• aditya mehrotra.

plan to reuse plastic: felfil EVO basic kit understanding and design [updates]

So I mentioned a few weeks ago that I'd found something that converts garbage into 3D printer filament. Today I want to unpack that and see if it's even viable. But first I want to point some things about about MIT's recycling policy.


https://web.mit.edu/facilities/environmental/reuse.html


https://www.insider.com/mit-research-andrew-mcafee-says-recycling-is-useless-2019-10


The first link is MIT's recycling policy, and we'll get to that in a second, the second link is the following article:

The main point of the article describes a view of an MIT researcher who believes that it takes so much energy to recycle these plastics that there's very little gain on the environment. Here are some highlights.


"The carbon benefits, the greenhouse-gas benefits of recycling are actually very, very small, really not worth it," McAfee said. "What is really environmentally unsound is what we were doing up until China put a ban on it, which is packing up all of our plastics, sending it across the ocean, to a country that engaged in environmentally very, very dirty practices, to try to recycle that."

It's true that the former China-US plastic recycling beltway is now shuttered, and that most of our plastic waste today ends up in landfills or burns.

The article goes on to talk about how instead of recycling we should be focusing on a Carbon Tax or Nuclear Power. But here's what I get out of this. What we're really saying is let's bury the plastic because it takes so much energy to recycle it that it isn't worth it in the end - we might as well make the new plastic. Right? So what we should be doing isn't stopping recycling of plastics, we should be finding a way to make it economically more viable. A method that doesn't require sorting or doesn't need all the energy it takes and I'm not saying turning it into 3D printer filament is that method. But I'm saying we can't say for sure that it isn't.


Image solar powered trash cans on the streets of cities that grind up the plastic into small chunks and extrude them. These filaments can be sold to local universities for test 3D prints of manufacturers of low-quality, mass-produced parts, or we can turn them into plastic bottles again ourselves. Re-usable plastic water bottles made from trash. This doesn't seem like the worst idea ever...

Now, it's time for me to look at the EVO and other 3D printer filament makers out there. We're also going to look at recyclebot. That might be even cheaper to make.

So those are the parts and drawings for recyclebot. The problem is the instructions are not very clear and incredibly difficult to decipher so I'm going to start with the EVO basic kit...


So let's start by reading this manual. I think it will give us a lot of knowledge on how to make one of these things...



Here are the components we need to complete the kit. Some electronics and the mechanical stuff we really don't need except for the BASIC KIT.



Here's how the heating elements connect to the basic kit.


Here's the wiring diagram of the kit.


Now I think it's important to start looking through everything and seeing how much one of these would cost to make. But even before that. I want to start coming up with a kind of design for a multi-extruder that can extrude maybe three filaments at once. And the reason for this is if we can extrude three filaments at once we can recycle at three times the rate of one evo. In this design we're going to come up with a trash can that can basically extrude one or more than one of these things and be powered by sunlight. It will include a grinder and everything and we'll start by designing it on CAD. We'll also design large-format 3D printer that can use the filament to then actually do something (also on CAD. We aren't going to build either of these things right now, but we will have designs ready by the end of the summer you know.



Here's the drawing/design I came up with earlier. This is the kind of idea we were thinking of where there is this solar-powered trash can that collects the bottles, shreds them, and then we'd collect the filament when it gets full. The other option is to have a large machine, single machine, that takes in all the plastic we collected from very simple and special collection

boxes and then makes it into filament. We sort by hand into types of plastic.


There are two models here. The trash can just simply combines all the plastic and extrudes it, we have a bunch of trash cans around campus that do this - which is expensive.


Or the second model with is we have a bunch of these simple trash cans that are only for certain types of plastics, and then at the end of the day all the plastics get collected, sorted into bins, and then go through this one large machine that turns them into filament. You know. The next day is saved for feeding the previous day's stuff through the machine. The second model is a lot cheaper and easier to maintain because the trash can idea requires a whole lot of these extruders and can get expensive/etc.


So let's work on the design for the second idea for now. To re-iterate:


There are multiple regular trash collectors around campus (corrugated plastic boxes) where we ask people to only throw out plastic bottles in them. Then we take the contents at the end of each day and shred them and the next day feed them through the large EVO machine that is responsible for making multiple types of filament. WE sort the plastics into four different categories, they get shred individually, they get extruded individually, then we have different types of filament we can use on the labs on-campus. 

Here and image of the EVO basic kit. It's really an interesting little device.

Now while we're looking at this, let's look at the auger for both of these devices, the EVO, and the recycle bot. The recycle bot's auger file was pretty useless (the simplified version), and I don't want to dig around in the docs to figure out where they put it. So let's look at the EVO's because if we can understand the design of that - that's the hardest component to acquire here (maybe besides the nozzle).



So that's what the Auger looks like. So the question becomes not, how can we get this specific device. The question becomes can we use something like this:



To design out own version of the EVO this summer. And I think the answer is yes, but first we need to figure out how these extruders work. Now let's use a section view in CAD and see the parts I'm most interested in.


Loookkk at tthattttt, the inner workings of the EVO's design and it's very impressive. So now let's talk about how it looks like this thing is built to work.


How Evo's Extruder Works:
The first thing to note is the speed at which the chips are pushed into the nozzle depends on the speed of the auger itself. That depends on the speed of the motor. 

It looks like the auger is supported by the walls of the melting chamber and the tube leading up to the chamber. 

The nozzle itself is just a cone leading to a tube with a heatsink on the end - I assume this is to cool-off the device. 


The diameter of the auger in the EVO is 14.00mm, that around 0.55 inches.



The question is, can we find a 14mm diameter auger?



Yes! we can find all of these things online. What this means is we can then also re-design the EVO so it uses some cheap auger drill bit, some metal that won't do ridiculous things when it heats up, and we can get a nozzle that extrudes 2,85mm filament. Now how would we replace the nozzle of the EVO? Well let's see if we can't find anything in the recyclebot docs.

So they actually used a regular ship-bore auger, Nichrome wire for the heating element, and...

Finally found it at this link: https://www.sciencedirect.com/science/article/pii/S2468067218300208


So we need to print this as well, this might have all the assembly instructions we need for a cheap version of the felfil. This recyclebot, now that we've found the docs, seems so much better because it seems cheaper and simpler. Here's the actual article: https://reader.elsevier.com/reader/sd/pii/S2468067218300208?token=C1317A57590E6E608B9E1B40821107E003AE8F13A3E0361C9122193D30B772152F7E19A82024B1FBF70630F908EEEFCF


For the latest version of the recycle bot, they've posted very detailed instructions and we're going to start looking into them to actually design our version of the recyclebot.


Before we get to our design we need to think about things like, how many extruders do we want/etc. According to this article, there are four major types of plastic used in plastic bottles: https://sciencing.com/kinds-plastic-gatorade-bottles-8206011.html


According to Felfil, here are the settings for most of these types of plastic: https://felfil.com/materials/?v=7516fd43adaa


We're going to combine Felfil's electrical design with the mechanical design of recyclebot, and increase the scale for our design. That's the main idea, let's put it in a box:


We're going to combine Felfil's electrical design with the mechanical design of recyclebot, and increase the scale for our design.

And let the design begin (over the course of the summer).


#updates #omgrobots #machinedesign #recycling

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