compliant mechanism

20 Articles

The Challenges Of 3D Printing Reliable Springs

April 27, 2026 by 19 Comments

Springs are great, but making them out of plastic tends to come with some downsides, for fairly obvious reasons. Creating a compliant mechanism that can be 3D printed and yet which doesn’t permanently deform or wear out after a few uses is therefore a bit of a struggle. The compliant toggle mechanism that [neotoy] designed is said to have addressed those issues, with the model available on Printables for anyone to give a shake.

The model in question is a toggle, which is the commonly seen plastic or metal device that clamps down on e.g. rope or cord and requires you to push on it to have it release said clamping force. Normally these use a metal spring inside, but this version is fully 3D printable and thus forms a practical way to test this particular compliant mechanism with a variety of materials.

The internal spring is a printed spiral spring, with the example in the video printed in PETG. You can of course also print it in other materials for different durability and springiness properties. As noted in the video, PLA makes for a very poor spring material, so you probably want to skip that one.

We covered compliant mechanisms in the past for purposes like blasters, including some that you can only see under a microscope.

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3D printed Origami mechanism

Origami On Another Level With 3D Printing

December 21, 2025 by 12 Comments

Origami has become known as a miracle technique for designers. Elegant compliant mechanisms can leverage the material properties of a single geometry in ways that are sometimes stronger than those of more complicated designs. However, we don’t generally see origami used directly in 3D printed parts. [matthew lim] decided to explore this uncharted realm with various clever designs. You can check out the video below.

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A human hand is shown in the bottom right corner of the picture, holding one end of a pencil. A white, segmented, mechanical tentacle extends from the bottom left corner of the image and wraps around the other end of the pencil.

3D Printed Cable-Driven Mechanisms – Some Strings Attached

May 3, 2025 by 10 Comments

One of the most basic problems with robotic arms and similar systems is keeping the weight down, as more weight requires a more rigid frame and stronger actuators. Cable-driven systems are a classic solution, and a team of researchers from MIT and Zhejiang University recently shared some techniques for designing fully 3D printed cable-driven mechanisms.

The researchers developed a set of four primitive motion components: a bending component, a coil, screw-like, and a compressive component. These components can work together in series or parallel to make much more complicated structures. To demonstrate, the researchers designed a gripping tentacle, a bird’s claw, and a lizard-like walking robot, but much more complicated structures are certainly possible. Additionally, since the cable itself is printed, it can have extra features, such as a one-way ratcheting mechanism or bumps for haptic feedback.

These printed cables are the most novel aspect of the project, and required significant fine-tuning to work properly. To have an advantage over manually-assembled cable-driven systems, they needed to be print-in-place. This required special printer settings to avoid delamination between layers of the cable, cables sticking to other components, or cables getting stuck in the mechanism’s joints. After some experiments, the researchers found that nylon filament gives the best balance between cable strength and flexibility, while not adhering tightly to the PLA structure.

We’ve seen cable-driven systems here a few times before. If you’re interested in a deeper dive, we’ve covered that too.

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3D Printed Blaster Does It With Compliant Components

December 17, 2024 by 20 Comments

The ease of integrating bendy parts into designs is one of 3D printing’s strengths. A great example of this is [uhltimate]’s six-shot blaster which integrates several compliant mechanisms. The main blaster even prints in one piece, so there’s not even any assembly required.

The ergonomics are unconventional, but the design is pretty clever.

The blaster itself has three main parts: the trigger, the sear, and the striker. Each of them rely on compliant mechanisms in order to function. The user pulls back the trigger, which hooks into and pulls back the striker. When the trigger is pulled back far enough, the sear releases the striker. This zips forward and slams into a waiting projectile, sending it flying.

The other interesting part is the projectiles and magazine in which they sit. The magazine fits onto the front of the blaster and pulling the trigger allows the magazine to drop down, putting the next projectile into firing position. After the final round is fired, the empty magazine falls away. It’s a pretty clever design, even if the ergonomics are a little unusual and it relies on gravity in order to feed. Tilt it too far sideways or upside down, and it won’t load properly.

