Which lens for wood?

[Tom Evans Milw]

I just purchased a used Trotec Speedy 300. It has a 1 1/2" focal point lens. I know that this works on the wood just fine, but should i plan on purchasing a longer focal point lens. I will using the laser to do everything from wood to engraving on Stainless with Cermark. My only experience is with a Vytek with the 4" lens.

One other note, Thank you all for all the advice you give fellow engravers. I love this site.

Regards,

[Chuck Stone]

a 1.5" lens should give you good, sharp engraving with fine detail. The 'down side' is that
the depth of field is less than the 4" lens you're used to. So that means you can't cut
through as thick a material and stay in focus. The 1.5" lens concentrates the beam more
than the 4" lens did, so your images should be nice and sharp and a bit higher power
density at the focal plane. I wouldn't be unhappy with that lens!

[Tom Evans Milw]

Thank you for info. I think the thickest i would cut is the 3mm birch. I like the idea of sharper images.

[Richard Rumancik]

Tom, you might be able to cut the 3mm birch with the 1.5" lens to your satisfaction but most people would probably use a 2" lens. The 1.5" lens will give a narrower kerf but it is most often used for engraving and marking. If you can achieve the speed and quality with the 1.5" there is no harm in using it.

The 1.5" lens will probably give you a .003" diameter beam and the 2" in the neighbourhood of .005" diameter.

But a 2" lens is considered more "general purpose". It will be more tolerant if your material is not 100% flat. In fact a lot of members here don't have/use a 1.5" and think that the engraving quality with a 2" is fine. I use my 1.5" quite a lot as I find I can get more precise parts/marking, but many people do without.

I have only used a 4" when cutting thick foam (1.0") due to increased depth of field. Personally I would not even try using the 4" lens for cutting wood as the beam diameter will be much larger (I don't know the diameter offhand.)

[Tom Evans Milw]

Richard, thank for the details. I ran a batch last night. The 1.5 cuts fine in one pass. I still think I will pick the other lenses up eventually. I am absolutely in love with my laser. The difference compared to what I was using before is unbelievable.
Regards,