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QMT Products: July 2016
Factory-wide metrology network

Etalon says its Absolute Multiline Technology makes self-controlled production a reality, with self-correcting machine tools not just making parts but checking their dimensions too. It used Control to give visitors a demonstration of how this smart technology can create metrological networks.

Absolute Multiline Technology monitors the geometric accuracy of machine tools by means of high-precision length measurements: An absolute distance interferometer measuring with sub-micrometer resolution serves as metrological centerpiece of a factory. It connects with any number of machines via a fibre optic network that may comprise more than 100 measurement channels. These measurement channels, equipped with miniature optical elements, are oriented along the machines’ axes, space diagonals and face diagonals of the machine working volume. Absolute Multiline Technology’s metrological network can cover any machine location and size – it has already been set up in factories supplying multiple machine tools with axis lengths of up to 12m.

The maximum measurement range is 40 meters and the optical fibers may travel several kilometers. Due to the large distances possible between the robust measurement sensors and the system electronics, measurements can be conducted under extremely rough environmental conditions.

Integrated into a machine tool, Absolute Multiline Technology can continuously monitor the geometry of the machine and initiate machine compensation in order to ensure the dimensional accuracy of the manufactured parts. To perform a standard-compliant machine tool check, a reflector from the tool magazine is interchanged, and a predefined program is executed at the push of a button to move the machine along the multiple measurement beams and thus identify their deviations. This test process takes approx. 20 minutes. Measurement uncertainty (95%) is specified with 0.5 µm per meter.

While conventional interferometers can only work with a continuous measuring beam, the Absolute Multiline Technology can deal with interruptions of its eye-safe infrared beam at any time without losing accuracy. The absolute distance is re-calculated in a fraction of a second. Hence, highest geometric precision is assured in the entire working volume of the machine. Thermal influences, wear, or collision-induced changes are reliably detected and compensated, if necessary. Geometric compensation is fully automatic with machine values calculated by comparison of the coordinates indicated by the machine and the length measured by the interferometers.  
Thanks to the machine tool’s autonomous geometrical verification in the entire working volume, it may also be used as coordinate measuring machine to inspect the manufactured components.

Especially for the quality assurance of large parts, this generates significant commercial benefits: A separate coordinate measurement machine and also time consuming clamping and re-clamping processes can be omitted.
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