Distance between 3rd mirror and lens/es

Hey everyone,

I’ve been struggling to find an answer for this one and was hoping you could help.

Is there any optimal distance between the final mirror (3rd mirror) and the lens itself? I have just bought some new lenses (50.8mm and 38.1mm II-VI’s) and a short nozzle from cloudray and wanted to know.

Everyone talks about the distance between the actual lens and it’s focal length to the material you’re cutting but I’ve never read about the distance between the final mirror and the lens…

Does it make a difference??

As I see it no. It does not

Thanks for the response, I was really unsure :sweat_smile:

The only ‘critical’ distance, if you could call it that, is the distance from the lens to you nozzle tip.

The longer the focal length, the further your lens gets from the nozzle tip so that the cone of the beam passes through the small hole without portions of it bouncing off the inside.

An engraving set up has a larger tip hole and keeps the nozzle up around 20mm above the work.

A cutting set up has a much smaller hole and puts the nozzle tip down in the 5 - 10mm above the work range. It also has unrestricted air flow directly down into the cut for maximum clearing of the out gasses.

A nice explanation, as I explained I have bought a shorter nozzle for the shorter focal length lens I have now got.

Been stuck using whatever Lens came with my machine so will be nice to experiment and see what these new ones can do!

As long as you have the ability to move the lens up and away from the nozzle as you increase focal length, you should be good.

You won’t see much difference in the engraving for the shorter focal lengths. In fact, the 2.5" will be a bit more forgiving that the 1.5" because it has a more ‘usable’ beam path due to the narrower beam cone.

Many set ups will have the ability to put the lens right down on the back of the nozzle, and up in the base of the lens tube. The gives you either a 1.5" & 2" combo, of a 2" & 2.5" combo. Beyond that it’s parts and pieces time.

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