Cant get the settings correct for this box, looking for some help

Hi all, we love this box and have made a good amount that worked out great. Problem is it seems every other one we cut out doesnt fit together properly(photo examples below) and I cant figure out what to change in the file settings. I’ve played with a bunch of the settings but not everything as im kind of just blindly making changes, printing a whole box, checking if it fits and then trying again.

Im hoping someone with a better understanding of the different settings could help me figure this out with me.

The photos here show that after its assembles, the lid is off centers, it wants to sit left and I cant figure out what to change. The one photo also shows the sizing of the finger joints seem to be off from the wood thickness.

Thank you so much in advance! I really want to figure this out and learn what im missing so I can keep making new things.

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burn

The burn correction aka kerf is the distance the laser has to keep from the edge of the parts. If the laser would cut right on the edge it would cut away the outside perimeter of the part. So the burn value is basically the radius of the laser - or half the width of the laser cut.

The value of the burn parameter depends on your laser cutter, the material cut and the thickness of the material. In addition it depends on whether you want the parts to be over or under sized. Materials that are spongy like wood can be cut oversized (larger burn value) so they can be press fitted with some force and may be assembled without glue. Brittle materials (like Acrylic) need to be cut undersized to leave a gap for the glue.

Note: The way the burn param works is a bit counter intuitive. Bigger burn values make a tighter fit. Smaller values make a looser fit.

Small changes in the burn param can make a notable difference. Typical steps for adjustment are 0.01 or even 0.005mm to choose between different amounts of force needed to press plywood together.

To find the right burn value cut out a rectangle and then measure how much smaller it is than its nominal size. The burn value should be around half of the difference. To test the fit for several values at once you can use the BurnTest generator in the “Parts and Samples” section.

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After looking at the photo closer. You should measure your material and double check that it is 3.5mm as you have in the settings.

Get some digital calipers, anyone laser cutting fitted pieces needs one.

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This was all really great info for me, thank you so much for taking the time! Im going to head to the forge and start testing tonight, really excited to find a balance that works the best. I think part of my struggles is I would come up with some settings that worked for a specific sheet of wood and assumed it would be good for others. Maybe with such a small joint size, I really need to be accurate as far as 3.4 or 3.5, that little bit seems like it would make a difference no after reading what you posted.

Thank you again, ill come back to share how it goes

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Good luck. Boxes are a lot of fun.

I have had wood vary from sheet to sheet. I have been bitten before with trying to get the fingers to fit.

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Are you using a living hindge or a metal one or is it friction fit?

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The box the OP linked to has an integrated hinge. I made the from festi before, they should fit.

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Ah yeah, I’ve had issues with them being crooked too actually

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Exactly this, those tiny differences add up.

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