Using With Powerful Lasers - Lasermet LS-200 Instruction Manual

LS-200 Instruction Manual
6

Using with Powerful Lasers

If the blade or beam dump become overheated, they will be permanently damaged. Moreover, once
damage has started to occur the situation is likely to deteriorate further unless immediate action is
taken to turn off the laser.
Modern lasers which cut or burn are now readily available. With regard to the shutter blade, it is
essential that it absorbs insufficient energy for it to be damaged, which means that the excess must
be reflected away towards the beam dump.
At 20°C ambient the standard stainless steel blade can dissipate about 5W. The copper blade option
can dissipate no more than about 2.5W.
Glass mirror options can dissipate less because they are not such good conductors.
Heating of metal or metal-surfaced glass blades is likely initially to cause oxidisation which darkens
the metal causing it to absorb and heat more.
Furthermore, there may be localised damage if the laser has a high power density, i.e. the beam is
concentrated in a small diameter. For metal blades this appears as ablation, in which the area where
the beam impinges reaches the melting point of the metal before conduction can carry the heat
away. For glass mirror blades the localised heating expands the glass causing it to crack.
In all cases once the point of contact of the laser beam ceases to reflect as well, it will heat and fail. If
the laser is left running when this happens, the shutter will be progressively damaged and burn-
through of the beam may occur. Once damage has occurred a 100W laser may burn through the
stainless steel blade. More powerful lasers will burn through quite quickly. Also, any optional blade
mirror that has been fitted will detach if it exceeds several hundred degrees Celsius.
Ultimately users must be aware of the hazards of operating powerful lasers and the suitability of any
shutter being used. Tests may need to be undertaken to establish the suitability of any shutter when
used with powerful lasers.
The blade should be checked before use to ensure that it is spotlessly clean, unoxidised and
unblemished. Appropriate optical cleaning methods may be required to clean the blade. It must be
understood that whilst a perfectly clean blade will successfully divert a beam, should a speck of
contamination at the surface occur rapid progressive failure and burn-through are possible. Risk
assessments should be undertaken to determine the effects of such an event and identify any
mitigation measures that may be necessary.
01297-53-000 Issue 4 19 January 2021
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