Zinc Sulfide Aspherical Surface Polishing Using Wheel Polishing

Aspheric optical parts are able to offer more design freedom,correct optical aberration,improve image quality,and extend the field of view and the working distance.They have been widely applied in the optical system of high-tech weapons and equipment.Especially in the infrared imaging system,they play important roles.The manufacturing accuracy of aspherical optical parts has a direct effect on the performance of system.The common machining methods of aspherical surface of infrared materials include single point diamond turning,ultra-precision grinding and deterministic polishing.In order to achieve the high quality and efficiency machining process of zinc sulfide aspherical surface,this paper follows the process of ultra-precision grinding and polishing.The key to the efficiency of this process is the reasonable connection between ultra-precision grinding and polishing technology.Focus on this situation,it is urgent to develop a practicable polishing technology which can be integrated with ultra-precision machine tool and accomplish aspherical surface polishing.The polishing module and the wheel type polishing system were developed which can be integrated with ultra-precision machine tool.The machining characteristics of multispectral CVD zinc sulfid were studied using surface textured polishing wheel.The tool influence function of textured surface wheel was developed.The multispectral CVD zinc sulfide aspherical surface polishing was achieved using the wheel polishing technology.The main research work is as follows:In order to achieve aspheric polishing,the wheel polishing system based on an ultra-precision tool was developed.The influence of positioning error of polishing wheel on the contact position was studied through simulating.And the positioning process of the polishing tool and main spindle was finished.The machining platform for machining textured surface wheel was developed.The surface texture was designed and its machining method was determined.The effect of the surface texture of the wheel on the material removal efficiency and the way of the material removal of the textured wheel tool were investigated by experiment.The effects of texture parameters on the material removal rate and surface roughness was studied by experiments for the circular hole texture wheel and the linear groove texture wheel respectively,and the reasonable texture parameters of circular hole for zinc sulfide machining was obtained.The difference of machining characteristics were studied under the position method and the force method,and their machining difference during tool wore process was also studied.The machined surface roughness value of the two methods are similar.For zinc sulfide polishing,the force method was chosen which can obtain more stable machining performance.The contact form between the textured polishing wheel and workpiece was analyzed.The Winkler elastic foundation was applied to model the polishing wheel and the contact pressure model was developed.The accuracy of the developed contact pressure model was verified under various processing conditions.The fitting relations between the material removal rate and normal polishing force and the relative velocity were established respectively by experiments.In order to achieve multispectral CVD zinc sulfide aspherical surface polishing,the tool influence function was developed using textured surface wheel polishing technology.The reason of axisymmetric workpiece central dent was analyzed.In order to restrain central dent,the method of controlling polishing force and main spindle speed was developed and the force varying model was established.The best force control method was obtained through calculating,and the polishing experiment were conducted to verify the controlling method.For the multispectral CVD zinc sulfide ultra-precision ground surface,the effects of removal depth on the surface roughness was studied by uniform removal experiments.A form figuring method was developed through controlling the infeed velocity of uniform removal.For multispectral CVD zinc sulfide aspherical surface,the uniform removal polishing experiment and figuring polishing were conducted respectively with the obtained infeed velocity and force controlling method,and the experiment results met the demands.The surface roughness were decreased evidently.Based on the above research results,the deterministic polishing of the aspherical surface of multispectral CVD zinc sulfide was achieved by the wheel technology base on the ultra-precision tool.