Filament Humidity Question

[RTLdan]

Hello All!
By putting together things I've read from various threads, I realized that a lot of my printing problems were likely due to moist filament.
I purchased my Rostock with a 2 pound spool of ABS. In my excitement I opened it all up. It took me nearly a year to finish my Rostock, and that whole time the ABS was out in the shop, exposed.

I also had a brand new roll of Taulman 618 that was still wrapped in plastic, but not vacuum sealed.
I have not actually printed with it yet, so I cannot say if it's suffering from moisture or not, but from everything I've read, the Nylon is very hygroscopic, and so there is good chance it needs drying. I'm essentially giving up on the ABS for right now, and looking at switching over to the Nylon. So of course, I want to make sure the Taulman is dry enough that it's not going to give me poor results that I could mistake for calibration problems.

I have no oven that I can use for drying purposes at the moment, so here is what I have done instead:

I have bought a hygrometer, put the filament spool in a zip lock bag with desiccant crystals (I used Fred Meyer's store brand kitty litter crystals) and zipped it up, then put the bag inside of an airtight plastic box. It has sat about week. The hygrometer is still reading around 52% humidity. Is this normal? I saw others talking about getting 15% RH with their spool enclosure.
I guess the real question is, what am I looking for in terms of RH, is my method even going to be effective enough, and of course, are there are any better ideas out there?

Thanks in advance!
-Daniel

[Jimustanguitar]

I'm no expert on the matter, but I try my best to keep my filament dry too (even ABS).

I'd assume that it would take heat to remove water from a material that's chemically attracted to it. The desiccant is good for keeping things dry, but not as effective at removing moisture after it's present.

Seen some interesting experiments with vacuum lately... Thinking about giving it a go myself.

[Cedric_K]

I work in plastics, especially in Injection Molding, and there are some plastics that would absorb moisture.

In industrial plastics, material (pellets, sheets, etc...) are dried in a "hopper dryer", that is like an oven with a grid, and hot air is blowed throught the pellets, by downside, thanks to the grid...

Each material is different, nylon is very hygrometric, we usually put them 2 hours at 90°C to lower the moisture rate near to 1%, and we have 3/4hours to transform the pellets before they take bake moisture... most of plastic materials take bake moisture as fast as they loose it while drying...

Don't make too much efforts to keep your material far from moisure, it's useless, only a drying before it gets transformed give a real result...

I don't know anything about 3d printing, but It look likes that moisture is a small problem for printing, I assure you that in injection molding or industrial extrusion, it becomes a big issue that avoid you to get conform parts...

[Tonkabot]

how about once it has been dried (in the oven or whatever) I store it in a cupboard that has a 100w bulb in it, (and/or is controlled to some higher than ambient temperature). If it is kept in this warm (say 120 F) cupboard will that keep it from sucking up any water?
Or what temperature would be needed?

If the cupboard is insulated well, it would not take much power to keep it warm all the time.

[Cedric_K]

It depend not really of the temp, but of the rate of moisture in ambiant air, that why the 2h spend into the hopper dried are so accurate : plastic is totaly isolated from external air... And that's why only a few hours after getting out of drier, plastic is back to its maximal level of moisture...

For me (but with 3D print purpose I can be wrong, im very far to be skilled), the only thing which makes sense, is to put the filament 4h at 80°Celsius on an oven (standard drying time and temp for ABS), and to use the filament without wasting time after that...

In plastics industry, these hopper are pretty large capacity, more than 100kg of pellets sometimes, and we have vaccum system to feed dried material to the machine, level of dried material nevers lowers because, because upside these hoppers, is also a vaccum system which pumps raw moistured material, this is not the same configuration that printing... This will be analog to drill the wall of your oven with a very small hole sized to your filament, and pulling the filament directly from the oven to the printer...

It's sure after a long 10hours printing, the end of the spool which is out of oven for 10 hours has taken bake moisture... so the end of printing (which is critical) is done with moistured material...

I give more details here : http://forum.seemecnc.com/viewtopic.php?f=36&t=6479

[Polygonhell]

FWIW the moisture problem is often overstated, it's at best a minor issue with PLA and ABS, I've left rolls of ABS and PLA out in the open for over a year without issues.
With Nylon and Polycarbonate it's a very real issue however.