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Fast Tool Servos for Precision Machining of Irregularly Shaped Surfaces


Fast Tool Servos are turning tools capable of high frequency motion not typically possible with conventional computer numeric control (CNC) tooling. Typical applications are turning of non-circular parts and chatter suppression. This particular design uses a piezoelectric actuator (PEA) to provide the base motion and a hydraulic amplifier design to increase the stroke of the device from the PEA stroke of 60 microns to the design stroke of one millimeter, a factor of approximately 16.

Like traditional hydraulic systems, this system uses fluid to transmit force and displacement between an input and output plate. Instead of trading displacement for force multiplication, the design uses a piezoelectric actuator to provide large-force, but small-stroke motion to the large-area plate to amplify the stroke at the smaller-area output plate. Fluid chamber behaves as a very stiff spring that also multiplies displacement.

The fast tool servo (FTS) is a custom-designed tool holder used to cut piston pin holes. Piston pin holes have a unique non-circular geometry, they have an oval hole with a trumpet-shaped profile. This geometry is difficult to create because the work piece must remain stationary. The FTS mounts to a lathe and is designed to accept multiple sizes of boring bars. It uses a piezoelectric actuator to actuate the boring bar about a flexure.


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