3D Finger Joints For Your Laser Cutter

A laser cutter is an incredibly useful tool and they are often found in maker spaces all over. They’re quite good at creating large two-dimensional objects and by cutting multiple flat shapes that connect together you can assemble a three-dimensional object. This is easier when creating something like a box with regular 90-degree angles but quickly becomes quite tricky when you are trying to construct any sort of irregular surface. [Tuomas Lukka] set out to create a dollhouse for his daughter using the laser cutter at his local hackerspace and the idea of creating all the joints manually was discouraging.

The solution that he landed on was writing a python script called Plycutter that can take in an STL file and output a series of DXF files needed by the cutter. It does the hard work of deciding how to cut out all those oddball joints.

At its core, the system is just a 3D slicer like you’d find for a 3D printer, but not all the slices are horizontal. Things get tricky if more than two pieces meet. [Tuomas] ran into a few issues along the way with floating-point round-off and after a few rewrites, he had a fantastic system that reliably produced great results. The dollhouse was constructed much to his daughter’s delight.

All the code for Plycutter is on GitHub. We’ve seen a similar technique that adds slots, finger-joints, and t-slots to boxes, but Plycutter really offers some unique capabilities.

3 thoughts on “3D Finger Joints For Your Laser Cutter

  1. Making castellated edges a part of the main piece is the wrong way to do this.

    A better way is to make the edge straight, so that the laser first cuts the edge straight, and add extra boxes or other cutout features as separate cuts to make the cutout features.

    If the castellated feature is the wrong size for whatever reason – for example, because your material isn’t the same thickness so the tabs don’t fit in the holes – it’s easy to hand-edit only the cutout features to make adjustments. Resizing the *entire* piece generally won’t work in these situations.

    I see a lot of projects using castellated edges or tab-and-slot assembly that can’t be adjusted in any reasonable way, and when cut either come out impossible to assemble or extremely loose in their assembly.

    Make the edges from separate cut-paths (separate from the main body of the piece) for easy adjustment.

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