OpenSCAD Handles The Math In 3D Printed Holder For Magnetic Spheres

August 28, 2018 by Donald Papp 35 Comments

3D printed holder mounted to bike wheel, fitting precisely 38 magnetic spheres around its perimeter. Tedious math? Not if you make OpenSCAD do it.

Off-the-shelf components are great; the world and our work simply wouldn’t be the same without. But one of the constraints is that one has to design around them, and that’s what led [Antonio Ospite] to create a parametric design in OpenSCAD for a 3D printed holder which snugly fits a number of magnetic spheres around its diameter.

If that sounds a bit esoteric, it will become much clearer in the context of [Antonio]’s earlier work in making a DIY rotary encoder out of a ring of magnetic spheres. He found that such a ring in front of two Hall effect sensors was low in cost, high in precision, and thanks to 3D printing it also had a lot of potential for customizing. But hampering easy design changes was the need for the spheres to fit snugly around whatever shape was chosen for the hardware, which meant constraints on the encoder diameter.

In this case, [Antonio] wished to create an encoder that could be attached to a bicycle wheel but needed to know what outer diameter would best fit a ring of magnetic balls perfectly, given that the balls were each 5 mm. OpenSCAD did the trick, yielding a design that fit the bike wheel and spokes while perfectly nestling 38 magnetic balls around the outside edge with a minimum of wasted space.

OpenSCAD is a CAD program that’s really more like a programming language than anything else. For those who are not familiar with it, [Brian Benchoff] walked through how to make a simple object in OpenSCAD, and [Elliot] has sung the praises of a few advanced functions. Now that this project makes DIY encoders easier, perhaps they could be used to add intuitive new controls to OpenSCAD itself.

PiPod: A Raspberry Pi Zero Portable Music Player

August 28, 2018 by Ben James 16 Comments

[Bram] wasn’t satisfied with the portable music playback devices that were currently available. He craved an offline music player that had a large storage capacity but found that this was only available in high-end, off-the-shelf options, which were far too expensive. [Bram] decided to make his own, powered by a Raspberry Pi zero. After building an initial prototype, the design was iterated a few times, with the latest version featuring a BOM cost of roughly €80.

The whole project is open source, with hardware and software files available on the project GitHub. A 2.2″ TFT displays the UI, which is of course completely customisable. Everything is squashed into a 3D printed case, which has the smallest form factor possible whilst retaining a decent amount of battery life. The electronics are what you’d expect: a boost converter to produce 5 V for the Pi from the 3.7V battery, a charge controller and a battery protection circuit. As a bonus, the battery voltage is monitored with a 12-bit ADC which reports to the Pi, enabling it to do a safe shutdown at low voltage, and display battery level on the UI.

Since the whole purpose of the device is to play audio, onboard filtered PWM wasn’t going to cut it, so instead a 24-bit DAC talks to the Pi via I2S. The audio player backend is VLC, so there’s support for plenty of different file types. A disc image of the whole system is available with everything pre-configured, and you can even buy the assembled PCB from Tindie.

Want to keep the look and feel of your old iPod? We covered an impressive restoration of a 6th gen model, upgrading the storage and battery significantly.

GPL Violations Cost Creality A US Distributor

August 27, 2018 by Tom Nardi 92 Comments

One of the core tenets of free and open source software licenses is that you’re being provided source code for a project with the hope that you’ll “pay it forward” if and when you utilize that code. In fact some licenses, such as the GNU Public License (GPL), require that you keep the source code for subsequent spin-offs or forks open. These are known as viral licenses, and the hope is that they will help spread the use of open source as derivative works can’t turn around and refuse to release their source code.

Unfortunately, not everyone plays by the rules. In a recent post on their blog, Printed Solid has announced they are ending their relationship with Chinese manufacturer Creality, best known for their popular CR-10 printer. Creality produces a number of printers which make use of Marlin, a GPLv3 licensed firmware that runs (in some form or another) a large majority of desktop 3D printers. But as explained in the blog post, Printed Solid has grown tired with the manufacturer’s back and forth promises to comply with the viral aspects of the GPL license.

Rather than helping to support a company they believe is violating the trust of the open source community, they have decided to mark down their existing stock of Creality printers to the point they will be selling them at a loss until they run out. In addition, for each Creality printer that is sold Printed Solid has promised to make a $50 USD donation to the development of Marlin saying: “if Creality won’t support Marlin development then we will.”

As is often the case when tempers are high and agreements break down, Printed Solid has also pulled back the curtain a bit as to the relationship they have had thus far with the manufacturer. According to the blog post, Printed Solid claims that some models of Creality printers have had a 100% fault rate, and that the company needed to repair and tweak the machines before sending them out to customers. The not so subtle implication being that Creality printers have been benefiting from the work Printed Solid has been doing on their hardware, and that purchasing a unit direct from the manufacturer could be a dicey proposition.

We’ve previously covered an issue with Creality’s CR-10S printer that required the end-user to replace an SMD capacitor just to get reliable results out of the machine, and of course we’ve talked of the extra work that’s often required when wrangling a low-end Chinese printer. It’s even more disheartening when you realize cheap machines sold by shady manufacturers are pushing open source manufacturers out of business.

