Trash Printer - Recycled Plastic 3D Print Head

This is a design for a low-cost extruder for printing objects directly from recycled plastic flakes instead of using filament.

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**UPDATE 6/12/22: I've just released the documentation for the Trash Printer Version 3 as my entry for the 2022 Hackaday Prize! This new release includes plans for the whole dang printer, not just the extruder. Check it out! **

In the fall of 2016, I built a 'Precious Plastic' open source plastic shredder, and started experimenting with what I could make with shredded plastic. Next, I built the Precious Plastic extruder, but I was frustrated at how difficult it was to create anything useful. So I began to modify the design, putting it on a vertical axis and trying to make it light enough to fit on a CNC router gantry. After many iterations, I finally got it printing in the Spring of 2019, and the results have been very promising! It is currently printing with Polypropylene (#5) and HDPE (#2), which make up over 50% of the plastic waste stream by volume. Here's how to build one!

This project is intended to be easy to replicate using widely available and easy-to-fabricate parts. It was inspired by the Precious Plastic movement, independently developed by Sam Smith, with a lot of help from a lot of people, especially Darcy Neal, Molly Miner, Nathaniel Garst, and Emma Pritchard.

This print head is simple but effective, and stands to be improved significantly. If you have skills and time to make mods and improvements, please do, and please share your work with the same level of detail that I have. If you appreciate this work, which is completely free and available to everyone at no cost, please consider supporting me on Patreon so that I can keep doing this!

The purpose of this design is to enable printing of large, strong, flexible objects directly from recycled plastic flakes made from common recyclable plastics (currently PP and HDPE), without the need to make filament. It is not intended to have the same resolution or rigidity of desktop printers, although with some improvement to the extruder, software, and gantry, much higher print quality is probably possible.

However, it's worth noting that the larger nozzle size of the Trash Printer is a major part of why this project works at all. Projects like the filastruder enable folks to make filament out of recycled plastic that can be used in existing desktop printers, but the problem with that approach is that without a ton of post-processing, truly post-consumer trash is always going to have little bits of food or labeling or dirt that will quickly clog a typical .2-.4mm printer nozzle, and common recyclable plastics have a lot more warp than ABS or PLA, and are much more difficult to print small parts with. Simply using a bigger nozzle (currently mine is about 4.5mm) and printing bigger stuff, is how the Trash Printer gets around this problem.

Parts printed out of recycled Polypropylene with a 4.5mm nozzle and a .4mm layer height end up being very thick and INCREDIBLY strong. 

You should be able to mount this extruder to any CNC gantry that can support a router, runs G-code and has at least a few inches of Z travel. I am using an "MPCNC" LowRider2 gantry, which costs under $500 in parts and is mostly 3D printable. You can find plans for that at

You will have to dial your extruder to your gantry and preferred software, I am using Repetier Host software, Marlin Firmware, running on a RAMBO 1.4 board at 24VDC. I am using an Solid State Relay (SSR) so that the 24DC from the control board switches 120VAC on and off to the band heater. The band heater is what allows for high-throughput, and I have "tricked" the software to control its temperature by telling it that it is the "heated bed".

Polypropylene and Polyethylene are both highly self-adhesive, which means excellent layer adhesion, but poor bed adhesion. I have solved this problem simply by printing directly onto Polypropylene sheets, eliminating the need for a large heated bed in order to get good adhesion. At the right temperature, the extruded PP will adhere but not fuse to the base-PP, and the parts simply pop off once the print is finished.

I am running the barrel heater (treated as bed heater in software) at 200C, and the hot end at 245C. I am not currently using a part fan, and I believe that if I did it would improve print quality, especially on smaller parts where layers have less time to cool.

Feel free to leave questions in the comments, and I will try to answer them as best I can, and please let me know if you replicate this design, as that is the ultimate test of any open hardware.

This project is a sub-project of my larger "Metabolizer" project, which was a finalist for the Hackaday Prize last year.

