Elucidation of the mechanism of chatter mark formation during end-milling and inverse analysis of chatter vibration by two-dimensional discrete Fourier transform of chatter mark

Abstract

Regenerative chatter vibration is a typical machining problem during cutting. The frequency and phase shift of regenerative chatter can be used as indicators to suppress regenerative chatter. However, direct measurement of chatter vibration during cutting is difficult for end milling because the tool blade rotates. Therefore, chatter vibration is generally measured indirectly, for example, from cutting noise or vibration transmitted to the spindle. The type and position of the installed sensors must be appropriately selected to accurately measure chatter vibration with these methods. This selection must account for the machine tool structure, cutting conditions, and the position where the chatter vibration occurs, making the measurement methods not universally applicable. When chatter vibration occurs during cutting, a periodic pattern called a chatter mark is formed on the machined surface. The chatter mark is formed by vibration during cutting, i.e., vibration information during cutting is directly recorded. Therefore, this paper proposes a method to analyze the frequency and phase shift of chatter vibration using a two-dimensional discrete Fourier analysis of the chatter mark based on the modeled formation mechanism of chatter marks, and further validates the proposed method by elucidating the mechanism of chatter mark formed by chatter vibration. First, a cutting simulation was performed based on the vibration displacement of the tool during chatter cutting obtained experimentally. This simulation elucidates the mechanism by which the vibration information of chatter vibration can be analyzed from the chatter mark. Subsequently, the chatter vibration parameters were analyzed from the chatter mark using the proposed method. The parameters were consistent with those analyzed from the vibration displacement of the tool, confirming the effectiveness of the proposed method.