Over my many years of many side-projects, getting mechanical parts has always been a creative misadventure. Sure, I’d shop for them. But I’d also turn them up from dumpsters, turn them down from aluminum, cut them with lasers, or ooze them out of plastic. My adventures making parts first took root when I jumped into college. Back-in-the-day, I wanted to learn how to build robots. I quickly learned that “robot building” meant learning how to make their constituent parts.
Today I want to take you on a personal journey in my own mechanical “partmaking.” It’s a story told in schools, machine shops, and garages of a young adulthood spent making parts. It’s a story of learning how to run by crawling through e-waste dumps. Throughout my journey, my venues would change, and so would the tools at-hand. But that hunger to make projects and, by extension, parts, was always there.
Open-Source Extruded Profile systems are a mature breed these days. With Openbuilds, Makerslide, and Openbeam, we’ve got plenty of systems to choose from; and Amazon and Alibaba are coming in strong with lots of generic interchangeable parts. These open-source framing systems have borrowed tricks from some decades-old industry players like Rexroth and 80/20. But from all they’ve gleaned, there’s still one trick they haven’t snagged yet: affordable springloaded T-nuts.
Did you think your printer stayed the same size when it heated up? Well, think again! According to [Mark’s] calculations, when heated, the bed can expand by as much as half a millimeter in the x/y direction. While x/y deformation seems like something we can ignore, that’s not always true. If our bed is rigidly fixed in place, then that change in dimension will only result in a warped bed as it tries to make space for itself.
Don’t give up yet though. As sinister as this problem may seem, [Mark] introduces a classic-but-well-implemented solution: and adjustable kinematic coupling. The kinematic coupling holds the bed at the minimum number of points to keep it rigid while exposing thumbscrews to dial in a level bed. What’s special about this technique is that the coupling holds the bed perfectly rigid whilst allowing it to thermally expand!
This is the beauty of “exact constraint” design. Parts are held together only by the minimum number of points needed to guarantee a specific relationship. Here that relationship is coplanarity between the the nozzle’s x/y plane and the bed. Even when the bed expands this relationship holds. Now that is magic.
With such a flood of 3D printed parts on the market, building a printer has never been easier! Nevertheless, it’s easy to pin ourselves into a corner re-tuning a poor design that skips a foundation on the base principles. If you’re curious about more of these principles behind 3D printer design, check out [Mark’s] thorough walkthrough on the CoreXY design.
3D Printer tool changers are bedazzling to watch, but even failed attempts at tool changers can yield something marvelous. Such is the case for [Raymond] who transformed a tool changer attempt into a perfectly capable z-level probe that uses the hotend itself as a limit switch.
The secret sauce behind this mechanism: a kinematic coupling. This coupling takes two planar surfaces and perfectly constrains them relative to each other by mating them together at exactly 6 points of contact. The result is that repeatedly separating and joining the two surfaces will always land them in the same spot within a few microns. To transform these surfaces into a switch, we need only run a small current between the points of contact. That was easy since there were all-metal balls and pins making the connection. Both surfaces are held together with magnets with the upper surface holding the hotend. To trip the limit switch, the printer simply lowers the z-height until the hotend “probes” the bed, defeating the magnets and breaking the current. Presto! No switches or P.I.N.D.A. probes. Just good old fashioned electricity and steel pins.
With so much focus on pricey probes and repeatable switches, it’s great to see some good old-fashioned geometry guiding the precision behind this printer’s sensing. It’s also heartwarming hear that the whole project was actually inspired by another coupling-equipped 3D printer that landed here a few years ago! Finally, if you’re curious to see some other folks getting some more mileage out of kinematic couplings, have a look at this homebrew CNC touch probe.
