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!
Advances in filaments for FDM 3D printers have come in leaps and bounds over the past few years, and carbon fibre (CF) reinforced filament is becoming a common sight. Robotics extraordinaire [James Bruton] got his hands on some CF reinforced PLA, and ended up building a completely over-engineered 3D printed skateboard. (Video, embedded below.)
[James] started by printing some test pieces with a 0.5 mm and a big 1.2 mm nozzle with and without the CF, which he subjected to cantilever deflection tests. The piece with CF was 20% stiffer than without.
[James] then built an extremely strong and cool looking skateboard deck with alternating section of the CF PLA and toughened PLA, totalling 2.7 kg of filament. It was extremely strong, so after bolting on a set of trucks and wheels, he did some mild riding at a local skate park, where it survived without any problems. He admits it was completely over-engineered, but points out in that the internal cavities in the deck is the perfect place for batteries on an electric long board.
Designing something from the ground up with the strength and weaknesses 3D printing in mind, leads to some very interesting and innovative designs, of which this is a perfect example, and we hope to see many more like it. We’ve featured a number of [James]’ project, including the remote controlled bowling ball he built for [Mark Rober] and his impressive OpenDog and Start Wars robots.
Getting good results from a 3D printer is like Goldilocks’ porridge. There are a lot of things that have to be just right. One common thing that gives people poor results is damp filament. This is especially insidious because the printer will work fine and then after some period time results degrade but it is no fault of the printer mechanics or electronics. There are many ways to attempt to dry filament, but [HydeTheJekyll] prefers using a slow cooker modified to operate with low air pressure.
We assume this works because the low pressure reduces the boiling point of water, allowing the water to boil off at temperatures that won’t distort the filament. The modifications aren’t very severe. You’ll need some hose and a pump along with some silicone caulk and petroleum jelly.
Have you ever thought that Nixie tubes are cool but too hard to control with modern electronics? And that they’re just too expensive? [david.reid] apparently thought so and decided to create his own version of a Nixie tube, and it doesn’t get much cheaper than this.
While working on a 3D printed locomotive with his son, [david.reid] used clear PETG (Polyethylene Terephthalate Glycol) 3D printer filament to move light from LEDs to various parts of the locomotive. He found this was a success, but roughed up the outside of the filament to see what would happen. Lo and behold, a warm glow appeared on the surface of the tube! Like any good hacker, his next thought was of Nixie tubes, as you have seeninmanyclocks.
His basic idea is that with a little heat you can bend the filament into any shape that you like ([david.reid] uses custom molds). You then use some sandpaper to roughen up the outside wherever you’d like light to show, and add an LED at the bottom to light it up!
[Alec Richter] had a good idea on how he could convert the leftover filament spindles from his 3D printer into multi-compartment storage. An empty spindle is fitted with several trays that rotate out from the circle for easy access. With multiple spools rotating on a central axle, you can really see how a bunch of parts could be organized in a column, though not being able to see through the sides probably limits its use somewhat — most of the modular component storage we’ve seen has clear trays.
He has designed drawer bases with removable compartment trays, along with alignment jigs to help you get the drawer installed perfectly the first time. You can download the designs (14 files!) but you need to sign up for an account first. Also, [Alex]s designs fit very specific spindles so be sure of your measurements, etc.