Making An Ultrasonic Cutter For Post-processing Tiny 3D Prints

January 7, 2019 by Donald Papp 59 Comments

An ultrasonic knife is a blade that vibrates a tiny amount at a high frequency, giving the knife edge minor superpowers. It gets used much like any other blade, but it becomes far easier to cut through troublesome materials like rubber or hard plastics. I was always curious about them, and recently made my own by modifying another tool. It turns out that an ultrasonic scaling tool intended for dental use can fairly easily be turned into a nimble little ultrasonic cutter for fine detail work.

Cheap ultrasonic scaler. The blue disk is for adjusting power. Foot switch not shown.

I originally started thinking about an ultrasonic knife to make removing supports from SLA 3D prints easier. SLA resin prints are made from a smooth, hard plastic and can sometimes require a veritable forest of supports. These supports are normally removed with flush cutters, or torn off if one doesn’t care about appearances, but sometimes the density of supports makes this process awkward, especially on small objects.

I imagined that an ultrasonic blade would make short work of these pesky supports, and for the most part, I was right! It won’t effortlessly cut through a forest of support bases like a hot knife through butter, but it certainly makes it easier to remove tricky supports from the model itself. Specifically, it excels at slicing through fine areas while preserving delicate features. Continue reading “Making An Ultrasonic Cutter For Post-processing Tiny 3D Prints” →

Turning LEGO Blocks Into Music With OpenCV

December 30, 2018 by Donald Papp 2 Comments

We’re not sure what it is, but something about LEGO and music go together like milk and cookies when it comes to DIY musical projects. [Paul Wallace]’s Lego Music project is a sequencer that uses the colorful plastic pieces to build and control sound, but there’s a twist. The blocks aren’t snapped onto anything; the system is entirely visual. A computer running OpenCV uses a webcam to watch the arrangement of blocks, and overlays them onto a virtual grid where the positions of the pieces are used as inputs for the sequencer. The Y axis represents pitch, and the X axis represents time.

Embedded below are two videos. The first demonstrates how the music changes based on which blocks are placed, and where. The second is a view from the software’s perspective, and shows how the vision system processes the video by picking out the colored blocks, then using their positions to change different values which has an effect on the composition as a whole.

Continue reading “Turning LEGO Blocks Into Music With OpenCV” →

See How Paper Maché Sculptor Uses Cloth For Tricky Spots

December 28, 2018 by Donald Papp 3 Comments

When is paper maché not paper maché? When it is cloth, of course. [Dan Reeder] has been putting his own spin on paper maché art since the 70s and demonstrates the technique of using cloth for tricky spots in his outstanding sculpture of an Ice Dragon. Thin strips of cloth are used just as paper would be, but give a much different structure and grant natural-looking folds to spots like eyelids, nostrils, and lips.

[Dan] feels that paper maché is an under-utilized and under-rated medium, and he puts out some stunning work on his blog as well as his YouTube channel. What’s great to see are his frank descriptions and explanations of what does and doesn’t work, and he’s not afraid to try new things and explore different ways to approach problems.

Enterprising hackers may not pick paper maché as their first choice to create creating custom enclosures, but it can be done and the accessibility and ease of use of the medium are certainly undeniable. One never knows when a tool or technique may come in handy.

When Unfolding An STL In Software, Math Isn’t The Tricky Part

December 27, 2018 by Donald Papp 14 Comments

Some time ago, [Trammell Hudson] took a shot at creating a tool that unfolds 3D models in STL format and outputs a color-coded 2D pattern that can be cut out using a laser cutter. With a little bending and gluing, the 3D model can be re-created out of paper or cardboard.

There are of course other and more full-featured tools for unfolding 3D models: Pepakura is used by many, but is not free and is Windows only. There is also a Blender extension called Paper Model that exists to export 3D shapes as paper models.

What’s interesting about [Trammell]’s project are the things he discovered while making it. The process of unfolding an STL may be conceptually simple, but the actual implementation is a bit tricky in ways that have little to do with number crunching.

For example, in a logical sense it doesn’t matter much where the software chooses to start the unfolding process, but in practice some start points yield much tighter groups of shapes that are easier to work with. Also, his software doesn’t optimize folding patterns, so sometimes the software will split a shape along a perfectly logical (but non-intuitive to a human) line and it can be difficult to figure out which pieces are supposed to attach where. The software remains in beta, but those who are interested can find it hosted on GitHub. It turns out that it’s actually quite challenging to turn a 3D model into an unfolded shape that still carries visual cues or resemblances to the original. Adding things like glue tabs in sensible places isn’t trivial, either.

Tools to unfold 3D models feature prominently in the prop-making world, and it’s only one of the several reasons an economical desktop cutter might be a useful addition to one’s workshop.

HD Video And Telemetry Link Uses Standard WiFi Hardware

December 27, 2018 by Donald Papp 3 Comments

[GlytchTech] decided to implement his own Digital Data Link (DDL) for his drone experiments, and by using a Raspberry Pi Zero and some open-source software, he succeeded in creating a mostly self-contained system that delivers HD video and telemetry using an Android phone as a display.

