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Design and Testing of a Long Stroke Fast Tool Servo for Ultra-precision Free-form Machining  

Kim, Ho-Sang (Center for robot and manufacturing tech., Institite for Adv. Eng.)
Lee, Kwang-Il (Center for robot and manufacturing tech., Institite for Adv. Eng.)
Publication Information
Journal of the Korean Society for Precision Engineering / v.26, no.2, 2009 , pp. 35-44 More about this Journal
Abstract
Long stroke Fast Tool Servo (LFTS) with maximum stroke of $432{\mu}m$ is designed, manufactured and tested for fabrication of optical free-form surfaces. The large amount of stroke in LFTS has been realized by utilizing the hinge and lever mechanisms which enable the displacement amplification ratio of 4.3. In this mechanism the peculiar shape was devised for maximizing the displacement of end tip in LFTS and special mechanical spring has been mounted to provide the sufficient preload to the piezoelectric actuator. Also, its longitudinal motion of tool tip can be measured by capacitive type displacement sensor and closed-loop controlled to overcome the nonlinear hysteresis. In order to verify the static and dynamic characteristics of designed LFTS, several features including step response, frequency response and cut-off frequency in closed-loop mode were experimentally examined. Also, basic machining result shows that the proposed LFTS is capable of generating the optical free-form surface as an additional axis in diamond turning machine.
Keywords
Long Stroke Fast Tool Servo; Ultra-precision Free-form Machining; Closed-loop Control; Piezoelectric Actuator; Capacitive Type Displacement Sensor; Displacement Amplification Mechanism;
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