Research On On-machine Detection Technology Of CNC Machining Accuracy And Its Error Correction Technology

By equipping numerical control(NC)machine tool with measuring probe and corresponding measurement and error correction processing procedure for parts machining accuracy inspection,an on-machine measurement(OMM)system with repair function is formed.This technology integrates machining,inspection and error correction on the same equipment,which avoids multiple clamping and repositioning errors,and can solve the problems such as difficult modifying of rejected parts and long auxiliary time.In this paper,to the demand of the domestic small and medium-sized machinery manufacturing enterprises,the key technologies of OMM for NC machining accuracy are deeply discussed,mainly including the following aspects:(1)By analyzing the main error sources of OMM,a fast calibration method on the spot is established for probe eccentricity and length error,and the pre-travel error of a home-made probe for OMM is measured accurately through experiments.To meet the requirement of high efficiency,a fast method for the probe pre-travel error compensation based on error data table is established.(2)Facing the problems existing in the display of hole features of parts based on STL format,a generation strategy of hole wall measurement points and the estimation method of normal vector are studied,and then an in-process inspection scheme of inner hole and cylindrical hole is established.At last,an in-situ correction compensation machining method for hole feature machining error is established and verified by an example.(3)A practical and feasible overall design of OMM with correction function for machining accuracy is established.According to the existing conditions of machining equipment and the problems faced by the machining accuracy inspection of hole feature parts,a relatively complete OMM system is built,which integrates on-machine measurement,error evaluation and real-time outputting second-order correction parameters.(4)At the last part of this thesis,a common model of stranding machine base for electrical machinery is taken as the experimental object,the concentricity of the main shaft holes at both ends of the machine base is measured on-machine and its correction processing test are completed.The experimental results show that the concentricity accuracy of the two holes has been greatly improved,which can meet the actual production needs.