SUNConferences, COMA '13

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Volumetric Geometric Accuracy Improvement for Multi-Axis Systems Based on Laser Software Error Correction
Sergey Grigoriev, Vladimir Teleshevsky, Vladimir Sokolov

Last modified: 2013-08-21

Abstract


Multi-axis systems with CNC-controlled displacements of moving parts are the basis of modern engineering industry. Various technological equipment – machine-tools, performing machining process by putting machined part into interaction with the tool`s cutting edge, moving along pre-set path - relates to multi-axis equipment. Measuring devices – CMMs and other devices with contact or non-contact interaction of measured part and scanning sensor – relate to multi-axis systems as well. Technological and measuring multi-axis systems have similar configurations: traditional Cartesian and polar configurations, Parallel mechanism configuration and hybrid configuration, combining both traditional and parallel kinds.
The accuracy for machine-tools and CMMs is primarily determined by their manufacturing and assembling technology. However, nowadays the technological reserves for accuracy improvement are almost used up, especially for precision machine-tools and CMMs. That is why a different way to improve accuracy, based on measurement and software correction of geometrical errors is of increasing importance.
The current report describes methods of laser software correction of volumetric geometric errors for multi-axis systems. A multi-function laser measuring systems precisely measures necessary spatial functions of the object: linear errors, angular errors, straightness errors etc. Next, a model of object’s geometric errors is determined based on the object’s kinematics. The model allows mapping error distribution within workspace by means of matrix transforms and measured spatial functions. Thus error mapping gives wide opportunities to compensate the errors by means of automatic CNC correction.
The results of simulation and experimental data on laser software correction are presented. The result is over 10 times accuracy improvement at axis length over 15 meters. The laser software correction system is described, based on “XL-80” laser interferometer by Renishaw (Great Britain) and CNC system “FlexNC” by Stankocenter (Russia), performing real-time error correction. Optimal correction strategy concept is proposed, providing least resulting error within maximal workspace area.

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