Research On On-line Inspection Method For Aspherical Parts

Aspheric optical parts are widely used in various high-precision technology fields by virtue of their functions in the optical system to effectively correct system aberrations,expand the system’s field of view angle,reduce the overall quality of the system and reduce the volume of the system.With the vigorous development of high-tech industry,the market demand for aspheric optical parts is increasing.How to improve the manufacturing capacity of aspheric parts is a major problem to be solved.Aspheric surface shape detection is a part of its processing technology.How to complete the surface shape detection accurately,quickly and efficiently is crucial to improving the processing efficiency of aspherical parts.At present,in the processing of aspherical parts,off-line detection is usually used,which will not only reduce the processing efficiency,but also affect the processing accuracy due to the secondary clamping error of the part.Therefore,in order to improve the processing efficiency of aspherical parts,this paper applies the online inspection of machine tools in the grinding and forming stage of aspherical parts,and integrates the process of part inspection-processing-reinspection on the machine tool.The main research work of the thesis is as follows:(1)Based on the analysis of the research status at home and abroad,it is determined to use the touch trigger probe as the inspection equipment for the online inspection of aspherical parts.After researching and designing the overall scheme of the online inspection system for aspherical parts,the working index of the system is proposed by analyzing the working principle of the system and the working process of the system.On the basis of researching the composition of the system,focus on the in-depth study of the probe system,design a probe structure with optical switch as the trigger mode,and design the signal transmission circuit of the probe system.Design the system software to realize the acquisition of probe position information and the generation of NC measurement programs.(2)Combining the system’s work indicators,a detailed analysis of the system’s error conditions is carried out to prove the feasibility of the system.The static pre-travel error of the probe and the non-coincidence error of the measurement coordinate system and the workpiece coordinate system are modeled,and the influence of the pre-travel error and the coordinate system non-coincidence error on the measurement accuracy is analyzed through simulation.(3)The least square method is used as the basic mathematical theory to study the data processing problem of aspherical contour points.First,the five-point cubic method is used as the method of data smoothing;secondly,the pre-stroke error and coordinate system noncoincidence error compensation are processed,and the Gauss-Newton iteration method is used to solve the problems(Δx,Δy,Δz,δx,δy,ΔR)Perform a separate solution.(4)Set up an experiment platform and use a trigger probe to perform online measurement on the parts after finishing.Firstly,calibrate the contour error of the ruby ball and plan the measuring points,and then measure the parts after the first fine grinding and the parts after the grinding treatment.The data detected by the profiler is used as the comparison standard.The experimental verification shows that the error between the detection result of the profiler and the profiler is less than 0.4μm,and the accuracy reaches the system technical indicators.