OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology Paper [19] presents a new method for estimating deviation from roundness based on an improved bat algorithm (BA). This method is based on the least gap approach and transforms the roundness deviation estimation into an optimization problem, where the goal is to find the optimal circle center. The authors highlight the high accuracy and efficiency of this method compared to traditional approaches. Paper [20] studies the use of morphological filters for functional evaluation of part profiles and compares them with the well-known 2RC and Gauss filters. The authors propose using mathematical morphology methods based on the theory of alpha shapes in combination with the Gauss filter to better determine the tribological characteristics of part surfaces. The studies considered aim to increase accuracy and optimize the measurement process, which is crucial for achieving high functional characteristics of manufactured parts. Based on the analysis of modern research, it can be concluded that most work focuses on ensuring the accuracy of diametrical size using the boring method. However, it is also important to address the accuracy of the shape. Therefore, the purpose of this work is to predict the radial displacement of the tool axis and to develop methods for ensuring the accuracy of hole shapes obtained during finishing by boring. The following tasks are set in this work: 1. Determine the relationship between deviations from roundness and cylindricity of machined holes and the technological parameters of mechanical processing. 2. Determine the magnitude of the radial displacement of the boring tool by developing a mathematical model capable of predicting the error magnitude in the resulting holes. 3. Develop a method for assigning machining passes that accounts for axis deviation of holes at roughing stages and radial displacements of the finishing tool, considering the influence of allowance size and unevenness. Methods The studies were conducted on milling machining centers from DMG MORI equipped with the Heidenhain TNC 620 CNC system (Germany): a three-coordinate model – DMC 635 V ecoline, and a fivecoordinate model – DMU 50 ecoline. The positioning accuracy along the x, y, and z axes of the machining centers’ executive components is 8 μm. The maximum spindle speed is 8000 min⁻¹, and the maximum feed rate is 24 m/min. The cutting tool was controlled and measured using a Heidenhain model TT140 optical contact sensor. A Heidenhain model TS 640 measuring probe was used to measure the diameter dimensions and the coordinates of the centers of the machined holes in three different sections. Measurements of deviations from roundness and cylindricity of the processed holes were carried out using the Roundcom–41C instrument. In this work, the method of the largest inscribed circle (MIC) was chosen to evaluate deviations from roundness [18]. The main factors influencing the formation of deviations from roundness were determined using harmonic analysis [16, 17]. Fig. 1 shows spectrograms of the decomposition coefficients obtained when measuring the part on the roundness meter. The materials selected for processing in this work were: – aluminum alloy EN AW-2024 (Al-Cu-Mg alloy), widely used in aircraft and automobile manufacturing due to its physical and mechanical properties; – structural steel AISI 5140 (0.4 C-Cr), which has a wide range of applications in mechanical engineering. Preliminary hole processing was performed by drilling using a drill from Sandvik Coromant (DIN 1899) R840–1400–30–A1A 1220. The diameter accuracy corresponded to the eighth quality grade. The processing conditions were as follows: – for aluminum alloy blanks: feed per revolution (Fu = 0.05; 0.075; 0.1) mm/rev, rotational speed (n = 800 ) min–1. – for steel blanks: feed per revolution (Fu = 0.05; 0.075; 0.1 ) mm/rev, rotational speed (n = 100 ) min –1. The processing depth (b) was 20 mm. The tool extension length was 179.691 mm, with the boring cutter extending 70 mm from the boring bar. The diameter of the holes processed ranged from 14 to 17 mm. For machining, a boring bar C5–391.37A–16 070 A and a carbide boring cutter R429U–E16–11066TC06 from Sandvik Coromant were used.
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