OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 7 No. 2 2025 Pearson goodness-of-fit test showed no basis for rejecting the hypothesis of normal distribution when conditions f > 100 and p > 0.05 are met. The sample Rz data deviate from the mathematical expectation of 5.357 μm by 0.389 μm on average. The data follow a normal distribution according to the 2σ rule with a probability of 0.9873. For neural network modeling, outliers were removed because they can distort results and reduce model ability to identify data patterns effectively [17]. For further experiments, depth and lateral pitch were kept constant at ap = 0.2 mm and ae = 0.4 mm [18], reducing the number of variable input parameters to three. Variable W is often considered stochastic and uncontrollable, introducing unexplained variance independent of explanatory variables and the model. Typically, W and r are treated as integral components of variability; their influence on Rz was considered fz = 0.4 mm/tooth, γ = 50°, D = 6 mm, z = 2. Results are shown in Fig. 3. Rational use of coolant is an important factor in increasing metal processing productivity. When using coolant, the roughness parameter Rz decreased by an average of 14 %. The dissipation rate depends significantly on cutting speed Vc (m/min) and material removal volume Q (cm³/min): , 1000 zj c S fzn z Q where: nc is the rotation frequency min –1; S zj is the cross-sectional area during milling with a ball-end tool, mm2: 2 1 2 1 1 2 cos 1 2 2 2 2 sin 2 2 sin tan 2 2 4 2 cos 1 2 2 2 2 sin 2 p p p zj p a R R R a a S fz a R R . The effect of coolant depends on rational choice of cutting conditions, tool wear, and tool/workpiece materials [19]. Coolant use and cutting speed of at least 75 m/min are necessary to achieve minimum roughness Rz, beyond which W has little impact on model performance. Surface roughness also depends on tool wear degree [20], with a strong negative correlation R = −0.95. As the number of machined workpiece surfaces (i, pcs) increases, dimensional tool wear occurs, typically within the range of 2 to 4 μm. This wear leads to an approximate 21 % increase in the Rz parameter relative to its minimum observed values. Fig. 2. Distribution of surface roughness parameter Rz
RkJQdWJsaXNoZXIy MTk0ODM1