A Primitive-Based Reverse Modeling Method for Obtaining the Editable CAD model of Reversed Parts

Abstract

By the traditional inversion methods, the model of the part reversed is obtained in mesh feature , which is hard to edit and redesign. In the paper, for the revised part, a modeling method to obtain the editable CAD mode was proposed. Firstly, an approach to construct the primitive structure tree used to describe the geometric structure of a part was proposed, by which the all the basic geometry primitives and their Boolean operations are logically arranged in tree format. Then, for each basic geometry primitive, a method to calculate the characteristics parameters and position and posture was proposed, which could be used to guide reversion measurement and modeling. For the basic primitives made of quadratic surface, a method for modeling the torus surface, whose model little research has been carried on, was proposed in which the torus surface equation is deduced by coordinate transformation method, has 8 independent parameters. Last, based on the guidance of primitive structure tree, a process for the characteristics parameters, minimum measuring points, forward modeling, positioning and assembly process was proposed, which could be used to direct measurements and to forward modeling. The example showed that the method proposed could be used to reverse the parts in the editable CAD model and provide for subsequent optimization design services.