Influence of cutting time on types of oscillations during blade processing

Abstract

Despite many years of research on the impact of vibrations on the quality of manufacturing parts and tool stability during machining, these problems are still relevant. One of the reasons is uncertainty regarding the pattern of occurrence of types of oscillations during mechanical processing and their effect during cutting. Therefore, the work aimed to determine the patterns of occurrence of types of oscillations during mechanical processing and their effect during cutting. The research was carried out when turning parts according to various schemes. Turning is a universal operation where it is possible to carry out continuous processing, intermittent turning, and different depths of cutting. During the experiments, a special device was used, with the help of which it is possible to provide different dynamic characteristics of the cutter. The cutting modes were chosen so that turning occurs with self-oscillations. With the help of eddy current sensors and an electrical contact device, oscillograms of the technological system's oscillations during cutting were recorded, with the cutting time and spindle turn marked on them. During the continuous turning of a cylindrical part, there are forced oscillations, which are superimposed firstly by the accompanying free oscillations of the technological system, and then by self-oscillations. After the first rotation of the part, the processing is carried out according to the wavy trace of the accompanying free oscillations, which, combined with the phase shift, creates the conditions for self-oscillation occurrence. When turning with a full depth of cut, there are forced oscillations on which self-oscillations are superimposed. When turning a cylindrical part with a groove, the cutter cuts into it with an impact at each turn. At the same time, there are forced oscillations during cutting, which are superimposed by the technological system's accompanying free oscillations and self-oscillations. Due to the wavy trace on the cutting surface, self-adjustment of the self-oscillations occurs in the transition zone after attenuating the accompanying free oscillations. During idling, free oscillations of the cutter take place. When turning an eccentrically fixed part, the cutting depth changes continuously. The excitation source of the forced and accompanying free oscillations is the action of the periodic cutting force. Under such conditions, self-oscillations do not occur. When turning inserts of a limited length during cutting, forced oscillations are applied, which are superimposed by the accompanying free oscillations of the technological system. Despite a wavy cutting surface, there is not enough time for self-oscillations to occur. The conducted studies show that during machining, there is a regularity of the action of the types of oscillated oscillations operating throughout the cutting time. At the same time, the accompanying free oscillations of the technological system are superimposed and act on them for a certain time, after which, due to transient processes, self-oscillations occur until the end of the cutting. Their characteristic features determine the types of oscillations that occur during cutting. When the types of oscillations during cutting are known, measures are prescribed to prevent their impact on the tool's quality of processing and stability.