Research And Applications On Improving And Maintaining The Accuracy Of CNC Maching Tools

At present,with the wide applications of precision machining,the requirements for the accuracy quality of NC machine tools are increasing.However,the accuracy of machine tools is dramatically decreased by various error sources,including cutting forces,thermal deformation errors,geometric errors and assembly errors of components and structures,axis servo control errors,machine itself weight and loads induced deformation errors and errors caused by CNC interpolation algorithms and vibrations.In addition,especially for domestic NC machine tools,the accuracy decrease is rather severe during the usage.Therefore,it is a tough problem to keep the accuracy and precision maintenance of machine tools for a long time.This study focuses on the accuracy quality improvement,maintenance and management of NC machine tools.The main contents of this thesis are as follows:(1)Calculation and analysis of the CPK(Complex Process Capability),analysis of the main factors affecting the precision qualiy of NC machine tools: To deeply and systematically analyze all the factors,identify the main influencing factors,and propose various methods to improve the accuracy of CNC machine tools via case studies in factories.(2)To find methods of improving and controlling the accuracy quality of NC machine tools based on the real-time compensation techniques: modeling of machine errors,development of the real-time error(or accuracy)compensation system,and the real-time compensation tests and application examples are given.(3)Research on the accuracy preservation and management or precision maintenance analysis of machine tools: In other words,the accuracy of the machine tool is increased after certain design and manufacture and accuracy compensation techniques temporarily,but it is also necessary to keep the machine tool with long-term high accuracy and precision stability via maintenance and management.In this research,maintenance methods of the accuracy when running the machine tool are given.(4)Real-time monitoring applications of machine tool operation status in the course of accuracy maintenance and management: for machine tools equipped with real-time compensation systems developed in this research,the accuracy conditions are identified based on several characteristics of state parameters,such as real-time axes positions,temperatures on key points,motor currents and etc.