We’ve seen compliant mechanisms used for projectile firing before, but this design really raises the bar in the way it does more than just firing the striker.

3D printing allows rapid iteration of designs, which makes devices that rely on compliant mechanisms much easier to develop and fine-tune.

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Flexures Make Robotic Fingers Simpler To Print

July 16, 2024 by 7 Comments

Designing an anthropomorphic robotic hand seems to make a lot of sense — right up until the point that you realize just how complex the human hand is. What works well in bone and sinew often doesn’t translate well to servos and sensors, and even building a single mechanical finger can require dozens of parts.

Or, if you’re as clever about things as [Adrian Perez] is, only one part. His print-in-place robotic finger, adorably dubbed “Fingie,” is a huge step toward simplifying anthropomorphic manipulators. Fingie is printed in PLA and uses flexures for the three main joints of the finger, each of which consists of two separate and opposed coil springs. The flexures allow the phalanges to bend relative to each other in response to the motion of three separate tendons that extend through a channel on the palmar aspect of the finger, very much like the real thing.

The flexures eliminate the need for bearings at each joint and greatly decrease the complexity of the finger, but the model isn’t perfect. As [Adrian] points out, the off-center attachment for the tendons makes the finger tend to curl when the joints are in flexion, which isn’t how real fingers work. That should be a pretty easy fix, though. And while we appreciate the “one and done” nature of this print, we’d almost like to see the strap-like print-in-place tendons replaced with pieces of PLA filament added as a post-processing step, to make the finger more compact and perhaps easier to control.

Despite the shortcomings, and keeping in mind that this is clearly a proof of concept, we really like where [Adrian] is going with this, and we’re looking forward to seeing a hand with five Fingies, or four Fingies and a Thumbie. It stands to be vastly simpler than something like [Will Cogley]’s biomimetic hand, which while an absolute masterpiece of design, is pretty daunting for most of us to reproduce.

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Flexures Keep This Printed Displacement Sensor In Line

May 18, 2024 by 5 Comments

When the job at hand is measuring something with micron-range precision, thoughts generally turn to a tool with a Mitutoyo or Starrett nameplate. But with a clever design and a little electronics know-how, it turns out you can 3D print a displacement sensor for measuring in the micron range for only about $10.

While the tool that [BubsBuilds] came up with isn’t as compact as a dial indicator and probably won’t win any industrial design awards, that doesn’t detract from its usefulness. And unlike a dial indicator — at least the analog type — this sensor outputs an easily digitized signal. That comes courtesy of a simple opto-interrupter sensor, which measures the position of a fine blade within its field of view. The blade is attached to a flexure that constrains its movement to a single plane; the other end of the flexure has a steel ball acting as a stylus. In use, any displacement of the stylus results in more or less light being received by the phototransistor in the opto-interrupter; the greater the deflection, the less light and the lower the current through the transistor. In addition to the sensor itself, [Bub] printed a calibration jig that allows precision gauge blocks or simple feeler gauges to be inserted in front of the stylus. The voltage across the emitter resistor for these known displacements is then used to create a calibration curve.

[Bub] says he’s getting 5-micron repeatability with careful calibration and multiple measurements of each gauge block, which seems pretty impressive to us. If you don’t need the digital output, this compliant mechanism dial indicator might be helpful too. Continue reading “Flexures Keep This Printed Displacement Sensor In Line” →

Pushing The Boundaries Of Tiny Mechanical Devices With Compliant Mechanisms

October 8, 2023 by 12 Comments

Mechanical actions underlie much of what makes modern day society function, whether it’s electric motors, combustion engines, switches, levers, or the springs inside a toy blaster gun that propel foam darts at unsuspecting siblings. Yet as useful as it would be to scale such mechanisms down to microscopic levels, this comes with previously minor issues on a macroscopic scale, such as friction and mechanical strength, becoming quickly insurmountable. Or to put in more simple terms, how to make a functioning toy blaster gun small enough to be handled by ants? This is the topic which [Mark Rober] explores in a recent video.

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