Dynamics of Fine Boring of Intermittent Surfaces

In this work, the nature of vibrations and the distinctive features of the dynamic system of a boring machine when processing intermittent surfaces are investigated. The periodic repetition of the plunge and exit of the tool is an additional perturbing factor that causes vibrations of a higher level during interrupted cutting than during continuous cutting. The defining feature of a closed dynamic system EDIS (elastically dissipative inertial system) is its non-stationarity. Here, closed and open states alternate in time due to periodic interruptions in the cutting process. Thus, the loss of stability in such systems occurs not only due to the presence of feedback, but also due to periodic changes in parameters. An experimental study of vibrations during intermittent cutting of specimens made of steel, cast iron and bronze was performed on the stand. Studied the main regularities of the development of oscillations and established their nature: periodic changes in equilibrium states and high-frequency vibrations that are excited at the moments of penetration and exit of the cutter into the groove. The vibrations decrement during cutting differs from that measured during the passage of the groove and can be expressed in terms of the parameters of a closed dynamic system. The results of the experiment are presented as dependences of the amplitudes of bending vibrations of the boring bars on the cutting speed. The patterns of changes in the levels of vibrations show that in interrupted cutting, the sources of vibrations are external influences on the cutting process and parametric disturbances. Examples of areas of stable and unstable solutions are given under harmonic parametric perturbation.