Research On The Machining Technology Of NC Grinding Aspheric Surface Based On Five Axis Machine Tool

The aspheric surface has the excellent optical performance that can well correct the system aberration and improve the imaging quality,which has been more and more widely applied in the optical system such as large visual field,large relative aperture.Currently the five-axis machine tool NC grinding is still the major means to produce the aspheric surface,the five-axis NC machining relies on CAM software to perform the pre-processing and post-processing so as to generate the NC codes.The more data processing procedures and long time have caused the machining period of aspheric surface to be extended;Moreover,there will be the problems occurred in the course of machining such as errors of software parameter setup,unreasonable processing parameter setup and unclear error analysis etc.,which all constrain the development and application of aspheric surface.In order to enable the NC machining of aspheric surface to be processed and normalized,the aspheric surface machining software based on the five-axis machine tool has been developed.This paper carries out the profound analysis to the relevant matters occurred in the course of machining,and the detailed content is as below:1.Based on HAAS-UMC750 B-C dual-table five-axis machine tool,the kinematic chain structure of machine tool is analyzed.Through the transformation of coordinate matrix,the relationship among machine tool coordinates,cutting tool coordinates and workpiece coordinates is established.The vector method calculation mathematical model for cutter location point of aspheric surface is raised as for the complexity of coordinates transformation algorithm,and finally the grinding experiment to verify the correctness of cutter location point algorithm has been performed.2.This paper performs the surface division and planning of grinding wheel path to the widely applied aspheric surface.According to the rotational symmetrical aspheric surface,the traditional equal arc-length and equal angle helix path algorithm has the obvious disadvantages.This paper combines with the advantages for these two algorithms to perform the mixed discrete so as to obtain the grinding wheel path;The grating path is applied to the off-axis aspheric surface,and a introduction is made to its generation steps and methods through the planning examples;As for the contour off-axis aspheric surface,this paper raises the algorithm of auxiliary circle calculating the coordinates transformation angle,and raises the new grinding wheel path point planning method on this basis,finally verifies the feasibility of this algorithm through the grinding experiment.3.Based on the principle of grinding and cutting,this paper develops the machining software that is closest to the spherical surface,and provides the calculation method for generating cutting grinding wheel inclination angle;According to the surface machining software of aspheric surface,the generation for cutter location point path of software,generation of NC codes and error compensation module are introduced.Through the calculating examples,an introduction is made to the machining software for the off-axis aspheric surface and contour off-axis aspheric surface.Finally this paper uses the software to generate the NC code grinding telescoping off-axis primary mirror,as well as verifies the correctness and practicability for writing the software4.This paper analyzes the error source that is possibly existed in the NC machining of aspheric surface,as well as carries out the research to the issues in the course of machining such as controllable tool setting error,adjusting error and grinding wheel parameter error etc.,and analyzes the influences of tool setting error to the error distribution of aspheric surface through the theories;Through the experiments,this paper studies the influences of adjusting error and grinding wheel parameter error to the error distribution of aspheric surface.According to the results of theoretical analysis and experimental research,the typical error distribution diagram caused by the various errors are drawn so as to provide the experience and technological support for the following machining of aspheric surface.