Abstract
The distinctive feature of the rapid prototyping process is that it produces parts layer by layer given the CAD models. The process proceeds by first slicing the geometric model of a part into layers in the computer, then reconstructs the physical part by producing these successive layers physically on top of each other. A standard interface is necessary to convey varied geometric descriptions of parts from numerous CAD packages to a rapid prototyping (RP) system. The STL (STereoLithography) format is the most commonly used interface for this purpose. Unfortunately, it suffers from many limitations, including the fact that the shape description is an approximation of the original part and it is frequently not robust. Therefore, other interfaces have being proposed by various researchers. This paper discusses several existing interfaces, including the STL file, for the RP systems. The strengths and weaknesses of these formats are analysed in the context of RP applications. A newly improved format is proposed. The new interface is a file format that supports the STL format, does not contain redundant information as in the case of STL format, and topological information are included. In addition to supporting facet boundary models, the new interface also supports precise models by using the edge-based boundary representation. Design considerations of the new interface and data structures for both facet models and precise models are discussed.