Micro machining and measuring center for micro machine parts using parallel kinematics

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This study proposed a micro coordinate measuring machine (micro CMM) based on a parallel mechanism instead of XYZ mechanism. Because the conventional CMM using XYZ mechanism consisting of three mutually orthogonal slide mechanism is not suitable for measurement with nano-order accuracy. This CMM is suited for precision measurement of the geometrical deviations of the micro parts with three dimensional profile. First, we performed the link configuration design using the error analysis by singular value decomposition. Obtained link configuration improves the moving accuracy and the measuring resolution. Moreover, we have designed the strut consisting of the prismatic joint, linear scale unit and the actuator. The inch-worm mechanism using piezoelectric actuators has been employed as the actuator of the strut. This struts also have a compensation device for joint motion errors, elastic displacements of the joints and links, and thermal deformations of the links. This device employs two rods connecting with the joints and a scale unit. The scale unit can measure the variation of the distance between the joints independently of the external load because the rods aren't subjected to the load. Moreover, temperature fluctuation has little effect on measured variation because the rods are made of Super Invar. This device is built in the experimental active prismatic joint of a coordinate measuring machine for micro parts. Experiments show that the device improves the stiffness and decreases the thermal expansion of the link.