OBRABOTKAMETALLOV technology Vol. 25 No. 3 2023 URSH is equipped with a special device for the pressing force calibration (fig. 9). The device allows determining the actual force of pressing the grinding wheel to the rail (in Newtons) depending on the current load in the windings of the electric motor. This dependence is further used to determine the actual cutting forces during operation based on the values of the current loads of the electric motor. The force of pressing the grinding wheel to the rail is measured by means of two force sensors. a b Fig. 9. Device for calibrating the pressing force of grinding wheel to rail: a – 3D-model of the device; b – general view of the device Taking into account the requirements for high-speed grinding wheels [21], research on the technology of high-speed rails grinding was carried out using grinding wheels “Machaon”, designed for a maximum grinding speed of 75 m/s (5,000 rpm). The tests were carried out with a grinding wheel angle of attack of 0.35°, at rotation speeds of 5,000 rpm. The roughness of the processed surface was estimated by the parameter Ra. During the research, the following measuring instruments were used: the control of the rotation speed of the grinding wheel during the grinding process was carried out by an electronic tachometer IT-5-FM “Termit” and a laser tachometer “Megeon 18005”; the installation of the transverse angles of inclination of the grinding motor and the angle of attack of the grinding wheel was carried out in accordance with measurements by a digital, three-axis accelerometer-inclinometer ATST 90, the pressing force was determined using a strain gauge sensor M50-0.5-S3, and the corresponding pressure in the pneumatic system was controlled using pressure converters ARIES PD100I-DI1,6-111-0,5; a rail profiler PR-03 was used to measure the transverse profile of the rail head before and after grinding and to assess the metal removal after processing; the width of the grinding track was monitored with a caliper SHCC-I-300-0.01; the surface roughness of the rail sample after processing was measured with a portable TR200 device. Results and its discussion Before conducting the research, the electric drive of the grinding head was adjusted, during which the dependence of the current load in the windings of the electric motor on the force of pressing the grinding wheel to the rail was established. The dependence of the power parameters on the pressure in the pneumatic system of pressing the grinding wheel to the rail was established to determine the parameters of the pneumatic system that provide the required force of pressing the grinding wheel to the rail and to assess its effect on the operating modes of the high-speed electric drive (fig. 10). It can be seen from the graph (fig. 10) that the greater the pressure in the pneumatic system, the greater the force pressing the grinding wheel to the rail. At the same time, it was found that the nominal pressing
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