Dual-Wielding Robot Carves 3D Shapes From Foam With Warped Wire

June 3, 2020 by Dan Maloney 28 Comments

“Every block of expanded polystyrene foam has a statue inside it and it is the task of the dual-arm hot wire-wielding robot to discover it.” — [Michelangelo], probably.

Be prepared to have your mind blown by this dual-wielding hot-wire 3D foam cutter (PDF). We’ve all seen simple hot-wire cutters before, whether they be manual-feed cutters or CNC-controlled like a 3D-printer. The idea is to pass current through a wire to heat it up just enough to melt a path as it’s guided through a block of polystyrene foam. Compared to cutting with a knife or a saw, hot-wire cuts are smooth as silk and produces mercifully little of that styrofoam detritus that gets all over your workspace.

But hot-wire cutters can’t do much other than to make straight cuts, since the wire must be kept taut. “RoboCut”, though, as [Simon Duenser] and his colleagues at ETH Zurich call their creation, suffers from no such limitations. Using an ABB YuMi, a dual-arm collaborative robot, they devised a method of making controlled curved cuts through foam by using a 1-mm thick deformable rod rather than a limp and floppy wire for the cutting tool. The robot has seven degrees of freedom on each arm, and there’s only so much the rod can deform before being permanently damaged, so the kinematics involved are far from trivial. Each pass through the foam is calculated to remove as much material as possible, and multiple passes are needed to creep up on the final design.

The video below shows the mesmerizing sweeps needed to release the Stanford bunny trapped within the foam, as well as other common 3D test models. We’re not sure it’s something easily recreated by the home-gamer, but it sure is fun to watch.

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Milling A Custom 6-Pin DIN Connector

May 22, 2020 by Tom Nardi 18 Comments

When [Charles Ouweland] found himself in need of a DIN connector that had a somewhat unusual pin arrangement, he figured he could fashion his own in less time than it would take to have a replacement shipped to him. In the end it sounds as though it took a lot longer than expected, but given the worldwide situation, we don’t doubt this bespoke connector was still put to work before its eBay counterpart would have arrived.

More importantly, the connector [Charles] produced looks fantastic. If we weren’t told otherwise, we’d have assumed the finished product was commercially produced. Although to be fair, he did have a little help there. The housing and pins themselves were pulled from a sacrificial connector; his primary contribution was the insulating block that holds the pins in their proper position.

So how did he make it? He had considered using a piece of scrap material and just putting the holes in it with a drill press, but he was worried getting the aliment right. Instead, he decided to call his cheap CNC router into service. By routing his design out of copper clad PCB, he was even able to tie the appropriate pins together right in the connector.

Admittedly, we don’t see a lot of hardware that still uses DIN connectors these days. But this tip is certainly worth filing away just in case. You never know when you might find an old piece of hardware that just needs a little TLC to get up and running again. Who knows, you might even find a dumpster full of them.

CNC Plasma Cutter Filter Gets The Slag Out

May 16, 2020 by Dan Maloney 10 Comments

No matter what kind of tools and materials you use in your shop, chances are pretty good that some process is going to release something that you don’t want to breathe. Table saw? Better deal with that wood dust. 3D-printer? We’ve discussed fume control ad nauseam. Soldering? It’s best not to inhale those flux fumes. But perhaps nowhere is fume extraction more important than in the metal shop, where vaporized bits of metal can wreak respiratory havoc.

Reducing such risks was [Shane Wighton]’s rationale behind this no-clean plasma cutter filter. Rather than a water table to collect cutting dross, his CNC plasma cutter is fitted with a downdraft table to suck it away. The vivid display of sparks shooting out of the downdraft fans belied its ineffectiveness, though. [Shane]’s idea is based on the cyclonic principle common to woodshop dust collectors and stupidly expensive vacuum cleaners alike. Plastic pipe sections, split in half lengthwise and covered in aluminum tape to make them less likely to catch on fire from the hot sparks, are set vertically in the air path. The pipes are arranged in a series of nested “S” shapes, offering a tortuous path to the spark-laden air as it exits the downdraft.

The video below shows that most of the entrained solids slow down and drop to the bottom of the filter; some still pass through, but testing with adhesive sheets shows the metal particles in the exhaust are much reduced. We like the design, especially the fact that there’s nothing to clog or greatly restrict the airflow.

Looking for more on CNC plasma cutter builds? We’ve got you covered, from just the basics to next-level.

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Is It A Toy? A Prototype? It’s A Hack!

May 16, 2020 by Elliot Williams 2 Comments

Some of the coolest hacks do a lot with a little. I was just re-watching a video from [Homo Faciens], who after building a surprisingly capable CNC machine out of junk-bin parts and a ton of ingenuity, was accidentally challenged by Hackaday’s own [Dan Maloney] to take it a step further. [Dan] was only joking when he asked “Can anyone build a CNC machine out of cardboard and paperclips?”, but then [Homo Faciens] replied: cardboard and paperclip CNC plotter. Bam!

