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Finger Joint Box

Ok last project post of the season:) - I never remember to post stuff anymore, usually because it’s out the door before I can grab a pic of it!

Nothing crazy here, finished this one up over the long holiday weekend.  I needed a box at work to house parts for an electric pneumatic valve.  This was my first go at something like this and since work was picking up the tab for the material and my time, figured it was a good way to do something new.  It was 3mm black acrylic and the back panel had brass threaded inserts installed so we can take the panel off if something inside needed to be fixed.  I can’t say I had fun running acrylic glue over all the joints inside and out, but it’s a strong little box and has made this week at work a whole lot easier! The pics are from the test fit before I glued it up and took off the paper.

I would like to run some tests to get the kerf value dialed in, the material was a little too tight. The laser cuts don’t form a square edge and the thicker the material, the worse it is.  Had to run a file over all the fingers, but in the end it’s still a nice way of doing things. It took a bit more than 3 hours to cut out and assembled is roughly 4x3x5".


5 comments

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Tom B

Looks great and nice to see more acrylic projects here on the forum

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Tom B

Why did you 45˚ the corners of that one side like a picture frame?

 

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Domenic

Nice one, Wayne.

You are correct that the laser beam isn't perfectly parallel. It's actually shaped like an hourglass, which means, depending on where along the beam you are, you may end up with slight variations in the kerf on the top and bottom of the cut.

We sometimes try to place the focus point in the exact centre of the material. This will mean you will get pretty close to even kerf on the top and bottom. But this only works up to material about 3mm thick.

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Wayne Bitting

 

@Tom - mitered the corners because I wasn't sure if I would be able to build the entire thing and keep everything square.  If the box was a little off I was worried I would break the back panel frame.  I ended up needing to hit one of the pieces with a bit of sandpaper.  What I should have done was lay out the artwork for those pieces to save material.  My hobby background is woodworking and its always best to end up with the biggest chunk of scrap at the end of the project in case you mess up!

@Domenic - with the beam shape being an hour glass what would you recommend for the laser kerf value for 3mm and 1mm thick material?

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Domenic

The kerf depends a lot on the material.

I would start with a kerf allowance of 0.1mm for both materials and work from there.

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