Synrad Novanta OEM ti Series, User Manual

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CONTROLLING LASER POWER PAGE | 40
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 being processed.
Optics are fragile and must be handled carefully, preferably by the mounting ring only. Be careful to
select optics that are thick enough to withstand the maximum assist gas pressure available for the
process. This is especially important in metal cutting applications using high-pressure assist gases.
Cleanliness is another important issue affecting performance and becomes increasingly important as
laser power increases. Dirty or scratched lenses will underperform, exhibit a vastly shortened lifetime,
and may fail catastrophically.
When the application requires air (instead of nitrogen) as an assist 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 com-pressed shop air is the only choice
available, it must be filtered and dried to ISO 8573-1:2010 Class 1, 2, 1 specification shown in the table
below.
Assist Gas Specifications
Table 4-1 Assist gas purity specifications.