These days, budget CNC builds are mainstream. Homebrew 3D printers and even laser cutters are old hats. Now I find myself constantly asking: “where’s it all going?” In the book, Designing Reality, Prof Neil Gershenfeld and his two brothers, Alan and Joel, team up to answer that question. In 250 pages, they forecast a future where digital fabrication tools become accessible to everyone on the planet, a planet where people now thrive in networked communities focused on learning and making.
Designing Reality asks us to look forward to the next implications of the word “digital”. On its surface, digital means discretized, but the implications for this property are extreme. How extreme? Imagine a time where cnc-based fabrication tools are as common as laptops, where fab labs and hackerspaces are as accepted as libraries, and where cities are self-sufficient. The Gershenfelds invite us to open our eyes into a time where digital has vastly reshaped our world and will only continue to do so. Continue reading “Books You Should Read: Designing Reality”→
Trash is relative. When my coworker accidentally lit an ABS-barbecue inside the company laser cutter, he made trash. The wreckage was headed for the dump, but I managed to save it and pass it on to my friend [Amy]. Four months later, she phoenixed it back to life from the trash-it-was to a glorious new system more powerful than the original. This is her story, carefully told in detail in a three-part series (part one, part two, part three) that takes us on a journey from trash to triumph. She even recorded video of the entire process (also embedded below)
Get your notes out because while [Amy] spares every expense to keep this project cheap, she spares no expense at laying out the details for anyone’s path to success when working with these beasts.
As far as origin stories go, our story starts at my last employer’s office. I was in the machine shop asking one of our MechEs a question when the intern points a finger towards the corner of the room and asks: “hey is that supposed to be on fire?” I turn around to see billowing flames coming from our budget Chinese laser cutter. “Nope!” I say. “We need a fire extinguisher!” But our MechE was already on it. In half a moment he returned with an extinguisher. With one squirt the fire was out, but the machine was caked with a nasty powdery debris. It turns out another coworker had committed the almighty sin of laser cutting: he turned it on and walked away. Better yet, it was cutting ABS with a disconnected air nozzle.
This cutter was headed to the dump, but a few shenanigans later, I managed to divert this heap to [Amy]. The paint job was an absolute disaster on the outside, and the gooey ABS-and-powder mixture had caked over the inside. [Amy] dug in, stripping off the paint flakes and re-coating it. Apart from the belts, she salvaged every other part inside the machine. Her secret: “IPA and steel wool.” From there, she built her own fume extractor and lofted the whole system onto a frame she welded herself so that she could push both extractor and cutter around her wood shop as a unit. These days, it’s seeing some mileage for cutting out jigs for her woodworking projects.
Perhaps what’s truly special about this project is that she restored it with the camera rolling. As if building projects isn’t hard enough, getting the right lighting and camera angles while you’re doing the work is even more work! There’s no drop-down lofted camera setup in her garage, so each documented step is carefully set up so it captures what’s happening onscreen. While the IPA-and-steel wool might’ve been one nifty trick, by the end of these videos you’ll find that there really aren’t any secrets: just one engineer who sees the dignity in a project done well and has the patience to carry it out.
Get to know [Amy] on her blog, and you’ll discover the true finesse of her scavenging and engineering wielded hand-in-hand. From Ukuleles borne of fallen tree branches to a garage woodshop bootstrapped from a series of Craigslist adventures, it’s no surprise that a broken laser cutter would find a new life when it landed in her hands.
I was always a sucker for art classes in my early days. There was something special about getting personal instruction while having those raw materials in your hands at the same time. Maybe it was the patient voice of the teacher or the taste of the crayons that finally got to my head. Either way, I started thinking: “I want to do this; I want to teach this stuff.”
Last year at Hackaday Superconference I got my chance. Hardware workshops with real hardware were so rare; I just had to bring one to the table! What follows is my tale of joys and woes bringing together a crew to take their first few steps into the world of cable-driven animatronics. If you’re thinking about getting your feet wet with teaching your own hardware workshop, read on. I’ve packed this story with as much of my own learnings as I could to set you on a path to success.