Despite the best efforts of the RepRap community over the last twenty years, self-replicating 3D printers have remained a stubbornly elusive goal, largely due to the difficulty of printing electronics. [Brian Minnick]’s fully-printed 3D printer could eventually change that, and he’s already solved an impressive number of technical challenges in the process.
[Brian]’s first step was to make a 3D-printable motor. Instead of the more conventional stepper motors, he designed a fully 3D-printed 3-pole brushed motor. The motor coils are made from solder paste, which the printer applies using a custom syringe-based extruder. The paste is then sintered at a moderate temperature, resulting in traces with a resistivity as low as 0.001 Ω mm, low enough to make effective magnetic coils.
Brushed motors are less accurate than stepper motors, but they do have a particularly useful advantage here: their speed can be controlled simply by varying the voltage. This enables a purely electromechanical control system – no microcontroller on this printer! A 3D-printed data strip encodes instructions for the printer as holes in a plastic sheet, which open and close simple switches in the motor controller. These switches control the speed, direction, and duration of the motors’ movement, letting the data strip encode motion vectors.
Remarkably, the hotend on this printer is also 3D-printed. [Brian] took advantage of the fact that PEEK’s melting point increases by about 110 ℃ when it’s annealed, which should allow an annealed hotend to print itself. So far it’s only extruded PLA, but the idea seems sound.
The video below the break shows a single-axis proof of concept in action. We haven’t been able to find any documentation of a fully-functional 3D printer, but nevertheless, it’s an impressive demonstration. We’ve covered similar printers before, and if you make progress in this area, be sure to send us a tip.
Rather, it’s limited – not controlled. The actual speed of the motor depends on the load. This is why they’re less accurate.
BLDC motors using simple offset commutation behave the same way: they simply try to run as fast as they can give the input voltage. It’s the same action of commutation, only using Hall sensors instead of brushed switches.
Some may ask “Why?” To me (core RepRap dev of old, and RepRapMicron dev of today) this is a nuanced important advance. Once the principles of printing all of a 3D printer are established, the reliance on the shape and size of commodity parts goes away. Then the machines can be miniaturized, and the printing of microelectronics and MEMS (who knows, even nanoscale) becomes possible.
More importantly – once you can genuinely self-replicate replicators then there is no possibility of control of them.
Grey goo???
What’s scarier to me is the general public having no means of detecting or creating a countermeasure to Grey Goo, or other more feasible nanoscale threat. Some such threats are desirable by military agencies, and because of their small and replicating nature, they or their fabrication technology will be “liberated” one way or another – probably for personal gain.
Having nanoscale technology in the hands of everyone is the best way to detect and adapt, possibly even preempt, this. I certainly would not like to be in a position where this stuff only exists in military labs, operating under the principle of “security by obscurity.” But it may have happened already :)
High voltage seems like a pretty solid countermeasure to electronic-based grey goo.
You might think high voltage would zap it. Sadly, not so much for two reasons: Voltage is measured across things, and nanomachines are very, very small so the voltage across any particular one from a 10KV discharge over a millimetre would amount to only a few volts. Secondly, the mechanisms are likely to be mechanical, operated either by chemical bonding or electrostatics rather than current microelectronics – and those electrostatics would be operating at volts/metre that would make the designers of particle accelerators dribble.
If gray goo is an angry mob of bare IC dies, there are plenty of obvious countermeasures. Electrostatic discharge is their traditional nemesis. But you could also use corrosive chemicals. Flamethrowers. Infrared energy. Scotch tape. A Super Soaker full of salt water.
Most gray goo scenarios in fiction are really horror movie tropes with a veneer of nanotech over just plain magic. They never seem to consider what sort of feedstock the nanites need to replicate – if it’s pure silicon, they could only infest existing electronics or their production line. How much fuel does each nanites carry, and where do they get it? If a microprocessor gets infested with nanites, can they find enough fuel to walk to the RAM chip to continue spreading or do they have to wait for someone to shake the circuit board to move them? Do they have enough stored energy to dig out if you bury them in sand, or free themselves if they are stuck on a piece of tape? And what if peeling the tape generates a spark?
Grey goo scenarios start with the assumption that it’s physically possible to make something the size of a bacterium that is vastly more complex, has vastly more energy and computing power, than a bacterium.
In other words, “if spherical cows could fly”.
I’ll start worrying when the printers can manufacture their own supplies from their environment.
Envisioning a rover that goes out in search of discarded plastic bottles to make it’s own filament. Sort of reminiscent of the robot MIT built that went around collecting slugs to power it’s bioreactor.
4 years old video…
2D printers use DC motors instead of servos, a cheap workaround involving an optocoupler and a disk of measured increments on the axis as the error signal.
With non-planar slicing now becoming popular, we’ll be seeing 3D printers that look like robotic arms instead of the traditional 3-axis bed.
Its a cool project. In their current state I don’t think I’d want to use one of those motors for anything personally but, maybe in 5 years after some advances I would. Who knows. A 3D printed hot end would be a really interesting challenge
A 3d printed hotend is easy:
Step 1. Acquire time on a $500,000+ powdered metal sintering 3D printer.
Step 2. Waste that time printing a hotend you could better make (surface finish in channel) with a $300 chinesium mini mill and $20 in tooling.
Step 3. Loss!
hahaha what a ridiculous hack
i wanted to point out the real reason we don’t 3d print printers is that pieces like extrusion and coated steel plates are just so mechanically superior. but then i saw 3d printed motor and wooo they’re on a different trip entirely
I wonder what fun artifacts will be produced by heat warping the entire bed and structure over time. Most parts won’t reach melting point, but many areas I see will eventually hit glass transition