| Guideway and ball screw are key components of CNC machine tools and machining center. The ball screw plays the role of precision transmission and positioning, and the guideway plays the role of support and guidance, whose thermal deformation will seriously affect the processing precision of CNC machine tools. The thesis aims to improve the precision of CNC machine tool feed system. A series of analyses and researches have been done for feed system of a CNC machine tool to find out the factors of influencing the improvement of system precision, and a feed system thermal error compensation scheme has been researched through mathematical modeling, finite element analysis and other means。The thesis establishes the mathematical model of Ac servo feed system through system analysis, uses MATLAB software to simulate the system and verifies its property, simulates system with different speed loop gains, the results shows the system gain which includes speed loop gain influence on its stability through comparing. The thesis uses Pro/E software to establish solid models of guide and ball screw, researches the finite element mesh and boundary conditions, and establishes their finite element model of thermal characteristics by ANSYS software based on the above researches. A detailed analysis for the temperature field and the thermal deformation of the feed system are carried out, and the effective ways of reducing the impact of thermal deformation are proposed according to the main factors of affecting feed system thermal deformation. Thermal error compensation scheme of the ball screw feed system is researched, and temperature measuring points are arranged based on the correlation analysis between node temperature and thermal drift of the ball screw. Thermal error compensation model of a CNC lathe ball screw system is established by using multiple linear regression method, and the compensation model is preliminarily test with the data samples.
|
PDF Full Text Request