Positioning errors of a numerically controlled machine and a fixture are
related through a mathematical model to the statistical total error in the
position of the machine tool, and maximum allowable amounts are assigned
for each of the individual contributing factors to the total error. The
relationship between the machine and fixture is checked by a probe mounted
in the machine spindle. Functioning and alignment of the probe are checked
with the probe. Global positioning accuracy of the machine is checked
throughout a working envelope of the machine using a laser measuring
instrument. A master coordinate system relative to the ways of the machine
is created within the laser instrument by calculating a linear fit of
machine position coordinates acquired as the machine is moved along each
of two perpendicular axes of the machine, and the master coordinate system
is used for the global accuracy and fixture accuracy checks.
