Calculation Of Multi-axis Machining Contour Error Based On Interpolation Data Of Nc System

With the rapid development of manufacturing industry technology,the equipment manufacturing industry is increasingly demanding the processing quality of CNC machine tools.Contour error,as an important evaluation index of processing quality,is increasingly demanding in high-precision CNC machining.The calculation of the contour error throNXh the interpolation data of the NC system to evaluate the processing quality is of great significance for the interpolation data quality evaluation and processing contour error prediction.In the traditional method of calculating the contour,the contour error is generally calculated by tracking error or the simulation.Since the existence of the rotation axis in the multi-axis machining,the tracking error of each axis does not reflect the contour error well,and the contour error of the simulation calculation is difficult to establish contact with processing interpolation points.In order to better analyze multi-axis machining data,this paper proposes that the relative distance between the tool’s 3D shape-generating profile and the theoretical surface is regard as the contour error,it provides a new assessment method for analysis of interpolate data.According to the method of modeling the instantaneous contour of circular surface,and using two adjacent interpolation points to estimate the speed of cutter shaft,the3 D shapegenerating profile of the cutter is modeled on the ATP cutter.Therefore,the contour proposed in this paper is applicable to the general tool’s contour error calculation.For the difference of free surface milling and ruled surface milling,contour error modeling is performed for two kinds of milling method.When free surface milling is undercut,the shortest distance between the3 D shape-generating profile and the theoretical surface is regared as the contour error and the Hausdorff distance between the overcut portion of the 3D shape-generating profile and the theoretical surface is regared as the overcut contour error.in the ruled surface milling,the 3D shape-generating profile is discretized into a set of points,and the shortest distance from these points to the theoretical surface is regared as the contour error.Regardless of the contour error calculation of free surface milling and ruled surface milling,the key question is to solve the shortest distance between the 3D shape-generating profile and the theoretical surface.This paper uses the particle swarm algorithm to solve the shortest distance between the 3D shape-generating profile of tool and the theoretical surface.The quantity of interpolation data is large and the calculation of the contour error at each interpolation point does not interfere with each other,so OpenMP parallel computing technology is used to accelerate the calculation of the contour error,and the SpatiaLite database is used to storage massive interpolation data which reduce the requirements for computer memory.Based on the research above,this paper develops the contour error calculation module in the multi-axis machining analysis software,and compares the contour error of the point milling process with the calculation results in the NX simulation to verify the calculation method of the contour error in this paper.