Non-collocated active vibration suppression of both rough-machining and finishing in ram-type milling machine using an electromagnetic actuator

Abstract

This paper presents the non-collocated active damping system (NCADS) applied to a ram-type milling machine for achieving high-throughput machining of both rough- and finishing-milling. When installing an active damping system to practical ram-type milling machines, the available locations are limited due to the space constraints and the interference against machining processes. Therefore, it is often the case that the non-collocated configuration of the active damper becomes inevitable. Such non-collocated active damping system (NCADS) may require high force–density actuators to compensate the poor controllability, and right half-plane zeros caused by the NCADS make it challenging to maximize the active damping performance while securing the controller stability. In addition, the different vibration characteristics during the rough- and finishing-milling require the vibration control strategies adapted to the machining operations. We propose the sensitivity function shaping methods in NCADS for high-throughput operation of both rough- and finishing-milling. Using the proposed method, we increase the dominant-mode dynamic stiffness of the ram structure by 154% for rough-machining operations, and thereby increase the chatter-free cutting depth up to 3.5 mm. Also, in the high-speed finish-milling test, we reduce the retainer vibration by 58% and thereby suppress the associated beating mark on the surface profile, achieving the surface roughness reduction by 40%. The results validates the high-throughput machining performance of the proposed vibration suppression control methods in both rough- and finishing-milling.