Author: Aaron Beckendorf

5 Articles

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.

Continue reading “3D Printed Cable-Driven Mechanisms – Some Strings Attached” →

A man is shown on the left of the screen, speaking to the camera. On the right of the screen, a Smith chart is displayed. At the top of the screen, the words "TWO METHODS" are displayed.

A Gentle Introduction To Impedance Matching

May 2, 2025 by 8 Comments

Impedance matching is one of the perpetual confusions for new electronics students, and for good reason: the idea that increasing the impedance of a circuit can lead to more power transmission is frighteningly unintuitive at first glance. Even once you understand this, designing a circuit with impedance matching is a tricky task, and it’s here that [Ralph Gable]’s introduction to impedance matching is helpful.

The goal of impedance matching is to maximize the amount of power transmitted from a source to a load. In some simple situations, resistance is the only significant component in impedance, and it’s possible to match impedance just by matching resistance. In most situations, though, capacitance and inductance will add a reactive component to the impedance, in which case it becomes necessary to use the complex conjugate for impedance matching.

The video goes over this theory briefly, but it’s real focus is on explaining how to read a Smith chart, an intimidating-looking tool which can be used to calculate impedances. The video covers the basic impedance-only Smith chart, as well as a full-color Smith chart which indicates both impedance and admittance.

This video is the introduction to a planned series on impedance matching, and beyond reading Smith charts, it doesn’t really get into many specifics. However, based on the clear explanations so far, it could be worth waiting for the rest of the series.

If you’re interested in more practical details, we’ve also covered another example before. Continue reading “A Gentle Introduction To Impedance Matching” →

A graph is shown of the percentage reflection of visible light as a function of wavelength. Four lines are traced on the graph, which all approximate the same shape. In the top left, two purple shapes are shown, which the spectral chart describes.

Paint Mixing Theory For Custom Filament Colors

April 28, 2025 by 11 Comments

Recycling 3D filament is a great idea in theory, and we come across homemade filament extruders with some regularity, but they do have some major downsides when it comes to colored filaments. If you try to recycle printer waste of too many different colors, you’ll probably be left with a nondescript gray or brown filament. Researchers at Western University, however, have taken advantage of this pigment mixing to create colors not found in any commercial filament (open access paper).

They started by preparing samples of 3D printed waste in eight different colors and characterizing their spectral reflectance properties with a visible-light spectrometer. They fed this information into their SpecOptiBlend program (open source, available here), which optimizes the match between a blend of filaments and a target color. The program relies on the Kubelka-Munk theory for subtractive color mixing, which is usually used to calculate the effect of mixing paints, and minimizes the difference which the human eye perceives between two colors. Once the software calculated the optimal blend, the researchers mixed the correct blend of waste plastics and extruded it as a filament which generally had a remarkably close resemblance to the target color.

In its current form, this process probably won’t be coming to consumer 3D printers anytime soon. To mix differently-colored filaments correctly, the software needs accurate measurements of their optical properties first, which requires a spectrometer. To get around this, the researchers recommend that filament manufacturers freely publish the properties of their filaments, allowing consumers to mix their filaments into any color they desire.

This reminds us of another technique that treats filaments like paint to achieve remarkable color effects. We’ve also seen a number of filament extruders before, if you’d like to try replicating this.

A 3D printer frame made of red plastic is shown on the left-hand side of the image. On the right-hand side, there is a large motor with a plastic frame attached to the frame. Next to the 3D printer, a blue plastic mesh is being fed through a red plastic frame.

The Most Printable 3D Printer Yet

April 20, 2025 by 17 Comments

Despite the best efforts of the RepRap community over the last twenty years, self-replicating 3D printers have remained a stubbornly elusive goal, largely due to the difficulty of printing electronics. [Brian Minnick]’s fully-printed 3D printer could eventually change that, and he’s already solved an impressive number of technical challenges in the process.

[Brian]’s first step was to make a 3D-printable motor. Instead of the more conventional stepper motors, he designed a fully 3D-printed 3-pole brushed motor. The motor coils are made from solder paste, which the printer applies using a custom syringe-based extruder. The paste is then sintered at a moderate temperature, resulting in traces with a resistivity as low as 0.001 Ω mm, low enough to make effective magnetic coils.

Continue reading “The Most Printable 3D Printer Yet” →

A man is looking at a volumetric display while using one finger to interact with it. Two roughly-spherical blue shapes are visible in the display, and he is moving his index finger toward one of them.

Elastic Bands Enable Touchable Volumetric Display

April 14, 2025 by 12 Comments

Amazing as volumetric displays are, they have one major drawback: interacting with them is complicated. A 3D mouse is nice, but unless you’ve done a lot of CAD work, it’s a bit unintuitive. Researchers from the Public University of Navarra, however, have developed a touchable volumetric display, bringing touchscreen-like interactions to the third dimension (preprint paper).

At the core, this is a swept-volume volumetric display: a light-diffusing screen oscillates along one axis, while from below a projector displays cross-sections of the scene in synchrony with the position of the screen. These researchers replaced the normal screen with six strips of elastic material. The finger of someone touching the display deforms one or more of the strips, allowing the touch to be detected, while also not damaging the display.

The actual hardware is surprisingly hacker-friendly: for the screen material, the researchers settled on elastic bands intended for clothing, and two modified subwoofers drove the screen’s oscillation. Indeed, some aspects of the design actually cite this Hackaday article. While the citation misattributes the design, we’re glad to see a hacker inspiring professional research.) The most exotic component is a very high-speed projector (on the order of 3,000 fps), but the previously-cited project deals with this by hacking a DLP projector, as does another project (also cited in this paper as source 24) which we’ve covered.

While interacting with the display does introduce some optical distortions, we think the video below speaks for itself. If you’re interested in other volumetric displays, check out this project, which displays images with a levitating styrofoam bead.

Continue reading “Elastic Bands Enable Touchable Volumetric Display” →