Five-axis milling vibration attenuation of freeform thin-walled part by eddy current damping

Passive control has been effective in damping the machining vibration of thin-walled parts. However, physical addition onto the part causes the dynamics change and limits the engagement of cutting tool, especially in the application of multi-axis machining. Utilizing the non-contact eddy current damping, a two-degree-of-freedom apparatus is designed after experimental investigation into the magnet combination, magnetic flux density and magnetic flux mode on damping behaviors on a specifically designed platform. The apparatus is set up by mounting on the stationary spindle head of a five-axis CNC machine tool. The included neodymium magnets, and then the induced eddy current damping force are able to follow the feeding cutter through the control of two servo motors, keeping out of touch with the thin-walled part to be damped. As the damping force is able to resist the vibration of the machining point induced by the cutting force directly, it allows the design with less volume and mass (i.e. magnets and conductors). In the end, hammer tests are performed to verify the additional damping ratio imposed by the apparatus. Three-axis milling tests of a thin-walled frame are carried out to validate the damping of the apparatus, and five-axis milling tests of thin-walled blade type part are conducted to demonstrate its controllable damping and adaptability to complex tool path.