Proceedings of the
ICMT 2003 conference in Taipei, Taiwan, ROC, December 2-6, 2003.
axis of rotation and the
position coordinate is inside the parenthesis. 2.2 The laser vector measurement technique
In the
conventional body diagonaldisplacement measurement,
the target trajectory is a straight
line and it is possible to use the
corner cube as target [2,3]. The
new vector measurement method or Sequential Diagonal Measurement Method [4,5] differs from the
traditional
method because each axis
is moved separately
and the positioning error is collected after each single movement of the X axis, of the Y axis and
than of the Z axis, as shown in Fig. 1.
For this reason, 3 times more data is
collected and also the positioning error
due to each single
axis movement can be
separated. The collected data can be
processed as the projection of
the displacement of each single axis
along the diagonal. The 12 sets of
data can be used to determine the 3D
volumetric positioning errors. As shown in Fig. 1 the
laser is pointing in the positive diagonal
direction and the sequence is moving x-axis, stop, collecting data, moving y-axis,
stop, collecting data, moving
z-axis, stop, collecting data and continue until reached the other corner.
Here the laser beam direction and the moving direction are not the same,
hence it is not
possible to use a conventional laser
interferometer. A single
aperture laser with a flat-mirror as target is needed. 2.3Measurement results
Measurement has
been performed on a
5-axis horizontal
machining center with a working volume
of X from 0 to 650 mm, Y from 0 to 500 mm,
and Z from 0 to 500 mm. The measured
squareness is XY -3.9 arcsec,
YZ -7.88 arcsec and ZX -10.03 arcsec.
The measured
volumetric positioning errors
are shown in Fig.
2. Fig. 2a is the displacement
errors (top traces),
vertical straightness (middle traces) and
horizontal straightness (lower traces)
errors of X-axis. Fig. 2b is the
displacement errors (top traces), vertical straightness (middle
traces) and horizontal
straightness (lower traces) errors of
Y-axis. Fig. 2c is the
displacement errors (top
traces), vertical straightness (middle
traces) and horizontal
straightness (lower traces) errors of
Z-axis. It is noted that the maximum
straightness error is 24 µm which is much
larger than the maximum displacement error 6.5 µm. For many other measurement results see Ref.
[6]. Z (Xe, Ye, Ze)
PPP Diagonal
Dz Y Dy Dx (Xs, Ys, Zs)
X
Fig 1, The vector
measurement, laser is pointing in the ppp
diagonal direction and sequence is moving x-axis, stop, collect data, moving y-axis, stop,
collect data, moving z-axis, stop, collect
data and continue.Fig 2a, Measured volumetric positioning errors of
X-axis, top traces are displacement
errors, middle traces are vertical
straightness errors and lower traces are
horizontal straightness errors.Fig 2b, Measured
volumetric positioning errors of Y-axis, top traces are displacement errors,
middle traces are vertical straightness
errors and lower traces are horizontal
straightness errors.
