Ultra-precision ELID Grinding Of Super-hard Microstructured Optical Functional Surfaces

Micro-structured optical functional components have important application in thefields of electronics, mechanics and aerospace for their special optical properties. Themolds of glass hot molding replication technique for mass production ofmicro-structured optical functional components are difficult to machine due to theirhigh hardness and brittle. Ultra-precision grinding is the most efficient method tomanufacture these micro-structured molds. While the electrolytic in-process dressing(ELID) grinding is an efficient method for grinding super-hard materials, which iswidely applied in industry because of its grinding efficiency and surface quality.Based on the reviews about the ultra-precision ELID grinding of super-hardmicro-structured functional components, this paper considers that the ELID grindingwill be an applicative method for the machining of micro-structured components.Therefore, with the existing V-shape diamond wheel and ELID grinding system, theELID grinding experiments of WC and Si3N4was conducted.Firstly, the preparation of the experiments are conducted, including dressing thediamond wheel with EDM, design of the ELID electrode and drawing the experimentplan. On the basis of these preparations, the study about the influence of grindingmethod, ELID power supply parameters, the electrode spacing and buffing on thequality of microstructures are carried out. The results shows that the high efficiencydeep grinding, low power supply parameters, the electrode spacing of0.8mm and twicebuffing are the best technological parameters.Secondly, based on orthogonal experimental design and analysis principles, theorthogonal experiments of WC and Si3N4with ELID grinding and ordinary grindingwas conducted, which the factors are grinding depth, feed rate and wheel speed. And themain considerations are the V-groove corner radius of top and bottom, surfaceroughness and profile accuracy. By comparing the results, it can conclude that the feedrate is the main parameter to impact the angular properties and that the grinding depthmainly impact the surface quality of the V-groove, while the wheel speed don`t play animportant role.Finally the method of cross section SEM is adopted to detect the subsurfacedamage, in particular, the thickness of subsurface damage is observed by SEM andnano-indentation respectively. the results show that the subsurface of ELID grinding islower than the ordinary grinding both on the material of WC and Si3N4,and thethickness of subsurface is grown with the increase of grinding depth. Respectively, theresults detected by nano-indentation is more accuracy than which detected by SEMdirectly, and when the grinding depth is300μm, the thickness of WC subsurface damage detected by the nano-indentation is16.4μm.