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.

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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]

Giant 3D Printed Lock Helps Teach Picking

August 22, 2018 by Tom Nardi 12 Comments

Despite what the media might tell you, picking locks isn’t just for spies and guys wearing balaclavas. Those who pick as a hobby, or even competitively, think of locks as logic puzzles. Each lock is a unique challenge, and defeating it requires patience, dexterity, and perhaps most importantly the experience that comes from regular practice. But where does one start if they want to get into the world of recreational lock picking, also known as locksport?

Many people begin their journey on a practice lock, usually made of clear plastic so you can see its inner-workings. That’s fine for the individual, but what if you’re trying to demonstrate lock picking to a group? [John Biggs] may have the solution for you, assuming you’ve got the time and material. His huge 3D printed cutaway lock, and appropriately sized tools, allow even the folks in the back of the room to see how basic picking techniques work.

A print of this size is nothing to sneeze at; a quick peek on the reference printer here at the Hackaday Chamber of Secrets indicates you’re probably looking at the better part of 20 hours to print everything out. Once printed you’ll likely need to take a file and some sandpaper to all the surfaces to make sure things operate smoothly. It doesn’t appear to be a terribly challenging print all things considered, but we wouldn’t call it a beginner’s project either.

The only non-printed part in this design is the springs, which [John] mentions he hasn’t quite found the solution for yet. They need to be fairly weak or else the lock is too hard to pick, but springs large enough to work with the pins are usually pretty strong. This might be a perfect application for some custom wound springs.

After you’ve mastered the PLA lock, it might be time to make your own picks and see if anyone is giving free lock picking workshops in your area.

Automated Turntable For 3D Scanning

August 21, 2018 by Tom Nardi 16 Comments

Those just starting out in 3D printing often believe that their next major purchase after the printer will be a 3D scanner. If you’re going to get something that can print a three dimensional model, why not get something that can create said models from real-world objects? But the reality is that only a small percentage ever follow through with buying the scanner; primarily because they are notoriously expensive, but also because the scanned models often require a lot of cleanup work to be usable anyway.

While this project by [Travis Antoniello] won’t make it any easier to utilize scanned 3D models, it definitely makes them cheaper to acquire. So at least that’s half the battle. Consisting primarily of a stepper motor, an Arduino, and a EasyDriver controller, this is a project you might be able to assemble from the parts bin. Assuming you’ve got a pretty decent camera in there, anyway…

The general idea is to place a platform on the stepper motor, and have the Arduino rotate it 10 degrees at a time in front of a camera on a tripod. The camera is triggered by an IR LED on one of the Arduino’s digital pins, so that it takes a picture each time the platform rotates. There are configurable values to give the object time to settle down after rotation, and a delay to give the camera time to take the picture and get ready for the next one.

Once all the pictures have been taken, they are loaded into special software to perform what’s known as photogrammetry. By compiling all of the images together, the software is able to generate a fairly accurate 3D image. It might not have the resolution to make a 1:1 copy of a broken part, but it can help shave some modeling time when working with complex objects.

We’ve previously covered the use of photogrammetry to design 3D printed accessories, as well as a slightly different take on an automated turntable a few years ago. The process is still not too common, but the barriers to giving it a try on your own are at least getting lower.

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Texture Trick For 3D Prints From The Stone Age

August 21, 2018 by Tom Nardi 14 Comments

Arguably one of the most difficult aspects of 3D printing is trying to make the finished product look like it wasn’t 3D printed. It can take a lot of time and work to cover up the telltale layer lines (or striations, if you want to get fancy), especially if your 3D printer isn’t perfectly calibrated. While there aren’t many shortcuts to achieve a glass-like finish on 3D printed parts, if your end goal is to make something that looks like stone, [Wekster] has a tip for you.

He demonstrates the technique by building a gorgeous recreation of the main gate from Jurassic Park. The process gives the relatively smooth plastic the gnarled look of rough-hewn stone with very little in the way of manual work. While it’s true there’s no overabundance of projects this stone-look finish will work for, it’s definitely something we’ll be filing away mentally.

So what’s the secret? [Wekster] first coats the 3D printed parts with common wood filler, the sort of stuff available at any hardware store. He then wraps them in clear plastic wrap, allowing the wrap to bunch up rather than trying to pull it taught. For extra detail, he digs into the plastic wrap here and there to create what will appear to be gaps and cracks on the finished piece. The wood filler is then left to dry; a process which normally only takes a few minutes, but now will take considerably longer as the plastic wrap will be keeping the air from it.

Once its hardened and unwrapped, [Wekster] sprays it with a base coat of color, and follows up with a few washings with watered down black and gray paints. This technique is well known to anyone who’s done miniature or model painting; serving to highlight the surface texture and give the finish more depth. With this method, anything that resembles a layer line in the print is long gone, and the surface looks so complex and detailed that at first glance few would believe it’s plastic.

[Wekster] also used wood filler during the finishing process for his Fallout 4 “Thirst Zapper” replica. In the past we’ve shown how you can smooth out 3D printed parts with epoxy and taken a very scientific look at using UV resin as a conformal coating, but maybe it’s time we give wood filler a shot.

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A Tiny Steering Wheel You Can Print

August 17, 2018 by Lewin Day 7 Comments

Racing games are a great way to test drive that Ferrari you can’t quite afford yet, and the quality of simulations has greatly improved in the last 30 or so years. While there are all manner of high-quality steering wheels to connect to your PC or home console, many gamers still choose to play using a typical controller, using the thumbstick for steering. What if there was something in between?

What we have here is a tiny steering wheel you can print for an Xbox One controller, that mounts to the controller frame and turns rotational motion into vaguely linear horizontal motion on the thumbstick. It does come with some pitfalls, namely blocking a button or two and it also obscures some of the D-pad. However, for those of you driving in automatic mode without using the buttons to shift gears, this could be a fun device to experiment with. Files to print your own are available on Thingiverse.

It’s a neat hack, and there’s plenty of room to take the idea further and personalise it to suit your own tastes. While you’re there, why stop at steering? You could make your own custom buttons, too!

[via Gizmodo, thanks to Itay for the tip!]

Leather Working With A 3D Printer

August 14, 2018 by Al Williams 22 Comments

No, you can’t print in leather — at least not yet. But [Make Everything] has a tutorial about how to produce a custom leather embossing jig with a 3D printer. From a 3D printing point of view, this isn’t very hard to do and you might want to skip over the first six minutes of the video if you’ve done 3D printing before.

The real action is when he has the 3D print completed. He glues the stamp down to some wood and then fits the assembly to a vise that he’ll use as a press. After wetting the leather, the wood and 3D printed assembly sandwiches the piece and the vise applies pressure for ten minutes. He did make the leather a bit oversized to make alignment more forgiving. After the embossing is complete, he trims it out.

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