A High Torque 3D Printed Harmonic Drive

May 24, 2021 by Danie Conradie 5 Comments

Actuators that are powerful, accurate, compact, and cheap are like unicorns. They don’t exist. Yet this is what [3DprintedLife] needed for a robotic camera arm, so he developed a custom 3D printed high torque strain wave gearbox to be powered by a cheap NEMA23 stepper motor.

Strain wave gears, otherwise known as harmonic drives, are not an uncommon topic here on Hackaday. The work by deforming a flexible toothed spline with a rotating elliptical part, which engages with the internal teeth of an outer spline. The outer spline has a few more teeth, causing the inner spline to rotate slowly compared to the input, achieving very high gear ratios. Usually, the flexible spline is quite long to allow it to flex at one end while still having a rigid mounting surface at the other end. [3DprintedLife] got around this by creating a separate rigid output spline, which also meshes with the flexible spline. Continue reading “A High Torque 3D Printed Harmonic Drive” →

This DIY Split-Flap Display Does Both Time And Weather

April 29, 2021 by Donald Papp 5 Comments

With little more than four economical stepper motors, a Raspberry Pi Zero, and a 3D printer, [Thomas Barlow] made himself an awfully slick Smart Flip Clock that can display not only the time, but also weather data as well. This is done by adding a few extra graphics to some of the split-flaps, so numbers can also be used to indicate temperature and weather conditions succinctly. Displaying the time has to do without a colon (so 5:18 displays as 518), but being able to show temperature and weather conditions more than makes up for it.

According to the project’s GitHub repository, it looks as though each split-flap has thirteen unique positions. The first ten are for numerals 0 through 9, and the rest are either blank, or used to make up a few different weather icons with different combinations. A Python script runs on the Raspberry Pi and retrieves weather data from OpenWeather, and the GPIO header drives the display via four geared stepper motors and driver boards. The rest of the hardware is 3D printed, and [Thomas] helpfully provides CAD models in STEP format alongside the STL files.

The basic design of a split-flap display is really quite versatile, and enterprising hackers have been putting delightful new twists on them for years. There has been a split-flap display used as a kind of flip-book animation, and we’ve also had the pleasure of seeing an entire Tarot deck used for esoteric, automated readings.

Faux Stained Glass Effect, With 3D Printing And Epoxy

April 22, 2021 by Donald Papp 14 Comments

Like the looks of stained glass, but not the amount of work, skill, and materials involved? Well, [Northern Geometry] shows how to sidestep all that nonsense and use a 3D printed frame, epoxy, and some alcohol-based inks to create a pretty good fake stained-glass effect piece of art.

A smooth polypropylene board is the key to a glassy smooth back.

[Northern Geometry] has played with this idea before, but shares some refinements and tips on getting the best results. One suggestion is to begin by securely taping the 3D printed frame to a smooth polypropylene board as a backer. Giving the cured resin a smooth surface is important to get the right look, and since resin will not bond to the polypropylene, it can be used as a backer to get that done.

Once the frame is mounted, pour a small amount of epoxy into each cavity and ensure it gets into every corner, then let it cure. The thin bottom layer of resin will seal things as well as create a glassy-smooth backing that is the perfect foundation for finishing the piece with colored resin as needed.

Once that is done, and everything has had plenty of time to cure fully, just pop the piece off the board. Check it out in the video embedded below, where [Northern Geometry] shows the process from start to finish.

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To Lovers Of Small Boxes: A 3D Printable Design Just For You

March 28, 2021 by Donald Papp 7 Comments

Print them at 50% scale for a far cuter (and much less useful) result.

[Jacob Stanton]’s design for 3D-printable, stacking and locking boxes is a great example of design for manufacturability (DFM). MicroStacks show how part of good DFM is taking the manufacturing method’s strengths and weaknesses into account. [Jacob]’s boxes are created specifically with 3D printing in mind, which is great design whether somebody is making one, or dozens.

The boxes have sturdy parts that all print without any need for supports, fasteners, or post-processing. In addition, since no two 3D printers are quite alike and some print better than others, the parts are also designed to be quite forgiving of loose tolerances. Even on a printer that is less well-tuned than it could be, the design should still work. The boxes also have a nice stacking feature: a sturdy dovetail combined with a sliding tab means that once boxes are stacked, they’re not coming apart by accident unless something breaks in the process.