Self Folding Origami From A 3D Printer

August 27, 2018 by Al Williams 12 Comments

If you’ve done much 3D printing, you probably curse how plastic warps as it cools down and heats. There’s nothing more upsetting than watching a six hour print start curling off the bed and starting its inexorable march to the trash can. However, researchers at Carnegie Mellon have found a way to harness that tendency to warp with heat to make self-folding structures like those seen in the video below. There’s a paper about how it works available, too.

The Thermorph process uses commercially-available 3D printers, but requires special software. You might wonder why you would want to fold, say, a rose, when you could just print it as a fully-formed 3D model. The paper suggests that printing self-folding structures is faster and can save up to 87% on print times for the right models.

Continue reading “Self Folding Origami From A 3D Printer” →

3D Printing A Printing Press

August 26, 2018 by Jenny List 3 Comments

If you move among artists, you may have encountered a few printmakers. They create a drawing by cutting through a wax layer that has been deposited on a sheet of copper, then etching the plate and removing the wax. Ink is then rolled onto the plate and cleaned from the flat surface, remaining in the cracks created by the etching. A print is made by putting inked plate and a sheet of paper through a roller press at significant pressure, squeezing the ink from the cracks onto the paper. The result is a beautiful print, but the press required to do the job is by no means cheap.

[Martin Schneider] has addressed this expense with his Open Press project, by producing a printmaking press that can be 3D-printed for a fraction of the outlay of a traditional press. It’s by no means a large model, but appears no less functional for it.

The form of the press is straightforward enough, with a print bed that is drawn between a pair of rollers by a rack-and-pinion gear, and as you would imagine the construction is quite substantial. It’s all CC licensed, and you can make one for yourself if you would like, by downloading the files from Thingiverse.

It’s fair to say that printmaking hasn’t appeared much here, but we can see this press could have significant use beyond artistic applications. Meanwhile it’s a great example of 3D printing providing the means to reduce the barrier to entry for something that was previously quite an expensive pursuit.

A Peek At The Mesmerizing Action Of A Cycloidal Drive

August 24, 2018 by Donald Papp 34 Comments

Cycloidal drives are fascinating pieces of hardware, and we’ve seen them showing up in part due to their suitability for 3D printing. The open source robot arm makers [Haddington Dynamics] are among those playing with a cycloidal drive concept, and tucked away in their August 2018 newsletter was a link they shared to a short but mesmerizing video of a prototype, which we’ve embedded below.

A 10:1 Cycloidal Drive [Source: Wikipedia, image public domain]

A cycloidal drive has some similarities to both planetary gearing and strain-wave gears. In the image shown, the green shaft is the input and its rotation causes an eccentric motion in the yellow cycloidal disk. The cycloidal disk is geared to a stationary outer ring, represented in the animation by the outer ring of grey segments. Its motion is transferred to the purple output shaft via rollers or pins that interface to the holes in the disk. Like planetary gearing, the output shaft rotates in the opposite direction to the input shaft. Because the individual parts are well-suited to 3D printing, this opens the door to easily prototyping custom designs and gearing ratios.

[Haddington Dynamics] are the folks responsible for the open source robot arm Dexter (which will be competing in the Hackaday Prize finals this year), and their interest in a cycloidal drive design sounds extremely forward-thinking. Their prototype consists of 3D printed parts plus some added hardware, but the real magic is in the manufacturing concept of the design. The idea is for the whole assembly to be 3D printed, stopping the printer at five different times to insert hardware. With a robot working in tandem with the printer, coordinating the print pauses with automated insertion of the appropriate hardware, the result will be a finished transmission unit right off the print bed. It’s a lofty goal, and really interesting advancement for small-scale fabrication.

Continue reading “A Peek At The Mesmerizing Action Of A Cycloidal Drive” →

Marines 3D-Print Part To Repair Multi-Million Dollar Fighter

August 23, 2018 by Dan Maloney 71 Comments

The good news: all you need to complete the repair you’re working on is one small part. The bad news: it’s only available in a larger, expensive assembly. The worst news: shipping time is forever. We’ve all been there, and it’s a hard pill to swallow for the DIYer. Seems like a good use case for 3D-printing.

Now imagine you’re a US Marine, and instead of fixing a dishwasher or TV remote, you’ve got a $123 million F-35 fighter in the shop. The part you need is a small plastic bumper for the landing gear door, but it’s only available as part of the whole door assembly, which costs $70,000 taxpayer dollars. And lead time to get it shipped from the States is measured in weeks. Can you even entertain the notion of 3D-printing a replacement? It turns out you can, and it looks like there will be more additive manufacturing to come in Corps repair depots around the world.

Details of the printed part are not forthcoming for obvious reasons, but the part was modeled in Blender and printed in PETG on what appears to be a consumer-grade printer. The part was installed after a quick approval for airworthiness, and the grounded fighter was back in service within days. It’s encouraging that this is not a one-off; other parts have been approved for flight use by the Marines, and a whole catalog of printable parts for ground vehicles is available too. This is the reality that the 3D printing fiction of Lost in Space builds upon.

And who knows? Maybe there are field-printable parts in the disposable drones the Corps is using for standoff resupply missions.

[via 3D-Printing Industry]