Everyone loves colourful 3D prints, but nobody loves prime towers, “printer poop” and all the plastic waste associated with most multi-material setups. Over the years, there’s been no shortage of people trying to come up with a better way, and now it’s time for [Roetz] to toss his hat into the ring, with his patent-proof, open-source Roetz-End. You can see it work in the video below.
The Roetz-End is, as you might guess, a hot-end that [Roetz] designed to facilitate directional material printing. He utilizes SLM 3D printing of aluminum to create a four-in-one hotend, where four filaments are input and one filament is output. It’s co-extrusion, but in the hot-end and not the nozzle, as is more often seen. The stream coming out of the hot end is unmixed and has four distinct coloured sections. It’s like making bi-colour filament, but with two more colours, each aligned with one possible direction of travel of the nozzle.
What you get is ‘directional material deposition’: which colour ends up on the outer perimeter depends on how the nozzle is moving, just like with bi-color filaments– though far more reliably. That’s great for making cubes with distinctly-coloured sides, but there’s more to it than that. Printing at an angle can get neighboring filaments to mix; he demonstrates how well this mixing works by producing a gradient at (4:30). The colour gradients and combinations on more complicated prints are delightful.
Is it an MMU replacement? Not as-built. Perhaps with another axis– either turning the hot-end or the bed to control the direction of flow completely, so the colours could mix however you’d like, we could call it such. That’s discussed in the “patent” section of the video, but has not yet been implemented. This technique also isn’t going to replace MMU or multitool setups for people who want to print dissimilar materials for easily-removable supports, but co-extruding materials like PLA and TPU in this device creates the possibility for some interesting composites, as we’ve discussed before.
As for being “patent-proof” — [Roetz] believes that through publishing his work on YouTube and GitHub into the public domain, he has put this out as “prior art” which should block any entity from successfully filing a patent. It worked for Robert A. Heinlein with the waterbed, but that was a long time ago. Time will tell if this is a way to revive open hardware in 3D printing.
It’s certainly a neat idea, and we thank [CityZen] for the tip.
Heinlein opensourced the waterbed?? How am I just now hearing of this
Well he didn’t patent it, but he described it in such detail in his fiction that later “inventors” couldn’t patent the basic concept due to his “prior art”.
People sometimes forget that Heinlein’s later work was kind of R-rated, and had a minor theme of redesigning beds for erotic benefit.
One thing that lodged in my pre-teen memory was that he believed that the height of a couple’s bed should be customized based on the height of the man’s waistline, to enable certain standing positions.
He had opinions on birthing beds too. In “Time Enough for Love” they have a birthing scene in a small spaceship that can carefully accelerate to “pull” the newborn downward (instead of using forceps).
RAH dreamed up the modern water bed whilst convalescing from TB in the 30s. Being stuck in bed for weeks has a way of focusing a man’s mind on the discomforts of standard bedding– particularly if they’re stuck a hospital bed. Especially a 1930s Navy hospital bed, which was doubtless far from the then state of the art in comfort.
He later described his design in great detail in a number of his works (both stories and IIRC essays in collected works, though that may have been later) — enough so that when someone sought to patent the water bed in the 1970s it was found that there was no grounds for a patent as Heinlein’s works constituted “prior art”. Apparently at the peak of the water-bed fad, something like one in five American households had one, and it was all thanks to a guy some dismissed as a hack writer of penny dreadfuls.
I don’t see how you can control the direction of the print for a general model. The geometry of the model forces the direction of the head (on the outline) and you can’t do anything about it. Maybe if the bed had another axis of rotation it would make sense to be able to control the color, and even then, it would be very grayish, like only 1/4th of the hue you’d expect. I guess he should be able to make a better effect by changing the extrusion ratio of the initial filaments (so if he wants yellow, just run the yellow extruder at 100% and the other color at 0%) so the actual color is based on real physical properties instead of a toothpaste trick. When changing color, the bed orientation could be used to start using the paste sooner.
There’s something I haven’t understood yet is why the multicolor print don’t poop in the infill area instead of wasting this. I’d have thought it would make the object stiffer since instead of wasted plastic it would be used for stronger parts. And it’s only a software feature not requiring any hardware change.
This is an extraordinarily good question.
Wild-ass guess: because you’d need to be sure that you have sufficient infill space/distance to get the job done? But then, you could just do layer infill if you needed to, at least sometimes. My guess, though, is that it’s not sufficiently general purpose.
Edit: I looked it up, it’s called “purge to infill”. And I was right about it working most of the time. Freaking great idea!
Oh you sweet summer child (-:
Very neat idea. One thing he didn’t address, which I clearly cannot be the only one to think of, is varying the extrusion of the different filaments.
Reduce the extrusion of one filament to zero, increase the other 3 filaments by 1/3rd to make up for it, and now you have a pie cut into three slices. Similarly for two and even one filament. And of course, any variation in between should also be possible.
The comment about laminar flow in the hot end raises the alternative, twisting the flow into a spiral somehow. Depending on how tight the spiral is, you may be able to get filament mixing, or close enough to approximate it.
I wonder how well the result holds up to sanding, the different colors being very close to each other depending on deposition angle.
There is a prior art with rotating nozzle. I also recall also a giant printer with at least 4 if not more hotends and direct drives extruders (i was even using a second motion system top that was moving in the opposite direction to compensate the vibrations due to the heavy tool head).
I’m a little mixed with the SLM part because it has a very rough surface and that’s not what you want in there. But there are probably methods to smooth it.
Extrude honing is a thing but I don’t know how well it’d work on something so small
haha i never heard of bi-color filament before! what a hack! like the self-striping yarn you can buy for knitting projects
There already is a rotating nozzle implementation by nozzleboss,
that uses the same effect for instant color changes.
https://www.youtube.com/shorts/UyP4f2rYaCU
and a link to the reddit discussion
https://www.reddit.com/r/3Dprinting/comments/1eqi4q7/i_built_a_rotating_mixing_nozzle_to_print_with/
I also tested rotating the bed instead of the nozzle. This gives you infinite rotation without worrying about cables and bowden tubes, but is slower. (but still looks cool, check https://hackaday.io/project/185758-3d-printer-with-rotating-nozzle)
Putting prior art on the internet won’t stop a patent from being approved, as the patent process only checks for prior in patents (yes, I know what you think, I think that as well). But it can be used as proof to then fight any lawsuit that the patent would be used in to invalidate that patent.
Depends perhaps on the jurisdiction/country.
In Europe not only patent documents are used as prior art during the examination but also all kinds of (scientific) journals and sometimes even videos from youtube.
What are the application fees?
In the USA it’s a financial disaster to spend all that money on something un-enforceable.
For normal people it’s a disaster to spend all that money on something enforceable.
Unless your intent is just lawsuits, but in that case, you’ll always find a reason.
The process is the problem.
People working in ‘good faith’ have incentive to do their own GD search for prior art.
Except the lawyers, of course.
Never ask a lawyer if you should spend money on lawyers.
It’s also a good idea to NOT do a patent search if you just want to build something and sell it.
Being unaware makes you not liable for punitive damages and the scumbag’s shyster bills.
Maybe gcode could be changed to extrude unwanted color into infill so that it’s used but not seen?