OBRABOTKAMETALLOV Vol. 25 No. 4 2023 technology milling. In addition, the forces Fz, Fy approximately correspond to the tangential Pz and radial Pу forces during penetration and when the tooth leaves contact, if t is equal to half the cutter diameter To carry out the research work, a standard methodology used for conducting experiments to determine cutting forces was chosen. However, to determine the forces Pz and Py, we made a number of deviations from this technique. A four-flute (z = 4) cutter was used; the milling width was less than 2 mm. The milling depth t was slightly less (0.2 mm) than half the cutter diameter d (t ≈ 0.5∙d – 0.2). This deviation from the standard approach made it possible to calculate the components of the normal N and tangential F forces acting on the front surface of the cutter tooth using certain forces Pz and Py. In this case, the rake angle was taken into account. DynoWare software was used to analyze the data. The sensitivity of the dynamometer is 7.5 N, its measurement error is ±0.005 %. The scatter in measuring cutting forces was no more than 15 %. This error is due to the wear of the milling cutter. If there is wear, it is necessary to make a reconfiguration. However, it is very difficult to ensure the accuracy of the adjustment to the required width and depth of milling, even with a slight wear of the cutter during experiments. Carbide end mills produced by GESAC (China) were chosen as the tool. The hard alloy consisted mainly of tungsten carbides and a cobalt binder (~8 %). Its parameters are given in table 2. The rear angle was 5º, the rake angle amounted to 7º. We used cutters covered with a coating, the characteristics of which are given in table 3. The choice of the cutters with such a coating is determined by the processing conditions. In the experiments we used up and down dry milling. Down milling was carried out with a 4-tooth cutter of d = 8 mm, milling width of which was B = 2 mm, the spindle speed was n = 500 rpm, the feed was sm = 104 mm/min. A large feed value was chosen in order to test the selected tool in extreme operating conditions. Up milling was also carried out with a 4-tooth cutter of d = 8 mm at B = 2 mm, n = 500 rpm, sm = 28 mm/min. When choosing cutting modes, we proceeded from the experience of the work performed by the authors in [28]. Ta b l e 2 The main parameters of the milling cutters used Factory marking Coating Diameter, D, mm Helical flute angle, ω, ° Number of teeth, z UP210-S4-08020 AlCrSiN 8 35 4 Ta b l e 3 The main parameters of the coating of the milling cutters used Coating HV0.05 μ T AlCrSiN 3,300 0.4 1,100 Results and discussion Obtaining specimens by electron-beam surfacing and studying its microstructure At the first stage of the work, we prepared specimens intended for subsequent machining. Since the technology used for printing specimens by means of an electron beam by surfacing the wire is quite new, there are practically no standard modes for producing specimens. Printing modes are mainly depend on the material being printed and the geometric dimensions of the specimens. We presented the technology for selecting the printing modes for the stainless steel 0.4 % C-13 % Cr in more detail in [28]. The beam current value was ranging within some limit to determine the optimal printing modes. During the experiments, 6 different beam current values were used. The value at which the highest quality specimen was obtained gaining the fewest defects and a smooth surface was then used to obtain the remaining specimens.
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