Computers in Industry 41Ž. 2000 261±277 www.elsevier.nlrlocatercompind Migrating from IGES to STEP: one to one translation of IGES drawing to STEP drafting data Mangesh P. Bhandarkar a, Blair Downie b, Martin Hardwick b, Rakesh Nagi a,) a Department of Industrial Engineering, 342 Bell Hall, State UniÕersity of New York, Buffalo, NY 14260, USA b Department of Computer Science and Center for AdÕanced Technology in Automation, Robotics and Manufacturing, Rensselaer Polytechnic Institute, Troy, NY 12180, USA Received 12 January 1998; accepted 21 June 1999 Abstract This paper focuses on a procedure for converting product design data from an Initial Graphic Exchange Specification Ž.IGES format into Standard for the Exchange of Product Model Data Ž. STEP format. IGES is used for representing design and topology information in a platform independent format. The failure of the IGES standard to provide information other than drawing and solid modeling has led to the emergence of a new international standard for product model data exchange Ž.ISO 10303 called STEP. STEP is designed to support a product through its entire life cycle. The STEP standard consists of a set of application protocols. An application protocol is specific to a particular engineering domain. In this case, STEP application protocol 202 is used because it defines the constructs necessary to represent the associative draughting information described by IGES. The translator parses the IGES file and converts it into the corresponding STEPŽ. AP202 format. To test the conformance of the generated STEP file we have written code to enable visualization of an Application Protocol 202Ž. AP202 STEP file. The visualization uses the Open Inventor Toolkit available for the Silicon Graphics platform. The visualizer reads the STEPŽ. AP202 file and converts the geometry and related annotations into the corresponding Inventor specific format. The file can then be viewed using the default Inventor viewer. q 2000 Elsevier Science B.V. All rights reserved. Keywords: IGES; STEP; Translation 1. Introduction rapidly to the market. This has led to the emergence of a new manufacturing paradigm called Agile Man- The past few years have seen a change in manu- ufacturing, where multiple companies cooperate un- facturing strategies and technologies. The markets der flexible virtual enterprise structures. The impetus have become more and more fragmented, and com- is on producing products of better quality in the least petitiveness has increased. For a manufacturing en- amount of time and at the best possible price. terprise to be competitive and thrive in such a dy- Agile manufacturing makes use of modern infor- namic environment it must be capable of adjusting mation technology to form a virtual enterprise. Part- ners must maintain a high amount of communication ) Corresponding author. Tel.: q1-7166452357; fax: q1- and data exchange between themselves for the suc- 7166453302; e-mail: [email protected] cess of the virtual enterprise. Data exchange does not 0166-3615r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. PII: S0166-3615Ž. 99 00052-4 262 M.P. Bhandarkar et al.rComputers in Industry 41() 2000 261±277 mean just verbal communication, but the companies the development and implementation of STEP in the must exchange complete information about their United States. Similar organizations exist in Ger- products, all the way from design, manufacturing to many, United Kingdom and Japan. Many companies inspection and shipping. This information should be are providing tools to access and manipulate STEP available to each relevant partner over the entire life data. Also, the development in Internet related soft- cycle of the product. ware has led to a rapid increase in STEP-based Researchers have recognized the need for an in- product data exchange over the world wide web. ternational standard for product data exchange which CAD software vendors and third parties for systems would facilitate the seamless exchange of data. Com- like AutoCAD, PROrEngineer, CATIA, Unigraph- panies in their own efforts have also recognized the ics, Microstation, Trispectives and ACIS, have STEP same need. Attempts were made in the past to de- interfaces in their new releases. As the acceptance velop an international standard for data exchange. and the use of STEP-based information exchange The earlier efforts led to the Initial Graphic Ex- increases, a need for translation services to convert change SpecificationŽ. IGES , which stores drawing information represented in legacy file formats like information in an ASCII or binary neutral format IGES into STEP will arise. In addition to this is also which can then be exchanged between various users. the fact that the current version of IGES may be the Many Computer Aided DesignŽ. CAD software ven- last and a policy will be developed for companies to dors support IGES. Files in the IGES format can be migrate to STEP. We have realized this requirement loaded into these packages and in turn saved back and the current paper focuses on our