OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 5 2 3 0 2 ( , ) ( , ) r x t n x t N t EG F ∂ = ∂ − , (15) where ( , ) n x t is the normal to the machined surface; 0 0 0 0 ( , ) ( , ) ( , ) ( , ) ( , ) r x t r x t x t n x t r x t r x t x t ∂ ∂ ∂ ∂ = ∂ ∂ ∂ ∂ . (16) For the convenience of perception, in the future, instead of (k1 и k2), we will consider the principal radii of the machined surface curvature 1 1 1 R k − = and 2 2 2 R k − = . Studying the principal radius of the machined surface curvature in cross section (fig. 7) for the milling cutter with d = 30 mm, j = 90°, l = 20° and x = 0° confirmed that it reaches the lowest value at the point of the surface being formed by the middle of the RPI cutting edge (t = 0) and increases as it moves away from the middle (curve 1). The study also showed (fig. 7) that an increase in the angle of rotation of the cutter (at x = 20°, curve 2) leads to a decrease in the principal radius of curvature. Fig. 8 shows graphs of the change in the main curvature of the machined surface in the cross section (at the point t = 0) at different angles of rotation of the cutter with parameters x ∈ [0;45°] with parameters d = 30 mm, j = 90° and angle l = 10° (line 1) and l = 20° (line 2). Fig. 7. Change of the main radius of curvature (R) on different sections of the processed surface in cross-section Fig. 8. Change of the main radius of curvature (R) of the processed surface in cross-section from the angle x
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