Adding Recycling Codes To 3D Prints

Every little plastic bauble you interact with has some sort of recycling code on it somewhere. Now that we’re producing plastic 3D printed parts at home, it would be a good idea to agree on how to recycle all those parts, and [Joshua Pearce]’s lab at Michigan Tech has the answer; since we’re printing these objects, we can just print the recycling code right in the object.

The US system of plastic recycling codes is particularly ill-suited for identifying what kind of plastic the object in question is made of; there are only seven codes, while China’s system of plastic identification uses 140 identification codes. This system for labeling 3D printed parts borrows heavily from the Chinese system, assigning ABS as ‘9’, PLA as ’92’, and HIPS as ‘108’.

With agreed upon recycling codes, the only thing left to do is to label every print with the correct recycling code. That’s an easy task with a few OpenSCAD scripts – the paper shows off a wrench made out of HIPS labeled with the correct code, and an ABS drill bit handle sporting a number nine. 3D printing opens up a few interesting manufacturing techniques, and the research team shows this off with a PLA vase with a recycle code lithophane embedded in the first few layers.

20 thoughts on “Adding Recycling Codes To 3D Prints

  1. I like the idea, I wonder how practical it is. I can import geometry and do an extrude cut, but then there’s the issue of sharing the file. I do ABS, the next person is probably going to do PLA unless it’s critical to the design and even then, most people would just use the material they know or have than switch to have the correct type.

    So that leaves a few options: I could export a second variant (more work for me, making it less likely that I share), the next person would have to regenerate it, which is work for them, or they could just build it from a material different from the label and really screw things up if it gets recycled incorrectly.

    That said, I understand recyclers often have a means to identify plastics with some kind of quick scan, which I think uses some kind of high energy photons, I don’t know what wavelengths though.

    1. It doesn’t necessarily need to be an impression added by the artist at design time.
      For example, a feature could be added to the MakerWare software for the makerbot that allows the user to specify their printing material. After that, the code sent from the application to the printer could be modified to impression the plastic type on the underside of the model (provided there was enough surface area to fit it, perhaps the user could manually place the code if the software can’t auto-fit it).
      This would remove the burden from the model designer, leaving it an option for the printer to include the plastic information at their leisure, or to not include it at all.

      1. Letting the software figure out where to put the recycle code might screw up an important face or something. What about developing a designated “block” somewhere on the print whose sole purpose is for printing the recycling code? I don’t know enough to make good suggestions, but let’s say we can introduce a flag somewhere in the file that identifies the purpose of the block. Recommend every file includes this block somewhere on the final item. If the file is printed using software that doesn’t recognize the tag, then the block is blank and a flat (or curved or whatever) surface is printed. However, if the software recognizes the tag, then it can automatically include the code within this block and print it accordingly based on user settings. Thereby avoiding excess work on both the creator and er…. creat… um printer? Te guy who creates the file and the guy who prints.:)

    1. Maybe some kind of universal “token” in the design the, the software reads it and puts the proper plastic code on the print, or if you print in chocolate it just puts YUM on it.

      1. “or if you print in chocolate it just puts YUM on it.”

        …Now you got me wondering about the feasibility of objects printed in chocolate. I think I saw something about that, actually… Maybe choco-printing novelty versions of an object for a celebratory banquet or something?

  2. While it might seem like a good idea, I really doubt anyone ever actually looks at those codes. It just seems rather unlikely to me that a recycling center would actually disassemble every single product into it’s individual parts and look up the code on every single one, instead of just grinding everything into small bits and separating whatever can be separated by density or such.

    1. I can see a use for it even on just a personal scale… I’ve only had a printer since February, and already I’ve got a sizable collection of filaments, many times with the same colors in both ABS and PLA… So it’d be nice to know, at some point down the line, when something is no longer needed or I’ve made a better version or something. “Did I print this in ABS or PLA?!”

      Because while I currently have no use for PLA scraps, ABS can at least be used to make ABS/Acetone welding goop for joining prints. (Or using as filler, etc.)

  3. Our trash collectors will not take plastics unless they are labeled with the triangle and a number 1-9. The Chinese markings would not be accepted. I doubt that the guys in the truck would know a piece was mislabeled.

  4. How about just making a stamp you heat up and stamp your finished parts with? Then you don’t have .stl files with the wrong plastic marked on them. That and PLA doesn’t recycle very well, might as well throw it in the compost pile.

  5. I called around to a couple of dumps a couple of weeks ago asking where they would prefer I put PLA scraps. They told me to just put it in the household trash. I read something about bioplastics screwing up the recycling of “normal” plastics for some reason.

    1. PLA does not recycle well, all plastics must be sorted before recycling. Your PLA is not labeled, therefore it can’t be easily sorted and some bits and pieces could get in with the HDPE, or PET and would adversely affect these petroleum plastics recyclability. That and PLA biodegrades and is compostable there is no reason to recycle it as composting is in a way recycling it back to CO2 and H20, with some biomass. PLA comes from corn and sugar beets so CO2 is captured to make it.

  6. I like the idea, their head is in the right place, but this is just adding complexity to prints and increasing the likelihood of them going awry. Such as..

    “Oh no, the text broke through an edge and created an opening!”
    “Oh no, the gaps for the text caused a non-uniformity and things started drooping!”
    “Oh no, the text caused the part not to stick as well due to less surface area on the print-bed and it popped off half-way through”

    followed by:

    “Hmm.. good thing I can recycle it properly at least?”

  7. One thing that becomes very clear very quickly when you try to recycle plastic for 3D printer filament is that the voluntary recycling codes used in the US are not useful for recycling.

    I’ve been following Joshua Pearce’s publications through academia.edu for a while and he’s really trying to do something. I hope he succeeds, but what I think we need is an association of 3D printing recyclers to help push for change.

  8. The end goal is to have some label on everything, so you throw it in your 3D unprinter and it unprints it correctly automatically. You can enable that by putting a QR code (or something like a QR code) on everything that is 3D printed (and even on things that aren’t 3D printed, like cups and socks and boards). Then have a database online mapping codes to instructions for how to destruct that item, formatted so the unprinter can follow the instructions. There’s a zillion possible codes, you could have a different one for every grain of sand on earth if you wanted to, so the cost is mostly storing the instructions plus printing the code on the object. You could reuse existing instructions if that works.

  9. Great comments here!

    I’m currently looking for input from makers with experience and/or pics of recycling codes on 3d prints.

    With so many different kinds of filaments on the market, and concern over proper disposal growing, I’m compiling a snapshot of the current state of the effort to promote the proper recycling code on 3d prints. For this I need your help.

    Do you or someone you know include recycling codes on prints to help in the identification and proper disposal of materials after intended use? Do you have pics?

    Do you have a system in place in your lab to identify the filament used for the purpose of recycling or reusing the material again?

    I will credit and acknowledge all info and images to the respondents and I’ll post a link to my report here on this forum. The report will not be sold and is meant to contribute to the discussion more than anything else.

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