Experimental Study on Pulsed Electromagnetic Field Assisted Planar Magnetic Abrasive Finishing

The work aims to add pulse assisted magnetic field in the traditional plane magnetic abrasive finishing process to increase the magnetic induction intensity in the processing area and the dynamic change of magnetic induction intensity during processing, enrich the movement form of abrasive particles during processing, complicate the grinding path, reduce the surface roughness of workpiece, and obtain better surface topography of workpiece. The effects of the assisted magnetic field on the motion state of the abrasive in processing were studied by analyzing the forces of the abrasive particles with or without the assisted magnetic field, and the motion mechanism of the abrasive under the pulse assisted magnetic field was studied. The magnetic field generated by the different shape of the pole head of the electromagnet was simulated and compared with Ansoft Maxwell, and the optimal pole head shape was determined. At the same time, the distribution of magnetic induction lines in the processing area was compared when the electromagnet was on and off, and the trajectories of abrasive under constant magnetic field and pulsed magnetic field were compared. The surface morphology and specific surface roughness of SUS304 stainless steel without assisted magnetic field, with constant assisted magnetic field and pulse assisted magnetic field were compared by experiments. The distribution of magnetic abrasive was affected by magnetic induction line in the magnetic abrasive finishing process. Under the action of pulse assisted magnetic field, the magnetic abrasive in the processing area made periodic reciprocating motion with the change of magnetic induction line, and there was a more complex grinding track in the processing. The magnetic induction intensity curves generated by three different shapes of magnetic poles in the processing area were simulated. The peak values of magnetic induction intensity at the midpoint of horizontal plane, conical surface and hemispheric surface were 655, 636 and 702 mT, respectively. The SUS304 stainless steel plate with the original surface roughness of 0.46 μm was taken as the test object. A hemispherical electromagnet pole head was used when the processing clearance was 2 mm, the speed of the permanent magnet pole was 800 r/min, and the feed speed was 5 mm /s. The following methods were used to grind the workpiece for 30 min respectively: the electromagnet was not energized, the electromagnet was energized with 0.8 A DC current, and the electromagnet was energized with 1 Hz, duty cycle was 50%, and the current amplitude was 0.8 A unidirectional pulse current. After finishing the machining, the surface morphology of the three kinds of workpiece was compared. The results showed that there were still some original textures on the workpiece surface without the assisted magnetic field. Under constant assisted magnetic field, the original texture of the workpiece surface was removed, but there were obvious arc-shaped grinding traces on the surface. The surface morphology of the workpiece was smoother under the pulse assisted magnetic field. After grinding, the surface roughness of the workpiece was reduced to 0.28, 0.13 and 0.06 μm, respectively. Pulsed magnetic field assisted magnetic abrasive finishing in improving processing area of magnetic induction intensity at the same time, can make the magnetic abrasive have periodic motion when processing, complicate the grinding trajectory, and promote the renewal of the abrasive. Compared with the traditional magnetic abrasive finishing and constant magnetic field assisted magnetic abrasive finishing process, the surface morphology of workpiece processed by pulsed magnetic field assisted magnetic abrasive finishing is more smooth, and has lower surface roughness. © 2022, Chongqing Wujiu Periodicals Press. All rights reserved.