Unique 3D Printer Has A Print Head With A Twist

December 2, 2024 by Dan Maloney 26 Comments

If you’re used to thinking about 3D printing in Cartesian terms, prepare your brain for a bit of a twist with [Joshua Bird]’s 4-axis 3D printer that’s not quite like anything we’ve ever seen before.

The printer uses a rotary platform as a build plate, and has a linear rail and lead screw just outside the rim of the platform that serves as the Z axis. Where things get really interesting is the assembly that rides on the Z-axis, which [Joshua] calls a “Core R-Theta” mechanism. It’s an apt description, since as in a CoreXY motion system, it uses a pair of stepper motors and a continuous timing belt to achieve two axes of movement. However, rather than two linear axes, the motors can team up to move the whole print arm in and out along the radius of the build platform while also rotating the print head through almost 90 degrees.

The kinematic possibilities with this setup are really interesting. With the print head rotated perpendicular to the bed, it acts like a simple polar printer. But tilting the head allows you to print steep overhangs with no supports. [Joshua] printed a simple propeller as a demo, with the hub printed more or less traditionally while the blades are added with the head at steeper and steeper angles. As you can imagine, slicing is a bit of a mind-bender, and there are some practical problems such as print cooling, which [Joshua] addresses by piping in compressed air. You’ll want to see this in action, so check out the video below.

This is a fantastic bit of work, and hats off to [Joshua] for working through all the complexities to bring us the first really new thing we’ve seen in 3D printing is a long time.

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Metric And Inch Threads Fight It Out For Ultra-Precise Positioning

September 21, 2022 by Dan Maloney 20 Comments

When you’re a machinist, your stock in trade is precision, with measurements in the thousandths of your preferred unit being common. But when you’re a diemaker, your precision game needs to be even finer, and being able to position tools and material with seemingly impossibly granularity becomes really important.

For [Adam Demuth], aka “Adam the Machinist” on YouTube, the need for ultra-fine resolution machinist’s jacks that wouldn’t break the bank led to a design using off-the-shelf hardware and some 3D printed parts. The design centers around an inch-metric thread adapter that you can pick up from McMaster-Carr. The female thread on the adapter is an M8-1.25, while the male side is a 5/8″-16 thread. The pitches of these threads are very close to each other — only 0.0063″, or 161 microns. To take advantage of this, [Adam] printed a cage with compliant mechanism springs; the cage holds the threaded parts together and provide axial preload to remove backlash, and allows mounting of precision steel balls at each end to make sure the force of the jack is transmitted through a single point at each end. Each full turn of the jack moves the ends by the pitch difference, leading to ultra-fine resolution positioning. Need even more precision? Try an M5 to 10-32 adapter for about 6 microns per revolution!

While we’ve seen different thread pitches used for fine positioning before, [Adam]’s approach needs to machining. And as useful as these jacks are on their own, [Adam] stepped things up by using three of them to make a kinematic base, which is finely adjustable in three axes. It’s not quite a nanopositioning Stewart platform, but you could see how adding three more jacks and some actuators could make that happen.

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Stewart Platform Wields Magic Fingers To Massage Your Scalp

August 4, 2022 by Dan Maloney 13 Comments

Attention Hackaday editors: We on the writing crew hereby formally request budget allocation for installing a Stewart platform head massager on the chair of each workstation in the secret underground writer’s bunker. We think the benefits that will accrue thanks to reduced stress alone will more than justify the modest upfront costs. Thank you for your consideration.

OK, maybe that request is going nowhere, but having been on the receiving end of these strangely relaxing springy scalp stimulators, we can see where [David McDaid] was going with this project. As he clearly states up front, this is a ridiculously over-engineered way to get your scratchies on, but there’s very little not to love about it. Stewart platforms, which can position a surface with six degrees of freedom and range in size from simple ball balancers to full-blown motion simulators, are fascinating devices, and we can’t think of a better way to learn about them than by building one.

Like all Stewart platforms, [David]’s is mechanically simple but kinematically complicated, and he takes great pains to figure out all the math and explain it in an approachable style. The device is mounted with the end-effector pointed down, allowing the intended massagee to insert their noggin into the business end and receive the massage pattern of their choice. Looking at the GIFs below, it’s easy to see why [David] favors the added complexity of a Stewart, which makes interesting patterns like “The Calmer” possible. They’re all intriguing, although the less said about “The Neck Breaker” the better, we’d say.

Hats off (lol) to [David] for this needless complex but entertaining build.

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LEONARDO, a hybrid drone and bipedal robot

LEONARDO: The Hopping, Flying Bipedal Robot

October 7, 2021 by Dan Maloney 22 Comments

We appear to have a new entry atop the “Robots That Creep Us Out” leader board: meet LEONARDO, the combination quadcopter/bipedal robot.

LEONARDO, a somewhat tortured name derived from “LEgs ONboARD drOne,” is actually just what it appears to be: a quadcopter with a set of legs. It comes to us from Caltech’s Center for Autonomous Systems and Technologies, and the video below makes it easy to see what kind of advantages a kinematic mash-up like this would offer. LEO combines walking and flying to achieve a kind of locomotion that looks completely alien, kind of a bouncy, tip-toeing step that really looks like someone just learning how to walk in high heels. The upper drone aspect of LEO provides a lot of the stabilization needed for walking; the thrust from the rotors is where that bouncy compliance comes from. But the rotors can also instantly ramp up the thrust so LEO can fly over obstacles, like stairs. It’s also pretty good at slacklining and skateboarding, too.

