OBRABOTKAMETALLOV technology Vol. 25 No. 1 2023 Introduction One of the main directions in the development of machine-building production is to increase the reliability of mechanical processing of spatially complex surfaces by using a real-time monitoring system designed to obtain reliable information on the state of the milling process and make the necessary control decisions [1–6]. To solve the problems of controlling the milling process, many authors study the change in the active contact zone of the end milling tool and the workpiece. Pimenov D. et al. [7] presented practical recommendations for assigning the orientation of the tool to the workpiece, taking into account the milling dynamics to ensure surface roughness. Tan L. et al. [8] studied the effect of tool path contours on ball-end tool wear and surface roughness during milling. The results showed that the use of the bottom-up tool path contour makes it possible to ensure the minimum amplitude parameters of roughness, and the prevailing type of tool wear is adhesive. Issues related to monitoring the state of technological equipment at industrial enterprises are considered in the works of scientists Kozochkin M.P., Sabirov F.S. [9]. In the work of Shaffer D. et al., acoustic signals were investigated as a way to control the operation of technological equipment [10]. Experimentally with different cutting conditions, mathematical models were statistically determined showing the change in acoustic signal for end milling with a single cutting edge. Kozlov A.A., AL-Jonid Khalid, in their study determined the basic requirements for diagnosing and predicting the wear of a cutting tool in real time [11]. Chen et al. proposed a real-time monitoring system [6] with error compensation to improve accuracy in the production of spatially complex parts [12]. Cheng DJ. et al. [13] studied the effect of cutting parameters on the roughness of the machined surface [6]. Clayton Cooper [14], Anayet U Patwari et al. [15] analyzed the correlation of surface roughness parameters with the sound level based on the acoustic signal. Authors Sahinoglu A. and Rafighi M. [16] investigated the effect of cutting parameters on surface roughness, vibration, sound intensity of technological equipment during machining. Many authors have proposed ways to ensure the output characteristics of processing by controlling the elastic deformations of the tool relative to the workpiece, taking into account the state of the dynamic system (DS) [17–20]. The analysis of scientific works made it possible to formulate the direction of this research: to generalize and gain new knowledge, as well as to clarify the applicability of an acoustic complex that registers a signal through the air to control the cutting process, with filtering interference and noise in real time. The purpose of the work is to determine the effect of the inclination orientation of the ball-end tool on the surface roughness value using real-time monitoring during milling on CNC process equipment. At the same time, on the basis of empirical data, it is necessary to develop a model for the dependence of the roughness of the machined surface on the feed rate, diameter and orientation of the tool with the correlation of the obtained values and vibroacoustic diagnostics. Research methodology Machining was carried out in climb milling using a cutting fluid (coolant) on workpieces with Al-Mg6 properties, by hard alloy ball-end mills with a TiN coating with a diameter of D = 8 mm and a number of teeth z = 1, z = 2. The feed per tooth was fz = 0.2 mm/tooth, the allowance for all specimens was ap = 0.4 mm, the lateral pitch ae = 0.2 mm. The overhang ratio of the tool is assumed to be l/D = 4. The rotation frequency (n) of the milling machining center DMG DMU 50 Ecoline was for a double-edge cutting tool 1,500 min–1, for a single-edge cutting tool 3,000 min–1. The use of coolant is an important factor in the intensification of the cutting process, since the hard alloy has a low resistance to tensile stresses [21]. When using coolant, films are formed on the contact surfaces of the tool and workpiece material, which help to reduce adhesive wear. Dimensional wear control of the cutting tool was carried out using a Heidenhain TT140 contact measuring sensor. The accuracy of straightness when measuring the roughness parameters with the Surfcom 1800D instrument was Δ = ± (0.05 + 1.5L / 1,000). Vibroacoustic diagnostics (Fig. 1) was carried out us-
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