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Keith Winter
03-22-2016, 5:41 PM
Hi Guys,

What would you guys estimate the real power loss you get from changing lens size from 2" to 3"?
1) Power loss for cutting
2) Power loss for engraving

Scott Shepherd
03-22-2016, 6:20 PM
1) None
2) None

:p

I don't see any differences when changing lenses. I use the same settings.

Gary Hair
03-22-2016, 6:55 PM
If you were right on the edge of the necessary power for a 2" lens you might have to adjust, but I doubt you would see much difference between the two. The only difference I see between my 1.5" and a 2.5" is in the quality of the mark - 1.5" is much sharper and crisper, especially on anodized aluminum.

Keith Winter
03-22-2016, 7:25 PM
Thank you!

Dan Hintz
03-23-2016, 6:14 AM
Power density drops about 25%, give or take, but that may have no real effect on what you're doing.

John Noell
03-23-2016, 1:40 PM
Can you expand on that Dan?

Gary Hair
03-23-2016, 2:19 PM
Can you expand on that Dan?

I'm not Dan, but I'll give my version of the answer...

When you increase the spot size you are spreading the same amount of power over a larger area so the density of the power will decrease.

John Noell
03-23-2016, 6:02 PM
Thanks Gary. I thought maybe he was headed in another direction. If the area of the spot is still small enough (i.e., within the depth of field), you may well not notice any difference (e.g., when cutting coconut shell with a 3" versus 1.5" lens). I don't. :) (However, the longer FL lens lets me cut really curved surfaces instead of leaving wide burns that don't go all the way thru in the parts at the top or bottom of the curve.)

Kev Williams
03-23-2016, 8:46 PM
Awhile back I did a cutting test on my 80w Triumph just to see what would happen, and got the opposite results I was expecting-

With the 2" lens, going very slowly I could get thru a 1" thick piece of cherry in one pass...

But with the 3" lens I couldn't get all the way thru it at all. Going slower and/or more passes just made for more charcoal.

I figured the 3" lens would get thru it better due to the longer focus range, but it seems the increased focus couldn't overcome the power density loss...

Dan Hintz
03-24-2016, 9:10 AM
When you increase the spot size you are spreading the same amount of power over a larger area so the density of the power will decrease.

This ^^^^^. A 2" FL lens has about a 5mil spot size. Moving to a 3" FL lens gives a spot size of around 7-8mils, so your power density drops off quite a bit.

As mentioned earlier, with engraving the larger spot size leads to a less sharp image. With cutting, it can go either way; the reduced power density could mean you are no longer able to vaporize the material, or the increased waist length could mean you can cut through thicker materials.

Whether or not this has a noticeable effect on your final product is a personal call.