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Plastic recycled 3D printer Answered

Planning to design a 3D printer that takes plastic bottles as input, I mean long narrow pieces of plastic bottles are fed as the printing filament. What will the difficulties in realizing such a design?

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NitroG1982

2 months ago

As I see it there are a few problems. It doesn't seem possible given how FFF printers work currently.

1. not all plastic bottles will be made of the same identical material so the temp required for an even melt will not be the same bottle to bottle.

2. getting filament diameter perfect with little variance is difficult. usually this is accomplished by pre-making the spool with specific pressure and temp with the strand dropping straight down while it cools and being spooled on the floor. trying to apply this directly to the print process seems like it wouldn't work. mostly because 3d printing is all about calibration and consistency.

3. The heat and mechanics of the machine may eat up more money in power and maintenance than ordering spools of plastic and using a traditional FFF drive system. it may seem more efficient to use the heat to both make the filament and print it at the same time. but I think you will find that getting the feed speed to match the print speed impossible or calibrated to an extremely slow speed. which will mean the printer runs for longer using more power.

4. You are going to need a good way to break down the material as much as possible before going into whatever melting crucible you design. larger pieces take longer to melt. inconsistent size = inconsistent material.

5. rather than a traditional drive system used in FFF printing. you will need one that uses some sort of auger to grab little bits of broken up plastic and force them in with consistent pressure and heat to maintain the constant predictable flow of plastic coming out of the nozzle required for printing.

6. A "hopper" of some kind is going to be needed unless you plan on standing there hand feeding chunks of plastic. then how do you deal with hopper jams mid print? how do you design a stationary hopper that will feed into an auger that has to move around with the print head? it comes down to either the material it's self needs to be solid enough to transfer from one to the other without it's diameter changing (so you would have to melt it twice anyway). or the entire bit that recycles the plastic has to be attached to the moving print head. which is a lot of weight to throw around.

It seems in my opinion. that in order to have reliable FFF print material you need to have it prepared ahead of time. or you need to design a whole new type of printer with a stationary head that has only the platform moving around to deal with. the only way current FFF printers are able to print is because they have a solid flexible consistent material they can feed into the moving print head. i'm not saying it's impossible but you will be reinventing the wheel basically as i can't see a way to modify any existing printer I know about to work in this way.

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iceng

2 months ago

Simply monitor filament ahead and let elegant software adjust for variations in real-time :-)

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petercd

2 months ago

Consistently accurate plastic entering the extruder.

The software calculates extrusion based on volume of plastic.

In my case, I specify the diameter as 1.75mm, which is consistent for the entire spool.

Any variation will result in either over or under extrusion, throwing out dimensional accuracies.

Best bet would be as Yonatan24 suggested, one machine to create the filament from recyclables.

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Yonatan24

2 months ago

Remember you need clean plastic, and many recycled plastic bottles aren't clean enough. Makes more sense to create separate machines, one for creating the filament and the other for printing, the 3D printer...

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Jack A Lopez

2 months ago

I have heard/read stories of printing with HDPE, or making filament from discarded HDPE.

e.g.

https://www.instructables.com/id/Build-your-own-3d...

However I am not so sure about printing with PET, which is the other popular plastic (or most popular?) used for making plastic bottles.

You did not mention which kind of plastic bottle.

I am guessing that you are thinking of PET (poly ethylene terephthalate), since I have seen instructables for turning PET bottles into thin strip, or "string", just by simple cutting, e.g.

https://www.instructables.com/id/PET-Bottle-String...

https://www.instructables.com/id/DIY-Plastic-Strin...

I dunno. I asked DuckDuckGo to show me, "3d printing with pet", and one of the top returns was this page,

http://3dprintingfromscratch.com/common/3d-printer...

giving an overview of the qualities of different kinds of printable plastics. Of course that article is written from the perspective of people who just buy big spools of factory-made plastic filament, as if that were the only way to do it.

Certainly buying a thing is the easiest way to do it, if you have unlimited amounts of money.

If you want to look at it from the perspective, of, uh, "What kind of plastics are available in trash?" I think the Wikipedia article titled, "Resin identification code"

https://en.wikipedia.org/wiki/Resin_identification...

is an appropriate introduction to the kinds of common plastics that can be found in the recycling bins.

Regarding technical challenges, I can only guess. Perhaps problems with cleaning and separating the bottle's plastic, from other contaminants, like glue, labels, etc. Problems with making a filament, or strip, with constant area cross section, or building a melter-printing-head that is robust enough to compensate for filament with varying cross section area, so it deposits the exact volumes it is supposed to, as the print progresses.

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rickharris

2 months ago

I would imagine getting the flow of material to be continuous. You might get better results by first making the bottle into a filament.

Alternatively you could use some kind of glue gun type of system where material in a chamber is compressed, melted and squeezed from a nozzle your still working with a limited amount of material though.

You also need to limit the material to the same kind of plastic so it all melts at the same temperature.