Using 1-Arc-Second Levels
L-730 Measuring the Flatness of a Frame
To level a surface, the laser is first put on an instrument stand or stable mounting surface and leveled in two axes. Next, a single-axis target (1532/1533 or A-1519-2.4ZB/1520-2.4ZB) is placed on 1 reference point and zeroed (done electronically by pressing a button on the target or readout).
The target is then moved to a measurement point on the surface, where it displays the deviation of that point from the reference point. If the display shows a "+" that means the measurement point is higher than the reference point, and conversely, if it displays a "-" then it means the point is low relative to the reference point.
If the measurement point happens to have an adjustment pad under it, it can then be adjusted, using the target and readout as a live digital indicator, until the display shows zero. The measurement point is then in the same level plane as the reference point.
The levels can be calibrated in the field using an easy 15-minute procedure and usually hold calibration for several months.
L-740 Measuring Surface Plate Flatness
Using Reference Points Instead of Level
To use reference points instead of levels, the laser is mounted as described above. Next, three reference points are chosen on the surface and the laser is "bucked in" (or made parallel) to these points, using 1, 2 or 3 single-axis targets. Finally, the targets are moved to other points on the surface and deviations from the reference points are measured and displayed on the readout.
Using Plane5 Flatness Software
Our Plane 5 software can be used with the L-730/L-740 to quickly download flatness data for analysis and reporting. In fact, if the user is simply taking data, Plane5 employs a least-squares, best-fit algorithm to eliminate any slope errors in the data from the laser not being parallel to the surface. What this means is that you do not have to buck the laser into reference points to check the flatness, which saves about 10 minutes of setup time.
It works like this: First, the laser is placed on the surface and roughly leveled. This gets the laser plane approximately parallel to the surface. Next the target is set up on one point and zeroed. Then the grid pattern is laid out in Plane5 and on the surface itself. For repeatability, it is important to mark the data points on the surface.
Finally, the target is moved along the surface and when at each data point, the space bar is pressed and the point is recorded. The software can be programmed to average up to 25 readings per data point to remove and remaining noise in the system. Typically average of 5 to 10 readings is good enough even for the highest grade of surface plates. Once all the points have been take, the software automatically calculates the flatness data and it can be reviewed in the report section of the software.
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 same machine bed or table that is to be aligned, adjusting it will most likely move the laser and thus affect the setup.