OBRABOTKAMETALLOV Vol. 27 No. 1 2025 technology Study of cutting forces during sample machining The experimental results presented below focus on the analysis of cutting forces during the milling of Inconel 625 specimens produced by wire arc additive manufacturing (WAAM). The aim of the experiment was investigating the influence of cutting modes on cutting forces in WAAM-processed material with high hardness and heterogeneous microstructure. To maintain controlled experimental conditions, the milling width (B) was held constant at 2 mm throughout the experiment series. This ensured that with a small milling depth (t = 1 mm), only a single cutting tooth was engaged at any given time, allowing for the acquisition of cutting force profiles on a pertooth basis as the cutter rotated (Fig. 5). The presence of the angle of inclination of the helical line of the main cutting edge of the tooth at the periphery of the cutter ω = 40º (sometimes the symbols β or ψ are used) also forces to reduce the milling width B. When increasing the milling width B, the next tooth may start cutting, although the previous tooth has not yet finished cutting. This factor is more important for small diameter milling cutters (dcutter < 12 mm) and when the milling depth t > 0.4∙dcutter is increased. Minute feed (fmin) was chosen as the main variable cutting parameter in the series of experiments under consideration, while other cutting parameters (cutting depth t , cutting speed V) were constant. This approach allowed us to evaluate the influence of the minute feed rate on the value of cutting forces in isolation from other factors. The data on cutting forces obtained during the experiment were processed using the least squares method to approximate the empirical relationships. This made it possible to obtain analytical expressions describing the dependence of cutting forces on the minute feed. To visualise the results of the experiment, graphs were plotted showing the maximum values of cutting forces in each machining cycle (Fig. 4). Utilizing maximum cutting force values mitigates the influence of force fluctuations inherent in the milling process on the observed effect of smin. These fluctuations arise from variations in chip thickness during cutter rotation, radial runout of the cutter teeth, material heterogeneity, and minor vibrations within the machinetool-workpiece system. This approach allows to obtain more generalised and reliable results reflecting the general tendency of change of cutting forces depending on the minute feed, moreover, the destruction of a cutter tooth is influenced by the highest force on any tooth. Fig. 4. Graph of the change in the highest values of cutting forces Ph, Pv and Px (N) depending on the feed rate fmin (mm/min) (B = 2 mm, V = 15,8 m/min, t = 1 mm) Feed along the sample: 1 – Phmax, 2 – Pvmax, 3 – Pxmax; Feed across the sample: 4 – Phmax, 5 – Pvmax, 6 – Pxmax
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