Research On Ultra-precision Machining Technology Of Large-scale Fresnel Roller Mould

Fresnel lens is a typical microstructured functional surface,and as large-scale Fresnel lenses are more and more widely used in optical systems and products such as photovoltaic power generation systems,projection lighting systems and laser TVs,the market demand and quality requirements are becoming higher and higher,so there is an urgent need of high-efficiency and high-precision manufacturing process for large-scale Fresnel lens.The Roll-to-Roll(RTR)ultra-precision replication process has the advantages of high efficiency,high precision and low cost,so it is an ideal manufacturing process for microstructured functional surface.At present,the RTR manufacturing process for Fresnel lenses has not been fully developed,and the main reason is that as a key part of the RTR manufacturing process for large-size Fresnel lenses,the manufacture of radial Fresnel roller molds places stringent requirements on the static and dynamic characteristics,motion accuracy and temperature control accuracy of the machine tool.At the same time,the complex surface shape of the radial Fresnel structure determines the complexity of the tool machining trajectory,which requires the machine tool to have a special structural layout and more axes.requiring the machine tool to have a special structural layout and more motion axes.Therefore,the manufacturing process of the Fresnel roller mold has become an important technical problem faced by the large-size Fresnel lens manufacturing process now.In order to solve the manufacturing problem of large-sized Fresnel roller molds,this dissertation designed and built a rotary slow tool servo device,which was integrated into the ultra-precision machine tool for processing roller molds independently developed by our group to obtain a special ultra-precision machine tools for processing Fresnel roller molds,and on this basis,the research on the processing technology of the Fresnel roller mold was carried out.Firstly,this dissertation analyzed the functional requirements of the machine tool based on the processing principle of radial Fresnel roller molds,designed the layout of the machine tool and calculated the tool path.This dissertation integrated a Rotary Slow Tool Servo(RSTS)device on the self-developed 3-axis ultra-precision machine tool for roller molds to form a special 5-axis machine tool for processing radial Fresnel roller molds.After that,a special diamond tool was designed according to the requirements of the profiling method.Based on the principle of arc-equal Archimedes spiral,the planning of tool path for processing Fresnel roller molds was completed.In this paper,the tool nose radius compensation method and the tool nose centering error compensation method were designed and the tool path was generated and the movement amount of each axis of the machine tool was calculated according to the principle of multibody kinematics.Taking into account that when the diamond tool was installed,there was a self-alignment deviation in the position of the tool tip,which caused the center of the tool tip arc to not coincide with the axis of rotation of the A and B axes and affected the accuracy of the radial Fresnel mold surface.In this paper,the tool selfaligning error compensation method was designed,including the error detection method based on CCD computer vision,the establishment of error model and the development of error compensation algorithm.In this paper,the kinematics model of the machine tool was established based on the multi-body system theory,and the movement of each axis of the machine tool was solved according to the designed points on the tool path.Finally,the verification experiment of the radial Fresnel molds machining by profiling was carried out on the special 5-axis machine tool.Afterwards,the profile of the processed Fresnel structure was detected along the direction of the generatrix of the workpiece using a profilometer.The detection results show that the actual machining surface shape of the radial Fresnel mold was consistent with the design surface shape,and the error value of the facet angle was less than 0.05°,which meat the accuracy requirements and verified the feasibility of the Fresnel roller mold processing by the profiling method.