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This paper presents a 5-axis machine tool compensation method that uses tool tip measurements recorded throughout the joint space to construct a set of compensation tables. The measurements can be taken using a laser tracker, permitting rapid measurement at most locations in the joint space. To compensate the machine tool, the measurements are used to identify a kinematic model, and then that model is used to construct an optimal set of compensation tables. The kinematic model is composed of the nominal, or ideal, kinematics with additional (unknown) six degree of freedom errors inserted between each of the joints. The error kinematics are identified using the measurement data and a maximum likelihood estimator. The identified model is then projected onto a joint-compensation space that maps to the compensation tables in the machine tool controller. Simulations of the approach are provided using measurement data from a Flow International 5-axis machine tool equipped with a Siemens 840D controller. The simulation results show a mean residual error of .076 mm, which is a 76.8% reduction from the uncalibrated machine tool.Copyright © 2013 by ASME |
