Machine Tool Component 4: Eddy Current Damper

An alternative way to achieve tunable dampers for machine tool chatter has been explored. We have looked for ways of being able to decouple stiffness and damping effects in the damper. Tunable stiffness has been implemented by designing a rotary spring with variable stiffness in function of its orientation. Controlling this spring with a motor, the stiffness of the damper can be tuned within a certain range. This spring generates almost no damping. Eddy current effect is used for producing the damping. A combination of magnets and copper plates produce this effect by their relative vibration. The damper was designed not only to be tunable, but also self-tuning. The damper incorporates an accelerometer. A real time processing controller has been developed, which reads this vibration level, and automatically detects whether chatter is being produced or not. When it does, it sends a signal to the motor in the damper that tunes the spring, therefore setting the damper in the optimal conditions for eliminating chatter. The concept has been patented.