3D Printed Axial Compressor Is On A Mission To Inflate Balloons

January 29, 2024 by Donald Papp 5 Comments

[Let’s Print] has been fascinated with creating a 3D printed axial compressor that can do meaningful work, and his latest iteration mixes FDM and SLA printed parts to successfully inflate (and pop) a latex glove, so that’s progress!

Originally, the unit couldn’t manage even that until he modified the number and type of fan blades on the compressor stages. There were other design challenges as well. For example, one regular issue was a coupling between the motor and the rest of the unit breaking repeatedly. At the speeds the compressor runs at, weak points tend to surface fairly quickly. That’s not stopping [Let’s Print], however. He plans to explore other compressor designs in his quest for an effective unit.

Attaching motor shafts to 3D printed devices can be tricky, and in the past we’ve seen a clever solution that is worth keeping in mind: half of a spider coupling (or jaw coupling) can be an economical and effective way to attach 3D printed things to a shaft.

While blowing up a regular party balloon is still asking too much of [Let’s Print]’s compressor as it stands, it certainly inflates (and pops) a latex glove like nobody’s business.

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Magnetic Gearbox, Part 2: Axial Flux Improves Performance

July 27, 2023 by Dan Maloney 13 Comments

The number of interesting and innovative mechanisms that 3D printing has enabled always fascinates us, and it’s always a treat when one of them shows up in our feeds. This axial flux magnetic gearbox is a great example of such a mechanism, and one that really makes you think about possible applications.

The principles of [Retsetman]’s gearbox are simple for anyone who has ever played with a couple of magnets to understand, since it relies on that powerful attractive and repulsive force you feel when magnets get close to each other. Unlike his previous radial flux gearbox, which used a pair of magnet-studded cylindrical rotors nested one inside the other, this design has a pair of disc-shaped printed rotors that face each other on aligned shafts. Each rotor has slots for sixteen neodymium magnets, which are glued into the slots in specific arrangements of polarity — every other magnet for the low-speed rotor, and groups of four on the high-speed rotor. Between the two rotors is a fixed flux modulator, a stator with ten ferromagnetic inserts screwed into it.

In operation, which the video below demonstrates nicely, the magnetic flux is coupled between the rotors by the steel inserts in the stator so that when one rotor moves, the other moves at a 4:1 (or 1:4) ratio in the opposite direction. [Retsetman] got the gearbox cranked up to about 8,500 RPM briefly, but found that extended operation at as little as 4,000 RPM invited disaster not due to eddy current heating of the inserts or magnets as one might expect, but from simple frictional heating of the rotor bearings.

Torque tests of the original gearbox were unimpressive, but [Retsetman]’s experiments with both laminated stator inserts and more powerful magnets really boosted the output — up to a 250% improvement! We’d also like to see what effect a Halbach array would have on performance, although we suspect that the proper ratios between the two rotors might be difficult to achieve.

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Printed Axial Generator Is Turned By Hand

October 15, 2022 by Bryan Cockfield 19 Comments

While desktop 3D printing is an incredible technology, it’s got some pretty clear limitations. Plastic parts can be produced quickly in a 3D printer but can be more expensive or take longer to make than parts from materials like wood. Plastic parts can also be weaker than materials like metal. If a 3D printer is all you have on hand, though, you can often make some design choices that improve the performance of a plastic part over other materials. That’s what [1970sWizard] did to make this axial hand-cranked generator.

Besides a few pieces of off-the-shelf hardware and the wire and magnets, the entire generator is printed. The actual generator is made from coils of wire with exposed leads which snap into a plastic disc which acts as the generator’s stator. The magnets also snap into a separate disc which is the rotor of the generator and is attached to the drivetrain, with no glue or fasteners required. A series of gears on two other axes convert the torque from the hand crank into the high speed necessary to get usable electricity out of the generator.

The separate gear shafts were necessary to keep from needing a drillpress, which would have allowed fewer axes to be used. This entire machine can be built almost entirely with a desktop 3D printer, though, which was one of the design goals. While it’s largely a proof-of-concept, the machine does generate about 100 mW of power which is enough to slowly charge USB devices, power lights, or provide other sources of very small amounts of energy. If you do have access to some metalworking tools, though, take a look at this hand-cranked emergency generator.

