Will Engraving Aluminum Damage Laser?

A question for all you knowledgable people: Will engraving aluminum damage the laser?

A friend of mine works an 8,000 watt industrial laser at his business. He says polished stainless steel, glass and mirrors won't harm a laser, but engraving (not cutting) aluminum will cause the beam to go back thru the modulator on his machine and burn it out. He says it's not a "physical" property of the aluminum, rather a "metallic" property. He's not sure if the same holds true for our kinds of lasers, but suggested that if I do engrave aluminum that I tilt one end up slightly so the beam doesn't go directly back thru the lens.

I don't believe our tabletop size lasers have modulators and anodized aluminum engravables are sold for our purpose. Does anyone have any opinion on this subject?

Hard to believe that the diffuse reflection from aluminum could cause any damage.

Maybe he has molten metal spalling up into the optics?

When "engraving" anodised aluminium, we are really only burning out the black or coloured dye from the oxide matrix on the surface of the metal. This is normally done at high speed and low power, since the oxide matrix is very efficient at absorbing the energy applied : this means that there is very little power reflected back into the optics. So no, it won't damage an engraving laser.

Your friend with the 8kW laser is probably talking about engraving into the metal (i.e. vapourising it) which is a whole different ball-park.

Joe,

The way those big lasers are set-up is the gas is flowing meaning that the source of the beam is right above the lens on those systems.

With these engraving systems they are considered flying optic systems.

We move the beam with mirrors

on the big boys the source is moving thus the difference and why he would not be able to do it and it would never have any effect on the small engravers.