16
Measuring Flatness
To measure flatness, a horizontal, continuously rotating laser plane is “bucked in” or adjusted so that it is
parallel to three reference points on a table, set of ways, or a surface.
1.
Place all the targets on one reference point and adjust them up or down so they detect the laser
plane.
2.
Zero the targets.
3.
Reposition the targets so that one target sits on each reference point.
4.
Using the PITCH and ROLL adjustments, adjust the laser scan plane until all three targets
produce the same value or zero, thus making the laser parallel to the reference points.
This may also be accomplished by using one target, zeroed on the closest reference point to the laser,
and moving it back and forth from the reference points until it produces a reading of zero at all three
points.
5.
Move the target to user-specified points on the surface.
The resulting reading is a measure of the deviation from the reference point, helping to produce a
flatness profile. The measurement will show either a plus (+) or a minus (-) sign. A plus reading
indicates that the target is
higher
than the reference points and a minus reading means the target is
lower
than the reference points.
Measuring Squareness
After bucking in the laser to the five reference points described in
Measuring Straightness and Measuring Flatness, (to determine the
straightness and flatness of the machine's axes) measuring
squareness is a simple process. To
truly
measure squareness, one
must compare the least-squares, best-fit line of the one axis to the
other axis. If this is not done, bad reference points or severely worn
ways might produce what looks like a squareness error, but in fact
is not. To facilitate this type of analysis, our software programs may
be used to automatically calculate the best-fit line.
To measure Y-to-Z squareness:
1.
Lower the column/spindle to its lowest Z position and
position a target horizontally to pick up the vertical laser
plane that is perpendicular to the X-axis (parallel to the
Y-axis).
2.
Zero the target and traverse (raise) the column along its axis.
The data produces a measurement of both the straightness of the Z-axis and the squareness of the Y-
axis to the Z-axis.
To measure Z-to-X squareness:
1.
Position and zero the target to detect the vertical laser plane that is parallel to the X-axis.
2.
Traverse the column upward.
The resulting data is a measure of the Z flatness and Z-to-X squareness.
To measure X-to-Y squareness:
1.
Position and zero the target to detect the vertical laser plane that is parallel to the X-axis.
2.
Traverse the table or column (whichever is moveable) along the Y-axis.
The result is a measure of both Y straightness and X-to-Y squareness.
Figure 11 –
The X, Y and Z Axes
