Proceedings of the Measurement Science
Conference, Los Angeles, LA January 24-25, 2002
1 A laser Non-contact Measurement of Static
Positioning and Dynamic Contouring Accuracy of a CNC Machine tool
Charles
Wang Optodyne, Inc.
1180 Mahalo Place
Compton, Ca 90220
and
Gianmarco Liotto
Optodyne
Europe Via Veneto,5
20044-Bernareggio (MI )
tel. 039 6093618
optodyne@attglobal.net Abstract For
accurate and fast machining, both the static volumetric positioning accuracy,
including the 3 displacement
errors, 6 straightness errors,
and 3 squareness errors,
and the dynamic contouring accuracy, including the
errors due to the servo mismatch,
servo lag, loop gain, acceleration and deceleration, are very important. Conventional
measurement techniques, such as laser
interferometers and telescoping ballbars, are complex, inefficient and time
consuming. Reported here
are a new laser vector measurement
technique for the measurement of the
volumetric positioning accuracy and a
laser/ballbar technique for the measurement of dynamic contouring accuracy. Measurements have
been performed on a JOBS-LINKS 5-axis
linear motor machine with the laser
vector technique. The volumetric positioning accuracy has been
improved by 300% with the volumetric
compensation. The basic theory, the hardware, the data collection and processing, and the measurement results are
described. I.
Introduction
In order to improve the
positioning accuracy of a machine tool it is important to measure the
volumetric errors, including the linear
displacement errors, the geometrical errors of straightness and squareness of all the 3 axes and the sag and deformation
errors. The check of dynamic behavior completes the information on the machine status.
With the new generation of CNC machines, it is possible to
obtain better performance machines even at
better prices using the software compensations providing that the errors are
repeatable and measurable.
In this paper a new laser vector
method for the measurement of the
volumetric positioning errors
of a machine tool or coordinate
measuring machine (CMM) is described. The laser vector method
measures the vector errors, which are the linear displacement errors,
the vertical straightness
errors, the horizontal straightness errors,
and squareness errors, instead of only the
linear displacement errors
measured by the conventional
laser interferometer.
It is also possible to measure the angular errors and the errors due
to the sag or non-rigid body. The
measured errors were used for the machine compensation to improve
the accuracy. The basic concepts, the
theory, the measurement errors, and the experimental verification are described. The
performance or the accuracy
of a CNC machine
tool is determined by the linear
displacement error, the straightness error,
the angular error and the elastic error. A complete measurement of those errors is
very complex and time consuming, for
those reasons the Please click
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