Resin-Printed Gears Versus PLA: Which Is Tougher?

When it comes to making gearboxes, 3D printing has the benefit that it lets you whip up whatever strange gears you might need without a whole lot of hunting around at obscure gear suppliers. This is particularly good for those outside the limited radius served by McMaster Carr. When it came to 3D printed gears though, [Michael Rechtin] wondered whether PLA or resin-printed gears performed better, and decided to investigate.

The subject of the test is a 3D-printed compound planetary gearbox, designed for a NEMA-17 motor with an 80:1 reduction. The FDM printer was a Creality CR10S, while the Creality LD02-H was on resin duty.

The assembled gearboxes were tested by using a 100 mm arm to press against a 20 kg load cell so that their performance could be measured accurately. By multiplying the force applied to the load cell by the  length of the arm, the torque output from the gearbox can be calculated. A rig was set up with each gearbox pushing on the load cell in turn, with a closed-loop controller ensuring the gearbox is loaded up to the stall torque of the stepper motor before letting the other motor take over.

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A Nested Gear Clock

One of the most common projects we see here at Hackaday is a clock. It could just be that we as humans are fascinated by the concept of time or that making a piece of functional art appeals to our utilitarian sense. In that spirit, [Alexandre Chappel] set out to make a large mechanical clock with complex gears.

The initial design was made in Fusion360 over a week and then in a somewhat bold move, [Alexandre] started up the CNC and cut all the parts out of valchromat. The basic idea of the clock is that the numbers move on the clock, not the hands. So the clock should show 10:25 instead of moving hands to the 10 and the 5. Most of the clock is made of up stacked gear assemblies, geneva drives, and many bearings. A single stepper motor drives the whole clock, which [Alexandre] admits is a bit of a cheat since trying to add springs and an escapement would add complexity to an already complex clock. He did have to adjust and recut a few gears but most of the assembly came together nicely. Some 3d printed numbers dropped into the CNCed slots offers much-improved readability.

A few problems became apparent once the system was together. The numbers don’t quite line up perfectly, which is unfortunate. He mentioned that tighter tolerances on the gears would likely help there. A fatal design flaw on the smallest disk became apparent as it needs to turn a sixth of the circle whereas the outer circle is just turning a tenth of the circle. Mechanical advantage isn’t in [Alexandre’s] favor and the stepper skips some steps and it slowly makes its way towards the next second digit of the hour.

If you’re looking for more beautiful artistic clocks, why not check out this circuit sculpture one?

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wood strength tester

Shop-Built Rig Measures Strength Of Wood Accurately

Wood is an incredibly versatile material, but like everything else, it has its limits. Build a chair from weak wood and the worst that can happen is probably not that bad. But if you build machine tools from wood, the stakes for using the wrong wood can be a bit higher.

That’s the thinking behind the wood strength testing setup [Matthias Wandel] came up with. Previously, he had a somewhat jury-rigged test setup with a hydraulic bottle jack to apply force to the test piece and a bathroom scale to make measurements. That setup was suboptimal, so version two used a jackscrew to apply the force, but the bathroom scale still left the measurements open to interpretation. Version three, the topic of the video below, went with strain gauges and an A/D converter connected to a Raspberry Pi to automate data collection. The jackscrew was also integrated into the test setup with a stepper motor and, of course, [Matthias]’ famous wooden gears.

While the test rig is pretty simple in design, there’s a lot of subtlety to the calibration to make sure that it’s measuring the test material itself and not just compliance within the mechanism. It’s just another in a long line of data-gathering exercises that [Matthias] seems to groove on, like his recent woodshop electrical explorations.

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Waterjet-Cut Precision Pastry

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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This DIY Drill Press Is Very Well Executed

Plenty of projects we see here could easily be purchased in some form or other. Robot arms, home automation, drones, and even some software can all be had with a quick internet search, to be sure. But there’s no fun in simply buying something when it can be built instead. The same goes for tools as well, and this homemade drill press from [ericinventor] shows that it’s not only possible to build your own tools rather than buy them, but often it’s cheaper as well.

This mini drill press has every feature we could think of needing in a tool like this. It uses off-the-shelf components including the motor and linear bearing carriage (which was actually salvaged from the Z-axis of a CNC machine). The chassis was built from stock aluminum and bolted together, making sure to keep everything square so that the drill press is as precise as possible. The movement is controlled from a set of 3D printed gears which are turned by hand.

