文件的DTD fixturability反饋需要的 結構如圖4所示。</p>

21、<p>　　圖4.中間部分模型fixturability反饋DTD的XML文件。</p><p>　　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)品設計評價，中間部分模型的詳細信息可在這個階段。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

22、置屬性的孔來定位和信息的一部分建立一個基準誤差估計。每個定位孔上有定位元素限制。基準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

23、紹了夾具在機械加工能力，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對應非常差和5對應非常好?；鶞收`差估計，約束分析和變形分析屬性提供反饋的進程以及如何規(guī)劃每個可以是固定的中間部分模型。</p><p><b>　　附錄2：英文原文</b></p><p>　　Fixture design information support for integrated

24、 design</p><p>　　and manufacturing</p><p>　　F. MERVYN, A. SENTHIL KUMAR* and A. Y. C NEE</p><p>　　Although a vast amount of research has been conducted on developing</p><

25、p>　　computer-aided fixture design systems, the need for information exchange</p><p>　　between the fixture design domain and other manufacturing domains has</p><p>　　not been thoroughly dealt

26、with. This paper addresses this gap in fixture design</p><p>　　research through the development of appropriate information models for</p><p>　　computer-aided fixture design systems to support in

27、tegrated design and</p><p>　　manufacturing. A fixture design activity model is presented that relates</p><p>　　fixture design to other design and manufacturing activities. The implementation<

28、/p><p>　　of the information models in XML and the exchange of the information</p><p>　　models based on an XML messaging approach are also discussed.</p><p>　　Keywords: Fixture design;

29、Integrated design and manufacturing; Information</p><p>　　modelling; XML</p><p>　　1. Introduction</p><p>　　In an aim to reduce product lead-time and cost as well as improve product

30、quality,</p><p>　　enterprises seek the integration of the various engineering processes involved in the</p><p>　　design and manufacture of a product. Proper integration will allow the different&

31、lt;/p><p>　　domains involved in the realization of a product to make decisions taking into</p><p>　　account the requirements of other domains, resulting in overall optimal solutions for</p>

32、<p>　　the design and manufacture of a product. Computer-aided systems play a key role</p><p>　　today in aiding the different domains carry out their tasks. A crucial factor in the</p><p>　　

33、success of developing integrated design and manufacturing systems lies in the ability</p><p>　　to exchange information among the various computer-aided systems.</p><p>　　The fixture design domai

34、n has seen a vast amount of research in developing</p><p>　　computer-aided systems. Fixtures are devices that serve the purpose of holding a</p><p>　　workpiece securely and maintaining a consist

35、ent relationship with respect to the tools</p><p>　　during a manufacturing process (Nee et al. 1995). Various approaches have been</p><p>　　adopted in developing interactive, semi-automated and

36、automated fixture design</p><p>　　systems. Bi and Zhang (2001) present a recent review of these efforts. Despite the</p><p>　　vast amount of research, the need for information exchange between t

37、he fixture</p><p>　　*Corresponding author. Email: mpeask@nus.edu.sg</p><p>　　International Journal of Production Research</p><p>　　ISSN 0020–7543 print/ISSN 1366–588X online 2006 T

38、aylor & Francis</p><p>　　http://www.tandf.co.uk/journals</p><p>　　DOI: 10.1080/00207540500465303</p><p>　　design domain and other manufacturing domains has not been thoroughly d

39、ealt with</p><p>　　(Mervyn et al. 2003a). Appropriate information models describing fixture design</p><p>　　knowledge and specifications could help to significantly improve product quality and&l

40、t;/p><p>　　reduce product lead-time. The aim of this paper is to take a step towards addressing</p><p>　　this need through the development of appropriate information models for computeraided</p&

41、gt;<p>　　fixture design systems to support integrated design and manufacturing. The</p><p>　　scope of this work is limited to machining fixtures.</p><p>　　This paper is organized as follo

42、ws: section 2 discusses the related research carried</p><p>　　out in developing manufacturing information models; section 3 presents an activity</p><p>　　model for fixture design; section 4 pres

43、ents the different fixture design information</p><p>　　models to support integrated design and manufacturing, while section 5 presents an</p><p>　　example of the information models implemented u

44、sing XML. Section 6 describes the</p><p>　　exchange of the fixture design information models based on a messaging approach</p><p>　　and section 7 concludes the paper.</p><p>　　2. Re

45、lated research</p><p>　　The importance of information exchange in manufacturing has seen the development</p><p>　　of various information models for representing the machining process. ISO 10303&

46、lt;/p><p>　　Part 213 (ISO, 1997) is a STEP application protocol (AP) for storing and exchanging</p><p>　　process plan information for numerically controlled machined parts between</p><p&

47、gt;　　dissimilar computer-aided process planning (CAPP) systems. The scope of AP 213</p><p>　　includes planning information of NC process plans, task instructions to manufacture</p><p>　　a part u

