Assigning the turning mode based on assessment of the dynamic quality of machine tools

Abstract

Background. Machining on lathe machines using automation means is a complex process that depends on the properties of the dynamic system (DS) of the machine, therefore, determining cutting modes based on the minimum value of the attenuation coefficient of the autocorrelation function of vibration acoustic oscillations is an urgent task of machine building. Materials and methods. The vibrations that occur during the processing of critical parts determine the dynamic quality of the machines, the quality of the surface layer and the resistance of the cutting tool, therefore, it is necessary to identify control methods. Increased efficiency of the process is provided by forced cutting modes, which can lead to deterioration of processing quality and premature wear of the cutting tool. The theoretical definition of rational cutting modes causes certain difficulties, so the experimental search for a solution to the problem is most relevant. In order to select rational cutting modes on turning and grinding groups machines, it is proposed to use the stability reserve of the DS of the machine as the most informative characteristic, which should be determined from the transfer function of the DS using the autocorrelation function (ACF) of vibrations. A condition for the identification of the DS machine is the preliminary identification of the ACF, which can be implemented using vibration records during cutting. Pre-filtering of oscillations is carried out to exclude low-frequency range containing frequencies caused by oscillations of machine system elements and to leave frequencies associated with cutting process. Cut modes are assigned to the highest stability margin, which ensures high surface quality. Results and conclusions. There is an unambiguous analytical relationship between the oscillation index and the damping coefficient of the ACF, which makes it possible to calculate the α coefficient, by the value of which it is possible to estimate the stability margin of the ET in various cutting modes and select the most appropriate one. The study of vibrations of machines for processing high-precision parts makes it possible to appropriately control the technological mode, using the level of vibrations as one of the indicators of its quality.

Keywords

• turning
• autocorrelation function
• integral estimates
• cutting modes
• attenuation factor
• vibroacoustic oscillations
• stability margin