"PullStruder" : how to make 3D printer filament from recycled plastic bottles

This project is one of the ten finalists of Hackaday's challenge reuse recycle revamp : https://hackaday.com/2022/06/28/2022-hackaday-prize-reuse-recycle-revamp-finalists/

full details are given here : https://hackaday.io/project/185196-pullstruder-from-plastic-bottle-to-pet-filament

Hackaday's video here : https://youtu.be/PqkdHVK8vhg

Please do not hesitate to "like" both this video and the project on hackaday !

I saw on youtube a few videos of guys recycling plastic PET bottles into 3D printer filament spool.

Finally I tried to make my own "pullstruder".

https://youtu.be/1_BWXhT5Y-I

You will need :

• to put some pressure into a PET bottle (2 bar). This is optionnal
• hot gun the bottle to remove all the "carvings" and get an "almost cylinder" : (video 0:20)
• cut the bottle into a ribbon : (video 1:35) . Plans for a really good "roller cutter" are here : https://davehakkens.nl/community/forums/topic/pet-ropes-and-filaments-making-v4/ . see this video https://www.youtube.com/watch?v=Yf6-j2Gy0FI
• you can make "cheaper" one but not as good with a simple cutter blade
• build an extruder. For this first prototype, I simply drilled a cylinder of aluminium à 1.75mm diameter.
• Then I made a conical shape from 1.75mm to 10mm. So that the filament can enter the hotend and is progressively curved to 1.75mm.
  to produce heat I simply used a cheap chineese PID controler equiped with a thermocouple sensor
  https://s.click.aliexpress.com/e/_AX9gl4
• the PID is controlling a ceramic band heater : https://s.click.aliexpress.com/e/_A9NXK6
• Then I designed a winder using an old wiper motor. You will need really a lot of torque to pull the ribbon. A strong and well reducted motor is a MUST...

Finally I successfully "pullstruded" my first filament. One bottle produces 6m of PET filament. (video 3:12)
And I tried to print with this filament the gear to adapt the wiper motor to this winder !
The temperature to print must be high enough. After several failures I got a working set point at 260°C
The printed part adheres very well to the bed at PETG temperature (90°C).
Apart for the filament temperature, the settings are the same as regular PETG.
[update] = better results got with 270°C temperature. see specs here https://juggerbot3d.com/pet-filament-review/
The batman's batarang was printed with this setting. Much more "glossy" print.

Now for the width of the ribbon... Here is what I did :
considering that a 1.75mm filament as a section of 2.4mm square
considering that my bottle has a thickness of 0.25mm, then the width should be 2.4/.25 = 9.6mm
I tuned my roller cutter to get (almost) this width, and you can see the result in this video !

With a hole of 1.75mm the filament when pulled has a kind of oval shape and U shape... It is 2mm wide by 1.5mm. It turns out that 2mm is not a problem for my Prusa Mk2S :-)
And I believe that the section is close enough to 2.4mm^2 as the printed result is not that bad.

Still some improvement to be done but for a first attempt I am quite satisfied !

[edit nov 21] : added a filament fix part. Use it with a 8mm piece a metal pipe. insert a rope on one side with a knot on the tip. then slide the filement into the hole, fold it and fiw it as on the picture.

[edit jan 22] : added a picture where the same part is printed half with normal filament and half with the same filament but dried at 65°C during 1h30.
The effect of drying the filament just before use is HUGE. Much more shinny and almost transparent as the filament is.

[edit feb 22] : added two pictures of the pullstruder nozzle. Drill from 12mm to 1.5mm. As simple as this !