The drill press is capable of drilling holes in most materials, including metal, and although small it would be great for precision work. [ericinventor] notes that it’s not necessary to use a separate motor, and that it’s possible to use this build with a Dremel tool if one is already available to you. Either way, it’s a handy tool to have around the shop, and with only a few modifications it might be usable as a mill as well.

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3D Printed Dogbox Transmission Kicks Your Desk Into High Gear

It’s often been our experience that some of the most impressive projects are the passion builds, the ones where the builder really put in their all and obsessed over every detail. Even if they don’t always have a practical application, it’s impossible to look at the final product and not respect the accomplishment.

Case in point, this absolutely incredible 3D printed model of a sequential “dogbox” transmission created by [Indeterminate Design]. All of the STL files and a complete bill of materials are available for anyone brave enough to take on the challenge. It might never be mounted to a vehicle and driven around the track, but you can still flick through the gears and watch the complex gearing do its thing.

Even if you don’t want to necessarily build the model itself, [Indeterminate Design] takes you through the concepts behind this unique transmission and how it differs from the sort of gearboxes us lowly commuter drivers are familiar with. He’s even nice enough to explain what a dogbox is.

Put simply, this type of transmission allows the driver to simply move the gear change forward and backwards to step through the gears like in a video game. This prevents you from having to navigate an H-pattern gear shift while dealing with all the other stresses of competition driving. Watching it in action, you can certainly see the appeal.

If you prefer your printed gearboxes to be of the practical variety, we’ve certainly seen plenty of those as well. They’re perfect for next time you need to move an anvil around the shop.

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Hackaday Links: March 15, 2020

Just a few weeks ago in the Links article, we ran a story about Tanner Electronics, the Dallas-area surplus store that was a mainstay of the hacker and maker scene in the area. At the time, Tanner’s owners were actively looking for a new, downsized space to move into, and they were optimistic that they’d be able to find something. But it appears not to be, as we got word this week from James Tanner that the store would be shutting its doors after 40 years in business. We’re sad to see anyone who’s supported the hardware hacking scene be unable to make a go of it, especially after four decades of service. But as we pointed out in “The Death of Surplus”, the center of gravity of electronics manufacturing has shifted dramatically in that time, and that’s changed the surplus market forever. We wish the Tanner’s the best of luck, and ask those in the area to stop by and perhaps help them sell off some of their inventory before they close the doors on May 31.

Feel like getting your inner Gollum on video but don’t know where to begin? Open source motion capture might be the place to start, and Chordata will soon be here to help. We saw Chordata as an entry in the 2018 Hackaday Prize; they’ve come a long way since then and are just about to open up their Kickstarter. Check out the video for an overview of what Chordata can do.

Another big name in the open-source movement has been forced out of the organization he co-founded. Eric S. Raymond, author of The Cathedral and the Bazaar and co-founder and former president of the Open Source Initiative has been removed from mailing lists and banned from communicating with the group. Raymond, known simply as ESR, reports that this was in response to “being too rhetorically forceful” in his dissent from proposed changes to OSD, the core documents that OSI uses to determine if software is truly open source. Nobody seems to be saying much about the behavior that started the fracas.

COVID-19, the respiratory disease caused by the newly emerged SARS-CoV-2 virus, has been spreading across the globe, causing panic and claiming lives. It’s not without its second-order effects either, of course, as everything from global supply chains to conferences and meetings have been disrupted. And now, coronavirus can be blamed for delaying the ESA/Russian joint ExoMars mission. The mission is to include a Russian-built surface platform for meteorological and biochemical surveys, plus the ESA’s Rosalind Franklin rover. Program scientists are no longer able to travel and meet with their counterparts to sort out issues, severely crimping productivity and forcing the delay. Social distancing and working from home can only take you so far, especially when you’re trying to get to Mars. We wonder if NASA’s Perseverance will suffer a similar fate.

Speaking of social distancing, if you’ve already decided to lock the doors and hunker down to wait out COVID-19, you’ll need something to keep you from going stir crazy. One suggestion: learn a new skill, like PCB design. TeachMePCB is offering a free rigid PCB design course starting March 28. If you’re a newbie, or even if you’ve had some ad hoc design experience, this could be a great way to productively while away some time. And if that doesn’t work for you, check out Bartosz Ciechanowski’s Gears page. It’s an interactive lesson on why gears look like they do, and the math behind power transmission. Ever wonder why gear teeth have an involute shape? Bartosz will fix you up.

Stay safe out there, everyone. And wash those hands!