Experimental Research On Laser Dressing Of Arc-shaped Resin-bonded Diamond Grinding Wheels

The grinding process based on supeabrasive grinding wheels is the key technology for the preparation of curved parts of hard and brittle materials such as ceramics and cemented carbide.The arc-shaped resin-bonded diamond grinding wheel is a kind of superabrasive tool prepared with resin as bond and diamond as abrasive grain.It can be widely used in the ultra-precision grinding of many difficult-to-cut materials.Although this type of abrasive tool has excellent wear resistance,as the grinding process progresses,the working surface of the grinding wheel will inevitably wear or block,and the contour shape of the grinding wheel is difficult to main tain.In order to improve the efficiency,accuracy and quality of the grinding process,the grinding wheel must be dressed regularly.Laser dressing technology is a dressing technology with great dressing advantages,it can be applied to the dressing of m any types of grinding wheels.In order to achieve the precision and low damage dressing of convex arc-shaped diamond grinding wheels,this paper systematically carried out laser profiling and sharpening research of single diamond grains,abrasive blocks an d arc-shaped resin-bonded diamond grinding wheels using a research method combining theoretical analysis and process experiments.The specific contents are as follows:1)An experimental platform for laser dressing was built,and the influence of process parameters on the laser profiling topography and quality of grinding wheels was explored through process experiments.The mechanism of formation and removal of graphite layer on the surface of diamond grains was revealed.For the first time,a clear interface between graphite and diamond was observed after profiling,and it was explained that diamond is first converted into graphite during the profiling process,and then removed by oxidation or gasification.A method for reducing the degree of graphitization of diamond grains by increasing the finishing profiling time was proposed.2)Based on the area estimation algorithm calculation principle of the laser removal threshold,the influence rule of the laser spot overlap rate on the grain removal threshold was explored,and the sharpening experiment of the resin-bonded diamond block was carried out.Finally,the high efficiency and low damage sharpening of the diamond grinding wheels was realized.It was found that the grain removal threshold decreased first and then stabilized with the increase of the laser spot overlap rate.Using the optimized process parameters for sharpening,the surface of the grinding wheel with excellent topography and sharpening quality was obtained.3)The pyrolysis mechanism of phenolic resin during sharpening was analyzed by XRD,EDS and Raman spectrometer.It was found that after the ablation,a loose and porous carbon layer is formed on the surface of the bonding agent,and some benzene derivatives are attached to the surface of t he grinding wheel in the form of recondensate,resulting in an increase in the proportion of C element and a decrease in the proportion of O element in the bond.The results of EDS and XRD confirmed that after sharpening,the diamond element reacted with C r in the filler Cr₂O₃ to generate Cr₃C₂,which is beneficial to improve the holding performance of the bond to the diamond grains.4)The laser dressing method of convex arc-shaped diamond grinding wheel was proposed,the types and sources of dressing er rors and their influence on the profiling accuracy of the grinding wheel were analyzed.After profiling,the size error of the arc radius of the abrasive block is controlled within 4%,an d the minimum value of the position error along the X axis is 4.6?m.The minimum value of the roundness error e_s of the circular arc in axial section and the circular run-out error e_r in the cross section of the abrasive block are 15.6?m and 25.9?m,respectively.The large circle run-out error is mainly caused by the rotation error of the experimental platform itself.A new method of laser sharpening based on the principle of layered scanning was used to sharpen the surface of the profiled grinding wheel.After sharpening,the surface topography of the grinding wheel is good.