It’s easy to see how LEO’s multimodal locomotion system solves — or more accurately, avoids — a number of the problems real-world bipedal robots are going to experience. For now, LEO is pretty small — only about 30″ (76 cm) tall. And it’s rather lightly constructed, as one would expect for something that needs to fly occasionally. But it’s easy to see how something like this could be scaled up, at least to a point. And LEO’s stabilization system might be just what its drunk-walking cousin needs.

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Trippy Tripteron Kinematics Brainteaser

June 1, 2021 by Chris Lott 18 Comments

[JK Lee] has been experimenting with a monorail tripteron motion control system (video, embedded below) and trying to improve performance with varying tweaks to the design and with varying degrees of success. But [JK] is enjoying this project — he was inspired by an idea that maker [Nicholas Seward] proposed — building a tripteron on two rails (video), or even building one on a single rail (video). He is making good progress, most recently working on solving a vertical bounce issue. He is focusing on the middle arm, as this arm carries most of the weight. You can see a brief video explanation of the kinematics of the monorail tripteron that [JK] made (he warns us that English is not his native language, so focus on the equations and diagrams and not the grammar).

If you’re not familiar with the tripteron, it was conceived, along with the quadrupteron, at the Robotics Laboratory at Université Laval in Canada and patented by their researchers back in 2004. We wrote about an early implementation of a tripteron by [Apsu] back in 2016. These recent experiments, reducing the mechanism down to a single or double rail, are interesting.

Other than cool projects for makers like [Nicholas] and [JK] who enjoy tinkering, are there any applications of tripterons and/or quatrupterons in the real world? Let us know in the comments below. Thanks to [Littlejohn] for sending in the tip.

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Waterjet-Cut Precision Pastry

March 6, 2021 by Elliot Williams 20 Comments

We need more high-end, geometric pastry in our lives. This insight is courtesy of a fairly old video, embedded below, demonstrating an extremely clever 2D CNC mechanism that cuts out shapes on a cake pan, opening up a universe of arbitrary cake topologies.

The coolest thing about this machine for us is the drive mechanism. A huge circular gear is trapped between two toothed belts. When the two belts move together the entire thing translates, but when they move in opposite directions, it turns. It seems to be floating on a plastic platform, and because the design allows the water-jet cutting head to remain entirely fixed, only a small hole underneath is necessary, which doubtless simplifies high-pressure water delivery and collection. Rounding the machine out are cake pans make up of vertical slats, like on a laser- or plasma-cutter table, that slip into registration pins and let the water pass through.

The kinematics of this machine are a dream, or perhaps a nightmare. To cut a straight line, it does a cycloid-shaped dance of translation and turning that you simply have to see in motion. Because of this intricate path, the cake-feed speed varies along the way, so this machine won’t be perfect for all applications and relies on a thin kerf. And we can’t help thinking how dizzy the cake must get in the process.

Indeed, the same company put out a relatively pedestrian two-arm motion cutter (another video!) that poses different kinematic problems. It’s essentially a two-arm plotter with a moving table underneath that helps increase the working area. Details are scarce, but it looks like they’re minimizing motion of the moving table, doing the high frequency small stuff with the stiff arms. Presumably someone turned the speed on the previous machine up to 11 and spun a cake off into the room, causing them to rethink the whole move-the-cake-around design.

Of course, watercut pastry isn’t limited to exotic CNC mechanisms. This (third!) video demonstrates that a simple Cartesian XY bot can do the job as well.

If you think about it, using high-pressure pure water to cut foodstuffs is a win on many levels. We’d just miss out on licking the knife. Thanks [Adam G DeMuri] for the awesome comment that lead us to a new world of watercut edibles.

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The Jolly Cart-Pushing Robot

September 14, 2020 by Orlando Hoilett 4 Comments

[Lance] loves making simple robots with his laser cutter. He finds great satisfaction from watching his robots operate using fairly simple mechanisms and designs a whole slew of them inspired by different animals, including a dinosaur and a dragon. His latest build is a jolly cart-pushing robot.

He cut each piece of his robot on his laser cutter, and in order to get the pieces to fit snugly together he made each tab a little bigger than its corresponding slot, ensuring the piece wouldn’t fall out. This also helps account for the loss in the material due to kerf, which is the bit of each piece of material that gets lost in the cut end of the laser cutter.

Making his robot walk was mostly as easy as attaching each leg to a simple DC motor such that the motor would rotate each leg in succession, pushing the robot along. From time to time, [Lance] also had to grease the robot’s moving parts using a bit of wax to help reduce friction. He even used a little rubber band to give the robot some traction.

[Lance] did a pretty good job detailing the build in his video. He also linked to a few other fun little robot designs that could entertain you as well. Pretty easy hack, but we thought you might find the results as satisfying as we did.

Robot companions may be here to stay. Time will tell.

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