Research On On-line Measurement And Real-time Error Compensation Of CNC Machining Accuracy

Machine tool manufacturing is a pillar industry in China's manufacturing industry.With the development trend of the integration and automation of machine tool structure,as well as the requirements of high precision,high efficiency and high quality,the machining accuracy of machine tools has attracted extensive attention.Application of real time measurement and error compensation technology of machining precision online,which can adapt to the features of a fixture part can be finished,in order to ensure the machining precision of the parts at the same time,greatly shorten the turnaround time,improve the production efficiency of machine.With the background of the national major projects” the core technology research and application demonstration project of flexible manufacturing system for high precision NC gear machine”,this paper takes the precision horizontal machining center THM6380 of Sichuan pushningjiang machine as the research object,having studied the overall design of the machine online measurement system and its existing problems,and gives the corresponding solutions.The main contents of this paper are as follows:(1)First,the paper analyzes the measuring principle of the on-line measuring system for machining accuracy of machine tools and the main steps of completing the measurement,according to the main part of the NC machine tool,machine body,servo system,numerical control system,measuring system and the computer system briefly introduces the overall structure of the measurement system.After analyzing the influence factors of the measurement system,the main factors affecting the measurement accuracy are obtained.This paper expounds the causes of measurement error from three aspects,which are geometric error,thermal error and system error;(2)Taking THM6380 as the research object,this paper analyzes the topological structure and the low order volume array of the machine tool,and establishes the geometric error prediction model of the machine tool based on the multi system theory.In order to measure the geometric error parameters of each axis of the machine tool,this paper proposes the nine-line method and the bar instrument to measure the required parameters.The validity of the model compensation method is verified by the experiment;(3)The calculation result of four key temperature measuring points from eight temperature measurement points in the initial machine with grey correlation theory,on the basis of the grey GM(1,4)prediction model of thermal error of machine tool,the model set up a mapping relationship between the thermal deformation of machine tool and the temperature measuring points,and according to its temperature machine the environment changes to computer bed thermal error.The accuracy of the compensation method is verified by comparing the experimental data before and after compensation;(4)After analyzing the mechanism of the error of the probe system,the compensation of the probe radius is proposed to reduce the measurement error.In this paper,the mathematical model of the calibration of the probe head of the probe system is established,and the compensation of the probe radius is presented by using the bilinear interpolation method.(5)Based on the precision horizontal machining center THM6380 as the experimental object,there were no error compensation,probe error compensation,error compensation and error compensation of machine tool overall four group experiments.The experimental results are compared and analyzed.