technical reference
38
Synrad
Series 48Series 48
Series 48Series 48
Series 48 operator’s manual
Table 3-1 Gas purity specifications
Purge Gas Specification
Nitrogen High Purity Grade 99.9500% purity or better
Air Breathing Grade 99.9996% purity or better
Air Compressed 99.9950% purity or better, water-free; oil filtered to 5 mg/m
3
or better; particulate filtered to < 1.0 micron; dried to lower
dew point below coolant temperature setpoint
Technical overview
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.
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 mini-
mum 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.
Optics are fragile and must be handled carefully, preferably by the mounting ring only. Cleanliness is
another important issue affecting performance; a dirty or scratched lens will underperform and exhibit a
vastly shortened lifetime. When the application requires air (instead of nitrogen) as a purge gas, use only
breathing quality air available in cylinders from a welding supply company. Compressed shop air contains
minute particles of oil and other contaminants that will damage optical surfaces. If compressed shop air is
the only choice available, it must be filtered and dried to the specifications shown in Table 3-1.
Caution
possible
equipment
damage
Small amounts of contaminants on the laser’s output window (or on
any optic in the beam path) can absorb enough energy to damage
the optic. Inspect all beam delivery optics periodically for signs of
contaminants and carefully clean as required. In dirty environments,
purge laser optics using filtered air or nitrogen to prevent vapor and
debris from accumulating on optical surfaces.
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