Investigation on the Chatter Vibration and Surface Texture in Vibration Assisted Micro-milling Process

Abstract

Regenerative chatter is an unstable form of self-excited vibration in the machining process. It is one of the main obstacles which limit the productivity and the surface quality. This thesis investigates the effect of vibration assistance on high frequency regenerative chatter in the micro milling process. External vibration is applied on the Al-6061 workpiece in a range of frequencies and amplitudes using the piezoelectric actuators. The chatter vibration is monitored using the sound pressure signal measured by a microphone. The chatter with vibration assistance in 1-D (feed or normal direction) and 2-D is studied. The effect of the frequency and amplitude of the vibration assistance on chatter is analyzed. It is concluded from the experimental study that the vibration assistance is able to effectively attenuate the high frequency chatter in the micro milling process.Surface texturing is an innovative technique to generate patterns on the surface. These surfaces can be used for friction reduction in several applications such as internal combustion engines, micro-electrical- mechanical systems (MEMS), micro-fluids etc. Electric discharge texturing, laser texturing and photolithography are some of the finishing processes applied to the machined surface to create surface textures. However, this requires a long process which makes it costly and time consuming. This thesis focuses on surface texture generation by micro side milling with vibration assistance. External vibration is applied on the workpiece at the frequency and input voltage which can generate micron level amplitude. The machined surface profile is measured using a 3-D profilometer. Surface textures created with and without vibration assistance is compared. The effect of feed rate and different types of tools on surface texture is also studied.