In the paper the problem of reasons elucidation in the matter of lathe instability at groove cross turning and boring is solved. As a tool for the analysis of a structure state there are used potentialities of modal monitoring, and in particular, a correlation of modal parameters, sets of proper characteristics of an elastic system (self-frequencies, modal coefficients damping and own forms of vibrations) of lathes designs with the state of bearings in spindle units. The application of a modal approach to the evaluation of a lathe design state or an elastic system is a new section in a dynamic analysis and may be called modal diagnostics. From the analysis of the modal parameter values of a lathe one traces their tie with the lathe design characteristics, and in particular, with the existence of sever rigidity anisotropy of a spindle unit front bearing and also with its insufficient tightness. Reasoning from the information mentioned of the modal parameters connection with the rigidity of a spindle unit front bearing and a state of bearing design the authors draw a conclusion of the technological state of a spindle unit design. In such a way, by the example of the design of two lathes in the paper there is shown a possibility of transition from experimental frequency characteristics through a procedure of modal diagnostics to the evaluation of the technological state of a spindle unit.
modal vibration diagnostics, lathe, spindle unit, dynamic rigidity, own frequency, coefficient of modal damping, modal ductility
1. Genkin, М.D. Vibroacoustic Diagnostics of Machinery and Mechanisms / М.D. Genkin, А.G. Sokolo-va. - М.: Mechanical Engineering, 1987. - pp. 288.
2. Dosko, S.I. Parametric identification of machines elastic systems (modal analysis): Can.Eng. Thesis / S.I. Dosko. - М., 1987.
3. Dosko, S.I. Modal diagnostics of engineering struc-tures. Principles, technology, examples of use / S.I. Dosko // Proceedings of the Inter. Scientific-Tech. Conf. “Intelligent Systems of Measuring, Control, Management and Production Control in Industry”. - М., 2014
4. Sabirov, F.N. Machines efficiency increase based on their diagnostics and vibration resistance in operation space: Can.Eng. Thesis / F.N. Sabirov. - М., 2009.
5. Gudimenko, N.N. Investigation of dynamic characteristics and vibration resistance of horizontal mil-ling machines: Can.Eng. Thesis/ N.N. Gudimenko. - М., 1974.
6. Tlibekov, А.Kh. Modeling and Optimization of Engineering Systems of Technological Machine Drives: Manual / А.Kh. Tlibekov, S.I. Dosko. - М.: Stankin, 2004.
7. Design, Computation and Control Methods of Spindle Units with Frictionless Bearings: method, directions / А.М. Figater, Е.А. Fiskin, S.Е. Bondar. - М.: ENIMS, 1970.
8. Pavlov, А.G. Dynamic Accuracy Control at Machining / А.G. Pavlov. - Krasnoyarsk: Publishing House of Krasnoyarsk Uni., 1989.
9. Simov, V.S. Analysis of spindle front bearing influence upon vibration resistance of lathes: Can.Eng. Thesis. - М., 1961.