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Homebrew Doorknob Caps For High-Voltage Fun

February 19, 2021 by Dan Maloney 15 Comments

Mouser and Digi-Key are great for servicing most needs, and the range of parts they offer is frankly bewildering. But given the breadth of the hardware hacking community’s interests, few companies could afford to be the answer to everyone’s needs.

That’s especially true for the esoteric parts needed when one’s hobby involves high voltages and homemade lasers, like [Les Wright]. He recently came up with a DIY doorknob capacitor design that makes the hard-to-source high-voltage caps much easier to obtain. We’ve seen [Les] use these caps in his transversely excited atmospheric (TEA) lasers, a simple design that uses high-voltage discharge across a long, narrow channel filled with either room air or nitrogen. The big ceramic caps are needed for the HV supply, and while [Les] has a bunch, they’re hard to come by online. He tried a follow-up using plain radial-lead ceramic capacitors, and while the laser worked, he did get some flashover between the capacitor leads.

[Les]’s solution was to dunk the chunky caps in acetone for a week or so to remove their epoxy covering. Once denuded, the leads were bent into a more axial configuration and soldered to brass machine screws. The dielectric slug is then put in a small section of plastic tubing and potted in epoxy resin with the bolts protruding from each end. The result is hard to distinguish from a genuine doorknob cap; the video below shows the build process as well as some testing.

Hats off to [Les] for taking pity on those of us who want to replicate his work but find ourselves without these essentials. It’s nice to know there’s a way to make unobtanium parts when you need them.

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Jigsaw Motor Uses PCB Coils For Radial Flux

July 16, 2019 by Dan Maloney 7 Comments

Electric motors are easy to make; remember those experiments with wire-wrapped nails? But what’s easy to make is often hard to engineer, and making a motor that’s small, light, and powerful can be difficult. [Carl Bugeja] however is not one to back down from a challenge, and his tiny “jigsaw” PCB motor is the latest result of his motor-building experiments.

We’re used to seeing brushless PCB motors from [Carl], but mainly of the axial-flux variety, wherein the stator coils are arranged so their magnetic lines of force are parallel to the motor’s shaft – his tiny PCB motors are a great example of this geometry. While those can be completely printed, they’re far from optimal. So, [Carl] started looking at ways to make a radial-flux PCB motor. His design has six six-layer PCB coils soldered perpendicular to a hexagonal end plate. The end plate has traces to connect the coils in a star configuration, and together with a matching top plate, they provide support for tiny bearings. The rotor meanwhile is a 3D-printed cube with press-fit neodymium magnets. Check out the build in the video below.

Connected to an ESC, the motor works decently, but not spectacularly. [Carl] admits that more tweaking is in order, and we have little doubt he’ll keep optimizing the design. We like the look of this, and we’re keen to see it improved.

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Mechanisms: Bearings

February 14, 2018 by Dan Maloney 49 Comments

They lie at the heart of every fidget spinner and in every motor that runs our lives, from the steppers in a 3D printer to the hundreds in every car engine. They can be as simple as a lubricated bushing or as complicated as the roller bearing in a car axle. Bearings are at work every day for us, directing forces and reducing friction, and understanding them is important to getting stuff done with rotating mechanisms.

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3D Printed Jet Engine

June 21, 2017 by Bryan Cockfield 21 Comments

In specific applications, jet engines are often the most efficient internal combustion engines available. Not just for airplanes, but for anything that needs to run on a wide variety of fuels, operate at a consistent high RPM, or run for an extended amount of time. Of course, most people don’t have an extra $4,000 lying around to buy a small hobby engine, but now there’s a 3D-printed axial compressor available from [noob_sauce].

As an aero propulsion engineer, [noob_sauce] is anything but a novice in the world of jet engines. This design is on its fourth iteration with a working model set to be tested by the end of the month. Additionally, [noob_sauce] created his own software that was necessary for the design of such a small, efficient jet engine which has all been made available on Git. So far the only part that has been completed has been the compressor stage of the engine, but it’s still a very impressive build that we don’t see too often due to the complexity and cost of axial compressor jet engines.

Of course, there are some less-complex jet engines that are available to anyone with access to a hardware store and a welder which don’t require hardly any precision at all. While they’re fun and noisy and relatively easy to build, though, they don’t have near the efficiency of a jet engine like this one. The build is impressive on its own, and also great that [noob_sauce] plans to release all the plans so that anyone can build one of these as well.