efforts in the into the IGES format. As effective as it might seem, development of a translator from the IGES drawing IGES is currently being used in the industry but specification into the relevant STEP format. lacks considerably in many respects such as the lack The paper is organized as follows. We first pre- of a formal information model, problems during file sent a brief overview of IGES and STEP followed by exchanges and manipulations, lack of life-cycle sup- a literature review. We go on to describe the current port and hard to understand file formats. problem on hand and present the work done in terms This led to the development of the Standard for of the coding and testing of the translator. To vali- the Exchange of Product Model DataŽ. STEP . STEP date the converted STEP file, work has also been became an ISO standard in 1993. STEP is published done to develop a visualizer. Finally we conclude in a series of parts which include the following: with a discussion and proposed further work. description methods, integrated resources, applica- tion protocols, abstract test suites, implementation methods and conformance testing. The information 2. Background in STEP is represented using an information model- ing language called EXPRESSwx 13 . STEP uses ap- This section briefly covers the history of elec- plication protocolsŽ. APs to specify the representa- tronic data exchange for product design information. tion of product information for one or more applica- The IGES standard which can be regarded as the tions. For example the application protocol that de- ``first modern electronic data exchange tool'' is de- fines the constructs for representing product shape scribed. We have also provided reasons as to why and assembly information is called `Configuration IGES did not gain much popularity, and also taken a Controlled Design', AP203. The draughtingŽ in ISO look at the STEP standard and it benefits over IGES. terminology drafting is spelled draughting, we will be using the ISO spelling throughout the paper. 2.1. Product data exchange history information can be represented in AP202, `Associa- tive Draughting' schema. In the 1960s and most of the 1970s, each CAD STEP has gained considerable importance due to system had its own file format for the representation active support from the automobile, aerospace and of product design information. Information transfer the defense sector. PDES Inc., an industryrgovern- was done by producing hard copy drawing from the ment consortium, has been formed for accelerating first systems and then manually reentering the draw- M.P. Bhandarkar et al.rComputers in Industry 41() 2000 261±277 263 ing information into the second CAD system. This the essential engineering characteristics of physical was a very tedious process, it was prone to errors objects. The application areas covered by IGES in- and caused the repetition of data in multiple file clude electrical, plant design, as well as mechanical formats. applications. As the number of CAD-based systems increased, IGES has information structures or entities to be the need for exchange of information between the used for digital representation and communication of various systems increased. At this early stage, elec- product definition data. In other words, the IGES tronic data transfer between the various systems was format treats the product definition as a file of achieved by using custom translator software to con- entities. Each entity, which is the fundamental unit vert data files from one system format to another. of data in an IGES file, is represented in an applica- Although custom translators were fast, efficient and tion-independent format. The entity representation reasonably accurate if written properly, this approach contains enough information to support the needs of suffered from the following drawbacks. The number most of the currently available CADrCAM systems. of custom translators required to transfer files be- The entities can be broadly classified into geometry tween all the CAD systems is equal to N=Ž.Ny1, entities and non-geometry entities which are elabo- where N is the number of CAD and engineering rated in the following. systems. Having custom translators between every Geometry entities represent the definition of the CAD system, even in a moderately sized organiza- physical shape and include points, curves, surfaces, tion, far outweighs the effectiveness of the transla- solids and relations which are collections of similarly tors. Also, writing, testing and maintaining custom structured entities. Non-geometry entities provide a translators is expensive and consumes considerable viewing perspective of which a planar drawing is amount of resources. composed, by providing annotation and dimension- With the increase in the number of CAD-based ing appropriate to the drawing. Non-geometry enti- engineering applications like designing, finite ele- ties further serve to provide specific attributes or ment analysis and process planning, along with the characteristics for individual entities.