On Process Mills:
Conventional methods of roll alignment usually use floor benchmarks (monuments) at the side of the machine as references. The L-742 andL-732 offer the versatility of using the benchmarks or of picking up a reference roll, such as a cooch roll on paper mills. However, we strongly believe that using a reference roll provides a more accurate reference and results in better alignments.
Benchmarks are usually set in a thin concrete floor, are rarely covered, and are routinely run over and nicked. More importantly, they move with their slab of concrete and rarely hold their position relative to the mill itself. Most floors in a typical plant have multiple slabs and are usually cracked throughout, creating instability of the monuments. Unless checked every time they are used, the use of the benchmark probably will result in significant alignment errors.
On Machine Tools:
When using any laser system, or any other alignment method, it is very important to be very careful with the selection of reference points. Keep in mind that the alignments will only be as good as the reference points. Choose poor reference points, like on the heavily worn portion of a machine's bed where all the work is performed, and it may take extra time bringing the machine back into tolerance. In other words, it could be the reference points that need alignment not the rest of the axis.
In metrology, it is recommended that some sort of data analysis be performed on a machine's axis before proceeding to the alignment stage. This step may save countless hours aligning a machine tool that only has a couple of bad points. Typically, a least-squares, best-fit algorithm is applied to a set of data for an individual axis. This algorithm calculates a line or a plane that best fits the data and will quickly show any bad data points. The data can also be adjusted so the alignment for each point would bring it parallel to the best-fit line or plane.