Not sure if this belongs here, but is it possible to adjust any parameter in LB to create a finer beam for cutting? I am using a 2" lens on my Thunder Nova 63. I am working with interlocking parts, and the initial cut burns away more of the material than I would like so that when I go to join together, there is some additional play. I understand Kerfing and the adjustments made there. Again I am trying to adjust the beam size to create a finer beam size so as to lessen the gap. Hope this is clear. Thanks in advance.
Changing the beam shape/size is a mechanical / physical task. Nothing that LightBurn can do anything about (besides moving the z-axis maybe). Kerf setting is the software way to tackle the problem, the rest would be hardware changes.
Thank you for the quick reply. Any thoughts on changing the mechanical / physical nature of the beam on how that might be accomplished?
The beam size is a physical property of the laser tube and the optics, so it’s not a configurable thing.
If you haven’t yet run a Material Test on the same material, that will help select the best combination of speed & power.
Depending on the material, a different focal length lens may produce better results, although the results won’t be night-and-day different and certainly depend on picking the proper speed & power combination.
For really precise fits, you must cut adjacent parts separately:
Which means you will get plenty of scrap, but that’s the result of optimizing for a precise fit rather than minimum material use.
The only way to achieve a smaller dot, is a shorter lens and/or the addition of a beam expander in your machine.
The downfall with a shorter lens, is that the depth of focus is smaller, so short lenses are not used in cutting operations.
What you are asking for seems mutually exclusive to me…
People make this interlocking stuff all the time, including me. They can be so tight you can’t get them together.
I think the issue is more of what are you are doing and with what? If you clarify what you are attempting that you need a smaller kerf it would help us help you.
People make very tight joints with thick saw blades…
What are you are doing that is different from the rest of us…?
And how did you come up with your machines kerf?
I wonder if your laser is focused?, … you should have a beam spot of approx. 0.07 mm, depending on the quality of your machine and whether everything is clean and precisely set.
Also be aware that you cannot expect the parts you cut out afterwards to fit tightly in the original part. This is what @ednisley describes and refers to.
I think 0.070mm spot size is very optimistic…
This indicates, with a 7mm beam, the spot size is, at best, 0.098mm (98um).
IMHO, if you can manage a 0.10mm spot out of a 2" lens, I think you are doing very well.
I’ve never seen a laser that produces a beam quality of 1, however, I don’t have deep pockets. My fiber is 1.4
Ok, so we say 0.1mm…
If I use 0.075 as kerf compensation and get a nice tight fit, how much material has my laser removed - roughly calculated?
It’s a bit academic and it doesn’t really mean anything either.
I just wanted to make sure @epiclaser has his focus under control.
Thank you for that explanation. I appreciate you, and all of the others taking the time to walk me through this.
Particularly given the cut isn’t a rectangle with parallel side walls.
Even in chipboard, the kerf taper makes the pieces fit properly in only one orientation; putting the other face upward means they don’t fit at all.
Aaaaand the direction of the taper depends on the material, focus level, speed, and probably moon phase.
So. Many. Variables.
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… I know and I haven’t taken into account the material thickness either.
But, we can agree that a normal, average Chinese CO2 laser has a laser beam of 0.1mm plus minus … 
Yes… that’s what I go with. 
I think the best choice is really a longer lens. I had hoped you would have responded with more information.
We are assuming a lot without knowing your actual materials or process… I think all of these answers can be valid depending on the actual use…
Good luck
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