Curve fitting method for ensuring global G2 continuity of tool path

Abstract

The invention belongs to the field of computer aided manufacturing and numerical control machining and specifically relates to a curve fitting method for ensuring global G2 continuity of a tool path.The method comprises the following steps: to begin with, establishing a fitting curve in a piecewise manner according to the discrete tool path; then, carrying out spline screening to determine splines needing bridging processing; cutting off the splines participating in bridging processing; and finally, establishing a B spline having five control points as a bridging curve c(t) between the two cut-off points. By controlling data point error between the bridging curve c (t) and a given data point Q, it is ensured that the bridging curve meets machining error; by controlling shape maintenance constraint conditions of the bridging curve, the bridging curve meeting fairness requirements is obtained; and finally, a curve having global G2 continuity and meeting machining error requirements andfairness requirements is established. The method can ensure G2 continuity of joints of the splines, constructs the spline curve having global G2 continuity and enables a numerical control processing product to have higher precision and better machining quality.

Description

technical field [0001] The invention belongs to the field of computer-aided manufacturing and numerical control machining, and more specifically relates to a curve fitting method for ensuring the overall G2 continuity of tool tracks. Background technique [0002] In the field of computer-aided manufacturing and CNC machining, firstly, the tool path is calculated according to the surface to be processed through the CAD / CAM system, and then the tool path is converted into program code through post-processing, and finally the corresponding G code is transmitted to the CNC system. The existing tool path is usually expressed by small line segments. This processing mode has the following disadvantages: (1) The tool path is composed of a large number of data points, and the storage capacity is large; (2) The tool path only has G0 continuity, and the system frequently adds Slow down, it is easy to cause vibration of the machine tool, reduce processing efficiency, and accelerate tool...

AI Technical Summary

Problems solved by technology

The existing tool path is usually expressed by small line segments. This processing mode has the following disadvantages: (1) The tool path is composed of a large number of data points, and the storage capacity is large; (2) The tool path only has G0 continuity, and the system frequently adds Slow down, it is easy to cause vibration of the machine tool, reduce processing efficiency, and accelerate tool wear; (3) The smoothness of the tool track is poor, and the machining accuracy and surface quality of the part contour are poor

Another method is to first ignore the continuity at the end points, fit the discrete data points into Bezier curves that meet the error requirements, and then use another Bezier curve for bridging processing to ensure the continuity of the local G2, so as to realize the spline as a whole. G2 continuous (Zhao Sheng, Bi Qingzhen, Wang Yuhan, etc. Tool path compression algorithm based on G2 continuous Bezier curve [J]. Journal of Shanghai Jiao Tong University, 2014, 48 (5)), the bridge curve of this method uses the middle two control points The overlapping cubic Bezier curve is only suitable for the case where the curvature of the spline splicing is 0, and the application is relatively limited

Images