PVC Pipe 1:2" Flange Spacer Kit.svg

Use this set of spacers with a white 3" PVC wye. The PVC fittings are slightly smaller than the ABS fittings. The holes are spaced for 1/2" NPT pipe flange.

svg+xml - 21.76 kB - 01/08/2020 at 19:15


ABS Pipe 3:4" Flange Spacer Kit.svg

Use this set of spacers with a black 3" ABS wye. The ABS fittings are slightly larger than the PVC fittings. The holes in this kit are spaced for 3/4" NPT pipe flange.

svg+xml - 21.32 kB - 01/08/2020 at 19:15


ABS Pipe 1:2" Flange Spacer Kit.svg

Use this set of spacers with a black 3" ABS wye. The ABS fittings are slightly larger than the PVC fittings. The holes in this kit are spaced for 1/2" NPT pipe flange.

svg+xml - 20.92 kB - 01/08/2020 at 19:15


svg+xml - 1.92 kB - 12/28/2019 at 21:35


svg+xml - 3.74 kB - 12/28/2019 at 21:35


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M K wrote 11/21/2021 at 02:44 point

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emmanuel wrote 06/26/2020 at 05:59 point

Hello, I've made a shredder with a modified vegetation shredder, and I try actually to use this material to print some object with my homemade prusa I3.

The actual problem is the form of the auger, wood dril or wodd screw ? of what diameter, into a pipe of what diameter ?

What is the diameter of your wood drille ?

do you know the granularity of your shredded plastic ? have made it with little wood screw (3mm into a 5 mm pipe), but he has shredded his plastic until powder, so very little granularity.

I actually make some tests.

but my main question is : where do you find PolyPropylene sheets ? and what thickness ?


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Drew Pilcher wrote 01/04/2020 at 01:29 point

Have you tried using your trash extruder to make filament? Then print with the filiment? There's a project called the "fillistruder" which has a similar auger design to yours.

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mflander wrote 01/01/2020 at 21:18 point

Awesome project! Looking forward to seeing more of your progress. I'm trying to gather as much tribal wisdom as possible about methods for improving HDPE print quality in general. Your work is more visionary but I think one of the first steps towards getting HDPE to becoming a mainstream printing material involves figuring out how to get consistently high print quality comparable to what you can get with PETG. Other than the RichRap project you reference below, do you have any recommendations to any projects or people who have focused on this aspect?

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RW wrote 12/29/2019 at 01:43 point

Great stuff. Would love to make space for one of these in the shop. Thinking it would be great for making bulky brackets and angles for joining other bulk material together. Like PVC pipe for frames of stuff, for those odd angles you can't get with plumbing parts and slot together plywood things you only need to cut square panels for. Custom mounts for things. Random crap like, I need a cable tidy/spool about yay big to tame that appliance cord.

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M K wrote 07/05/2019 at 23:31 point

Amazing progress Sam! I'm so stoked to see you in a hackaday email.  Wow!  The documentation in your video looks stellar. The gantry and new hot end look great. I love it! Kudos and good luck. 

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IT-Wizard wrote 06/24/2019 at 08:06 point

This kind of pioneer we need. Hat off mister.

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jqball2u wrote 06/19/2019 at 23:47 point

This is TOTALLY  *awesome*!!!

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Drew Pilcher wrote 06/19/2019 at 22:14 point

Awesome Idea! Whats the reasoning for the large diameter extruder nozzle? What would happen if you tried to use a regular extruder?

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Mateus Silva wrote 06/19/2019 at 23:37 point

If I had to guess, the wood auger bit acting as screw conveyor doesn't exert enough force to push the plastic through a regular extruder.

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Sam Smith wrote 06/20/2019 at 02:07 point

My new nozzle on my Version 3 extruder is 1/8" instead of 1/4", and we'll see where that gets me. I don't actually know what a regular 3D printer nozzle would do, but at this point the gantry I'm using isn't even tuned enough for that kind of resolution, so I'm not going to try it just yet. Check out the RichRap project if your looking for desktop-3D printer resolution from plastic flakes. The lower resolution allows for a lot of lee-way in the quality and consistency of the material, which is important if you want to use truly post-consumer plastic. HDPE and PP are extremely common and widely available, but they have high thermal warp issues and are often dirty, and so printing with a larger nozzle gives you a bit of wiggle room on both of those issues. That said, slightly higher resolution would be great, and I don't know where that lower limit is yet, but I'm trying to find out. I'll post when I've got the 1/8" nozzle printing with HDPE and hopefully that helps a little.

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