OBRABOTKAMETALLOV Vol. 26 No. 3 2024 technology In this case, the forces acting on a single abrasive grain are not enough to renew the abrasive grains, and consequently there is greasing of the grinding wheel surface. In this case, the minimum metal removal is observed, which is 0.1–0.15 mm depending on the modes. The increasing grinding wheel pressure, which is characterized by an increase in the current load of the motor, leads to a reduction in the influence of the wheel clogging effect. The dulled abrasive grains begin to renew themselves more actively with sharper grains, which provide greater metal removal. The graph shows that at peak points the metal removal reaches values of 0.28–0.35 mm depending on the grinding modes. A further increase in the grinding wheel load leads to a significant increase in the cutting forces, which significantly exceed the retention forces of the abrasive grains in the bond. This leads to the abrasive grains breaking out without chip removal. At the same time there is a decrease in metal removal down to minimum values of 0.03–0.1 mm. Thus, the extrema on the presented graphs (Fig. 5) characterize the maximum cutting ability of grinding wheels, and these values can be accepted as the optimal modes of operation of abrasive tools. The highest metal removal value of about 0.35 mm is provided at a grinding speed of 15 km/h. When the grinding speed increases to more than 15 km/h, a decrease in metal removal and a reduction in current load values are observed. So, at 15 km/h and 5,000 rpm, the maximum metal removal value is achieved with a current load of 105–110 A, and at 30 km/h and 7,000 rpm the maximum metal removal value is achieved with a current load of 95–100 A. This indicates that each grinding speed corresponds to its own required value of the grinding wheel pressing force to the rail to ensure optimum cutting forces. Taking into account the effective value of phase current for the new high-speed electric drive (100 A), the possible metal removal at different grinding modes and its optimal values were determined and are presented in Table 3. To ensure the motor current loads specified in Table 3, it is necessary to ensure the appropriate grinding wheel-to-rail pressure depending on the grinding conditions. The required grinding wheel-to-rail pressure is shown in Figure 6. The graphs (Fig. 6) show that with the operating range of current loads of the new high-speed electric drive of 90–100 A, depending on the grinding speeds, it is required to ensure the pressure in the pneumatic system for pressing the grinding wheel to the rail within the range of 0.7–1.8 atm. Fig. 5. Average values of metal removal at different current loads on windings of high-speed motor stator
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