The world of microwave RF design appears to the uninitiated to be full of unimaginably exotic devices, as engineers harness the laws of physics to tame radio signals to their will. Among the weapons in their arsenal are materials of known dielectric properties, from which can be made structures with the desired effects on RF that encounters them. This has traditionally been a difficult and expensive process, but it’s one now made much easier by the availability of 3D printer filaments with a range of known dielectric values.
It’s best to think of the structures which can be designed using these materials as analagous to Fresnel lenses we’re all used to in the light domain. The example piece given by Microwave Journal is a metasurface for use in a steerable antenna, something that would be a much more difficult piece of work by more traditional means.
Normally when we inform you of a new special filament we’d expect it to be more costly than standard PLA, but this filament is in a class of its own at 275 euros per kilogram. So the interest for most readers will probably be more in the technology than the expectation of use, but even then we can see that there will still be microwave experimenters in our range who might be tempted by its unique properties. We look forward to what is developed using it.
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.
If you’ve ever paged through the color samples at the hardware store trying to match a particular color, you know how hard it can be. Not only are there nearly limitless color variations, but each manufacturer has their own formulas and tints. Often times, the only way to get the exact color you need is to get it custom mixed.
Unfortunately, that’s not really an option when it comes to filament for your 3D printer. Will that roll of orange from Hatchbox actually match the orange from Overture? That’s where the Filament Librarian comes in. Created by [Joe Kaufeld], the project aims to catalog and photograph as many 3D printer filaments as possible so you can see exactly what you’re getting.
Now of course, if it was as easy as looking at pictures of filament swatches on your computer, you wouldn’t need this service to begin with. So what’s the trick? A custom automated camera rig, powered by the Raspberry Pi, is used to position, light, and photograph each filament sample in the library. So while [Joe] can’t promise your monitor is showing a perfect representation of each filament’s color, you can at least be sure they will all look correct in relation to each other. So for example, the site can help you figure out if the local Microcenter stocks anything that comes close to matching Prusament’s Galaxy Silver PLA.
[Joe] brought a collection of his samples along with his slick camera setup to the 2022 East Coast RepRap Festival so attendees could see first-hand how he adds a new filament to the database. With an easy-to-use touch-screen interface, it takes just seconds to get the camera ready for the next shot.
Now that he’s got the hardware and the procedure down, [Joe] is asking the community to help out by providing him with filament samples to process. It doesn’t take much: all he asks is you snip him off a couple meters of filament, write down what it is and who makes it on a pre-made form, and drop it in the mail. If you’re in the US, you can send it directly to his address in Indiana, and for those on the other side of the globe, he’s got a drop point in the Netherlands you can use.
We love a good passion project here at Hackaday, so here’s hoping that the Filament Librarian receives plenty of new filament samples from all over the planet to feed into that fancy camera setup of his.
Even if they don’t have one themselves, we’d wager the average Hackaday reader is at least vaguely aware of how a vacuum former works on a fundamental level. You heat up a plastic sheet until it’s soft, then use a vacuum pump to pull the ductile material down onto an object and hold it there while it cools off. It’s easy to build a vacuum forming rig yourself, but small commercial units are cheap enough that it might not be worth your time. If everything goes to plan, the technique is a quick and effective way of duplicating items around the home and shop.
So what’s the advantage? Well for one thing, it’s cheaper. Though admittedly, not by much. Going rate on Amazon seems to be about 90 cents per sheet for the real stuff, and some back of the envelope math shows the printed version coming in at around 30 cents given nominal filament costs. Whether or not those savings are worth the extra effort is certainly debatable.
But that’s not really the most interesting part. With printed sheets loaded into the vacuum former, you’ve got access to a much wider array of materials to work with. For example, [Nathan] shows off some very interesting flexible pieces he was able to produce using sheets of TPU. You can also experiment with different surface textures. These can not only be used to give your vacuum formed pieces a bit of interesting visual flair, but could actually have some practical applications. In the video we see how a printed mesh could be formed over a piece to create a conformal air vent or filter.
To be sure, there’s some room for improvement here. Not all the pulls were successes, and [Nathan] says getting the printed sheets up to the proper temperature can be tricky. But when it works, it works quite well, and we think there could be some untapped potential in this unexpected melding of new and old methods of at-home plastic production.
Recycling plastic into filament normally involves chopping it into tiny pieces and pushing it through a screw extruder. [JRT3D] is taking a different approach with PetBot, which cuts PET bottles into tape and then turns it into filament. See the videos after the break.
Cutting the tape and extrusion happens in two completely separated processes on the same machine. A PET bottle is prepared by cutting off the bottom, and the open rim is pushed between a pair of bearings, where a cutter slices the bottle into one long strip, as a driven spool rolls it up. The spool of tape is then moved to the second stage of the machine, which pulls the tape through a hot end very similar to that on a 3D printer. While most conventional extruders push the plastic through a nozzle with a screw, the PetBot only heats up the tape to slightly above its glass transition temperature, which allows the driven spool to slowly pull it through the nozzle without breaking. A fan cools the filament just before it goes onto the spool. The same stepper motor is used for both stages of the process.
We like the simplicity of this machine compared to a conventional screw extruder, but it’s not without trade-offs. Firstly is the limitation of the filament length by the material in a single bottle. Getting longer lengths would involve fusing the tape after cutting, or the filament after extrusion, which is not as simple as it might seem. The process would likely be limited to large soda bottle with smooth exterior surfaces to allow the thickness and width of the tape to be as consistent as possible. We are curious to see the consistency of the filaments shape and diameter, and how sensitive it is to variations in the thickness and width of the tape. That being said, as long as you understand the limitations of the machine, we do not doubt that it can be useful. Continue reading “PetBot: Turn PET Bottles Into Filament”→
[Proper Printing] has been trying to 3D print rims for his car for quite some time. However, the size of the print has led to problems with filament spools running out prior to completion. This led to endless headaches trying to join several smaller lengths of filament in order to make a single larger spool. After his initial attempts by hand failed, a rig was built to try and bring some consistency to the process. (Video, embedded below.)
The rig consists of a heater block intended to melt the ends of two pieces of filament so that they can be fused together. A cheap set of brass calipers was modified with a tube in order to form a guide for the filament, ensuring that it gets bonded neatly without flaring out to a larger size. Fan coolers are then placed either side of the heating area to avoid turning the whole filament into a hot mess.
Unfortunately, the rig simply didn’t work. The initial design simply never got the filament hot enough, with the suspicion being that heat was instead being dumped into the calipers instead of the filament itself. Modifications to reduce this sadly didn’t help, and in the end, more success was had by simply holding a lighter below a length of brass tube.
The filter works in a simple way. The Spongebob shell is 3D printed in two halves, with a hinge joining both parts. Inside each half, a section of sponge is stuck inside. The two halves are then closed with a snap fit, with the filament passing through a hole in Spongebob’s head and out through the (square) pants. With the sponge packed in nice and tight, dust is wiped from the filament as it feeds through bob to the printer.
While it’s important to install carefully to avoid filament feed issues, it’s an easy way to automatically clean filament during the printing process. You may be surprised just how dirty your filament gets after sitting on the shelf for a few months. Getting rid of such contamination decreases the likelihood of annoying problems like delaminations and jams. Avid printers may also want to consider making their own filament, too. Happy printing!