Kerf Offset Unsuccessful

I am unable to get kerf offset to work on the attached file. Is this an Open Shapes issue? When I click on a non-selected area and then Edit/Select Open Shapes, all four puzzle pieces get selected so I’m assuming that LightBurn sees these as an open shape?
PuzzleKerfTest.lbrn2 (16.3 KB)

Thanks in advance.

To apply the kerf it must be a closed object so Lightburn can determine the offset.

It looks like you have a single line between the parts? Where do you expect to ‘put’ the kerf?

The problem here is that if you want a puzzle piece cut like this the clearance between the parts will be the thickness of the laser beam. So they will be difficult to use.

Generally what I’ve found is that you have to break apart the pieces and cut them separately. There are a few people here that have made these. Give them a few and maybe you’ll get a better solution to your issue.

‘ungroup’ them, select all, then join selected shapes. Click to deselect everything, then apply the select open shapes. You will see the outline is closed, but not the internal parts.

I’ve seen these cut, maybe de focus to get a larger beam… But the kerf angle isn’t much use in this instance.

ctrl-Z ‘undoes’ what you’re last edit, there is actually a ‘queue’ of previous edit command…

Good luck


There is not much to add to what @Jack writes. None of your four puzzle pieces are closed, in fact they all share lines with each other.
When separated and closed, it is possible to assign kerf to the items. If you choose it, the parts, which Jack also correctly writes, must be cut separately.
But, I have made some simple puzzles in 3 and 4mm MDF and BB plywood, without any kerf and with a precisely focused laser, it worked amazingly well.

Pictured is your puzzle, separated, the parts are joined together and with a 0.25 mm notch. (just to demonstrate it)

PuzzleKerfTestretur.lbrn2 (8.6 KB)

Thanks to you both for the suggestions.

as an aside, this is some interesting reading from someone that makes puzzles commercially: the secret to clean laser cutting: Designing a better laser nozzle using 3D-printing – Nervous System blog

That is fascinating. I will try printing one out of PLA or PETG and, if successful, I will print one from something more durable like carbon fiber.

Thank you very much for the link!
I will keep you updated.

I could never get it to print correctly… and it was a different thread than my machines lens tube…


What kind of printing issues were you having? It seems to print OK for me. It would take some significant redesign to fit my laser’s lens tube so I’m looking at trimming it down to create an insert for one of my existing nozzles.

I use either an online puzzle generator of an extension in Inkscape to make mat board backed puzzle printed on my inkjet. These puzzles are created using a shared cut line system. My puzzles seem to work fine without any offset needed.
EDIT: I use a 1.5 inch lens.

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