Printing PET with large noozle

[mlapshin]

Hello guys, thanks for your awesome work, it's really helpful. I have a PET-related question, if you don't mind.

I'm interested in using PET to print human-scale objects (furniture, containers, sculptures, etc) with large 2mm-5mm nozzles and direct screw extruder. Assuming that flakes are properly dried before extrusion, do you think it's possible to get amorphous PET in result? I doubt that I'll be able to cool down extruded plastic fast enough with a fan, even a heavy one. What do you think of entire idea of using recycled PET to print large objects with thick walls, is PET a good material for that? Do I need to print underwater? :)

I publish my humble experiments on YouTube, but videos are in Russian.

[Maaphoo]

Cool bike. Thanks for the video link.

Printing large scale objects with PET is possible and you are correct that cooling is one of the main issues. Our friends at Robot 3d Printing and Re:3D have been printing large objects from PET pellets and pellet/flake mixes. I'm not sure if they have tested the % crystallinity or mechanical properties of their large PET prints, but they are able to get prints that are transparent, suggesting that they haven't completely crystalized. You will likely need some good cooling fans at the nozzle. I've wondered if chilled air would help much. Drooling from larger diameter nozzles is also in issue as PET tends to be fairly low viscosity when melted. One solution to this is to print in spiral vase mode.

Printing large thick walled objects might be fine. It all depends on what the items will be used for and what their mechanical properties are.

One thing that I have read about is adding sodium benzoate or talc to the PET during extrusion. It is supposed to provide nucleation sites for crystal growth. Maybe if smaller more numerous crystals can be formed the mechanical properties can be improved. I am unaware of anyone who has tried it for direct printing or filament. I have always wanted to try.

Printing under water has crossed my mind too! Hats off to anyone who gets that working.

If you decide to work on direct printing with PET, we'd love to know what you find out.

Thanks,

Matt

[mlapshin]

Hello Matt,

Thanks a lot for you comprehensive answer. The fact that commercial companies are using PET for printing corroborate that it's a right way to go. I've doubted about entire idea, but now I decided to give it a try. I'm finishing bath & puller right now, want to extrude some 1.75 filament and print with it on a desktop printer mostly to satisfy YouTube viewers. Thanks for your suggestion, I think I will do experiment with talc as well, it's pretty easy to buy. Another idea I have is to simulate a 3D printing process manually moving aluminium plate in front of extruder nozzle with a fan blowing on a "printed" model. This might be a cheap way to check if air cooling will work well enough.

I can update this issue with my progress, if you don't mind.

[Maaphoo]

Would love to hear updates about your progress. It is great to see more people working on printing from PET.

[mlapshin]

Was able to get almost usable filament, finally:

https://www.youtube.com/watch?v=J1vprT4VFro

Have you guys tried to use V-shaped aluminium extrusion in bath? It works very well for rod stabilising, but deforms filament a little bit, so it comes out not round. I had no luck with pulleys like in your design.

Will try to mix flakes with talc next time. Will let you know. Thanks and take care.

[Maaphoo]

Nice work! Thanks for the video.

We also had black blobs in our filament at first too. The main issue for us was label glue. We now remove it by wiping the glue with warm cooking oil and then washing with soap and water. Tedious but it works pretty well.

Yes we have moved away from guide rollers and also use an aluminum v in the water bath. The filament is very sensitive to disturbances. A defect catching on anything causes another defect where the plastic is entering the water. A friend recommended a foam coated guide roller at the end of the waterbath do dampen these disturbances.

One way to overcome the issue of imperfect filament is to use a diameter sensor on your 3D printer. We have done so and printed quite successfully. Here's our first print with filament ranging from 1.3 to 1.95 mm in diameter. The sensor measures from 2 different angles so it works ok for filament that isn't perfectly round:

Excited to hear about talc experiments.

[kanna19aero]

Hi Guys,

you have done a amazing job putting together and great inspiration for the 3d printing community and saving the plastic recycle environment. I would need some help regarding the electrical/electronic bit of it. could you please help me.

[Maaphoo]

Thanks @kanna19aero

Glad to see you are interested in the machine. Happy to do what we can to help out. Maybe open an issue called "Help with Electronics" or something more specific if you know specifically what your needs are. We can dive into specifics there and it will be available for others who have similar needs.

[kanna19aero]

Hi TechforTrade/Thunderhead-Filament-Extruder

I ve created the issue under Thunderware electronic bit readiness..

Will this be ok?

Thanks Kannan

On Tue, Jun 16, 2020 at 8:05 PM Maaphoo notifications@github.com wrote:

Thanks @kanna19aero https://github.com/kanna19aero

Glad to see you are interested in the machine. Happy to do what we can to help out. Maybe open an issue called "Help with Electronics" or something more specific if you know specifically what your needs are. We can dive into specifics there and it will be available for others who have similar needs.

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/TechforTrade/Thunderhead-Filament-Extruder/issues/3#issuecomment-644859146, or unsubscribe https://github.com/notifications/unsubscribe-auth/APTNUR2X5BDLOZTZ3JWBFTTRW6J5PANCNFSM4KOMVHZA .