joint

15 Articles

Small Print Bed? No Problem!

January 24, 2025 by 7 Comments

One of the major limitations of 3D printers is the size of the printable area. The robotic arm holding the printer head can only print where it can reach, after all. Some methods of reducing this constraint have been tried before, largely focusing on either larger printers or printer heads that are mobile in some way. Another approach to increasing the size of prints beyond the confined space typical of most consumer-grade 3D printers is to create some sort of joinery into the prints themselves so that larger things can be created. [Cal Bryant] is developing this jigsaw-based method which has allowed him to produce some truly massive prints.

Rather than making the joints by hand, [Cal]’s software will cut up a model into a certain number of parts when given the volume constraints of a specific 3D printer so it can not only easily print the parts, but also automatically add the jigsaw-like dovetail joints to each of the sections of the print. There were a few things that needed prototyping to get exactly right like the tolerance between each of the “teeth” of the joint, which [Cal] settled on 0.2 mm which allows for a strong glued joint, and there are were some software artifacts to take care of as well like overhanging sections of teeth around the edges of prints. But with those edge cases taken care of he has some working automation software that can print arbitrarily large objects.

[Cal] has used this to build a few speaker enclosures, replacing older MDF designs with 3D printed ones. He’s also built a full-size arcade cabinet which he points out was an excellent way to use up leftover filament. Another clever way we’ve seen of producing prints larger than the 3D printer is to remove the print bed entirely. This robotic 3D printer can move itself to a location and then print directly on its environment.

A pair of hands hold two dark brown boards perpendicular two each other on a light brown benchtop. There are two light brown oval dowels in the end of one board that then project toward holes in the opposite board. Circular holes in the oval dowels are visible perpendicular to the second board, and will match up with holes in the board once pressed in. A cylindrical dowel is laying next to the joint and will be placed into the circular holes once assembled.

Creating A Signature Wood Joint

December 1, 2024 by 25 Comments

We really love when makers make their construction techniques evident in an aesthetically-pleasing way, and [Laura Kampf] has created a clever joint that reveals how a piece is made.

[Kampf] is a big fan of using her domino joiner, which is similar to biscuits or dowel joinery, but she didn’t love how it hid the construction of the joint. She first figured out an “off label” use of the joiner by running it from the outside of the joint to show the exposed domino from one end.

Building on the concept to show an interesting contrast on both sides of the joint, she drilled a hole perpendicular the domino and placed a dowel through it, creating a locking joint. The choice looks great once a finish is applied to really accentuate the contrast, and another bonus is that if glue is only applied to the dowel and domino, it becomes trivial to separate the joint if needed by drilling out the dowel.

If you’d like to see some other interesting ways to join wood, how about this laser-cut wedge tenon, soda bottle heat shrink, or this collection of CNC joints.

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Emulating Biology For Robots With Rolling Contact Joints

May 17, 2024 by 9 Comments

Joints are an essential part in robotics, especially those that try to emulate the motion of (human) animals. Unlike the average automaton, animals are not outfitted with bearings and similar types of joints, but rather rely sometimes on ball joints and a lot on rolling contact joints (RCJs). These RCJs have the advantage of being part of the skeletal structure, making them ideal for compact and small joints. This is the conclusion that [Breaking Taps] came to as well while designing the legs for a bird-like automaton.

These RCJs do not just have the surfaces which contact each other while rotating, but also provide the constraints for how far a particular joint is allowed to move, both in the forward and backward directions as well as sideways. In the case of the biological version these contact surfaces are also coated with a constantly renewing surface to prevent direct bone-on-bone contact. The use of RCJs is rather common in robotics, with the humanoid DRACO 3 platform as detailed in a 2023 research article by [Seung Hyeon Bang] and colleagues in Frontiers in Robotics and AI.

The other aspect of RCJs is that they have to be restrained with a compliant mechanism. In the video [Breaking Taps] uses fishing line for this, but many more options are available. The ‘best option’ also depends on the usage and forces which the specific joint will be subjected to. For further reading on the kinematics in robotics and kin, we covered the book Exact Constraint: Machine Design Using Kinematic Principles by [Douglass L. Blanding] a while ago.

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Tricky 3D Printed Joinery Problem? Give Heat Staking A Try

February 3, 2024 by 15 Comments

When you just can’t 3D print something as a monolithic part, you’re going to have to join pieces together. In such cases, most of us instinctively include threaded inserts or nut slots in the design, or even reach for a tube of CA glue. But perhaps you should be thinking more along the lines of heat-staking your printed parts together.

Although you might not be familiar with the term, if you’ve looked inside anything made out of plastic, chances are good you’ve seen a heat-staked joint. As [Richard Sewell] explains, a heat-staked joint is nothing more than the classic mortise-and-tenon made from plastic where the tenon stands proud of the joint face so it can be softened with heat. The tenon spreads out so the joint can’t be pulled apart. A variant on the theme includes a mortise with a generous chamfer so the melted tenon can spread out, providing not only extra resistance to pull-out be also a more flush surface.

To melt the joint, [Richard] simply uses a soldering iron and a little pressure. To spread out both the heat and the force a bit, he uses the barrel of the iron rather than a tip, although we could see a broad chisel tip being used for smaller joints. Either way, a layer of Kapton tape helps keep the iron from getting gunked up with melted plastic. [Richard] lists a host of advantages for this kind of plastic joinery, including eliminating the need for additional hardware. But we think the best feature of this joint is that by avoiding monolithic prints, each aspect of a part can have its layer lines optimized.

While it probably isn’t applicable everywhere, heat-staking looks like a technique to keep in mind. We’d love to see [Stefan] over at CNC Kitchen do some of his testing magic on these joints, like he did for threaded inserts.

This Laser-Cut One-Piece Wedge Tenon Locks Wood Joints Tight

December 4, 2023 by 24 Comments

Woodworkers have always been very clever about making strong and attractive joints — think of the strength of a mortise and tenon, or the artistry of a well-made dovetail. These joints have been around for ages and can be executed with nothing more than chisels and a hand saw, plus a lot of practice, of course. But new tools bring new challenges and new opportunities in joinery, like this interesting “hammer joint” that can be made with a laser cutter.

This interesting joint comes to us from [Jiskar Schmitz], who designed it for quick, solid, joints without the need for glue or fasteners. It’s a variation on a wedged mortise and tenon joint, which strengthens the standard version of the joint by using a wedge to expand the tenon outward to make firm contact with the walls of the tenon.