An automated interface between CAD and CAM

Abstract

-The interface between CAD and CAM is an important phase in CAE (Computer Aided Engineering). There are many systems such as CAPP (Computer Aided Process Planning) that can solve this problem. But CAPP needs recognition of the features of a solid model that result from a complex procedure. This paper describes a new highly efficient method to link CAD and CAM from solid models to machinable models. INTRODUCTION Since geometric modeling has developed, the emphasis has been on the provision of geometry which will allow the representation of most engineering parts. Whether the geometric models are machinable has been ignored. Most geometric modeling researchers were concerned with the method of geometric modeling; they were not interested in CAM. As a result, manufacturing of mechanical parts from solid models is very difficult. In recent years, effort has been made directed towards application. Interface between design and manufacture has become a significant topic in CADCAM[I] (as we find CAD/CAM changes into CADCAM). Automatic recognition of machined surfaces from a 3D solid model is established for CAPP[2]. Coding method is always used in CAPP, which attempts to replace the interface. However, another way of linking design and manufacturing is to generate a cut path directly from 3D solid models. For example, in computer-integrated manufacturing of surface using octree encoding[3], octree data structure is applied to set up solid models and to generate rough-cut path, drill path, and cleaning path. In [4], ROMAPT plays a postprocessing role in CADCAM. There are two basic conventional methods to extract manufacturing information from a solid model: parallel plane sections and cellular decomposition. In this paper we describe a new method, triangulation and scanning, which can produce rough cut path and cleaning path freely. GEOMETRIC MODELING SYSTEM Our geometric modeling is based on a triangle subtriangulation algorithm. Figure 1 shows a model united by a cylinder and a block and their surfaces are triangulized. A group of primitive objects, such as cylinder, cone, sphere, torus and block, are triangulized for conFig. 1. A model wrapped by many triangle patches. figuring shape-complex models. Boolean shape operations (union, difference and intersection) between primitives focus on the intersection between two triangle patches. In that way, a complex model is represented as polyhedra with triangulated surfaces. Curved surfaces are approximated to any accuracy by using a number of triangle patches. MACHINED SURFACE OF MODELS By using the above system (Triangle Sub-Triangulation Modeling System) mechanical parts can be modelled. Figure 2 shows a convex mold produced by the modeling system. Its geometric and topologic information is recorded in a file so it can be translated, rotated and scaled. Furthermore, the output of 2D engineering drawing is available. After the design process is completed, CAM will depress because there is no interface to link them. Clearly, the surfaces of models are machined surfaces. If the cutter moves on the triangle patches in some rule, the shape of the machined part will be formed corresponding to the solid model. CUTI'ING TRACES AND CLOSED LOOPS AS we discussed above, a model is "wrapped" by triangle patches. Those triangle patches connect to each other according to a data structure. Figure 3 shows the relationship between the triangle patches. Each triangle patch must be connected by three patches. P(i) (i = l, 2, 3) stand for points, F(j) ( j ) ( j = 1, 2, 3) for faces and E(k) (k = l, 2, 3) for edges. The labels of P(i), F( j ) , E(k) comply with the following rules:

DOI: 10.1016/0097-8493(88)90056-8

Cite this paper

@article{Yeh1988AnAI, title={An automated interface between CAD and CAM}, author={Zhenghao Yeh and Daoning Ying}, journal={Computers & Graphics}, year={1988}, volume={12}, pages={349-357} }