48、sing NC machines, NC programming and in-process inspection information.</p><p>　　Wysk et al. (1995) developed a formal representation schema for process plans and</p><p>　　an associated factory

49、resource model. The scope of their work was on how process</p><p>　　plans can be used in a shop floor control environment, thus providing integration</p><p>　　between process planning and produc

50、tion execution. Xing et al. (1998) developed an</p><p>　　information model for CAPP by using object-oriented modelling and the PDES/</p><p>　　STEP data techniques. The model consists of the part

51、 information model, the</p><p>　　process plan information model and the production resource information model.</p><p>　　The process plan model contains information on manufacturing activities su

52、ch as</p><p>　　processes, setups and manufacturing operations. The manufacturing engineering</p><p>　　toolkit (METK) project at the National Institute of Standards and Technology</p><

53、p>　　(NIST) in the USA developed an information model for a process plan (Lee 1999) as</p><p>　　a means of integrating process planning and NC validation applications. The process</p><p>　　pla

54、n provides instructions on the sequence of processes for each product. Ryou and</p><p>　　Jerard (2001) recently developed a representation based on XML called numerical</p><p>　　control markup l

55、anguage (NCML) as an enabling technology to permit buyers and</p><p>　　sellers of custom machined parts to conduct e-commerce via the Internet. In the</p><p>　　representation, information regard

56、ing workpiece, setups, tool information and</p><p>　　tolerance is provided to allow users to judge the manufacturability of a part.</p><p>　　From the literature review, it was evident that the m

57、achining process information</p><p>　　models developed either do not provide information on fixtures or only provide</p><p>　　information on fixtures as a resource for shop floor execution syste

58、ms. The reason</p><p>　　for this is that the role of fixtures in integrated design and manufacturing has been</p><p>　　overlooked and not thoroughly explored. In the development of standard</

59、p><p>　　2 F. Mervyn et al.</p><p>　　information models, an activity model is normally developed first. Activity models</p><p>　　set the context in which information is exchanged betwee

60、n the different domains in</p><p>　　design and manufacturing, and thus determine the type of information captured</p><p>　　in information models. A review of some of these activity models can be

61、 found in</p><p>　　Feng (1996). In the activity models developed thus far, fixtures have only been</p><p>　　considered as a resource for manufacturing systems. The effect of fixtures on the</

62、p><p>　　design of a product has not been dealt with. Fixtures play a key role in determining</p><p>　　the accuracy of a product and also, the flexibility of a manufacturing system.</p><p

63、>　　The ability to effectively fixture a product should therefore be a concern in the design</p><p>　　of a product. This paper addresses this gap in current manufacturing information</p><p>　　

64、models by presenting a fixture design activity model that takes into account the</p><p>　　role of fixtures in product design and manufacturing. Appropriate fixture design</p><p>　　information mo

65、dels are then developed to support integrated design and</p><p>　　manufacturing. The information models are developed using XML as a file format</p><p>　　and exchanged based on a messaging appro

66、ach.</p><p>　　3. Fixture design activity model</p><p>　　The proposed fixture design activity model is as shown in figure 1.</p><p>　　The activities have been described using IDEF0 a

67、nd are only described at an</p><p>　　abstract level so that the information models are independent of the implementation</p><p>　　of these activities. As seen in figure 1, a fixture design syste

68、m for integrated design</p><p>　　and manufacturing performs two main activities, A1—Conceptual Fixture Design</p><p>　　and A2—Detailed Fixture Design.</p><p>　　The conceptual fixtur

69、e design activity is part of a conceptual process planning</p><p>　　activity, described in Feng and Zhang (1999), where they discuss the need for a</p><p>　　conceptual process planning activity

70、that supports conceptual product design by</p><p>　　determining the manufacturing processes, selecting resources and equipment, and</p><p>　　estimating manufacturing costs roughly. The output fr

71、om the conceptual process</p><p>　　Figure 1. Fixture design activity model.</p><p>　　planning activity is sent as feedback to the conceptual product design activity.</p><p>　　As par

72、t of the conceptual process planning activity, the conceptual fixture design</p><p>　　activity supports conceptual product design through an analysis of the difficulties in</p><p>　　fixturing th

73、e product during the machining of the product features, estimation of the</p><p>　　cost of the fixtures and the time taken to manufacture the fixture. The inputs to the</p><p>　　activity are the

74、 conceptual product design, the estimated quantity of the product to</p><p>　　be manufactured and the current fixture inventory. The tasks of the conceptual</p><p>　　fixture design activity are:

75、</p><p>　　. Determine the type of fixture to be used based on the estimated quantity of</p><p>　　the product to be manufactured.</p><p>　　. Determine difficulties in restraining a p

76、art during machining based on the</p><p>　　conceptual product geometry.</p><p>　　. Estimate the time and cost of designing and manufacturing new fixtures</p><p>　　if the current inv

77、entory of fixtures cannot be used.</p><p>　　The output of the conceptual fixture design activity is the information model,</p><p>　　conceptual design fixturability feedback. This information mod