The boxes as designed are about big enough to store AA cells. Not the right size for you? One nice thing about a 3D-printable design that doesn’t need supports is that it’s trivial to uniformly scale the size of the models up or down to match one’s needs without introducing any print complications in the process. You can watch [Jacob] assemble and demonstrate his design in the video, embedded below.

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Coil Winding Machine Makes It Easy

March 24, 2021 by Al Williams 19 Comments

[Mr Innovative] needed to wind some coils, and decided to make a machine to do the work. Making such machines has become a lot easier over the years. There was a time when we might probably have had to hack an old printer or scanner to get linear rods and stepper motors. Now, thanks to widespread 3D printing, we can order parts like that from lots of places. The 3D printing helps, too, to fabricate all the little custom widgets you need to put something like that together.

The machine looks great. It uses a number of parts that would look at home on a 3D printer or CNC build. We thought his Chinese mini table saw did a great job cutting the aluminum extrusions, but we did worry about the safety of his fingers. We’ll admit we are generally lazy and buy the extrusions precut.

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3D-Printed Press-Forming Tools Dos And Don’ts

March 13, 2021 by Dan Maloney 13 Comments

Press-forming is a versatile metal forming technique that can quickly and easily turn sheet metal into finished parts. But there’s a lot of time and money tied up in the tooling needed, which can make it hard for the home-gamer to get into. Unless you 3D-print your press-form tooling, of course.

Observant readers will no doubt recall our previous coverage of press-forming attempts with plastic tooling, which were met with varying degrees of success. But [Dave]’s effort stands apart for a number of reasons, not least of which is his relative newbishness when it comes to hot-squirt manufacturing. Even so, he still came up with an interesting gradient infill technique that put most of the plastic at the working face of the dies. That kept print times in the reasonable range, at least compared to the days of printing that would have been needed for 100% infill through the whole tool profile.

The other innovation that we liked was the idea to use epoxy resin to reinforce the tools. Filling the infill spaces on the tools’ undersides with resin resulted in a solid, strong block that was better able to withstand pressing forces. [Dave] didn’t fully account for the exothermic natures of the polymerization reaction, though, and slightly warped the tools. But as the video below shows, even suboptimal tools can perform, bending everything he threw at them, including the hydraulic press to some extent.

It sure seems like this is one technique to keep in mind for a rainy day. And hats off to [Dave] for sharing what didn’t work, since it points the way to improvements.

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Peek Into This Synth’s Great Design (And Abandoned Features)

March 9, 2021 by Donald Papp 30 Comments

[Tommy]’s POLY555 is an analog, 20-note polyphonic synthesizer that makes heavy use of 3D printing and shows off some clever design. The POLY555, as well as [Tommy]’s earlier synth designs, are based around the 555 timer. But one 555 is one oscillator, which means only one note can be played at a time. To make the POLY555 polyphonic, [Tommy] took things to their logical extreme and simply added multiple 555s, expanding the capabilities while keeping the classic 555 synth heritage.

The real gem here is [Tommy]’s writeup. In it, he explains the various design choices and improvements that went into the POLY555, not just as an instrument, but as a kit intended to be produced and easy to assemble. Good DFM (Design For Manufacturability) takes time and effort, but pays off big time even for things made in relatively small quantities. Anything that reduces complexity, eliminates steps, or improves reliability is a change worth investigating.

For example, the volume wheel is not a thumbwheel pot. It is actually a 3D-printed piece attached to the same potentiometer that the 555s use for tuning; meaning one less part to keep track of in the bill of materials. It’s all a gold mine of tips for anyone looking at making more than just a handful of something, and a peek into the hard work that goes into designing something to be produced. [Tommy] even has a short section dedicated to abandoned or rejected ideas that didn’t make the cut, which is educational in itself. Want more? Good news! This isn’t the first time we’ve been delighted with [Tommy]’s prototyping and design discussions.

POLY555’s design files (OpenSCAD for enclosure and parts, and KiCad for schematic and PCB) as well as assembly guide are all available on GitHub, and STL files can be found on Thingiverse. [Tommy] sells partial and complete kits as well, so there’s something for everyone’s comfort level. Watch the POLY555 in action in the video, embedded below.

Continue reading “Peek Into This Synth’s Great Design (And Abandoned Features)” →