Laser Calibration at the Speed of Light—Comparatively Speaking
High-speed data capture technique cuts calibration time 85 to 90%, minimizing downtime on key assets
The word “laser” implies “light speed” for the casual listener, but witnessing a bi-directional laser calibration run on just one linear axis of a CNC mill conjures up a completely different image of something less than light speed. A short 1-m axis can take 30 to 60 minutes as the machine axis moves in 10-mm increments and stops to pause and settle before the laser interferometer takes a reading. That pause can be as long as 23 seconds during some tests. The downtime it causes for calibration of a large, high-value asset can make a shop owner bite through nails. Depending on machine crashes and the quality system the shop adheres to, a machine may be out of action for several days each year to perform a laser calibration, so shop owners are always focused on this issue.
However, a technique that takes advantage of a feature in Renishaw’s XL80 laser interferometer reduces settling time to just 250 msec after each incremental axis move, cutting calibration times by 85-95 percent. In addition to reducing downtime on critical production assets, this methodology better reflects axis positioning accuracy under actual cutting conditions, where moves are fast and there is virtually no settling time before tool engagement with the work.