Theoretical And Experimental Research On Geometric Errors Of Ultra-precision Machining

Ultra-precision machining(UPM)technology is the leading method for creating the high quality surfaces with sub-micrometric form accuracy and nanometric surface roughness.Geometric errors,the main errors in UPM,greatly affect the surface quality,and the identification and compensation of these errors can improve it effectively.However,the currently used identification method without machining could not reflect the geometric errors in UPM accurately,which makes it difficult to further compensate for these errors efficiently and improve surface quality.Therefore,geometric errors in UPM that affect the surface quality are investigated in this dissertation and an accurate identification method for these errors is proposed to achieve critical geometric errors compensation.The studies in this thesis can be summarized as follows:Firstly,based on the multi-body system(MBS)theory,the relative motion between the tool and the workpiece during machining was described.A volumetric geometric errors model was developed to describe the mapping between geometric errors and the machining errors caused by them,and the parameterization of the volumetric geometric errors model was achieved.Secondly,the inverse mapping relationship of the volumetric geometric errors was further explored by designing the feature structures,and the identification model was established.The identification method of geometric errors in UPM was proposed based on the feature structures,and the geometric errors were obtained by machining of these workpieces on the five-axis ultra-precision machine tool,which verified the validity of the model and realized the accurate identification of geometric errors.Finally,based on the volumetric geometric errors model,the Sobol global sensitivity analysis method was used to further study the influence of each geometric error on machining accuracy.Combined with surface generation simulations,the key geometric errors that affect machining quality were elucidated in depth.This dissertation focuses on the identification of geometric errors in UPM and their effects on machining quality,and establishes the geometric errors model and the identification model.The identification method based on feature structures is proposed,and the influence of geometric errors is analyzed.The identification of geometric errors and their critical compensation are achieved,which provides theoretical guidance for the manufacture of high quality surfaces.