CHAPTER 8

CAD AND INTERFACES

Michael J. Wozny

INTRODUCTION

The systems aspect of rapid prototyping (RP) is one area where the differences between efforts in the United States, Europe, and Japan are particularly evident. The RP system, as shown in Fig. 8.1, extends beyond the solid freeform (SFF) machine itself and includes machine pre-operations, such as the preparation of geometry data, and machine post-operations, such as curing, support removal, and cleaning.


Fig. 8.1. The rapid prototyping "system."

The focus in this chapter is on those system elements that affect the shape of the part: the SFF machine's data interfaces (2D, 3D) to the external geometry-creating environments (MRI, CAD); the math (triangles) and data (STL file) representations of the geometric model; and the subsequent modifications of and additions to the original geometric model, in terms of orientation, scaling, nesting, distortion compensation, and support structures, to accommodate process-specific characteristics. This prepared model is used to generate the appropriate motion control signals in the equipment (slicing, scanning), which in turn drive portions of the physical fabrication process. Topics such as input material data and process parameter data are part of the process controller and not discussed in this report. Also not discussed here are input data about tolerances, features, and assembly configurations, since the JTEC/WTEC panel observed no specific project dealing with such research issues.

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Published: March 1997; WTEC Hyper-Librarian