Foundmental Research On Precision Grinding Process Of Micro-tooth Thread With Coarse-grain CBN Wheel

For micro-tooth thread grinding with large aspect ratio,interference of grinding rod and wear of grinding wheel during grinding are two important reasons affecting the length-diameter ratio and machining accuracy of workpiece.In this study,basic research on fine grinding process of micro-tooth thread with large abrasive CBN wheel was carried out to solve these two main problems.The principle of parallel-axis grinding of micro-tooth thread and the truncation design of grinding wheel,the experimental research on laser dressing of large abrasive V-shaped electroplated CBN grinding wheel and the experimental research on grinding process of large abrasive V-shaped electroplated CBN grinding wheel have been completed.The detailed research contents are as follows:(1)To solve the problem of low precision and serious wear of internal threads,a new method of grinding large wear-resistant grinding wheel with parallel axis was put forward.The grinding wheel truncation grinded with parallel axis was calculated by mathematical analysis method,and the grinding wheel truncation machining error was analyzed by means of computer-aided method,and the grinding wheel truncation was optimized.(2)The large abrasive V-shaped CBN grinding wheel was dressed by means of laser dressing according to the designed grinding wheel section.Basic experiments were carried out on the angle of laser incidence and average laser power.The method of laser tangential incidence was determined to be selected for shaping.The average laser power was selected as 30 W and the laser repetition frequency is30 k Hz.The overlap rate of scanning trajectory of laser dressing was simulated and analyzed from the angle of energy distribution.It was determined that the removal effect was better when the grinding wheel speed was over 7000r/min.The final selection of grinding wheel speed was 30000r/min and laser axial scanning speed was 1mm/s.The dressing time and depth were also verified by experiment.The time of grinding wheel dressing was 25 min according to the shape of grinding profile.(3)A formula for maximum undistorted chip thickness in parallel-axle thread grinding with large abrasive particles was proposed for parallel-axle grinding.Basic grinding experiments were carried out on grinding wheels with different laser dressing depths.The effects of different grinding feed speed,wheel speed and cutting depth on surface roughness,grinding force,tooth angle an d bottom round angle of grinding workpiece were studied.Comparing laser dressing with mechanical dressing,it was found that the grinding force of laser dressing grinding wheel was less than that of mechanical dressing.Considering the processing effect and efficiency comprehensively,the depth of laser dressing grinding wheel was selected500?m,feed speed was 0.2mm/s,speed of grinding wheel was 17000r/min,depth of cut was 5?m.