Stability of Milling Operations With Asymmetric Cutter Dynamics in Rotating Coordinates

Abstract

High-speed machine tools have parts with both stationary and rotating dynamics. While spindle housing, column, and table have stationary dynamics, rotating parts may have both symmetric (i.e., spindle shaft and tool holder) and asymmetric dynamics (i.e., two-fluted end mill) due to uneven geometry in two principal directions. This paper presents a stability model of dynamic milling operations with combined stationary and rotating dynamics. The stationary modes are superposed to two orthogonal directions in rotating frame by considering the time- and speed-dependent, periodic dynamic milling system. The stability of the system is solved in both frequency and semidiscrete time domain. It is shown that the stability pockets differ significantly when the rotating dynamics of the asymmetric tools are considered. The proposed stability model has been experimentally validated in high-speed milling of an aluminum alloy with a two-fluted, asymmetric helical end mill.

Numerical study on stability of composite cutter bar milling system in rotating coordinate frame

“…Figure 4 shows the chatter stability lobes of the milling system in rotating coordinate frame. The present model considers the internal damping of the cutter bar, whereas reference [23] does not. Consequently, it can be seen that the position of the lobe diagram calculated by the present model is higher than that of the lobe diagram in reference [23].…”

“…The dynamic chip thickness removed by tooth j is expressed in local coordinate frame ( Ȳj , Z j ) as follows [23],…”

“…Currently, most studies on the stability analysis of rotating cutter bar are conducted in fixed coordinate frame [15][16][17][18][19][20][21], while only a few are involved in rotating coordinate frame [22,23]. Eynian and Altintas [22] proposed a new prediction method for the milling process with asymmetric structural dynamics in rotating coordinates.…”

“…The stability of the characteristic equation of the system was investigated using the Nyquist stability criterion. Comak et al [23] studied the milling process with an asymmetric cutter in rotating coordinates. The stability lobes significantly differ due to the asymmetric of the structural dynamics of the system.…”

A novel harmonic solution for chatter stability of time periodic systems

“…The first consequence is that the cutting force rotates with it, thus the directional cutting force coefficients vary periodically [10]. Moreover, the presence of asymmetric stiffness of rotating parts [11] (i.e. two fluted end mills) or of the workpiece [12] (i.e.…”