RecycleBot v2.2

by jpearce, published

RecycleBot v2.2 by jpearce Oct 27, 2011



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A RecycleBot is a waste plastic extruder - that can take household polymer waste and turn it into valuable 3-D printer feedstock.

Information about the first RecycleBot can be found here: Recyclebot v1.0. This was a great proof of concept and based off of a hand-powered design - although fantastic from an environmental/appropriate technology perspective did not create filament of high enough quality to be particularly useful for open source 3D printers.

The design for the waste plastic extruder (Recyclebot v2.0 and v2.1) is heavily influenced by the Web4Deb extruder, which extrudes HDPE for use as a growth medium in aquaponics. Details of the Web4Deb design are here. As part of Mechanical Engineering course, that I supervised, Christian Baechler developed Recyclebot v2.0 an automated device to automatically convert household plastic waste into usable material to be fed into small scale rapid prototyping machines, such as the RepRap. This design was improved upon within the group - especially with the help of Matthew DeVuono to make v2.1. The results of this are extremely promising and the work will be published.

The RecycleBot work is now being carried out by members of the Michigan Tech in Open Sustainability Technology Research Group.

The v2.2 is -- I am sure over-designed -- but we needed a reliable tool (v2.0/v2.1 were made of wood and we kept breaking it and sending pieces all over the lab). I am sure the attached design is working though so felt ready to post.

Our goal is to have a fully automated system running off of an Ardruino. Imagine pressing a button for recyclable plastic 1-7, shredding your given plastic waste container in a office shredder, having the Recyclebot automatically shift its setting and output commercial grade 3-D printer filament while you go for lunch.

We are about half way there -- if anyone would like to help particularly on the controls side - please drop me a line. Improvements will be posted on a wiki first as we go and imported to Thingiverse when they are solid.

More info: Christian Baechler, Matthew DeVuono, and Joshua M. Pearce, “Distributed Recycling of Waste Polymer into RepRap Feedstock, Rapid Prototyping Journal, 19(2), pp. 118-125 (2013).


How it works
The Recyclebot consists of 3/4" (inner diameter) piping divided into a gearing, hopper and heating section. Shredded plastic is fed into the hopper and transported to the heating section by a 3/4” - 17" ship bore auger driven by a windshield wiper motor. Power is transferred from motor to auger using a sprocket and chain drive system with a 2:1 gear ratio to decrease speed and increase torque. The motor has a stall torque of 30Nm and runs at 35rpm on the low speed setting. The gearing section of the extruder body houses the auger and also provides support for a thrust bearing and collar used to counter axial force encountered during transportation of the ground plastic.

Plastic pushed into the heating section is melted and forced through a die producing plastic filament. The heating zone consists of insulated 14 gauge nichrome 80 wire wrapped around the barrel and secured with heat resistant Kapton tape. You can also use furnace cement between the piping and uninsulated nichrome to prevent short circuiting through the pipe at high temperatures. Fourteen gauge wire was chosen in an effort to create the heating zone with minimal power requirements. (Based on other work we are trying to create a completely solar powered distributed manufacturing tool set 3-D Printing of Open Source Appropriate Technologies for Self-Directed Sustainable Development.

Wire temperatures of 225C were achieved with 75W of power (15V, 5A). Temperature can be adjusted by altering the current passing through the nichrome wire - so that you can personalize the settings for a given polymer or mixture.

HDPE filament has been successfully produced with this method at an average rate of 90 mm/min and used to print parts. The filament diameter averaged about 2.8mm.

To do:

  1. Full mechanical assembly instructions
  2. Operation instructions
  3. Design improvements and post extrusion winding, cooling/solidification methods
  4. Electronics/software
  5. Experimental results on filament and RepRap print quality
  6. Tricks to print waste polymers successfully

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This is awesome and was actually looking into making one. I was wondering if you knew what would be needed to add specks or metallic to a filament. Could you use the same flakes used on cars or would something else be used? There is a filament I love the look of called vertigo grey by fillaminum. It has a white kinda speck to it that reminds me of the powder coating we use to use on car frames, atv’s and such. So was just curious what type of material would be best to add to a dark grey pellets to achieve diffrent specks within it. Thanks and keep up the awesome work.

This is a great idea. Has your team been successful in creating one?

Thank you -- yes absolutely...we have made many of these, published a few papers on the results and have continued to improve on the design. You can see the latest here http://www.appropedia.org/Recyclebot Version 6 should be out soon that will have almost all 3D printable parts :)

Instead of flatting it like he is could it not be drawn through a die to the 1.75mm or 3mm as needed?

This is very interesting to me. I wonder are there any harmful (to yourself or the environment) gasses that are produced when melting the plastic? or is that only when you burn plastic? what about if this were done with plastic from old computers that usually has fire retardant chemicals and such? because there is a lot of raw material in old computers and selling it as filliment could be a whole lot more profitable than other methods of recycling.

These are great points. We have been doing all of our experiments in a fume hood to avoid harming ourselves. It is pretty easy to burn the plastic when you are experimenting with different kinds. We have also only looked for the most part at food containers and personal care product containers....so no old computer shells. These fumes along with the ones we take for granted (e.g. ABS with the different colorants) should all be looked at carefully. If you know of anyone who has done this I would be very interested in their results. Thanks.

