INVESTIGATION OF THE DRAG FORCES ARISING IN THE MAGNETO-ABRASIVE TOOL DURING THE FINISHING OF CYLINDRICAL PARTS IN THE ANNULAR BATH

Abstract

The method has been developed and systematic studies have been carried out to measure the drag forces, that exerted by a magneto-abrasive tool on machined cylindrical parts with a diameter of 16 mm and the height of 30 mm, made of para-, ferro- and diamagnetic materials, in an annular working zone with the diameter of 200 mm with the working height of 30 mm at machining speeds in the range of 1 - 3 m / s, magnetic induction in the working areas varying in the range of 0.2 - 0.25 T. It is shown that the drag forces significantly depend on the magnetic and rheological properties of the magneto-abrasive tool. During magneto-abrasive finishing (MAF), the drag force for non-magnetic parts is almost the same and does not depend on the machining speed, and with an increase in magnetic induction in the working areas, its linear growth takes place. The coefficient of magnification of drag force determined by the magnetic field, for powders with a particle size of 400/315 µm is 960 N/T, and for a size of 200/100 µm it is 720 N/T. It is shown that the drag forces during the MAF of ferromagnetic parts vary in the range from 160 to 220 N and are 1.2–1.45 times higher than for non-magnetic parts, which is due to the action of forces of magnetic origin, the features of the interaction of structural elements of MAT with machined surfaces and the formation of blocking up zones between the surface of the part and the pole pieces of the annular bath. The periodic change in the drag forces of the MAT of the workpiece was established near their average value, and at elevated MAF speeds of more than 2–2.5 m/s, instabilities were recorded associated with a periodic decrease in the oscillation amplitudes of the drag forces as a result of rearrangement, changes in the dimensions and volumes of the structural elements of the magneto-abrasive tool and the conditions of their interaction with the machined surfaces.