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.

Behold A DIY, Kid-Friendly Table Saw

The “table saw” swaps the saw for a nibbler; here it is cutting corrugated cardboard in a manner much like the saw it replaces.

“Kid-friendly table saw” seems like either a contradiction, a fool’s errand, or a lawsuit waiting to happen; but this wooden table saw for kids actually fits the bill and shows off some incredible workmanship and attention to detail as well. The project works by using not a saw blade, but a nibbler attached to a power drill embedded inside.

Unsurprisingly, the key to making a “table saw” more kid-friendly was to remove the saw part. The nibbler will cut just about any material thinner than 3 mm, and it’s impossible for a child’s finger to fit inside it. The tool is still intended for supervised use, of course, but the best defense is defense in depth.

The workmanship on the child-sized “table saw” is beautiful, with even the cutting fence and power switch replicated. It may not contain a saw, but it works in a manner much like the real thing. The cutting action itself is done by an economical nibbler attachment, which is a small tool with a slot into which material is inserted. Inside the slot, a notched bar moves up and down, taking a small bite of any material with every stroke. Embedding this into the table allows for saw-like cutting of materials such as cardboard and thin wood.

The image gallery is embedded below and shows plenty of details about the build process and design, along with some super happy looking kids.

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Robotic Table Saw Automates Finger Joints

We’ve all seen finger joints or box joints, those interlocking puzzle pieces that make laser-cut plywood enclosures such a fixture for DIY projects. But laser cutters make finger joints look much easier to fabricate than they are with traditional woodworking tools, which often lead to disappointing results.

But this finger joint cutting robot is no traditional woodworking tool, and [timschefter] put a lot of work into building the rig. We have to admit that when we first saw the video below, the thought of having a table saw in our shop that could be turned on with a button on a phone gave us pause. But on closer analysis, it looks like safety was a major concern with this build. With a prominent e-stop and an interlock switch, the small table saw that forms the foundation of the robot should be safe enough. On the table top is a sled with a linear slide that moves the workpiece perpendicular to the blade, and the sled moves back and forth over the blade with pneumatic cylinders. The joint is set up with a custom app which calculates the pin width and spacing, which can be evenly distributed across the panel, or, for a bit of geeky fun, controlled to make a joint that encodes a message in Morse.

A lot of work went into this, and while it’s not the first robotic finger joint cutter we’ve seen, it’s pretty impressive. Now if it could only automate dovetails.

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