Geocaching On Mars: How Perseverance Will Seal Martian Samples With A Return To Earth In Mind

With the roughly 20-day wide launch window for the Mars 2020 mission rapidly approaching, the hype train for the next big mission to the Red Planet is really building up steam. And with good reason — the Mars 2020 mission has been in the works for a better part of a decade, and as we reported earlier this year, the rover it’s delivering to the Martian surface, since dubbed Perseverance, will be among the most complex such devices ever fielded.

“Percy” — come on, that nickname’s a natural — is a mobile laboratory, capable of exploring the Martian surface in search of evidence that life ever found a way there, and to do the groundwork needed if we’re ever to go there ourselves. The nuclear-powered rover bristles with scientific instruments, and assuming it survives the “Seven Minutes of Terror” as well as its fraternal twin Curiosity did in 2012, we should start seeing some amazing results come back.

No prior mission to Mars has been better equipped to answer the essential question: “Are we alone?” But no matter how capable Perseverance is, there’s a limit to how much science can be packed into something that costs millions of dollars a kilogram to get to Mars. And so NASA decided to equip Perseverance with the ability to not only collect geological samples, but to package them up and deposit them on the surface of the planet to await a future mission that will pick them up for a return trip to Earth for further study. It’s bold and forward-thinking, and it’s unlike anything that’s ever been tried before. In a lot of ways, Perseverance’s sample handling system is the rover’s raison d’être, and it’s the subject of this deep dive.

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A Practical Dual-Arm SCARA 3D Printer

We see a lot of 3D printers here at Hackaday, but as over the years the 3D printer has moved from being an exciting item in its own right to being an everyday tool, it’s increasingly rare for us to feature a build of one as a project. It’s especially rare for us to see a 3D printer that isn’t a variation of either an XYZ Cartesian design or a delta printer, but that’s what [bondus] has done with a printer based upon a parallel SCARA mechanism. If SCARA isn’t something you’re familiar with, it’s a design used in the world of industrial robots in which an almost humanoid jointed arm works in two dimensions, with the third being provided by raising or lowering the whole construction. It has the advantage of greater speed than Cartesian designs, at the expense of higher quality joints being required to maintain accuracy of positioning.

This is the second SCARA printer he’s built, and has a sturdy set of aluminium arms and substantial bearings. Drive comes via a pair of belts to some very large pulleys, and calibration is extremely important to ensure that both arms are in exactly the same plane. The curcular bed is on a lead screw that provides the Z axis.

The results are certainly impressive, both is speed and in print quality. We’ve placed a video of it in action below the break. Whether or not SCARA printers improve to the point of being ubiquitous isn’t something we can supply an answer to, but we’ve featured a small number of them in the past. Particularly memorable is this one using an industrial robotic arm.

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Wood SCARA Arm Gets A Grip

[Ignacio]’s VIRK I is a robot arm of SCARA design with a very memorable wooden body, and its new gripper allows it to do a simple pick and place demo. Designing a robot arm is a daunting task, and the fundamental mechanical design is only part of the whole. Even if the basic framework for a SCARA arm is a solved problem, the challenge of building it and the never-ending implementation details make it a long-term project.

When we first saw VIRK I in all its shining, Australian Blackwood glory, it lacked any end effector and [Ignacio] wasn’t sure of the best way to control it. Since then, [Ignacio] has experimented with Marlin and Wangsamas support for SCARA arms, and designed a gripper based around a hobby servo. It’s as beautiful to see this project moving forward as it is to see the arm moving ping-pong balls around, embedded below.

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Infinite Build Volume With RepRap On Wheels

The average 3D printer is a highly useful tool, great for producing small plastic parts when given enough time. Most projects to build larger 3D printed objects use various techniques to split them into smaller parts which can fit inside the limited build volume of most Cartesian-based printers. However, there’s no reason a printer need sit inside a box, and no reason a printer can’t roam about, either. Hence, we get the RepRap HELIOS on wheels.

[Nicholas Seward] created the HELIOS and entered it into the Hackaday Prize in 2017, using a SCARA arm to build a printer with a large build volume and no moving steppers. One of [Nicholas]’s students then did a test, in which the HELIOS was mounted on an angled motorized cart, giving the printer potentially infinite build volume in one axis.

