Implementation of a Designed Tool Post for Tool Vibration Compensation Using, PMN Actuators

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Tool vibration is a well-known fact in causing poor surface finish, accelerated tool wear, and unstable machining operations. Due to the availability of active or "smart" materials, researchers in the machine tool industry are now focusing on applying active control to attenuate tool vibration during machining.

In this thesis research, efforts are dedicated to investigating the mechanical and electrical behavior of a designed tool post structure in which lead-magnesium-niobate (PMN) actuators are used as built-in devices for vibration control. Research is focused on using finite element method (FEM) to identify the dynamic characteristics of the tool post, establishing an experimental testbed environment for experimental verifications, and implementing the tool post in a shop floor machining environment to test its performance, both mechanically and electronically.

Results obtained from this investigation has justified the tool post design for its effectiveness in carrying out vibration compensation during machining. A 10 to 20 percent of reduction has been observed with the PMN actuators in action. Significant findings of this research include 2 to 3 mm floating of the dynamic equilibrium position of the tool tip during the compensation, and the effect of interplay between actuator-driving frequency and workpiece rotation on in-process compensation. Control of the coupling coefficient deserves special, attention for maintaining an acceptable efficiency of conversion from electrical energy to mechanical energy. Knowledge gained from this study has provided guidelines not only for off- line optimization, but also for controller designs when PMN actuators are applied.