Attendant Free Vibrations and Their Role in the Formation of Macrorelief at the End Milling of Thin-Walled Structures When Changing the Radial Depth of Cut

The fourfold increase in the number of publications devoted to the milling of thin-walled structures over the past ten years indicates, on the one hand, their increasingly widespread use in high-tech products and, on the other hand, the challenges faced by the industry in their manufacture, including the vibrations that accompany the milling process. Chatter leads to the formation of macrorelief on the machined surface in the form of waviness, which negatively affects the efficiency of products containing thin-walled structures. Various studies of the mechanism of waviness formation agree on the decisive role of regenerative chatter in this process. However, their occurrence requires the presence of initial waviness. To the reasons and principles behind its formation, the existing research does not provide an answer. Analysis of vibration oscillograms for both up-cut and down-cut milling leads to the conclusion that during the contact time between the tool and the part, a specific type of vibration occurs—attending free vibrations (AFV)—which have a distinct first wave and serve as a trigger for waviness formation. The study of the AFV influence on the formation of the machined surface macrorelief is the novelty of this work. Statistical analysis of the results obtained shows the relationship between the parameters of the AFV and those of the waviness. This article continues a series of publications on the results of research into the influence of technological parameters on those of AFV and waviness. It is devoted to the study of the impact of the radial cutting depth during up-cut and down-cut end milling of thin-walled structures. The obtained results demonstrate that the height of the waviness increases with the growth of the radial depth of the cut, both during up-cut and down-cut milling, while its step decreases during up-cut milling and increases during down-cut milling.