空间弯管内表面磁粒研磨位姿轨迹优化试验研究

Experimental Study on Trajectory Optimization of Magnetic Particle Grinding on Inner Surface of Space Elbow

目的利用机械手对末端研磨装置姿态的灵活可控性,设计一种可变换研磨姿态的加工方式,以高效去除紫铜弯管内表面的材料缺陷,并解决其在常规加工方式下材料去除不均匀的问题。方法利用ADAMS和EDEM软件分别仿真模拟出磁轭以单一研磨姿态和变换研磨姿态驱动下磁性磨粒群在弯管内表面的运动轨迹和切、法向累计能量,并以此作为材料去除均匀性和研磨效率的评价指标。最后搭建试验平台对2种研磨方式进行试验验证。结果通过磁轭单一研磨姿态与变换研磨姿态(15°起始研磨偏角)2种加工方式对紫铜弯管内表面研磨50 min后的表面形貌可知,前者在加工区域内的研磨痕迹深浅不一、且分布差异性较大。测得表面粗糙度为0.3μm。后者在原始表面缺陷完全去除的前提下,仅留下了较浅的研磨痕迹,表面平整度较高。测得表面粗糙度为0.189μm。结论在相同的加工条件下,通过在合理范围内增大磁轭的起始研磨姿态偏角,可提高变换研磨姿态驱动下磁性磨粒运动轨迹线的覆盖率、结构致密程度、交错频率,有利于提高弯管内表面的研磨均匀性。同时在研磨过程中会增大磁场梯度的变化幅度,进而增强磁性磨粒群的流动性,对其切削刃替换及使用寿命方面有着积极的影响。研磨后弯管内表面所受的累计能量也会随之增加,最终实现了研磨效率的提高。

In the magnetic particle grinding test on the inner surface of the elbow,the yoke usually works in a single vertical grinding attitude.The magnetic abrasive particles driven by the yoke will continue to move in a single and parallel grinding trajectory on the inner surface of the elbow,which will lead to insufficient grinding coverage in the grinding area,and the grinding traces are likely to overlap and deepen,which is not conducive to the uniformity of grinding.Considering the flexible controllability of the manipulator to the attitude of the end grinding device,this paper proposes a processing method of yoke cyclic transformation grinding attitude.In the grinding process,the grinding trajectory of the magnetic abrasive particles was changed by adding a deflection angle to the initial grinding attitude of the head and end of the yoke grinding area,so that the superimposed grinding trajectory of the magnetic abrasive particles after the alternating movement of the forward feed and the reverse feed could show a cross-network structure,so as to increase the grinding coverage area of the grinding area,thereby improving the uniformity of grinding.On the premise of avoiding motion interference and insufficient magnetic stability,the deflection angle range of the yoke was selected through actual test.ADAMS simulation was used to simulate the trajectory of magnetic abrasive particles on the inner surface of the elbow driven by a single grinding attitude(0°deflection angle)and a changing grinding attitude(5°,10°,15°deflection angle).EDEM software was used to simulate and verify the grinding effect of the above grinding trajectory by placing dynamic magnetic field and magnetic abrasive particle group,and the grinding pressure of magnetic abrasive particles in the grinding process was simulated and analyzed.In order to improve the grinding efficiency,the magnetic field of spherical auxiliary magnetic poles of different sizes in the tube was simulated,and the selection of test size was completed.In the simulation results,it could be observed that with the increase of the initial grinding attitude angle of the magnetic yoke,the coverage rate,structural compactness and interleaving frequency of the magnetic abrasive particle trajectory were improved,which was beneficial to improve the grinding uniformity of the inner surface of the elbow.At the same time,the magnetic field gradient was increased in the grinding process,which had a positive impact on the cutting edge replacement and service life.After grinding,the cumulative energy on the inner surface of the elbow also increased,which meant that the grinding efficiency was improved.The simulation results were verified by the real test platform.The workpiece was a copper elbow with a diameter of 25 mm and a wall thickness of 1 mm.The processing parameters were set as follows:the yoke feed speed was 1 mm/min,the deflection angle was 0°,5°,10°,15°,the rotation speed was 750 rad/min,the grinding gap was 4 mm,the auxiliary magnetic pole wasϕ5 mm,and the abrasive particle size was 150μm.From the surface morphology after 50 min of processing,it could be seen that the grinding marks in the processing area of a single grinding attitude(0°deflection angle)were different in depth and had strong distribution differences.The measured surface roughness was reduced from 1.063μm before grinding to 0.3μm.In the processing area of 5°,10°and 15°alternate grinding attitude of the magnetic yoke,with the increase of the grinding attitude angle of the magnetic yoke,the grinding trace gradually became shallower,the surface flatness and the integrity of the defect removal were higher.The measured surface roughness was 0.273μm,0.222μm and 0.189μm,respectively.The amount of material removal was 72 mg,78 mg,89 mg and 106 mg,respectively.Observing the law,it can be found that the two are consistent with the change trend of the simulation results.Therefore,increasing the initial grinding angle of the yoke reasonably can effectively improve the grinding efficiency and obtain better surface quality after grinding.