OBRABOTKAMETALLOV Vol. 26 No. 4 2024 TECHNOLOGY models derived in [20]. Plotting the curves for surface roughness, microhardness, and roundness error involves changing one input parameter while maintaining the other two constant. Using a feed value of 0.2 mm/rev and three passes, the variation in surface roughness with cutting speed is shown in Fig. 2, a. Fig. 2, b shows the dependence of surface roughness on feed at a cutting speed of 300 rpm and three passes. And Fig. 2, c shows the dependence of surface roughness on the number of passes at a cutting speed of 300 rpm and a feed of 0.2 mm/rev. Comparing the NFMQL cutting condition with the dry cutting condition, lower levels of surface roughness are observed. It can also be observed that as the cutting speed increases to 360–380 rpm, the surface roughness decreases before increasing. In addition, it decreases with the increase of feed and the number of passes. However, an increase in surface roughness can be seen beyond feeds of 0.2–0.25 mm/rev and 3–4 passes. From Fig. 2, b, it can be seen that the optimum responses with varying feed can be obtained. The minimum surface roughness and roundness error can be obtained by using the feed values in the range of 0.18–0.22 mm/rev and the cutting speed and number of passes of 250–350 rpm and three, respectively. Fig. 3, a and Fig. 4, a depict the variation of microhardness and roundness error, respectively, depending on the cutting speed, obtained at a constant feed of 0.2 mm/rev and three passes. It can be seen that the microhardness increases with the cutting speed. However, this eff ect was more prominent for the NFMQL cutting condition. Higher microhardness values can be seen for the NFMQL cutting condition. It can be seen that the microhardness decreases beyond the cutting speed of 280–300 rpm. On the other hand, it can be seen that the roundness error decreases with the increase of the cutting speed (Fig. 4, a). However, it can be seen that it increases beyond the cutting speed of 300–350 m/min. The lower roundness error values can be seen when roller burnishing under NFMQL cutting conditions. Fig. 3, b and Fig. 4, b show the variation of microhardness and roundness error, respectively, depending on the feed, plotted using the cutting speed value of 300 rpm and three passes. Fig. 3, c and Fig. 4, c show the variation of microhardness and roundness error, respectively, depending on the number of passes, plotted using the cutting speed value of 300 rpm and the feed of 0.2 mm/rev. a b c Fig. 2. Surface roughness varying with a) cutting speed, b) feed, and c) number of passes a b c Fig. 3. Microhardness varying with a) cutting speed, b) feed, and c) number of passes
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