Development of Multi-degrees of Freedom Optical Table Dynamometer

Accurate measurements of cutting forces are critical in machining operations for maximizing production, detecting tool wear and failure, adaptive control and monitoring. Traditionally, cutting forces are measured using piezoelectric quartz force sensors or strain gauges. These types of sensors have limitations in that they are unable to measure static force signals. The quartz crystals of a piezoelectric force sensor generate an electric charge only when force is applied to or removed from them. Strain gauges suffer drifts over a long period time. In order to overcome the challenges, a novel table dynamometer is developed based upon laser optics to measure planar forces and moments in both the static and dynamic range. The developed table dynamometer allows the measurement of both the in plane linear movements and the in-plane rotations. In order to achieve high sensitivity, a monolithic, flexure-based mechanical amplifier is adopted into the proposed table dynamometer. A prototype of the developed system is fabricated and the sensitivity and frequency bandwidth of the system are experimentally investigated. The results showed good agreement between the optical force sensor and a reference force transducer. The proposed dynamometer is tested for use in the measurement of cutting forces and compared with a conventional piezoelectric dynamometer.