The L-720 has a continuously rotating laser plane and simultaneous plumb laser beam. It measures flatness, straightness/parallelism and squareness using 1 and 4-axis targets. The laser plane is flat to 1/2 arc second in a 180º sweep and 1/4 arc second in a 90º sweep. The plumb laser beam is square to the plane to within 1 arc second. The L-720's tilt base includes 1 arc second level vials.

The L-720 can check a machine's bed for flatness in 2 ways: using the built-in levels or 3 reference points. If level is used as a reference, the laser is first placed on an instrument stand or on the machine itself and leveled in 2 axes. A single-axis target (A-1519, A-1520 or A-517) is placed on the machine and adjusted so it reads zero (.000" or .0000"). This is the only reference point on the machine's bed. The target is then moved to a desired point for measurement. If the point is lower than the reference point, the readout will show a negative reading. If higher, it will show a positive reading. If an error is found, the bed can then be aligned using the target as a digital indicator. The readings can also be automatically downloaded into our Plane 5 for analysis and reporting.

The other method for checking flatness is using reference points on the machine bed. First, 3 reference points are chosen. Next, 3 single-axis targets are all zeroed on one of the points and then spread out to the 3 reference points. Then, the laser tilt base is adjusted in pitch and roll until all 3 targets produce the same measurement. This means the laser is "bucked in" to the reference points and can be moved to other points on the machine bed for measurement.

Once the laser has been "bucked in," it is easy to measure squareness of the columns. Starting at the lowest or highest point on the column, the T-212 4-axis target is affixed to the column horizontally and zeroed out using the micrometers on the target stand (T-230). The column is then raised (or lowered) and any deviation, in either axis, from zero is a measure of the squareness. And since the measurements are live, the column can be aligned using the target as a digital indicator.

To measure straightness of a machining center's X or Y axis, the L-720 has to be mounted horizontally on a right-angle bracket. The laser plane is then "bucked in" to 2 reference points along the axis. The target can either be mounted on the side of a way or the side of the table. After "buck in", the target can be placed along any point on the axis and the deviation from the reference points will be measured. Again, with live data, the laser and targets can be used fix any straightness problems encountered.

In most cases, two setups are all that is required to properly check the geometry of typical machining center.

A word of caution: if the machine is going to be aligned, rather than just measured, then it is important to put the laser on an instrument stand. If the laser is on the machine bed or table, adjusting it will most likely mover the laser and thus affect the setup.