Thermal Error Analysis And Modeling For Precision Translational Axis

Precision and ultra-precision machining technology has become an important part in the direction of machinery manufacturing. In order to meet the complex of curved surface and the precision of surface, precision machining accuracy is demanding increasingly. Translational axis,as the critical part of machine tools, influences the processing precision directly.With the application of grating ruler,linear guides and linear motor,the precision of translational axis increased. But, the change by internal heat and ambient temperature will make translation axis thermal deformation, resulting in thermal error which has a great influence on the precision of translational axis. So, it is necessary to analyze its accuracy, research the reason generating thermal error and variation, and establish a more accurate mathematical model, laying a base for error compensation. This paper is based on objects of grating ruler orientation,linear guideway rail,linear motor-driven translational axes. The main research aspects are following:1) Analyze the factors causing translational axis error firstly, and then analyze reasons causing thermal error, and kinematic relations parse error by the homogeneous transformation matrix. Finally,separating the thermal drift error and establish the spatial error model with thermal drift error only, by which, find out the mechanism that the thermal drift affects the accuracy of the translation axis.2) Analyze the thermal characteristics of linear guide and grating by the finite element method respectively. Achieve the magnitude and variation of the thermal drift error caused by the thermal deformation through the analysis of simulation results.Grating ruler is extremely sensitive to changes by temperature and thermal drift error will greatly change the translational axis positioning error.3) Obtain the thermal drift error by detecting translational axis straightness error and position error under different temperature conditions, verify the simulation results.By comparing the thermal drift error, the thermal drift error caused by the thermal deformation of the grating ruler is the main part.4) Separate the geometric errors and thermal drift error of translation axis positioning error from experimental data, coupled with the mechanism that grating thermal expansion affects positioning error, to establish thermal drift error model, which is proofed to be more accurate as a basis for error compensation.