Extension of process damping to milling with low radial immersion

Abstract

This paper investigates the stabilizing effect of process damping at low cutting speeds for regenerative machine tool vibrations of milling processes. The process damping is induced by a velocity-dependent cutting force model, which takes into account that the actual cutting velocity is different from the nominal one during machine tool vibrations. The chip thickness and the cutting force are calculated according to the direction of the actual cutting velocity. This results in an additional damping term in the governing delaydifferential equation, which is time-periodic for milling and inversely proportional to the cutting speed. In the literature, this term is often assumed to be constant and is considered to improve stability properties at low spindle speeds. In this paper, it is shown that the velocitydependent cutting force model captures the improvement in the low-speed stability only for turning operations and milling with large radial immersion, while it results in a negative process damping term for lowThis work has been supported by theÚNKP-16-3-I. New National Excellence Program of the Ministry of Human Capacities. This work was supported by the Hungarian National Science Foundation under grant OTKA-K105433. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007(FP/ -2013

Model of Force Interaction for Stability Prediction in Turning of Thin-Walled Cylindrical Workpiece

“…Another approach, which is also used in this paper, follows the research of Das and Tobias [13], who showed that even static models can be used to model process damping by more accurately considering the geometry of the cut with respect to the instantaneous direction of the cutting speed including vibration. This approach was applied, for example, by Molnar and Bachrathy [4,27] to cylindrical milling. One of the main complications of this approach, which this paper aims to address, is the integration of damping contributions for geometrically complex cutting edges where the local face and blade inclination angles change gradually.…”

A feedback controller for milling chatter vibration control using a new response matrix

“…Altintas considered cutting speed and acceleration to influence the curvature of the machining surface (Altintas, 2012; Altintas et al, 2008). Altintas model was updated by Turkes et al (2012); Yang et al (2016); Zhu et al (2017); Molnar et al (2017); and Feng et al (2018). The process damping is composed by applying shear angle oscillation, and change in cutting force, where a process damping ratio was generated by Turkes et al (2012).…”

“…Zhu et al (2017) developed the energy-based model for stability analysis and process damping identification. Molnar et al (2017) considered a velocity-dependent process damping in orthogonal cutting that differentiates between the actual cutting and nominal cutting during machine vibration. Furthermore, the plowing forces influence power spectral density and process damping through the cutter signal (Feng et al, 2018).…”

S-domain stability analysis of a turning tool with process damping

“…When the rate of energy supply is overbearing on the rate of energy dissipation instability grows. Process damping is a very helpful phenomenon at low speeds because it considerably enhances damping thus improving stability [17, 18].…”