Ultrafast Laser Dressing Of Micro Curved Surface Structure Grinding Wheel

Bronze-bonded diamond grinding wheel is widely used in the grinding of hard and brittle materials due to its excellent grinding performance and strong wear resistance.It is also an important tool for precision grinding of complex curved surfaces.In order to maintain the contour accuracy and sharpness of the diamond grinding wheel during the grinding process,it is necessary to dressing it regularly.Laser dressing avoids the force and dressing tool loss in the traditional mechanical dressing process,and provides an effective way for the precision dressing of micro-structured grinding wheels.Ultrafast pulsed laser has extremely high peak power and extremely short pulse width.It can process almost any materials,and has the unique advantages of small thermal effect and high machining accuracy.It is expected to achieve higher precision grinding wheel dressing.In order to realize the precision contour grinding of cemented carbide micro cylindrical array,this study had carried out the researches on the optimization of femtosecond laser and picosecond laser dressing process parameters of bronze-bonded diamond grinding wheel,the efficient precision dressing of surface micro-structure grinding wheel and the precision grinding of cemented carbide curved surface array.The main researches were as follows.Firstly,an optical path shaping system that converted the Gaussian beam into the Bessel beam was built,and the ablation thresholds of diamond abrasives and binders under femtosecond laser were calculated.The ablation results of Gaussian beam and Bessel beam under different defocus amounts were compared and analyzed.It was found that Bessel beam can perform material ablation in the focal depth range of 1.0 mm,and the dressing accuracy was better than that of Gaussian beam.The single factor variable methods(changing laser power density,laser scanning speed,grinding wheel speed,offset distance,etc.)were used to dress the rectangular groove of bronze-bonded diamond grinding wheel.The surface morphology and contour accuracy of the grinding wheel after dressing were analyzed,and the process parameters were optimized.In order to further improve the accuracy and efficiency of laser dressing and realize the dressing of complex contour of grinding wheel,the picosecond laser dressing of diamond grinding wheel was studied.The power density thresholds of removing diamond abrasive grains and binders by picosecond laser were calculated.The influences of different process parameters(laser power density,laser scanning speed,grinding wheel speed,offset distance,etc.)on the dressing effect of diamond grinding wheel were studied and optimized.The dressing accuracy and efficiency of picosecond laser and femtosecond laser were compared.The picosecond laser dressing method was selected to carry out the dressing experiment of diamond grinding wheel forming profile,and the contour accuracy of grinding wheel dressing was detected by graphite grinding complex mapping method.The contour error of the V-shaped groove of the dressed diamond grinding wheel was 8.8 μm,and the contour error of the arc-shaped groove was reduced from 18.8 μm after rough grinding to 5.1 μm after fine grinding.In order to reduce the problems of low processing efficiency and fast wear of grinding wheel in single-point contour grinding,the laser-dressing 100#,300#,600#and 1500#curved surface micro-structure grinding wheels were used as grinding tools,and the precision grinding of cemented carbide micro cylindrical array was carried out by rough and fine grinding method.The surface quality and contour accuracy of cemented carbide after each grinding stage were compared.The surface shape error of the workpiece was reduced from 20.2 μm to 6.8 μm,the surface roughness was reduced from 1.432 μm to 0.176 μm,and the comprehensive material removal rate was 0.183 mm3/min.The wear characteristics of diamond grinding wheels with different particle sizes were observed and analyzed.In the rough grinding stage,due to the long time of grinding,some abrasive grains were broken and detached.The fine-grained grinding wheels were mainly normal wear,and the surface of the 1500#grinding wheel was blocked after fine grinding.The wear resistance of grinding wheels with different particle sizes was analyzed by calculating the wear ratio.As the particle size of the grinding wheels decreased,the wear resistance of the grinding wheels decreased,and the grinding ratio decreased from 168 of 100#to 131 of 1500#.