Precision Wheel Truing And Grinding Of Super-hard Fresnel Lens Mold

Fresnel lenses are widely applied to solar cell system, infrared night view, opticalprojection and micro medical devices because of its excellent optical performance. Inrecent years, large-scale replication technology has received enough attention in termsof its high accuracy, low cost and high production efficiency. Generally, replicationtechnology mentioned above are injection molding and glass molding. Die steel andsilicon carbide are introduced to manufacture molds in order to reduce wear and extendservice life largely. And the quality of surface replicated will be improved to someextent. For machining mold, ultra-precision grinding becomes the key technology. ForFresnel lens molds are difficult-to-machine materials such as silicon carbide and diesteel, this thesis will explore wheel truing and grinding processing technology, based onmathematical model of Fresnel lens mold, in order to complete ultra-precision grindingof Fresnel lens molds with high efficiency.Firstly, according to mathematical model of Fresnel lens mold, grinding processingis analyzed and geometrical parameters of wheel are obtained with the purpose ofdesigning and customizing the grinding wheel. Meanwhile, experimental platforms ofwheel truing and grinding are set up.Secondly, for the grinding wheels with various grains and bonds, differentprecision truing methods are adopted. For resin bonded cubic boron nitride(CBN) B64wheel and metal bonded diamond D15A wheel, a CNC truing technique with rotationalGC dressing stick is employed. Form accuracy and surface topography of wheels areresearched. Meanwhile, calculate the truing ratio of different particle-sized GC sticks.The ratio of#180GC stick of truing resin bonded CBN wheel is largest, reaching to0.1012, bigger than that of truing metal bonded diamond wheel. And Ta block is used totrue resin bonded D3diamond wheel. The dressing parameters are studied to summarizetheir influence law on the radius of sharp edge. Then determine the optimum processparameters and the truing ratio can reach to69.9.Thirdly, orthogonal experiment of grinding the ring of Fresnel lens mold is used.CBN and diamond wheels are adopted to grind rings of Fresnel lens mold on the diesteel and silicon carbide, respectively. And analysis of different processing parameters’influence on the surface quality of the ring is made to optimize processing parameters.Finally, the degree of wheel wear is discussed in order to determine truing times inthe process of grinding. Based on optimized processing parameters, typical Fresnel lensmolds are machined. The results show plough phenomenon is notable on the die steel surface ground by resin bonded CBN wheel with bad surface quality, but relative goodbottom arc radius and intersect tip arc radius. Compared with metal bonded diamondwheel, the roughness and form accuracy of silicon carbide ring surface ground by resinbonded diamond wheel are lower, whereas bottom arc radius and intersect tip arc radiusdescend, due to severe wear of resin bonded diamond wheel.