The idea behind the SpeedBoatRace is how quickly you can print a Benchy — the little boat that is used as a test print for a 3d printer. Speeding up a print is quite tricky as it means moving the head quicker and giving layers less time to deposit and a whole other host of problems. So [Roetz] took a page out of a CPU designer’s playbook, and rather than increasing the latency, he raised the throughput. The original plan was for 20 hot ends, but due to cooling issues, that had to be reduced to 18. Perhaps even more impressive than the scale of the machine is that the only off-the-shelf parts on it are the fans for cooling. Everything else is printed or machined by [Roetz] himself. The whole run was completed in less than an hour, which technically gives him a sub 3.6 minute time per benchy, even accounting for a few that failed.
When it comes to innovation in FDM 3D printing, there doesn’t seem to be much room left to move the needle. Pretty much everything about filament printing has been reduced to practice, with more or less every assembly available off the shelf. Even the business end — the extruder — is so optimized that there’s not much room left for innovation.
Or is there? The way [David Leitner] sees it, there is, which is why he built this rolling-screw extruder (if you can get to the Thingiverse link, [David] cross-posted on reddit, too). Standard extruders work on the pinch-roller principle, where the relatively soft filament is fed past a spring-loaded gear attached to a stepper motor. The stepper rotates the gear, which either advances the filament into or retracts it from the hot end. [David]’s design instead uses a trio of threaded rods mounted between two rings. The rods are at an angle relative to the central axis of the rings, forming a passage that’s just the right size for the filament to fit in. When the rings spin, the threads on the rods engage with the filament, gripping it around its whole circumference and advancing or retracting it depending on which way it’s spinning. The video below shows it working; we have to admit it’s pretty mesmerizing to watch.
[David] himself admits there’s not much advantage to it, perhaps other than a lower tendency to skip since the force is spread over the entire surface of the filament rather than just a small pinch point. Regardless, we like the kind of thinking that leads to something like this, and we’ll bet there are probably unseen benefits to it. And maybe the extruder actually is a place for innovation after all; witness this modular nozzle swapping system.
Ground plastic bits go in one end, finished 3D-prints come out the other. That’s the idea behind [HomoFaciens]’ latest build: a direct-extrusion 3D-printer. And like all of his builds, it’s made from scraps and bits most of us would throw out.
Take the extrusion screw. Like the homemade rotary encoders [HomoFaciens] is known for, it appears at first glance that there’s no way it could work. An early version was just copper wire wrapped around a threaded rod inside a Teflon tube; turned by a stepper motor, the screw did a decent job of forcing finely ground PLA from a hopper into the hot end, itself just a simple aluminum block with holes drilled into it. That worked, albeit only with basically powdered PLA. Later versions of the extruder used a plain galvanized woodscrew soldered to the end of a threaded rod, which worked with chunkier plastic bits. Paddles stir up the granules in the hopper for an even flow into the extruder, and the video below shows impressive results. We also picked up a few tips, like using engine gasket paper and exhaust sealant to insulate a hot end. And the slip coupling, intended to retract the extruder screw slightly to reduce stringing, seems brilliant but needs more work to make it practical.
You might not think to use the word “rigid” to describe most 3D-printer filaments, but most plastic filaments are actually pretty stiff over a short length, stiff enough to be pushed into an extruder. Try the same thing with a softer plastic like TPE, though, and you might find yourself looking at this modified Bowden drive for elastomeric filaments.
The idea behind the Bowden drive favored by some 3D-printer designers is simple: clamp the filament between a motor-driven wheel and an idler to push it up a pipe into the hot end of the extruder. But with TPE and similar elastomeric filaments, [Tech2C] found that the Bowden drive on his Hypercube printer was causing jams and under-extrusion artifacts in finished prints. A careful analysis of the stock drive showed a few weaknesses, such as how much of the filament is not supported on the output side of the wheel. [Tech2C] reworked the drive to close that gap and also to move the output tube opening closer to the drive. The stock drive wheel was also replaced with a smaller diameter wheel with more aggressive knurling. Bolted to the stepper, the new drive gave remarkably improved results – a TPE vase was almost flawless with the new drive, while the old drive had blobs and artifacts galore. And a retraction test print showed no stringing at all with PLA, meaning the new drive isn’t just good for the soft stuff.
Batik is an ancient form of dyeing textiles in which hot wax is applied to a piece of cloth in some design. When the cloth is submerged in a dye bath, the parts covered with wax resist the pigment. After dyeing, the wax is either boiled or scraped away to reveal the design.
[Eugenia Morpurgo] has created a portable, open-source batik bot that rolls along the floor and draws with wax, CNC-style, on a potentially infinite expanse of cloth. The hardware should be familiar: an Arduino Mega and a RAMPS 1.4 board driving NEMA 17 steppers up and down extruded aluminium.
Traditionally, batik wax is applied with a canting, a pen-like object that holds a small amount of hot wax and distributes it through a small opening. The batik bot’s pen combines parts from an electric canting tool with the thermistor, heater block, and heater cartridge from an E3D V6 hot end. [Eugenia] built the Z-axis from scrap and re-used the mechanical endstops from an old plotter. Check out the GitHub for step-by-step instructions with a ton of clear pictures and the project’s site for even more pictures and information. Oh, and don’t resist the chance to see it in action after the break.
Let’s build a robot that gets hot. Really hot — like three times hotter than McDonald’s coffee. Then make it move around. And let’s get the cost in at around $100. Sounds crazy? Not really, since that describes the cheap 3D printers we all have been buying. [John] found out the hard way that you really need to be careful with hot moving parts.
The short story is that [John’s] Anet A8 caught on fire — significantly caught on fire. Common wisdom says that cheap printers often don’t have connectors for the heated bed that can handle the current. There have been several well-publicized cases of those connectors melting, especially on early production models of several printers. However, this printer had an add-on heater with a relay, so that shouldn’t be the problem. Of course, a cheap power supply could do it, too, but the evidence pointed to it being none of those things.
I always find it interesting that 3D printers — at least the kind most of us have — are mostly open-loop devices. You tell the head to move four millimeters in the X direction and you assume that the stepper motors will make it so. Because of the mechanics, you can calculate that four millimeters is so many steps and direct the motor to take them. If something prevents that amount of travel you get a failed print. But there is one part of the printer that is part of a closed loop. It is very tiny, very important, but you don’t hear a whole lot about it. The thermistor.
The hot end and the heated bed will both have a temperature sensor that the firmware uses to keep temperatures at least in the ballpark. Depending on the controller it might just do on-and-off “bang-bang” control or it might do something as sophisticated as PID control. But either way, you set the desired temperature and the controller uses feedback from the thermistor to try to keep it there.
If you print with high-temperature materials you might have a thermocouple in your hot end, but most machines use a thermistor. These are usually good to about 300 °C. What got me thinking about this was the installation of an E3D V6 clone hot end into my oldest printer which had a five-year-old hot end in it. I had accumulated a variety of clone parts and had no idea what kind of thermistor was in the heat block I was using.