Simply put, a joint is any structure that joins two pieces together. In 3D printing, designing joints in your model is a great way to connect parts and allow movement. This all happens without the use of glue or screws, making your design super efficient!
3D printed joints come in handy in all sorts of situations. If you’re designing a 3D printed object with moving parts, such as a treasure chest or a truck with wheels, chances are you’ll need some kind of joint to bring everything together.
But what types of joints are out there? How should you design one? What’s the best way to print them? Read on to learn some useful tips about 3D printed joints.
At least in the context of 3D printing, there are two main types of joints: interlocking and snap-fit.
Interlocking joints are the simplest, relying on friction between parts to stay together, like a really tight puzzle piece. Interlocking joints also don’t usually allow movement, except maybe in one direction. One example is the modular hive drawers designed by O3D: each drawer is attached by an interlocking joint.
Snap-fit joints are joints that require the part to bend and “snap” into place. (Think: safety buckle.) This way, the two parts are locked together but are often free to rotate in some directions. Snap-fit joints come in many shapes and sizes. Here’s a breakdown of a few common snap-fit joints:
Joints are particularly useful in hinges. Interested to know more? You’re in luck: 3D Printed Hinge – Great Curated Models to 3D Print.
Any joint needs some space between parts in order for them to fit together. This space is called clearance. 0.3 mm is good for most 3D printers, though this can fluctuate between 0.2 and 0.6 mm.
For example, if you’re designing a ball-and-socket joint with a ball radius of 5.00 cm, the inner radius of the socket part should be at least 5.03 cm, even if they need to fit very tightly together.
This is definitely subject to trial and error: In some situations, you want very little clearance between parts (e.g. interlocking joints), but in others, you want a lot of clearance (e.g. wheels on a car).
To test the clearance of your design, try printing out only the parts around the joint. That way, you can adjust the fit of your joint without wasting filament printing out a whole part.
Joints must be solidly designed so that they don’t break under the strain before snapping together. They have to be able to take a bit of bend and flex without snapping apart.
A good way to do this is to add a fillet or chamfer. A fillet replaces a sharp edge with a rounded one, while a chamfer replaces it with a flat edge. Either way, these structures add extra stability to a joint so that it’s less likely to break at the edge.
Make sure your part is only under stress during connection, not in its final position. This reduces the strain a part experiences and the chance that it will snap over time.
Another thing to consider is joint length and thickness. A long and thin cantilever may be flexible but easy to break. On the other hand, a short and thick cantilever may be strong but too stiff for joints to fit together. When designing, it’s best to find the sweet spot between the two.
Once the joint is designed, it’s time to print! Here are some tips to keep in mind:
Interested in having the perfect joint 3D printed for you? Why not use a 3D printing service? With Craftcloud, All3DP’s 3D printing and price comparison service, you can find the best service for your needs. Take advantage of professional service as well as a wide selection of materials and finishes!
Feature image source: McGybeer / Thingiverse
License: The text of "3D Printed Joints – The Basics" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.
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