Study On The Technique Of Truncating And Tapering Of Diamond Grain For Grinding Wheel And Its Application

Because of the low efficiency of precision micro-machining and the difficult recovery of cutting fluid to medical titanium alloy and molding die steel,it’s proposed to conduct high-efficiency dry grinding by coarse diamond wheel.However,the topography of diamond grains and the irregular distribution do cause the low machining accuracy.What’s worse,the shedding of grains will hurt the surface.Thus,instead of milling and buffing with cutting fluid in several processes,with the help of the energy which was produced by continuous pulse discharging transmitting from cutting chip to diamond grain surface,diamond grains can graphitize.And combined with mechanical action,the tips of micro grains can be truncated regularly and the number of active grains can have an increase,which can help to realize the dry mirror grinding on metal.Firstly,the diamond grain graphitization experiment and the impulse discharge removal experiment were conducted to analyze the graphitization and removal rate of metal bond with copper and iron electrodes.Then,with#46 and#140 metal bonded diamond wheels,the technology of micro-grains truncating and tapering by a fixed iron electrode and a rotated iron electrode was researched.Finally,with the diamond wheel whose micro-grains were truncated and tapered,the dry plane grinding and micro grinding on titanium alloy and die steel was conducted with the aim of analyzing the effect on machining quality by grain protrusion parameters and grinding parameters.Specific research results are as follow:(1)In the diamond grain graphitization experiment,compared with the copper,iron could lower the grain graphitization temperature at 750℃.In discharge truncating,the effective energy of spark discharge is 8.3 times higher than that of arc discharge.When spark discharging,compared to the copper electrode,the discharge temperature with the iron electrode is closer to the graphitization temperature of grains.What’s more,the dressing force was 2.13 times higher.(2)In the truncating of#46 grains,compared with the original,dry discharge truncating by a rotated iron electrode can lower the protrusion height by 10.0%and increase the truncated area,truncated stiffness and uniformity by 151.0%,185.0%and12.1%,respectively.In the tapering of 120°#140 grains,the 109°～132° forming angle of diamond grain tip was acquired on diamond wheel.(3)In the plane grinding experiment on die steel and titanium alloy with truncated#46 diamond wheel,the number of active grains increased and the cutting quantity of per grain decreased with the increase of cutting depth,which helped to lower the roughness of workpiece surface,Besides,with the cutting depth of 8 μm and 12 μm,the roughness of die steel and titanium alloy can obtain 0.078 μm and 0.600 μm respectively.(4)In the grinding experiment on die steel and titanium alloy with the tapered diamond wheel,the forming angle had the smallest error with 5%and 8%respectively with the cutting depth of 16 μm.And with the cutting depth of 8 μm,the smallest arc radius of tip was 250 μm and 150 μm respectively.Also,it is to be observed that the machined titanium alloy had no burr.