[Nicholas] expects the current basic setup to be capable of prints 200mm wide, 100mm high, and theoretically infinite length. There’s also potential to enable the device to create large curved parts by allowing the printer to steer itself with independently controlled motors.

There’s more work to be done, particularly to allow the printer to locate itself relative to its work space to avoid dimensional issues on large prints, but the preliminary results are highly impressive. We’ve seen other infinite volume printers, too – like this build using a conveyor belt design. Video after the break.

[Thanks to smerrett79 for the tip!]

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SandBot Happily And Tirelessly Rolls Patterns In Sand

The patience and precision involved with drawing geometric patterns in sand is right up a robot’s alley, and demonstrating this is [rob dobson]’s SandBot, a robot that draws patterns thanks to an arm with a magnetically coupled ball.

SandBot, SCARA version. The device sits underneath a sand bed, and a magnet (seen at the very top at the end of the folded “arm”) moves a ball bearing through sand.

SandBot is not a cartesian XY design. An XY frame would need to be at least as big as the sand table itself, but a SCARA arm can be much more compact. Sandbot also makes heavy use of 3D printing and laser-cut acrylic pieces, with no need of an external frame.

[rob]’s writeup is chock full of excellent detail and illustrations, and makes an excellent read. His previous SandBot design is also worth checking out, as it contains all kinds of practical details like what size of ball bearing is best for drawing in fine sand (between 15 and 20 mm diameter, it turns out. Too small and motion is jerky as the ball catches on sand grains, and too large and there is noticeable lag in movement.) Design files for the SCARA SandBot are on GitHub but [rob] has handy links to everything in his writeup for easy reference.

Sand and robots (or any moving parts) aren’t exactly a natural combination, but that hasn’t stopped anyone. We’ve seen Clearwalker stride along the beach, and the Sand Drawing Robot lowers an appendage to carve out messages in the sand while rolling along.

Wood Shines In This SCARA Robotic Arm Project

[igarrido] has shared a project that’s been in the works for a long time now; a wooden desktop robotic arm, named Virk I. The wood is Australian Blackwood and looks gorgeous. [igarrido] is clear that it is a side project, but has decided to try producing a small run of eight units to try to gauge interest in the design. He has been busy cutting the parts and assembling in his spare time.

Besides the beautifully finished wood, some of the interesting elements include hollow rotary joints, which mean less cable clutter and a much tidier assembly. 3D printer drivers are a common go-to for CNC designs, and the Virk I is no different. The prototype is driven by a RAMPS 1.4 board, but [igarrido] explains that while this does the job for moving the joints, it’s not ideal. To be truly useful, a driver would need to have SCARA kinematic support, which he says that to his knowledge is something no open source 3D printer driver offers. Without such a driver, the software has no concept of how the joints physically relate to one another, which is needed to make unified and coherent movements. As a result, users must control motors and joints individually, instead of being able to direct the arm as a whole to move to specific coordinates. Still, Virk I might be what’s needed to get that development going. A video of some test movements is embedded below, showing how everything works so far.

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Putting More Tech Into More Hands: The Robin Hoods Of Hackaday Prize

Many different projects started with the same thought: “That’s really expensive… I wonder if I could build my own for less.” Success is rewarded with satisfaction on top of the money saved, but true hacker heroes share their work so that others can build their own as well. We are happy to recognize such generosity with the Hackaday Prize [Robinhood] achievement.

Achievements are a new addition to our Hackaday Prize, running in parallel with our existing judging and rewards process. Achievements are a way for us to shower recognition and fame upon creators who demonstrate what we appreciate from our community.

Fortunately there is no requirement to steal from the rich to unlock our [Robinhood] achievement, it’s enough to give away fruits of price-reduction labor. And unlocking an achievement does not affect a project’s standings in the challenges, so some of these creators will still collect coveted awards. The list of projects that have unlocked the [Robinhood] achievement will continue to grow as the Hackaday Prize progresses, check back regularly to see the latest additions!

In the meantime, let’s look at a few notable examples that have already made the list:

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