13D Volumetric Positioning Measurement and
Compensation of 3-axis
Machines Using Vector Technique O. Svoboda
and P. Bach Research
Center of Manufacturing Technology Czech Technical University in Prague, Czech
Republic And
Gianmarco Liotto and
Charles Wang Optodyne, Inc., Compton, CA 90220 Email: optodyne@aol.com Abstract The worldwide competition and quality
standards such as ISO 9000 and QS
9000, demanded tighter tolerance and
regular maintenance of all machine tools. Twenty years ago, the largest machine
tool positioning errors are lead screw
pitch error and thermal expansion error. Now, most of the above errors have
been reduced by linear encoder and compensation. The largest machine tool positioning errors
become squareness errors and straightness
errors. Hence, to achieve higher 3D volumetric positioning accuracy, all 3
displacement errors, 6 straightness errors
and 3 squareness errors have to be measured and compensated. Using a conventional laser
interferometer to measure these errors is rather difficult and costly. It usually takes days of
machine down time and experienced operator
to perform these measurements. Optodyne has
developed a new laser vector measurement technique for the measurement
of these errors in a few hours instead of a
few days. The measured errors can be used to generate 3D volumetric compensation
files to compensate the volumetric
positioning errors and
achieve higher volumetric positioning accuracy.
To determine the angular errors, 3 displacement measurements along the same axis
but at different Abbe offsets can be used.
Hence all 18 errors can be determined. Reported here are the
basic theory and operation, the hardware, the data collection and
analysis, and the test results. Using
the laser vector technique the volumetric positioning errors of 4 Deckel
Maho Gildemeister 3-axis milling
machines with Heidenhain controller have been measured. For each axis, the linear
displacement errors were also measured at 3
different locations. Data were collected with 5 bidirectional runs over 4
machines. The averaged linear
displacement errors at the center of working volume, the pitch and yaw angular errors, and their statistical deviations
can all be calculated. The agreement
between all different measurements was within the statistical deviation.
Presented in the IDW2004 ,
Nashville, TN, May 10-14, 2004
