In a systematic manner, this paper investigates the effects of harmonic force components on the regenerative stability of an end milling process. By representing the milling force pulsation in a Fourier series expansion form, the dynamic force components and the average forces due to bi-directional dynamic feed rates are both included in the generalized system dynamics formulation. In the resulting expression for the stability criterion, the spectral features of the milling forces are integrated with the dynamics of the structure, showing the significance or insignificance of the dynamic components of the milling forces in affecting the stability of the milling process. Key system parameters discussed include the magnitude of the average and harmonic forces, the cutter helix angle and the spindle speed. It is shown that a low helix angle and a smaller number of cutting flutes increase the effect of dynamic forces on the system stability. The significance of the harmonic forces is exemplified by the special cutting conditions where the average force becomes zero and the stability limits would be infinite as predicted by models using the average force alone. Improvements in the accuracy of stability lobes resulting from the inclusion of the dynamic forces and the validity of the presented model in general will be illustrated by numerical simulation and verified by experiments as well as by comparison with published results.
Forced vibration or the steady state vibration in a milling process inevitably occurs due to the periodic excitation of the intermittent cutting engagement of the milling cutter on the work and the structure, and it almost always exist even in the absence of chatter in a stable milling system, leading to dimensional and surface error and premature wear in tool and machine components. In this paper, an analytical model for the forced vibration in an end milling process is derived and criteria in selecting cutting conditions to reduce the forced vibration are presented. The analytic expression for the forced vibration due to the periodic milling force is obtained as the product of the Fourier transform of the milling force and the frequency transform of the structure dynamics. Analysis of the vibration model shows that the structure vibration can be reduced by selecting cutting parameters so that the zeroes of the frequency transform of the milling process function are near the poles of the structure dynamics. A design equation in terms of cutter geometry, axial depth of cut and structure natural frequency is obtained for the conditions when the forced vibration can be minimized. The presented analysis is illustrated through numerical simulation and verified by experimental results.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.