When it comes to portable power, lithium-ion batteries are where it’s at. Unsurprisingly, there’s a lot of work being done to better understand how to maximize battery life and usable capacity.
While engaged in such work, [Dr. Michael Metzger] and his colleagues at Dalhousie University opened up a number of lithium-ion cells that had been subjected to a variety of temperatures and found something surprising: the electrolytic solution within was a bright red when it was expected to be clear.
It turns out that PET — commonly used as an inert polymer in cell assembly — releases a molecule that leads to self-discharge of the cells when it breaks down, and this molecule was responsible for the color change. The molecule is called a redox shuttle, because it travels back and forth between the cathode and the anode. This is how an electrochemical cell works, but the problem is this happens all the time, even when the battery isn’t connected to anything, causing self-discharge.
In Back to the Future, Doc Brown returns to 1985 with a version of his DeLorean time machine that has been modified with technology from the future. After telling Marty they need to go on yet another adventure, Doc recharges the DeLorean’s flux capacitor and time circuits by tossing pieces of garbage into the slick Mr. Fusion unit mounted to the rear of the vehicle. The joke being that, in the future, you could simply head over to the local big box store and pick up a kitchen appliance that’s capable of converting waste matter into energy.
Unfortunately, we’re nowhere near powering our homes with banana peels and beer cans. But if the Recreator 3D is any indication, the technology required to turn plastic bottles rescued from the trash into viable PET filament for your 3D printer is all but upon us. While there are still some aspects of the process that could stand to be streamlined, such as fusing multiple runs of filament together into one continuous roll, the core concepts all seem to be in place.
Creator [Josh Taylor] made the trip out to the 2022 East Coast RepRap Festival to not only show off the Recreator 3D, a project he’s been working on now for over a year, but to get people excited about the idea of turning waste plastic into filament. It’s not necessarily a new concept, and in fact [Josh] says earlier efforts such as the PETBOT are what inspired him to create his own open source take on the “pultrusion” concept.
According to [Josh], actually printing with the recycled filament isn’t that different from using commercial PETG, though it’s recommended you lower your speeds. A nozzle temperature of around 260 °C seems to work best, with the bed at 70 °C. Interestingly, the filament produced by the process is actually hollow inside, so the most critical change to make is increasing your extrusion rate to about 130% of normal to compensate for the internal void.
The current revision of the Recreator 3D, known as the MK5Kit, can be assembled using several core components salvaged from a low-cost Ender 3 printer in addition to a number of parts that the user will need to print themselves. For those who’d rather not source the parts, [Josh] says he hopes to get formal kits put together sometime next year, thanks to a partnership with LDO Motors.
[Ondřej Šraitr] has several videos, including the one you can watch below, about his PETamentor2 — a machine for turning PET bottles into printable filament. You can grab the files on Thingiverse, and there aren’t many parts you have to buy.
The device looks good, and from the videos, it appears to work well. A blade slices the bottle into a strip that feeds what is essentially a hot end that pushes out the filament. The blade is adjustable to set the amount of plastic fed at any given time which is important because you need enough to create a solid piece of filament but not any more than that.
Surprisingly, the bill of materials doesn’t include any sort of microcontroller. There is a PWM speed control module to drive the 7 RPM motor and a temperature controller. Of course, you need a power supply, a heater block and a heater. The nozzle is, oddly enough, a standard 0.4 mm nozzle. You drill it out to 1.5 mm and die swell takes care of getting to the final 1.75 mm size.
It takes about 45 minutes to eat up what looks like a 1-liter bottle. The filament produced looks good in the video. We aren’t sure, but we think that was a roll of solder used as a ballast weight on top of the bottle keeping it moving in a downward direction. Bottles imply wetness, of course, so after producing the filament, it needs to be dried.
This is the second version of the machine and we were a bit surprised that we never saw a video of the filament in use. But it looks like it would work and it isn’t like we haven’t seen this technique used before. In fact, we’ve seen it several times. We can’t remember any that looked as stylish as the PETamentor2, though, and we are interested to hear about anyone’s results with the resulting filament.
