Dynamics of Machining: Prediction and Suppression of Undesired Vibrations
May 6, 2019 — May 10, 2019
- Gabor Stepan ( Budapest University of Technology and Economics, Hungary)
Dynamics of metal cutting is a relevant research topic that has an essential theoretical background both in mechanics of solids and in dynamics of rigid bodies. The basic difficulty was summarized as early as 1907 by F. W. Taylor, the 3rd president of ASME:
“… Chatter is the most obscure and delicate of all problems facing the machinist – probably no rules or formulae can be devised which will accurately guide the machinist in taking maximum cuts and speeds possible without producing chatter…”
Chatter refers to the vibrations that may arise during cutting processes. This specific self-excited oscillation is mainly caused by the so-called regenerative effect. The undesired relative vibrations between the tool and the work-piece deteriorate the quality of machined surfaces. If the modal parameters, like natural frequencies, damping, vibration modes, are identified on a machine tool, and if the cutting force is estimated by means of well-established cutting mechanics models, then there is a chance to predict and to prevent chatter by selecting appropriate cutting parameters (feed rate, depth of cut and cutting speed) and achieve maximal material removal rates. During the last 100 years, the research methodology has developed parallel to the theoretical and numerical methods in mathematics, informatics, vibration theory, measurement techniques and nonlinear dynamics including chaos.
The advanced course provides a full spectrum of the research results in machining dynamics from the theoretical background of nonlinear delayed oscillators to the practical issues of modal testing. Mechanical and mathematical models are presented both in frequency domain and in time domain. Introduction is given to advanced numerical and software solutions to carry out virtual machining to optimize cutting parameters. The hardware-in-the-loop technique is introduced for enhanced design of improved tool geometries. Optimization of milling tool geometry (pitch and helix angles) is discussed. Methods involving partial modification of the machine tool structure are also presented, like the various dynamic vibration absorbers. Up-to-date experimental modal testing methods and their future development strategies are overviewed together with the sophisticated construction of the stability charts that are relevant for industrial applications. Research and commercial solutions for real-time chatter detection and process regulation are discussed. An industrial panel will bridge the state-of-the-art research results and actual industrial needs in machining dynamics.
The school is addressed to doctoral students, post-docs, early career researchers and engineers working at R&D departments of companies with interest in improving machining efficiency. The course is designed for participants working in the field of dynamics of machining and related topics like deep drilling, also to those interested in vibration measurement techniques, hardware-in-the-loop applications and/or in other fields of dynamics of delayed oscillators from traffic dynamics to human-machine systems in general.