Research On Mechanism And Restraining Technology Of The Repeatability Of Positioning Error Of Linear Axis And Error Evaluation Method Of Precision Machine Tools

High grade CNC machine tools are the basic equipment to guarantee the development of national defense and national industry,which are widely used in the fields of aerospace and precision machining.Linear motion axis is an important part of CNC machine tools.The repeatability of the positioning error of linear axis is the core accuracy index of machine tools,which reflects the stability and consistency of positioning error of machine tools.In this paper,some key techniques of restraining technology of the repeatability of the positioning error of linear axis and error evaluation method of precision machine tools are studied.The main contents are concerned with mechanism of repeatability of the positioning error of linear axis,restraining technology of the repeatability of the positioning error of linear axis,evaluation method of linear axis error and space error of machine tool.The mechanism of repeatability of the positioning error of linear axis is proposed based on the motion pose of the worktable.The mathematical model of the repeatability of the positioning error of the linear axis is established based on the static equilibrium equation and the anelastic properties of materials,and the influence of relevant factors on the repeatability of the positioning error is studied theoretically.A test-table for repeatability of the positioning error of linear axis is developed,and single factor experiments of the repeatability of the positioning error are carried out.The correctness of the theoretical model is verified,and the influence mechanism of relevant factors on the repeatability of the positioning error is also quantitatively studied.Based on the results of single factor experiment,a multi factor orthogonal experiment is designed and carried out,and the main influencing factors of the repeatability of the positioning error are obtained,which lays a foundation for the suppression of repeatability of the positioning error.According to the mechanism of the repeatability of the positioning error,a method of restraining the repeatability of the positioning error based on the assembly process.A hierarchical model of assembly error of guideway is proposed.The transfer mechanism of assembly error is studied.On this basis,the restraining methods of single guideway assembly error based on "mirror" anti deformation principle and double guideway assembly error based on span bridge method are proposed.The relationship between the bearing stiffness and the preload is studied.The preload method of bearing is put forward,which takes the pretension of ball screw as the step length,so that the bearing stiffness is in a reasonable range.The method is universal and can be used to design the assembly technology of machine tool linear axis.A multi-dimensionall evaluation method of linear axis error is proposed,which takes both position error and attitude error into account.The evaluation method of linear axis error is promoted from one-dimensional to multi-dimensionall.The method of measuring and evaluating spatial errors based on multi-beam laser interferometer is proposed,which makes up for the deficiency of evaluation method of spatial errors.The proposed evaluation method can reflect the positioning performance of linear axis and machine tool more comprehensively.The proposed evaluation method has been successfully applied to evaluate the linear axis error and the spatial error of a precision horizontal machining center.The research results in this dissertation provide a theoretical basis for restraining the repeatability of the positioning error of linear axes of precision machine tools,and have important theoretical significance and practical value for improving the accuracy consistency of precision machine tools.