This came out quite excellent. That’s 1.5" 2# crosslink PE foam.
I knew it would be able to cut it, but those walls are so much straighter than I would have thought.
The “normal” lens is a 2". The 4" has a deeper depth of focus, but there’s a tradeoff. The focal “point” is never actually a dimensionless point, it’s the waist where the beam’s diameter will be at its minimum, but it will still have a diameter. Due to optical diffraction rules, with everything else the same, a 4" lens will have twice the diameter at the focal point, reducing its energy density there by a factor of 4x.
It’s only where doing really deep channels in light material does this tradeoff work in your favor. I did some tests awhile back and it was worse than the 2" on cutting everything except foam. Actually I was still able to cut the 1.5" foam with the 2" lens, but I had to bring the work way too close to the nozzle, went at 20mm/s, and got a “good” cut. The 4" worked from a more normal distance,cut at about 30mm/s, and the cut quality was much better.
We’re working on how to handle swapping the tube to the 4" and back. Unfortunately the part sent to us has an issue with poor machining that I only got to work by adjusting the other optics and adjust back when done.
I do hope we can get this smooth enough that we can train members to swap the tube in and out. Obviously this would require the swap to be simple with no optics adjustments.