VOLUMETRIC LASER CALIBRATION
OF MACHINE TOOLS

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COMPTON, CA—A new Laser Calibration System for volumetric measurement and compensation of a 3-axis machine tool in less than two hours has been introduced by Optodyne, Inc. of Compton, California.  The system measures linear position errors, vertical straightness errors and horizontal straightness errors for all three linear axes and three squareness errors.

            By measuring volumetric errors, the machine tool can be compensated over the whole volume, which improves the accuracy of the machine tool, not just linear displacement.  For example, most machine tool calibration checks for displacement error, linear error parallel to the axis of movement.  However, this ignores the vertical straightness error that is perpendicular to the axis of movement and the horizontal straightness error that is perpendicular to the axis of movement and the vertical straightness direction.  The resulting error is a vector error, which consists of displacement error, vertical straightness error and horizontal straightness error. 

            With four body diagonal displacement measurements, volumetric accuracy can be determined, as recommended by the B5.54 standard.  Body diagonal displacement errors are sensitive to all the volumetric error components and therefore make an efficient test of volumetric accuracy.  The Vector method*, developed by Optodyne, can measure all three displacement errors, three vertical straightness errors and three horizontal straightness errors with just four setups.  So a three-axis machine tool with a one-meter cube volume can be checked in about two hours.  In the past, volumetric compensation required up to two days.

            With MCV-500 laser calibration equipment and SD-500 Vector measurement system, economical systems made by Optodyne, data can be collected for all these volumetric errors (3 linear, 6 straightness and 3 squareness) in about 2 hours (1-meter volume).

            The SD-500 Vector measurement system, also known as the sequential step diagonal system can be used to calibrate CNC machine tools, CMMs and other precision measuring machines and stages.  The SD 500 allows the operator to perform volumetric calibration tests for true volumetric compensation. The Vector measurement system provides a rapid and efficient way of measuring a machine's volumetric accuracy along a diagonal path through the work envelope of the machine. The software is easy to use and runs on Windows compatible PCs with an RS-232 interface.  The software enables the operator to collect and analyze data, generating information on linear errors, straightness errors, both vertical and horizontal, and squareness errors.  Data can be displayed on the screen of the computer or printed in tabular and graphic format. The software also generates axis specific files that can be used to generate volumetric compensation tables.

Optodyne, a California corporation, develops, manufactures and markets laser-based precision measurement equipment for machine tool calibration, metrology, OEM, and other industrial applications that require precision measurement.  The company's products are based on the patented Laser Doppler Displacement Meter (LDDM) technology developed by Dr. Charles Wang, Optodyne's president.