OBRABOTKAMETALLOV technology Vol. 26 No. 2 2024 force Ph does not occur so quickly, because this decrease begins earlier, even before the tooth approaches the exit point of the main cutting edge from the contact. In addition, the cutter has a slope of the cutting edge with an angle of ω (in some foreign sources this angle is indicated by the symbol β), which makes it impossible for the entire cutting edge to come out of contact with the workpiece at the same time. And the larger the milling width B and the larger the angle ω, the smoother the reduction of all forces will be. The rotation of the force vectors Pz and Py during the rotation of the milling cutter with a simultaneous increase in the uncut chip thickness ai during conventional milling leads to a slight discrepancy in the phases of changes in the forces Ph and Pv (see Fig. 14). When the cutting speed is increased from 75 to 94 m/min with the same feed fmin feed force Phmax along and Phmax across is less (see Fig. 15, compare graphs 1 and 5; 2 and 6). An increase in the milling depth t at V = 75 m/min leads to a less significant increase in the forcePvmax across (see Fig. 15, graph 3), and the force Pvmax along at V = 75 m/min even decreases slightly (see Fig. 15, graph 4), although theforcesPvmax alongand Pvmax across at different speeds differ alittle from each other (see Fig. 15, compare graphs 4 and 6; 3 and 7). At a cutting speed of V = 94 m/min, the force Pv during milling in the transverse direction relative to the feed direction during AT synthesis (Pvmax across) does not change with increasing milling depth t (see Fig. 15, graph 7). In the longitudinal feed direction, the force Pvmax along does not practically change with increasing cutting depth t and slightly depends on the cutting speed (see Fig. 15, graphs 4 and 8). This lack of influence of the milling depth t is explained by an increase in the force Pv already towards the operator at the last stage of cutting when turning the milling cutter, i.e. the tooth of the cutter begins to pull the workpiece towards the operator, and not push it away as in the initial stage. Only the force Phmax across decreases significantly with increasing cutting speed V (see Fig. 15, graphs 1 and 5), and the force Phmax along decreases slightly (see Fig. 15, graphs 2 and 6), and the remaining components of Pvmax along and Pvmax across (see Fig. 15, graphs 4 and 8, 3 and 7), Pxmax along and Pxmax across (graphs are not presented due to the absence of changes in the magnitude of these forces with increasing cutting speed) do not change. It is possible that with a significantly higher cutting speed (more than 130 m/min), the forces will decrease, as is observed when turning in the absence of an built-up edge due to an increase in the deformation rate in the zone of primary plastic deformation and a decrease in plasticity as opposed to an increase in the plasticity of the machined metal due to an increase in temperature [30]. An increase in the deformation rate leads to a decrease in the ductility of the metal and, as a result, to a decrease in the zone of primary plastic deformation, which causes a decrease in the cutting force. Conclusion During the preparation and during the execution of this study, it was possible to minimize the influence of third-party factors on the results due to a comprehensive study of both the parameters of the specimen and the tool, and the conditions of the technological environment for milling. Based on the performed research, the following conclusions are made: 1. The limiting milling modes have been determined, which ensure the absence of destruction of carbide cutters in the process of edge cutting (subtractive) machining of LMD steel 0.12-Cr18-Ni10-Ti (AISI 321), both along and across the growing direction. 2. When studying the cutting forces, it was found that an increase in the feed fmin in the range from 120 to 850 mm/min leads to a directly proportional increase in the forces Phmax, Pvmax and Pxmax described by linear equations. 3. An increase in the milling depth t by 2.5 times leads to a significant increase in the feed force Phmax, especially Phmax across up to 1,580 N, but at the same time the milling depth does not significantly affect the change in lateral and axial forces. 4. The roughness Ra of the machined surface depends on the direction of growing the additive specimen (workpiece), and when milling in modes (see Table 5) it depends more on the feed and cutting speed. At the same time, the lowest values of Ra = 0.438±0.23 μm (when milling along) and Ra = 0.510 ±0.15 μm (when milling across) are observed in the modes V = 94 m/min; fmin = 850 mm/min; t = 2.5 mm; B = 7 mm.
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