My favorite part of the cardboard project is not just the clever “encoder wheel” made of a bolt dipped in epoxy, with enough scraped off that it contacts a paperclip once per rotation. Nor was it the fairly sophisticated adjustable slides and ways that he built to mimic the functionality of the real deal. Nope.

My favorite part of this project is [Norbert] explaining that the machine has backlash here, and it’s got play there, due to frame flex. It is a positive feature of the machine. The same flaws that a full-metal machine would have are all present here, but due to the cheesy construction materials, you can see them with the naked eye instead of requiring a dial indicator. Because it wiggles visible tenths of an inch where a professional mill would wiggle invisible thousandths, that helps you build up intuition for the system.

This device isn’t a “prototype” because there’s no way [Norbert] intends it for serious use. But it surely isn’t just a “toy” either. “Instructional model” makes it sound like a teaching aid, created by a know-it-all master, intended to be consumed by students. If anything, there’s a real sense of exploration, improvisation, and straight-up hacking in this project. I’m sure [Norbert] learned as much from the challenge as we did from watching him tackle it. And it also captures the essence of hacking: doing something unexpected with tech.

Surprise us!

No Corners Were Cut On This Arduino Circle Cutter

May 8, 2020 by Tom Nardi 9 Comments

Hackers always have their eye out for a good deal, so when [Gadget Reboot] saw a good price on square stickers he had to pull the trigger. There was just one problem: his logo is a circle. He could have rectified the problem with a pair of scissors on a lazy afternoon, but we think building an elaborate circle cutting machine was a much better use of his time.

But this project isn’t just for the Giotto wannabes. Even if you don’t find yourself in need of an infinite supply of perfect paper circles, the video after the break provides an excellent case study in getting stepper motors to do your bidding; whatever that might be. [Gadget Reboot] walks the viewer through the design and construction of a dual stepper motor controller that could be used for a multitude of tasks.

With an onboard Arduino Pro Micro, OLED display, and rotary encoder, this controller just needs some custom software to make your CNC dreams come true. [Gadget Reboot] is even using low-cost optical endstops in this build, which are a great non-contact way of making sure your machine doesn’t go out of bounds. That’s particularly important when the machine happens to be wielding a razor blade.

If you’re a thoroughly modern hardware hacker who prefers using a web browser to twiddling knobs, then perhaps you’d be interested in the WiFi enabled stepper motor controller we covered recently.

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Given Enough Time, Even A Circle Can Get Complicated

May 5, 2020 by Tom Nardi 14 Comments

With the weather getting a little nicer, [Michael] thought that running some plant hangers off on his CNC router would be a simple stay-at-home project. After all, you just need to cut a couple circles out of a sheet of plywood…right?

Sure, but [Michael] realized that simply cutting out a ring wasn’t a very efficient approach. Unless you happen to need progressively smaller plant hangers, or maybe a new set of drink coasters, the center disc ends up being wasted material. That might not have been a big deal a few months ago, but when a trip to the Home Depot for more plywood could literally be hazardous to your health, that kind of inefficiency just won’t do.

He reasoned it would be better to break the ring down into sections, which could easily be nested so they fit neatly on a square plywood panel. Of course, now those sections need to be connected to each other in a way that’s strong enough for the ring to hold up the weight of the plant.

So that means extra pieces need to be cut out to serve as braces, and you’ll need to screw it all together, so better add some nuts and bolts to the BOM. You’ll probably want some eye bolts as well, but in a pinch you could just weld washers to the heads of screws like [Michael] did once he ran out of the good stuff.

Some would argue that the time [Michael] spent coming up with this revised design is more valuable than the wood he avoided wasting, which might be true if he was on the job and getting paid hourly. But when it’s a personal project, and quarantine has made sourcing materials difficult, we think it’s a fantastic example of working with what you’ve got on hand.

A Basketball Hoop That Never Lets You Brick

April 20, 2020 by Dan Maloney 25 Comments

With none of the major leagues in any team sport currently meeting, sports fans have a huge void that has to be filled with something. For [Shane Wighton], the machine shop is the place to go when sports let you down, and the result is this basketball backboard that lets you sink every shot every time.

When we first saw this, we thought for sure it would be some overly complicated motorized affair that would move the hoop to catch the basketball, sort of like the dart-catching dartboard we featured some time ago. And while that would be awesome and somebody should totally build that so we can write it up, [Shane]’s hoop dream is a lot simpler mechanically, even if the math needed to determine the proper shape for the backboard was complex. He wrote software to simulate throws from hundreds of positions to determine the shape for the board, which ends up looking like a shallow elliptic paraboloid. The software created a mesh that was translated into CNC tool paths in Fusion 360, and the backboard was carved from blocks of softwood.

The first tests were disappointing; instead of landing every shot, the board seemed to be actively denying them. [Shane] had to puzzle over that for a while before realizing that he didn’t account for the radius of the ball, which means the centroid never actually contacts the backboard. Rather than recalculate and create a new backboard, he just shifted the hoop out from the backboard by a ball radius. With that expedient in place, the setup performed exactly as calculated.

[Shane] may have taken the long road to hoops glory, but we appreciate the effort and the math lesson. And the fact that this ends up being the same shape as some antennas is a plus.

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