Research And Development Of RP-Oriented Data Processing Software Based On Mechanical Desktop (MDT)

With the development of rapid prototyping (abbreviated as RP hereinafter) technology, the part precision issue is becoming more and more important. And the prototyping precision has been greatly improved by ameliorating the processing skills and material properties. In the present rapid prototyping technologies, however, the STL file based data processing method and the staircase effect, which is inevitable during rapid prototyping process, restricts the further improvement of the part precision. Also, the existing RP-related software, including CAD system, the data processing system, and the monitoring and controlling system, are independent of one another. The preprocessing procedure of RP is so complicated that it requires the operators to be well-educated. Considering the above issues, this paper deals with the direct and adaptive slicing methods of CAD model, and develops the RP data processing software based on the Mechanical Desktop (MDT) software. The main work may be summarized as follows.(1) Presents a grid-based intersection algorithm of parametric surface and plane, which is characterized by effectiveness and conciseness, and has been successfully implemented in the RP data processing software.(2) After discussing all kinds of the existing algorithms, this paper presents a new kind of adaptive slicing algorithm by comprehensively considering the surface normal and the cross-section area. And for the same part, a comparison of the cusp height error distributions between the adaptive slicing and the equal-thickness slicing methods is given. The results show that the adaptive slicing method can greatly improve the manufacturing efficiency in the same cusp height error.(3) Based on a close research of the CAD model representation in MDT, this paper picks up the model information expressed in the boundary representation (B-Rep) using the development kits of ObjectARX and MDT API offered by Autodesk Inc.(4) The direct slicing data are processed so as to realize the sorting and fitting of short lines, the cutting tool compensation, the layer contour filling and the optimization of the scanning paths, etc.(5) Designs the architecture of RP data processing software according to the functional requirement of RP, and integrates all the functional modules. The software not only provides CLI file interface applied in the current RP systems, but also provides a initiatively-defined CLA file interface consisting of lines and arcs in order to lay a solid foundation for the forthcoming realization of monitoring and controlling modules and for the integration of CAD, CAPP and RP.The work in this paper will be beneficial to improving the part quality and simplifying the preprocessing procedures of RP. It might lead the rapid prototyping apparatus to be re-oriented to a new member of the modern CAD system family.