Investigation of the influence of cutting tool flank face contact forces on the dynamics of end milling

DOI: 10.34759/trd-2022-123-11

Аuthors

Zhukov N. A.^*, Kiselev I. A.^**

Bauman Moscow State Technical University, MSTU, 5, bldg. 1, 2-nd Baumanskaya str., Moscow, 105005, Russia

*e-mail: jukov.n@yandex.ru
**e-mail: i.a.kiselev@yandex.ru

Abstract

In the modern machinery 5 axis end milling operations are widely used in the production of thin-walled workpieces with complex 3D surface geometry [1-3]. Such processes are always accompanied by vibrations of different elements of the technological system (e.g., workpiece, tool): free, forced, parametric vibrations may arise, as well as self-oscillations. One of the most undesirable vibration types are regenerative self-oscillations, which may cause dynamic instability of the steady-state cutting process: these vibrations arise due to the fact, that each tooth of the mill is cutting the surface, formed by a previous tooth, so the time delay effect is introduced [4-6]. At the early investigations of cutting dynamics it was observed, that vibrations amplitudes of the technological system’s elements decreased while machining with low spindle speeds [7,8]. This effect was called “process damping” and its presence was explained by contact interaction between the flank face of the tool and the machined surface [9]. The intensity of process damping is the higher, the lower is the ration of the mill’s teeth pass frequency to the vibrations frequency [10].

Modern time-domain models of 5 axis end milling processes lack process damping accountment [17-19], so numerically simulated machining dynamics at low spindle speeds (comparatively to the arising vibrations frequencies) are not correct, which is extremely actual for machining of thin-walled workpieces from nickel and titan alloys. In this work a new time-domain numerical model of end milling dynamics of flexible workpieces is presented. This model allows to consider complex 3D contact forces between the workpiece and both rake and flank faces of the cutting tool during end milling dynamics simulation. Model’s structure and its main blocks are described. The developed model was used to perform numerical experiment on the influence of contact forces, arising on the flank face of the cutting tool, on the dynamics of the flexible workpiece end milling. Obtained numerical results qualitatively match well known experimental data from literature.

Keywords:

end milling, cutting dynamics, process damping, flank face, numerical modeling

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