Unique Planetary Gearbox can be Custom Printed for Steppers

Stepper motors are a staple in all sorts of projects, but it’s often the case that a gearbox is needed, especially for applications like the linear drives in CNC machines and 3D printers. In those mechanisms, a high-torque, low backlash gearbox might be just the thing, and a 3D printable split planetary harmonic drive for the popular NEMA 17 motors would be even better.

Right up front, we’ll say that we’re skeptical that any plastic gearbox can stay as backlash free as [SirekSBurom] claims his creation is. But we can see the benefits of the design, and it has some nice features. First off, of course, is that it’s entirely 3D printed, except for a few screws. That it mates perfectly with a NEMA 17 motor is a really nice feature, too, and with the design up on Thingiverse it shouldn’t be too tough to scale it up and down accordingly. The videos below show you the theory: the stepper drives a sun gear with two planet gears orbiting, each of which engages a fixed ring of 56 teeth, and an output ring of 58 teeth. Each revolution of the planets around the fixed ring rotates the output ring by one tooth, leading to almost 100:1 reduction.

We think the ‘harmonic’ designation on this gearbox is a little of a misnomer, since the defining feature of a harmonic drive seems to be the periodic deformation of a flex spline, as we saw in this 3D-printed strain wave gear. But we see the resemblance to a harmonic drive, and we’ll admit this beastie is a little hard to hang a name tag on. Whatever you call it, it’s pretty cool and could be a handy tool for all kinds of builds.

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DIY Syringe Pump Saves Big Bucks for Hacker’s Lab

If you had a choice between going to your boss and asking for funds for a new piece of gear, would you rather ask for $3000 to buy off-the-shelf, or $200 for the parts to build the same thing yourself? Any self-respecting hacker knows the answer, and when presented with an opportunity to equip his lab with a new DIY syringe pump for $200, [Dr. D-Flo] rose to the challenge.

The first stop for [Dr. D-Flo] was, naturally, Hackaday.io, which is where he found [Naroom]’s syringe pump project. It was a good match for his budget and his specs, but he needed to modify some of the 3D printed parts a little to fit the larger syringes he intended to use. The base is aluminum extrusion, the drive train is a stepper motor spinning threaded rod and a captive nut in the plunger holders, and an Arduino and motor shield control everything. The drive train will obviously suffer from a fair amount of backlash, but this pump isn’t meant for precise dispensing so it shouldn’t matter. We’d worry a little more about the robustness of the printed parts over time and their compatibility with common lab solvents, but overall this was a great build that [Dr. D-Flo] intends to use in a 3D food printer. We look forward to seeing that one.

It’s getting so that that you can build almost anything for the lab these days, from peristaltic pumps to centrifuges. It has to be hard to concentrate on your science when there’s so much gear to make.

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Pint-Sized, Low-Cost CNC Machine

A little MDF, a little plywood, some bits of threaded rod – put it all together and you’ve got this low-cost desktop CNC build using very few parts you’d need to go farther afield than the local home center to procure.

We’ve seen lots of e-waste and dumpster diving CNC builds here before; what’s appealing here is not only the low price tag of the build but also its approachability. As the short videos below show, [Thimo Voorwinden] does an admirable job of using the tools and materials he has on hand. We also appreciate the modularity of the build – the X- and Y-axis carriages are nearly identical and could be interchanged to alter the dimensions of the work area, or even replaced with a larger carriage if needed. The Z-axis is a little different from the usual low-end CNC build in that it doesn’t use a Dremel or other small rotary tool but rather mounts the handpiece of a flexible shaft rotary tool. Keeping the motor off the machine allows for more torque, less vibration, and reduced dead load.

The end result is a desktop CNC for about €200 with a work area large enough to fabricate small wooden and plastic parts, or to mill foam blocks for use as casting molds. It looks like [Thimo] has more in store for his little CNC machine, and we’re looking forward to seeing what improvements he can come up with.

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Modified Servo Adds Focus Control to Telescope

Scanning the heavens with a telescope is a great way to spend long, clear winter nights, but using a manual telescope can get to be a drag. A motorized mount with altitude and azimuth control is basic equipment for the serious observer, but adding a servo to control the focus of your telescope is one step beyond your average off-the-shelf instrument.

Having already motorized the two axes of the equatorial mount of his modest telescope as a senior project, [Eric Seifert] decided to motorize the focus rack as well. His first inclination was to use a stepper motor like he did on the other two axes, but with a spare high-torque servo at hand, he hacked a quick proof-of-concept. The servo was modified for continuous rotation in the usual way, but with the added twist of replacing the internal potentiometer with an external linear pot. Attached to the focus tube, the linear pot allows [Eric] to control the position and speed of the modified servo. Sounds like controlling the focus will be important to [Eric]’s planned web interface for his scope; we’ll be looking for details on that project soon.

