Abstract: An ER damper for controlling machine chatter is developed. The theoretical and experimental results show that the stiffness and damping of ER damper are growing with the increase of the electric field strength applied, the vibration response of main vibration system (arbor) witl reduce by raising electric field strength in a certain scope. As far as the electrical field strength selected is appropriate, the vibratory amplitude of milling machine arbor will decrease to 50%~80% as low as that in common milling. All experiments presented here re performed on a horizontal knee and column type milling machine.

Key words: Dampling, Electro-rheological, ER damper, Fluid (ERF), Stiffness, Vibration control