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Rapid prototyping processes produce parts layer by layer directly from the CAD model. The processes proceed by first slicing the geometric model of a part into layers. A standard interface is necessary to convey varied geometric descriptions from numerous CAD packages to Rapid Prototyping (RP) systems. The STL (STereoLithography) format is the most commonly used interface for this purpose. Unfortunately, it is an approximate model and is frequently not robust. Therefore, other interfaces are proposed to be used for RP systems. This paper, Part 1, will discuss several existing interfaces including the STL file for the RP systems. The strengths and weaknesses of these formats when used for RP systems are analysed. Furthermore, a new improved format is proposed by the authors in Part 2. In that paper, the design considerations and data structure of the new format are introduced. [ABSTRACT FROM AUTHOR]

The STL (STereoLithography) file format, as developed by 3D Systems, has been widely used by most Rapid Prototyping (RP) systems and is supported by all major computer-aided design (CAD) systems. However, it is necessary to improve the STL format to meet the development needs of RP technologies. In Part 1, several existing and proposed formats have been discussed. This paper, Part 2, will present an improved interface between CAD and RP systems. The new interface is a file format that supports the STL format, removes redundant information in the STL format and adds topological information to balance storage and processing cost. In addition to supporting facet boundary models, the new interface supports precise models by using the edge-based boundary representation. This paper discusses the design considerations of the new interface and data structures for both facet models and precise models. Finally, a comparison of the new interface and the STL file format will be made. [ABSTRACT FROM AUTHOR]