78、el will provide product</p><p>　　designers with feedback on fixturability problems and also provides a metric for</p><p>　　product designers to compare different initial designs in terms of fixt

79、uring concerns.</p><p>　　The inputs to the detailed fixture design activity are the type of fixture</p><p>　　information from the conceptual fixture design activity, the intermediate part model,

80、</p><p>　　the faces of the intermediate part model that will be machined and the fixture</p><p>　　inventory information. The intermediate part model is the geometry of the part</p><p&

81、gt;　　in between setups. As an example, figure 2 shows a part that requires three setups</p><p>　　to machine the features. The intermediate part models to be fixtured at each setup</p><p>　　are s

82、hown in the figure. The intermediate part model can be derived once the</p><p>　　manufacturing sequences are determined. It should be noted that the conceptual</p><p>　　fixture design activity r

83、eceives the entire part model as an input. The fixture</p><p>　　Figure 2. Example part and intermediate part models.</p><p>　　inventory provides the necessary information on the available fixtur

84、e elements to be</p><p>　　used in fixture design.</p><p>　　The tasks of the detailed fixture design activity are:</p><p>　　. Design the fixture for each setup. This includes carryin

85、g out fixture layout</p><p>　　design and fixture configuration design.</p><p>　　. Evaluate how well the designed fixture fulfils its functions of accurately</p><p>　　locating, restr

86、aining and supporting a workpiece.</p><p>　　. Generate the necessary instructions for shop floor handling of fixtures. This</p><p>　　includes arriving at a proper sequence for clamping the workp

87、iece and the</p><p>　　force that each clamp should be actuated with.</p><p>　　The outputs of the detailed fixture design activity are the information models,</p><p>　　intermediate p

88、art model fixturability feedback, fixture assembly configuration and</p><p>　　workpiece loading instructions.</p><p>　　The intermediate part model fixturability feedback information model provid

89、es</p><p>　　feedback to the process planner on how well each intermediate part model between</p><p>　　setups can be fixtured. The feedback will allow the process planner to arrive at the</p&g

90、t;<p>　　optimal process plan taking into account fixturing considerations.</p><p>　　The fixture assembly configuration information model serves two purposes.</p><p>　　Firstly, it provides

91、 tool path planners with information on the fixture assembly</p><p>　　configuration. This information can then be used to generate the fixture assembly for</p><p>　　checking of interference betw

92、een the tool path and fixture elements. Secondly, it</p><p>　　allows shop floor personnel to construct the fixture assemblies based on the provided</p><p>　　information.</p><p>　　Th

93、e workpiece loading instructions information model provides shop floor</p><p>　　personnel instructions on how the workpiece should be located and restrained on</p><p>　　the fixture.</p>&

94、lt;p>　　4. Fixture design information models</p><p>　　This section describes the details of the various fixture design information models</p><p>　　to be generated by the fixture design activit

95、ies. The information models have been</p><p>　　implemented using XML. Two approaches can be used when representing data using</p><p>　　XML; the first is to use a document type definition (DTD) a

96、nd the second is to use</p><p>　　an XML schema. In this work, we represent the data using a DTD. A DTD defines</p><p>　　the elements that can appear in an XML document and the way in which they

97、can</p><p>　　appear. The structure of the DTD of each information model is explained in this</p><p>　　section. These files are to be generated by a developed computer-aided fixture design</p&

98、gt;<p>　　system (Mervyn et al. 2003b).</p><p>　　4.1 Conceptual design fixturability feedback</p><p>　　The DTD of the conceptual design fixturability feedback XML file is shown in</p>

99、;<p>　　figure 3 and is made up of four groups of information:</p><p>　　(i) the identity of the product design that the evaluation is carried out for,</p><p>　　(ii) the type of fixture to

100、be used,</p><p>　　(iii) the geometric evaluation of the conceptual design, and</p><p>　　(iv) the estimated cost and time to manufacture the fixture.</p><p>　　Figure 3. DTD of concep

101、tual design fixturability feedback XML file.</p><p>　　The type of fixture is to be determined based on the estimated quantity of</p><p>　　products to be manufactured. The type of fixture could e

102、ither be ‘dedicated’</p><p>　　or ‘flexible’. Generally, a dedicated fixture is used for high volume production and</p><p>　　a flexible fixture is used for low volume production.</p><p

103、>　　The geometric evaluation should be intuitive to the product designer to</p><p>　　understand the effect of the product geometry on the fixture design. The information</p><p>　　should also b

104、e computer interpretable for use in an automated environment. In order</p><p>　　to do this, the geometric evaluation has been mapped to the features of the product</p><p>　　design. Each feature

105、of the product to be machined has three attributes, ‘location’,</p><p>　　‘restraint’ and ‘support’. These attributes are representative of the functions of a</p><p>　　fixture. They thus describe

106、 the ability to fixture the part during the machining of the</p><p>　　feature. Although several features can be machined in a single setup, this mapping</p><p>　　has been adopted to allow the pr