We like the simplicity of this solution, and it’s a trick worth keeping in mind for other projects.  But if fancy steppers and servos aren’t your thing, fear not — astrophotography is as easy as slapping a couple of boards together with a hinge.

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Hackaday Links: November 27, 2016

[Prusa]’s business is doing great. This year, he released the Prusa i3 Mk. 2, a four color upgrade to the printer, and sales are through the roof. There’s just one problem: Paypal just locked his funds. Prusa is turning away from Paypal and given Paypal’s history, this will eventually be worked out. Be warned, though: don’t use Paypal for your hardware business. We’ve seen this same story played out too many times before.

Those millennials are always on their phones. How do you get rid of that distraction? Airplane mode? No, that’s stupid. Put those phones in a metal box. It’s the exact same thing as airplane mode – which is free – but this extra special metal box costs $45 and ships in March. Is this metal box different from any other metal box, like a cookie tin, perhaps? Probably not.

Nothing to see here, folks.

The holidays are here, and it’s time for Cards Against Humanity to do something stupid with other people’s money. This year, they’re throwing money into a hole. No, really. People are contributing money to dig a gigantic hole. There’s a livestream of the digging. Five dollars lets the dig continue for another few seconds. Join in on the holiday spirit: throw your money into a hole.

You don’t want to throw your money into a hole? Buy some stuff on Tindie! There’s robots, CNC controllers, servo drivers, MIDI arpeggiators, USB testers, power supplies, blinky glowy things, and retro gaming stuff. Go plug your Raspberry Pi into some of these gizmos.

The Mechaduino is a board that clips onto a ubiquitous NEMA stepper motor to turn it into a servo motor.  It won 5th place in the Hackaday Prize last month, and we can’t wait to see it integrated into a closed-loop 3D printer. [Chris] came up with an Ethernet-enabled servo-stepper conversion, and now it’s a project on Kickstarter. Of course, you can buy a Mechaduino right now, making the future of stepper motor-controlled desktop CNC very interesting.

Individually addressable RGB LEDs exist, and we’re waiting for Clark Griswold to electrify his house in red, green, and blue. Until then, [Michel built a holiday ornament loaded up with 16 WS2812b LEDs. The star features caps and diodes to make everything work as it should and requires only three wires per star.

Rotating Frame Will Change Your View of Vertical Images

[Tim] was tired of compromising his portrait-oriented digital photos by shoehorning them into landscape-only frames. Unable to find a commercial solution, he built his own rotating digital photo frame from a 27″ LCD TV.

It uses a Raspi 3 to find [Tim]’s pictures on a giant SD card. He originally wanted to have the Pi pull pictures from Google Photos and display them randomly, but the API doesn’t work in that direction. Instead, a Python script looks at the pictures on the SD card and determines whether each is landscape or portrait-oriented. If a picture was taken in portrait-mode, the display will rotate 90 degrees. Rotation is handled with an Arduino, a stepper motor, and some 3D-printed herringbone gears. The first version was a bit noisy, so [Tim] re-printed the motor mount and the pinion gear out of flexible filament.

[Tim] designed the mount and frame himself and laser-cut the pieces out of birch plywood. We like that he accounted for the front-heaviness and that he covered the high voltage circuitry with acrylic to mitigate the risk of shock. All the code and design files are available on his project page. Make the jump to see a brief demonstration followed by a walk-through and stay for the six-minute slide show.

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The Evolution of a DIY Circuit Board Plotter

In this three part video series we watch [Dirk Herrendoerfer] go from scraps to a nice 3D printed assembly as he iterates through the design of a pen plotter for making circuit boards.

[dana] mentioned [Dirk]’s work in the comments of this post which describes a different process. Many permanent markers stick to copper well enough to last through the chemical etching process. While hand drawing definitely produces some cool, organic-looking boards, for sharp lines and SMDs it gets a bit harder; to the point where it becomes advisable to just let a robot do it.

Of course, [Dirk] was aware of this fact of life. He just didn’t have a robot on hand. He did have some electronic detritus, fishing line, an Arduino, scrap wood, brass tubes, and determination.  The first version‘s frame consisted of wooden blocks set on their ends with holes drilled to accept brass rods. The carriage was protoboard and hot glue. Slightly larger brass tubing served as bushings and guide. As primitive as it was the plotter performed admirably, albeit slowly.

The second version was a mechanical improvement over the first, but largely the same. The software got a nice improvement. It worked better and had some speed to it.

The latest version has some fancy software upgrades; such as acceleration. The frame has gone from random bits of shop trash to a nicely refined 3D printed assembly. Even the steppers have been changed to the popular 28BYJ-48 series. All the files, software and hardware, are available on GitHub. The three videos are viewable after the break. It’s a great example of what a good hacker can put together for practically no money.

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