[Estefannie] is a proud cat owner, but one of her cats has a bad habit of eating plastic. That means she needs to keep an eye on that cat’s bowel movements, but with two cats in the house, it’s difficult to know who did what. Thus, she whipped up an AI system to log her cats bathroom visits and give her peace of mind.
It’s not the most glamorous project — [Estefannie] notes she took over 50,000 pictures of her cats using the litterbox to train Microsoft Azure’s Custom Vision model. But after some work, it could readily identify which cat was using the litter box when fed images from a NoIR camera. The system then differentiates between number 1 and number 2 via the time the cat spends in the litter box. It’s not perfect, but it works.
The Raspberry Pi runs a Node.JS server to collate the results, paired with a website front-end for easy data display. That way, anyone on [Estefannie’s] WiFi network can see who did what from a browser. We’ve seen cat litter boxes put on the Internet of Things before, and we’ve even seen people hack litterbox DRM, too.
While the price of 3D printers has come down quite a lot in the past few years, filament continues to be rather pricey especially for those doing a lot of printing. This has led to some people looking to alternatives for standard filament, including recycling various forms of plastic. We’ve seen plenty of builds using various materials, but none so far have had this level of quality control in the final project.
What sets this machine apart from others is that it’s built around an Arduino Nano and includes controls that allow the user to fine-tune a PID controller during the conversion of the recycled plastic into filament. Different plastic bottles have different material qualities, so once the machine is started it can be adjusted to ensure that the filament produced has the exact specifications for the printer. The PCB is available for download, and the only thing that needs to be done by hand besides feeding the machine to start it is to cut the plastic into strips for the starter spool. There is also a separate 3D printed tool available to make this task easy, though.
When you’re lucky enough to have a dog in your life, you tend to overlook some of the more one-sided aspects of the relationship. While you are severely restrained with regard to where you eliminate your waste, your furry friend is free to roam the yard and dispense his or her nuggets pretty much at will, and fully expect you to follow along on cleanup duty. See what we did there?
And so dog people sometimes rebel at this lopsided power structure, by leaving the cleanup till later — often much, much later, when locating the offending piles can be a bit difficult. So naturally, we now have this poop-shooting laser turret to helpfully guide you through your backyard cleanup sessions. It comes to us from [Caleb Olson], who leveraged his recent poop-posture monitor as the source of data for where exactly in the yard each deposit is located. To point them out, he attached a laser pointer to a cheap robot arm, and used OpenCV to help line up the bright green spot on each poop.
But wait, there’s more. [Caleb]’s code also optimizes his poop patrol route, minimizing the amount of pesky walking he has to do to visit each pile. And, the same pose estimation algorithm that watches the adorable [Twinkie] make her deposits keeps track of which ones [Caleb] stoops by, removing each from the worklist in turn. So now instead of having a dog control his life, he’s got a dog and a computer running the show. Perfect.
We joke, because poop, but really, this is a pretty neat exercise in machine learning. It does seem like the robot arm was bit overkill, though — we’d have thought a simple two-servo turret would have been pretty easy to whip up.
Plastic is a remarkable material in many ways. Cheap, durable, and versatile, it is responsible for a large percentage of the modern world we live in. As we all know, though, it’s not without its downsides. Its persistence in the environment is quite troubling, so any opportunity we can take to reduce its use is welcome. This 3D printed machine, although made out of plastic, is made out of repurposed water bottles that have been turned into the filament for the 3D printer.
While there’s not too much information available on the site, what we gather is that the machine cuts a specific type of plastic water bottle made out of PET plastic into strips, and then feeds the strips into a heated forming tool. The tool transforms the strips into the filament shape and spools them so they are ready to feed back into a 3D printer. As a proof of concept, it seems as though this machine was made from repurposed plastic, but it could also be made using whatever filament you happen to have on hand.
As far as recycling goes, this is a great effort to keep at least some of it out of landfills and oceans. Unfortunately, plastic can’t be recycled endlessly like metal, as it will eventually break down. But something like this could additionally save on some filament costs for those with access to these types of bottles. Other options for creating your own filament also include old VHS tapes, but you will likely need a separate machine for that.