USB tethered Android phone used as a display and touch interface.

The link uses standard WiFi hardware in a slightly unusual way to create a digital data link that acts more like an analog system, with a preference for delivering low latency video and a graceful drop-off when signal quality gets poor. A Raspberry Pi Zero, Alfa NEH WiFi card, external antenna, battery, and a 3D printed enclosure result in a self-contained unit. Two are needed: one for each end of the link. One unit goes on the drone and interfaces to the flight controller, and the other is for the ground station.

A companion android app allows for just about any old Android phone to serve as video feed, on-screen display of telemetry data, and touchscreen interface.

The software is DroneBridge (GitHub repository) and it implements Wifibroadcast which uses WiFi radios, but without the usual WiFi functionality. A Raspberry Pi is the usual platform, but there’s also an ESP32 port. The software is capable of even more, but so far suits [GlytchTech]’s needs just fine, and he was able to refine his original Watch_Dogs-inspired hacking drone with it.

Cortex 2 Is One Serious 3D Printed Experimental Rocket

December 25, 2018 by Donald Papp 9 Comments

Rocketry is wild, and [Foaly] is sharing build and design details of the Cortex 2 mini rocket which is entirely 3D printed. Don’t let that fool you into thinking it is in any way a gimmick; the Cortex 2 is a serious piece of engineering with some fascinating development.

Cortex 1 was launched as part of C’Space, an event allowing students to launch experimental rockets. Stuffed with sensors and entirely 3D printed, Cortex 1 flew well, but the parachute failed to deploy mainly due to an imperfectly bonded assembly. The hatch was recovered, but the rocket was lost. Lessons were learned, and Cortex 2 was drafted up before the end of the event.

Some of the changes included tweaking the shape and reducing weight, and the refinements also led to reducing the number of fins from four to three. The fins for Cortex 2 are also reinforced with carbon fiber inserts and are bolted on to the main body.

Here’s an interesting details: apparently keeping the original fins would result in a rocket that was “overstable”. We didn’t really realize that was a thing. The results of overstabilizing are similar to a PID loop where gain is too high, and overcorrection results in oscillations instead of a nice stable trajectory.

Cortex 2 uses a different rocket motor from its predecessor, which led to another interesting design issue. The new motor is similar to hobby solid rocket motors where a small explosive charge at the top of the motor blows some time after the fuel is gone. This charge is meant to eject a parachute, but the Cortex 2 is not designed to use this method, and so the gasses must be vented. [Foaly] was understandably not enthusiastic about venting hot gasses through the mostly-PLA rocket body. Instead, a cylindrical cartridge was designed that both encases the motor and redirects any gasses from the explosive charge out the rear of the rocket. That cartridge was SLA printed out of what looks to us like Formlabs’ High Tempurature Resin.

Finally, to address the reasons Cortex 1 crashed, the hatch and parachute were redesigned for better reliability. A servo takes care of activating the system, and a couple of reverse-polarity magnets assist in ensuring the hatch blows clear. There’s even a small servo that takes care of retracting the launch guide.

The rocket is only half built so far, but looks absolutely fantastic and we can’t wait to see more. It’s clear [Foaly] has a lot of experience and knowledge. After all, [Foaly] did convert a Makerbot printer into a CNC circuitboard engraver.

Lenses For DIY Augmented Reality Will Get A Bit Less Unobtainable

December 25, 2018 by Donald Papp 13 Comments

You may remember that earlier this year Leap Motion revealed Project North Star, a kind of open-source reference design for an Augmented Reality (AR) headset. While it’s not destined to make high scores in the fashion department, it aims to be hacker-friendly and boasts a large field of view. There’s also an attractive element of “what you see is what you get” when it comes to the displays and optical design, which is a good thing for hackability. Instead of everything residing in a black box, the system uses two forward-facing displays (one for each eye) whose images are bounced off curved reflective lenses. These are essentially semitransparent mirrors which focus the images properly while also allowing the wearer to see both the displays and the outside world at the same time. This co-existence of both virtual and real-world visuals are a hallmark of Augmented Reality.

A serious setback to the aspiring AR hacker has been the fact that while the design is open, the lenses absolutely are not off the shelf components. [Smart Prototyping] aims to change that, and recently announced in a blog post that they will be offering Project North Star-compatible reflective lenses. They’re in the final stages of approving manufacture, and listed pre-orders for the lenses in their store along with downloadable 3D models for frames.

When Leap Motion first announced their open-source AR headset, we examined the intruiguing specifications and the design has since been published to GitHub. At the time, we did note that the only option for the special lenses seemed to be to CNC them and then spring for a custom reflective coating.

If the lenses become affordable and mass-produced, that would make the design much more accessible. In addition, anyone wanting to do their own experiments with near-eye displays or HUDs would be able to use the frame and lenses as a basis for their own work, and that’s wonderful.