CAD data exchange: Difference between revisions

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Revision as of 06:29, 17 February 2019

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'''CAD data exchange''' is a modality of [[data exchange]] used to translate data between different [[Computer-aided design]] ([[Computer-aided design|CAD]]) authoring systems or between CAD and other downstream [[CAx]] systems.

Many companies use different CAD systems internally and exchange CAD data with suppliers, customers and subcontractors.<ref name=":2" /> Transfer of data is necessary so that, for example, one organization can be developing a CAD model, while another performs analysis work on the same model; at the same time a third organization is responsible for manufacturing the product.<ref name=":05">Xu, X. (2009).&nbsp;''Integrating advanced computer-aided design, manufacturing, and numerical control: Principles and implementations''. Hershey, PA: Information Science Reference.</ref> The [[Comparison of computer-aided design editors|CAD systems currently available in the market]] differ not only in their application aims, user interfaces and performance levels, but also in data structures and data formats<ref>{{Cite book|url=https://link.springer.com/chapter/10.1007/978-3-642-82426-5_21|title=Product Data Interfaces in CAD/CAM Applications|last=Schuster|first=R.|date=1986-01-01|publisher=Springer Berlin Heidelberg|isbn=978-3-642-82428-9|editor-last=Encarnação|editor-first=Prof Dr-Ing José|series=Symbolic Computation|pages=238–251|language=en|doi=10.1007/978-3-642-82426-5_21|editor-last2=Schuster|editor-first2=Dr-Ing Richard|editor-last3=Vöge|editor-first3=Dr-Ing Ernst|chapter = Progress in the Development of CAD/CAM Interfaces for Transfer of Product Definition Data}}</ref> therefore accuracy in the data exchange process is of paramount importance and robust exchange mechanisms are needed.<ref name=":05" />

The exchange process targets primarily the geometric information of the CAD data but it can also target other aspects such as [[metadata]], knowledge, manufacturing information, tolerances and assembly structure.

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=== Direct model translation ===

Direct data translators provide a direct solution which entails translating the data stored in a product database directly from one CAD system format to another, usually in one step. There usually exists a neutral database in a direct data translator. The structure of the neutral database must be general, governed by the minimum required definitions of any of the modelling data types, and be independent of any vendor format.<ref name=":05" /> Major CAD systems, such as [[SolidWorks]], [[PTC Creo]], [[Siemens NX]] and [[CATIA]] can directly read and/or write other CAD formats, simply by using ''File Open'' and ''File Save As'' options.<ref name=":15" /> This option is limited by the fact that most CAD formats are proprietary therefore direct translators are typically unidirectional, partially functional and not standardized.<ref>{{Cite journal|last=Bondar|first=Sergej|last2=Shammaa|first2=Abdul|last3=Stjepandić|first3=Josip|last4=Tashiro|first4=Ken|date=2015-07-20|title=Advances in Parameterized CAD Feature Translation|url=https://www.researchgate.net/publication/280086553_Advances_in_Parameterized_CAD_Feature_Translation280086553|journal=ResearchGate|volume=2|issue=Transdisciplinary Lifecycle Analysis of Systems|doi=10.3233/978-1-61499-544-9-615}}</ref>

=== Neutral file exchange ===

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* [[IGES]] (Initial Graphics Exchange Specification) – originated around the late 1970s and initially published by the American National Standards Institute (ANSI) in 1980 preceding the large-scale deployment of the CAD technology in the industry.<ref>{{Cite journal|last=Björk|first=Bo-Christer|last2=Laakso|first2=Mikael|title=CAD standardisation in the construction industry — A process view|journal=Automation in Construction|volume=19|issue=4|pages=398–406|doi=10.1016/j.autcon.2009.11.010|year=2010}}</ref> This file format considers the product definition as a file of entities, with each entity being represented in an application-independent format.<ref name=":05" /> After the initial release of [[ISO 10303|STEP (ISO 10303)]] in 1994, interest in further development of IGES declined, and Version 5.3 (1996) was the last published standard.<ref name=":15" />

* [[AutoCAD DXF|DXF]] ([[Drawing Exchange Format|Drawing eXchange Format]]) – developed by [[Autodesk]] in 1982 as their data interoperability solution between [[AutoCAD]] and other CAD systems. The DXF is primarily 2D-based and its format is a tagged data representation of all the information contained in an AutoCAD drawing file, which means that each data element in the file is preceded by an integer number that is called a group code indicating the type of following data element. As most commercial application software developers have chosen to support Autodesk's native [[DWG]] as the format for AutoCAD data interoperability, DXF has become less useful.<ref name=":05" />

