Novanta v40, User Manual

Page: 49 / 104

OPTICAL SETUP PAGE | 49
Optical setup
After selecting a laser for a CO2 laser processing system, the two most important elements to consider
are:
1 Delivery optics to transmit the beam to the work area; and (2) focusing optics to focus the beam
onto the part or material to be processed. Each element is crucial in the development of a reliable
laser-based material processing system and each element should be approached with the same
careful attention to detail.
Delivery optics
Divergence, or expansion, of the laser beam is important for materials processing since a larger beam
entering the focusing optic produces a smaller focused spot. Because the laser beam diverges slowly,
increasing by four diameters over one meter, this means that for optimum performance the laser should
be mounted a distance of 40–60 inches (1.0–1.5 meters) away from the work area and no closer than 30
inches (0.75 meters). Right angle turning mirrors are often used in conjunction with the laser mounting
position to obtain this distance. Following figure shows how right-angle turning mirrors in a “flying
optics” setup create this longer beam path.
Expander/collimators are optical devices that reduce beam divergence while at the same time increasing
beam diameter by a selectable magnification factor. Adding an expander/collimator to the “flying optics”
setup shown above would substantially reduce beam divergence and any variance in beam diameter
caused by the changing optical path length. In fixed-length delivery systems where the laser is
positioned only one meter away from the focusing optic and a small spot size is required, an
expander/collimator is again the best solution to provide the required beam expansion before reaching
the focusing optic.
Figure 4-2 “Flying optics” beam path
Focusing optics
When selecting a focusing optic, the primary consideration should be material thickness and any vertical
tolerances that occur during final part positioning rather than making a selection based only on minimum
spot size. The chosen focal length should create the smallest possible focused spot while providing the
depth of field required for the material to be processed.