Automatic identification method based on standard for the exchange of product model data-compliant numerical control data interface (STEP-NC) intersection features

Abstract

An automatic identification method based on STEP-NC intersection machining features comprises construction of machining feature adjacency graphs, determination of intersection features, segmentation of the intersection features, matching of machining features and STEP-NC expression of the machining features. The method firstly identifies the intersection features by utilizing a mode based on combination of graphs and traces, the traces refer to convex edges produced by intersection of features, and in order to guarantee that no public volume is included among the features and to reduce independent features of production, based on the principle of priority processing of feature base-face, constructs an ordered intersection features split factor queue; Secondly, the method encodes the machining features during feature matching, and identifies the machining features by the aid of the existing relatively mature database query technology, so that a time-consuming subgraph matching algorithm is avoided; and finally, according to the ISO10303-238 protocol, the method stores the identified machining features in a STEP file in a hidden mode in order to provide consistent interface for the follow-up computer aided process planning (CAPP) and the computer-aided manufacturing (CAM).

Description

technical field [0001] The invention relates to a method for automatically identifying intersecting features based on STEP-NC. Background technique [0002] The part modeling established by traditional CAD generally only contains pure geometric topological information, such as vertices, edges, faces and the geometric relationship among them. Machining feature recognition is to transform the geometric shapes represented by these pure geometric information into processing features with specific meanings. In recent years, although 3D CAD has gradually adopted the modeling technology based on design features, the design features do not always carry the manufacturing information necessary for the CAPP system. Therefore, in the CAPP system, processing feature recognition is a necessary step that should be completed first. At the same time, in the CAD / CAPP / CAM integration process, no matter whether the CAD output is pure geometric information or a design feature model generate...

AI Technical Summary

Problems solved by technology

The problem with this type of method is that it is impossible to ensure that the added virtual connections are correct, and ultimately need to use subgraph matching to identify features, and subgraph matching is an NP problem, which is very time-consuming

The problem in this algorithm is: first of all, when adding virtual links, it is not very reasonable to exclude some convex edges in the smallest subgraph as useless edges, because these convex edges are originally generated due to the intersection of features Secondly, there will be a common volume between the identified features. When dealing with the common volume, we can only randomly start from an identified feature to solve the common volume problem one by one, and new features will appear at this time.

Automatic identification of intersecting features is also a very important step in STEP-NC, but there are relatively few studies on this at home and abroad.

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