* [[VDA-FS]] ([[Verband der Automobilindustrie]] – Flächenschnittstelle) – created by the German Association of the Automotive Industry in 1982 as an interoperability method for free-form surfaces.<ref>Product data interfaces in CAD/CAM applications: design, implementation and experiences:Encarnacao, Schuster and Voge, Springer-Verlag, Berlin. 250 pp (250 x 165&nbsp;mm) (1986) 128 DM. (January 01, 1987).&nbsp;''Computer-aided Design,&nbsp;19,''&nbsp;3, 158-158.</ref> This format differs from other formats in that it only supports the communication of free-form curve and surface data with associated comments, but no other geometric or non-geometric entities. Therefore, it is limited to representations by parametric [[polynomial]]s, but this covers the great majority of free-form CAD systems. It includes [[Bézier surface|Bézier]], [[B-spline|B-Spline]] and [[Coons patch|Coons]] tensor product types of surfaces and corresponding curves.<ref name=":2">{{Cite book|url=https://link.springer.com/chapter/10.1007/978-3-642-82426-5_13|title=Product Data Interfaces in CAD/CAM Applications|last=Nowacki|first=H.|last2=Dannenberg|first2=L.|date=1986-01-01|publisher=Springer Berlin Heidelberg|isbn=978-3-642-82428-9|editor-last=Encarnação|editor-first=Prof Dr-Ing José|series=Symbolic Computation|pages=150–159|language=en|doi=10.1007/978-3-642-82426-5_13|editor-last2=Schuster|editor-first2=Dr-Ing Richard|editor-last3=Vöge|editor-first3=Dr-Ing Ernst}}</ref> The VDA-FS specification is released in the German Industrial Standard DIN 66301.<ref>{{Cite book|url=https://link.springer.com/chapter/10.1007/978-3-642-82426-5_16|title=Product Data Interfaces in CAD/CAM Applications|last=Phebey|first=T.|date=1986-01-01|publisher=Springer Berlin Heidelberg|isbn=978-3-642-82428-9|editor-last=Encarnação|editor-first=Prof Dr-Ing José|series=Symbolic Computation|pages=176–183|language=en|doi=10.1007/978-3-642-82426-5_16|editor-last2=Schuster|editor-first2=Dr-Ing Richard|editor-last3=Vöge|editor-first3=Dr-Ing Ernst|chapter = The Implementation of the VDAFS Geometric Data Interface on Computervision's CDS 4000 CAD/CAM System}}</ref>

* PDES (Product Data Exchange Specification) – originated in 1988 under the Product Definition Data Interface (PDDI) study done by [[McDonnell Aircraft]] Corporation on behalf of the U.S. Air Force. PDES was designed to completely define a product for all applications over its expected life cycle, including geometry, topology, tolerances, relationships, attributes, and features necessary to completely define a part or assembly of parts. PDES can be viewed as an expansion of IGES where organizational and technological data have been added. In fact, the later PDES contained IGES. The development of PDES under the guidance of the IGES organization and in close collaboration with the [[International Organization for Standardization]] ([[ISO]]) led to the birth of [[Standard for the Exchange of Product model data|STEP]].<ref name=":05" />

* [[Standard for the Exchange of Product model data|STEP]] ([[ISO 10303]] – [[Standard for the Exchange of Product model data|STandard for the Exchange of Product model data]]) – the work with the ISO 10303 standard was initiated in 1984 and initially published in 1994, with the objective to standardize the exchange of product data between [[Product Lifecycle Management|PLM]] systems. It is a very comprehensive set of specifications covering many different product types and many life cycle phases. STEP uses the neutral ISO 10303-11 format, also known as an EXPRESS [[Database schema|schema]]. The EXPRESS schema defines not only the data types but also relations and rules applying to them.<ref name=":15" /> STEP supports data exchange, data sharing and data archiving. For data exchange, STEP defines the transitory form of the product data that is to be transferred between a pair of applications. It supports data sharing by providing access to and operation on a single copy of the same product data by more than one application, potentially simultaneously. STEP may also be used to support the development of the archive product data itself.<ref name=":05" /> STEP consists of several hundred documents called [[List of STEP (ISO 10303) parts|parts]]. Every year new parts are added or new revisions of older parts are released. This makes STEP the biggest standard within ISO. The 200-series parts STEP are called Application Protocols (AP),<ref name=":15" /> with the specific parts directly related to CAD systems:

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* modification on hollow bodies into solid bodies.<ref name=":3" />

Some CAD systems have functionalities to compare geometry of two models.<ref>{{cite web|title=Compare Parts and Drawings|url=http://www.solidworks.com/sw/products/3d-cad/compare-parts-drawings.htm|date=2017-11-27}}</ref><ref>{{cite web|last1=Madhavi|first1=Ramesh|title=Comparing Drawings, Models and PCBs with PTC Creo View|url=http://www.ptc.com/cad-software-blog/comparing-drawings-models-and-pcbs-with-ptc-creo-view}}</ref> So, user can compare the model before and after translation from one CAD to another one to estimate quality of the translation, and to fix found defects. But often such functionalities can compare only [[tessellation]]s of two models. It is really hard algorithmic problem to compare topological elements of two 3D models and restore their associativity to show groups of modified faces, because there are very different representation of geometry data in different CAD systems, but sometimes it is possible. For instance, the component LEDAS Geometry Comparison based on [[C3D]] kernel can be integrated in [[CAD]] system (like [[Autodesk Inventor]], <ref>{{cite web|title=LEDAS Geometry Comparison Licensed for Inventor Plug-in|url=http://www.tenlinks.com/news/ledas-geometry-comparison-licensed-for-inventor-plug-in/|date=Apr 21, 2016}}</ref>) to compare 3D models and pinpoint all of the differences between them.<ref>{{cite web|title=Geometry Comparison from LEDAS now supports all major MCAD formats with DATAKIT libraries|url=http://www.datakit.com/en/news/geometry-comparison-from-ledas-now-supports-all-major-mcad-formats-with-datakit-libraries-137.html|date=February 17, 2015}}</ref>

== MultiCAD Digital Mockups ==