Related -- lets hope the Filabot group gets the waste plastic extruder/shredder combo to work. It is a tricky project -- sort of like combining the recyclebot with the RepRap extruder head. At least for now I think you can have a bit better control with doing it in stages --using either a commercial shredder or something like one of these:



hi this is a french project :

movie of v2 : http://www.youtube.com/watch?v=Z0pf8CX8nF8http://www.youtube.com/watch?v...

movie of v1 : http://www.youtube.com/watch?v=XhsRjhnGQ7shttp://www.youtube.com/watch?v...

a wiki : http://reprap.org/wiki/MiniRecyclebothttp://reprap.org/wiki/MiniRec...

the extrusion is vertical, not horizontal

the plastic pass throught a gear pump

Thanks for sharing Karl - that looks like a great approach-- I will have to get my wife to help with the translations.

have a look with http://translate.google.com/http://translate.google.com/

put the adresse website, you can understand most of the text.

there is just the text in the picture who is not translate.

thank you for sharing you re experience too =-X

How hard would it be to condense this technology onto the top of a 3D printer extruder? It seems like that could save a step.

You are right it can be put on the 3D printer directly. However, making the filament first and then feeding into an extruder definitely offers advantages in repeatability and accuracy.

MIT has done some work with a direct 1-stop recycling machine that could take a milk jug and print out a cup, all in one machine. They used an auger drive and the extrusion rate is a function of pwm of the motor - they used a 5mm nozzle though so needs some TLC to get better resolution. Check out

This project has a great goal of combining and open source shredder with a recyclebot -- lets hope they get it going.

Would I be able to come check this out at some point? I currently live down in Negaunee, went to tech for computer science (I have interest in just about any math/science though), and finished my RepRap not long ago. I have a lot of interest in putting something like this together. I'm quite interested to know if I'd be able to be involved in your MOST group if non-students are available to help out. Can't say I can help out much with solar, but I love RepRap :) Overall, I have a great desire to help promote applied sustainability

This is the sole reason I smile these days when buying all those otherwise pesky milk"cartons" with plastic caps and what not, but foremost I'm an even "moar" avid recycler today!

Thank you for all those good (mining) days to come!

great idea.,...im a glass worker ..and i was hopeing u could use recycled stuff the way i can with glass

NICE 8-)

Can you provide dxf files.

I work on projects in the developing world, and I've been thinking that this sort of thing would be great to trial in some remote village. If they could recycle their plastic into useful items, with the help of such a device and a 3D printer, it could be really cool... only they would need electricity I guess, which mainly isn't the case. I saw one project with a solar powered 3D printer. The time has maybe not yet come for such a project, but it will, with the help of guys like you who are researching good solutions. Thanks.

If you want a super-strong building substrate to replace the wood that can be worked by hand try concrete reinforced with wire. This has been used to great effect for lathes and might work equally well for filament extruders.

Been exploring this a bit lately myself and I keep getting the same answer from everyone: "filament is cheap, recycling never works, just forget about it.

Glad to see you're not forgetting about it.

Also it is not cheap if you are in a remote area. Or SPACE!

good point .... think about it... you can make parts as you need them, when you do not need them anymore just transform them

Another thing to consider if you have one of these working, is extruding your own filament from virgin ABS pellets. I am exploring an automated filament maker, ever since I saw RecycleBot 1. The aim is to get into the less than 4$/kg material cost zone, and at 1$/kg the virgin material would do great.

It has been an interesting day so far...

I've got about 4 pounds of failed pla prints just waiting for this. I should buy a blendtech to answer the age old question: "will an outhouse with skipped steps blend?"

Any idea how many times one can extrude that stuff before the material properties drop drastically? Reusing it once makes for four extrusions (factory, reprap, recyclebot, reprap). Yikes! Should also make for some interesting colors when all scrap gets mixed together.

Ditto to Jim's comment - although I am fairly sure we are going to see mechanical properties slowly degrade - right now we are putting together tests to follow ASTM standards to be able to make a valid comparison against commercial filament -- but also to look at the multiple printing down-cycling effect.

One of the areas that will need to be improved to be able to handle large failed prints is a more robust shredder. If anyone has any ideas - we would love to hear them.

Most of the plastics we print with are thermoplastics - so as long as you keep them below their T(g), you shouldn't notice any degradation from heat.

That's in theory - in reality, anything that's flammable oxidizes on exposure to air, and heat accelerates the process. If you were to scorch some ABS or PLA, I would imagine it won't extrude so well after recycling... If you're keeping to the lowest possible extrusion temperatures, you should be
able to run plastic through again and again.

There might be a way to recondition the plastic while you're running it through the recyclebot, too. Maybe a solvent that works on oxidized plastics but not chain-linked polymers?

Very excited to see this. Looks very simple to build, I'm going to start saving up any ABS that I find in the trash for the day when I build one of these. I've got the motor and a lot of the bits already, looking forward to seeing more info. A YouTube video would be great!

What do you do with the filament as it leaves the extruder? I assume you can't just let it fall or it wouldn't be round, would it?

We have been messing around with timing a mechanical spooler turned by a small motor and using an old Makerbot filament spool. I am not convinced this is best way to go though -- commercially water quenching is often used and we have some experiments for that in the hopper.

I would guess that the main concern with water quenching is the increase in moisture that is absorbed by the plastic filament while inside the water bath. If you keep the water temperature cold and the time in the bath to a minimum followed by immediate drying you can limit the effect.

Also, the bottom-of-die-to-top-of-water-tank distance can effect the filament geometry and surface finish.

You will probably need some sort of underwater roller with a controlled speed that is set by ratio to match your extruder speed.

Water absorption is not a significant problem with ABS; it is with PLA (but then PLA can be difficult to recycle to begin with as it starts to degrade), and it is definitely no problem with PE, hence why milk bottles are usually made out of it.

Nylon is usually considered one of the worst thermoplastics for water absorption problems, taking up as much as 1% (depending on the nylon), but since PLA is so chemically close to sugars, hence digestible by microbes, water contact is a big no-no.

Water quenching is what came to mind for me. I was thinking that having a vertical screw and extruding over water, looping through the water and going up into a spooling mechanism would be ideal.