An Experimental Study On Picosecond Laser Dressing Of Parallel Electroplated CBN Grinding Wheel

Cubic boron nitride?CBN?grinding wheel has been widely used in the grinding of hard and brittle materials because of its high hardness,high toughness,high temperature resistance,good thermal stability and excellent grinding performance.Due to the mechanical effect,chemical effect and thermal effect in the grinding process,the CBN grinding wheel will be worn to a certain extent after a period of time.Because the electroplated CBN grinding wheel has only one coating,it is difficult to dress,which limits its further development and application.In order to solve the problems of difficult dressing of electroplated CBN grinding wheel,a set of picosecond laser ablation test platform and flat electroplated CBN grinding wheel picosecond laser dressing test platform are designed and built in this paper.A series of experimental studies on the dressing of flat electroplated CBN grinding wheel by picosecond laser are carried out.The specific work is as follows:?1?The test materials,main equipment and main testing instruments used in the dressing test are introduced in detail.?2?The wear mechanism and common failure modes of CBN grinding wheel in grinding process are analyzed in detail,and the laser dressing mechanism of flat electroplated CBN grinding wheel is introduced.The picosecond laser dressing test scheme and process parameters of flat electroplated CBN grinding wheel were determined.?3?The picosecond ablation test of bond and the scanning ablation test of flat electroplated CBN grinding wheel were carried out,and the effects of experimental parameters such as average output power of pulse laser,laser monopulse energy and repeated scanning times on laser dressing were studied.The experimental results show that weak ablation mainly occurs on the material surface when the average laser output power is less than 50W,and strong ablation occurs when the average laser output power is more than 50W.The increase of laser scanning times will lead to the increase of material removal.However,if the scanning times are too high?for example,the average laser power is more than 12 times at 60W?,the microstructure change and phase transformation reaction will be stronger,and the ablation area of flat electroplated CBN grinding wheel will form a more obvious deterioration layer.Large molten droplets are formed on the surface of the grinding wheel,which affects the grinding performance of the grinding wheel.Therefore,the average laser power P_avg=40W and 50W are selected as the laser tangential shaping power,and the laser average power P_avg=30W is selected as the laser radial dressing power.?4?The tangential shaping test and radial dressing test of the electroplated CBN grinding wheel are carried out by using the optimized process parameters.When the average output power of the pulse laser is P_avg=50W?corresponding to the laser single pulse energy I=125?J?and the surface of the grinding wheel is scanned repeatedly for20 minutes,The best shaping effect of electroplated CBN grinding wheel can be obtained.The protruding height of CBN abrasive particles is more uniform,the surface profile runout of grinding wheel is reduced from 225.35?m to 47.81?m,and the profile accuracy of grinding wheel is effectively improved.When the average power of the pulsed laser P_avg=30W?corresponding to the laser monopulse energy I=75?J?,the defocus?=2mm,and the dressing wheel is repeatedly scanned for 8minutes,the CBN particles protrude evenly on the surface of the grinding wheel,the protruding height is about 30?m,and an obvious cutting edge is formed at the tip of the abrasive.The dressing effect is good.?5?The grinding test of grinding wheel shows that the surface scratch interval of workpiece ground by flat electroplated CBN grinding wheel is small.The results show that the regular grinding edge is formed and the grinding performance is improved after dressing the electroplated CBN grinding wheel.