The Great Filament Bakeoff


#1

After doing a series of prints over a week and a half, I noticed a slight crackle every once in a while, and this seems to come from the extruder. Switched over from the PLA to PETG and after a couple of days the crackle returned.
This is by no means at the rice crispy stage but does seem to indicate that the filament has taken on a bit of moisture from the environment.

Simply placing the reels of filament in a sealed container with dessicant won’t remove any moisture already in the filament - this will only provide a dry environment for storage.

The usual way to cure this, I understand, is to bake the filament in an oven at 40° - 60° for 1 to 2 hours. My question is regarding convection ovens. My gut feeling is that convection should be turned off (i.e. a setting used which doesn’t use convection) as any given humidity would be circulated in the “drying” environment. Perhaps the door should be left ajar even.

Any practical experience from the community in this regard?
Anyone tried a microwave? :shudder:


#2

I use color changing silica packets that are rechargeable. You in your box and they absorb all the moisture and change color when they need to be recharged. They seem to work really well so far. You can recharge by putting them on defrost in the microwave.


#3

I’m well aware of these silica packets. They are generically referred to as a form of dessicant, and as I mentioned in my post, these will only help maintain a dry environment for storage of the filaments but will not remove any moisture that has already been absorbed by the filament.

I’m also aware that silica gel dessicant as well as activated charcoal (as opposed to chemical dessicants such as calcium chloride etc.) can be reactivated in an oven including a microwave. (BTW some types of kitty litter are also effective and can also be reactivated by heating :wink:)

My question however, concerns the actual drying of filament which has already absorbed moisture.


#4

From my understanding of pages I’ve read on the internet, I’m pretty sure the packets/rice/kitty litter will take moisture out of the filament while keeping the air dry too.


#5

In the manual of my Ultimaker 3 there is a small chapter about this.
They suggest to put the reel into the original cardboard box and put it on the heated printbed and turn it up to about 50°C.
A normal kitchen oven is not prefered becaus the temperature is not very stable and can vary more than +/- 10°C.


#6

After further research and discussion with experienced users, it appears, much to my surprise that a convection oven (electric as opposed to gas) is to be preferred over a standard oven. (Definitely not a microwave for filament as this could cause deformity of the filament due too the forced outgassing.) The dessicant can also be reactivated at the same time. The preferred (professional) method would be a vaccuum chamber, but we don’t all have one of those.

@Johnny : Dessicant will in fact remove some of the moisture from filament over a period of time however this takes rather a long time - days in fact and the desiccant would need to be reactivated during that time. PET-G can take on a lot of moisture in a single day resulting in poor prints. Having to wait a week or so between prints is not always acceptable. For the dessicant drying to be really effective, the filament should literally be buried in the dessicant - not adviseable with anything other than silica gel beads however due to dust and impurities coating the filament.

@rojaljelly : Unfortunately the snapmaker bed is rather small in comparison with the 1Kg spools I have.
I’ve checked my oven with two thermoprobes and found the variance to be under 5% at 50°. So long as the temperature remains under the transition spec there should be no problem.


#7

To be honest I have dozens of opened PETG filaments stored only in the cardboard box. I have no troubles with 6 months old reels…


#8

That might very well be. It all depends on the humidity of the environment. My shop has a relatively constant RH of ca. 42% - this is because it is adjacent (an anteroom) to my music studio in which the environment is controlled. After about 2 weeks of having the roll of PET-G on the machine I have noticed a bit of crackling sound - not constant, but now and then there will be a tiny popping sound which is indicative of moisture in the filament. I haven’t noticed any degradation of the printed results however.
I’m just anticipating the eventuality :wink: