[Solved] PET Temperature
In one of your recent videos "step by step: how to recycle PET bottles from A-Z" I can see, that your Airid uses a different user Interface. When I try to set the temperature at your recommended 140°C for PET drying, it only lets me set it to a maximum of 110°C. An Update for the Airid is not available on your homepage. I want to recycle PET bottels too, so I would like to be able to use the same settings as a benchmark for my kind of PET.
Hello @hsu_hh ,
Thank you for being interesting in our PET videos 😉
I am sorry, for it took me a bit of time to investigate the situation. You are totally right : PET should be dried at 140°C. Our Airid Dryers are capable of reaching 160°C.
Your Airid currently runs an older firmware version. I will send you a private email with more detail in just a moment.
I am very sorry about the inconvenience.
Hello and thank you for the very instructive forum.
To build on this topic, I have dried my PET for 4hours at 160 C qui I see no change in weight.
As far as I know, by releasing its moister the pet should lose weight right?
From videos seen here and there is should be about 5%.
Am I right?
ok I found my answer - it seems the weight moisture weight is only about o.o5%.
So quite difficult to measure.
Hello @valentin ,
Thank you very much for asking, and also for replying 😉
You are right : the target moisture content is typically 0.05%wt. Some manufacturers even recommend 0.025%wt.
In order to measure this, you would need to use a special moisture analyzer device. (this would pretty much be a very accurate weighing scale combined with a heated chamber).
If you do not have access to such a device, you can try extruding your PET. If the extrusion test is succesful without any bubbles, then it means the drying step was good enough.
Do you have any further questions ? I would be curious to hear about your results.
This video might help https://youtu.be/HBCOyyY73e0
Thank you Louis.
I have measured a slight loss of weight.
I will test the extrusion very soon. I keep you posted.
No problem @valentin ,
I am always glad to help !
It is very hard to measure such small weight differences. A typical drying process would remove moisture from 1%wt to 0.05%wt. A very accurate scale is needed.
Yes, please let me know how your test goes.
Recycling PET can be tricky, but it is a matter of finetuning each parameter very precisely.
We have done this several times with different kinds of PET.
Even if your very first run i not 100% successful, I am sure we can have a look together and do some troubleshooting.
Looking forward to seeing your results 😉
The drying process seems to work fine. I measure on my precision scale a consistent weight reduction and I have no bubble while extruding. The good old hoven seems to work.
I didn't manage to extrude a good filament (yet). I spent 17 hours straight fine-tuning yesterday and I'm still not quite there yet.
My profile is quite different from yours.
274/273/272/268 - 70% fan seems to work the best for me. So much more hot than you.
The RPM don does not seem to have much impact.
You talked in your previous message about 'different type of PET' but I never found anything about it.
Do you mean that each manufacturer has his own little recipe or that there PET for bottle, PET for food container etc... with consistent difference and therefore I should segregate the different PET?
Thanks again for your support.
We should soon try PP - You have not yet tried it right?
Hello @valentin ,
Wow, that is a long long experiment !
Indeed, your temperatures are quite high. At those temperatures, the PETs that we processed were way too liquid ; it was impossible to pull them into filament, and the flow was extremely weak.
70% fancooling is also very high. With such a high percentage, our output was freezing inside the nozzle. But I imagine a lot of cooling is needed when the temperatures are high.
Types of PET
Here, I am refering to "grades" of PET. This corresponds to what you said : each PET manufacturer has a secret PET recipe, so each PET is different. Even two PET bottles can be made of different food-PETs, if that makes sense.
Isolating one unique type of PET is a good plan, because then you can remove the "incompatibility between two PETs" from the picture. However, if your ultimate goal is to process a stream of 10-20 types into one filament, well, testing each of the 10-20 types might take a lot of time.
At 3devo we tried both : one type, then another type, then the "random" mix. All these experiments did work, eventually.
We have successfully processed several grades of PP - also recycled one https://support.3devo.com/recycled-pp-material-report/
PP is tricky, capricious, because of its high crystallinity. It tends to solidify into oval filament, and adheres badly during printing. There are workarounds, luckily.
Can you please send me a picture or short video of your PET output ? This could be the key for me to help you as efficiently as possible. If you have a datalog, that could also help.
Do you have any questions ?
Thanks for your reply Louis.
You are right. My temperatures were far too high and therefore the mix too liquid. We are learning ;)
going for a higher temperature is not the magical solution ;)
Your temperature works quite well (265/267/267/265) but I'm always facing the same issue.
After a while (more or less 15 mn) the nozzle gets colder and the flow slowly reduces.
I have tried to improve the insulation (I have added a silicone cover initially made for 3D printer) but it is not enough.
Today I'm playing with the RPM and a bit with the temperatures... with no real success.
My record is 21 mn extrusion with a RPM at 2.8 and there mp at 1 at 267.
Always a pleasure @valentin 😉
You are right : nozzle insulation is key. The way I tackle this is simple :
- cover the hole around the nozzle with the magnetic plate
- angle the fans as 'downward' as possible
- because of thermal inertia and the distance between H1 and the tip of the nozzle, heating the nozzle up can take quite some time. Maintaining the nozzle temperature is also difficult. Without chaning any parameters, the nozzle will perhaps spend 10-20min decreasing its temperature, causing the clogging. Maybe this is what you experienced.
I recommend the following :
- set the fancooling on 0%
- set the speed on 5RPM (that will build up a bit more pressure and also bring more heat to the tip of the nozzle)
- start with a low fancooling percentage, typically 20%. Try to pull some filament. If it is obviously still too malleable (getting squished by the puller), then increase the cooling slightly (30%).
- when you find a % that solidifies the filament sufficiently, keep pulling the filament in those conditions for 30min. If you see some PET solidifying at the tip, it means the nozzle temperature has not reached an equilibrium (the nozzle is not receiving enough heat and/or too much heat is extracted).
What you are experiencing with PET is totally normal. It was designed to be quite sensitive to cooling.
Are my indications clear/relevant ?
Because it all comes down to finetuning at this stage, it is difficult for me to really put my finger on the exact problem. If you wish to share a short video of your output with me, you can do so on this forum or at email@example.com.
Yes! Your comments are extremely helpful and you have described exactly what I'm experiencing.
I'll try increasing the RPM a bit and see if it helps.
My coming experiments are:
- Try with a single kind of PET also next week
- Improve the insulation of the pipe with Fire Retardant Casing Pipe
I keep you posted.
And thank you again for your precious support!
Hello @valentin ,
Perfect, do keep me posted !
I am glad I can be of some help, but I can imagine this process can be very obscure and tedious.
With multiple successful PET experiments in mind, I am very confident about your project. There must be a way to make it work smoothly.
The finetuning step is all about small adjustments and observation. If you feel like you have reached a deadend, or like I don't manage to help you properly, please let me know. I want to make sure you are satisfied with your results.
- I have improved the nozzle insulation but it didn't change anything.
- We have selected a few similar PET bottles in order to try a homogenous batch - again no change.
SO I have given up on PET for now and trying PP.
I had early success but again, the flow went down and I'm fighting with the setting again ;)
Would you be kind enough to share the file of your circular fan you are talking about in the data sheet?
Didn't managed to reproduce consistently your result so far.
I realize you have used a 2mm nozzle when mine is a 3mm nozzle (the default nozzle is 3mm right?).
Do you know if it makes a big difference?
My main problem with the PP is the filament that keeps twisting on itself. Still trying to find the right settings.