Investigation Into Accuracy Design And Assembly Error Control Of High-precision Horizontal Machining Centers

High-speed,high-precision and high-reliability machining center has become the development direction of modern equipment manufacturing industry.Many countries takes the development of high-end CNC machine tools as a primary task.Precision horizontal machining center is an important kind of CNC machine tool products,with a high degree of automation,high processing efficiency and other advantages,which is widely used in the aerospace,aviation,precision moulds and other fields.In this dissertation,the accuracy design and assembly error control of high-precision horizontal machining centers are studied.Experiments are carried out to prove the feasibility and correctness of the proposed models and methods,which provides a theoretical basis for improving the accuracy of precision horizontal machining center from design to assembly.Based on the the multi-body system theory,the geometric error model of the machine tool is established.With the combination of the chance constraint planning theory and the geometric error model,the optimization problem of the geometric accuracy design of the machine tool is put forward.The geometrical accuracy of the machining center is designed by solving this optimization problem with the Monte Carlo algorithm and genetic algorithm.The problem of geometric accuracy design based on terminal error of the machine tool is solved.Based on the Hertzian contact theory,a non-linear error propagation model of roller guide rail based on deformation compatibility is proposed.This model can analyze the relationship between the straightness or parallelism error of the guide rail and the error of moving parts and explain the basic law of the error average effect of the guide rail.Using this nonlinear model and error average effect,an optimization problem of the installation accuracy of the guide rail is built.Considering the error form of the guide rail,an installation accuracy design method of the guide rail is put forward.Then the problem of installation accuracy design of the guide rail according to the moving parts accuracy is solved.Based on differential vector model,a whole machine deviation model considering assembly deformation and guide error is proposed.The model combines the nonlinear roller guide error propagation model with the differential vector model.It forms a definite linear relationship between the joint surface geometric and deformation deviation and the final assembly deviation of the machine.With this model,an assembly error control strategy of precision horizontal machining center is put forward.Using the finite element simulation,the error propagation model of the guide rail is verified and the influence of the deformation of machine parts on assembly error is analyzed.The effectiveness of the proposed methods and models are verified through the experiment of guide rail installation and the design and assembly experiments of machine tools.The research results of this dissertation have important theoretical and practical value for the enhancement of precision guarantee system of CNC machine tools and the improvement of the design and manufacturing technologies of precision machining centers in China.