In this paper, a neutral file format—STEP (Standard for the Exchange of Product model data) is used to transfer geometrical data from CAD tools to assembly analysis tools. JSDAI (Standard Data Access Interface for STEP binding to JAVA) is used to read geometrical data from the CAD STEP files. After all necessary geometrical data is extracted from the CAD STEP files, the interference relationships between parts are analyzed. The methods developed for using JSDAI to extract geometrical data from CAD STEP files and for determining interference relationships between parts in the assemblies are introduced.

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Most CAD tools currently do not have advanced capability built in for directly analyzing the feasibility of product assembly during the design stage. As a result, the feasibility of product assembly has to be analyzed using external assembly analysis tools. To integrate external assembly analysis tools with CAD tools, geometrical data from the CAD models must be extracted from CAD files and imported into the assembly analysis tools. To transfer geometrical data between CAD tools and assembly analysis tools, a neutral file format is needed. STEP (standard for the exchange of product model data) is a neutral file format for convenient and reliable data exchange between different design and manufacturing systems. Therefore, STEP is considered as one of the most popular formats for saving designs. As a result, to evaluate designs, extracting geometrical data from CAD-STEP file is important. Comparing with some other currently available methods, first translating STEP file into XML and then using Java DOM to get geometrical information from XML file is much better. This paper explores the process of extracting geometrical data from a CAD-STEP file for assembly sequence planning. A STEPXML translator, Java-XML parser and DTD (document type definition) generator are used on the JDK 1.4 platform. In this project, DOM (document object model) is applied as the API (Application Programming Interface) for XML.

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