Interesting humidity and filament experiment

I'm hoping it was moisture - I had terrible problems getting a good print from it. Was Prusa filament.
 
I was doing some reading as to what the equilibrium RH vale vs. moisture content in the silica gel. I wasn't able to pin it down but it appears that you won't be able to remove all the moisture. I would suggest baking the filament at a temperature shy of your melt temperature and storing in a well sealed environment. Silica gel is dried at a temperature of around 130 to 140ºC so any temperature above that would be an improvement on using silica gel to remove water.

The drying temperature could be reduced if you are using a vacuum. About 12 years ago, I acquired a vacuum oven. The only problem was the silicone seal was missing and although it is available, the cost is prohibitive. I tried an adhesive backed EDPM gasket but the combination of the vacuum and heat just sucked it in. However, if restored to working condition, it would be ideal for the purpose.
 
WobblyHand said:
I'm hoping it was moisture - I had terrible problems getting a good print from it. Was Prusa filament.
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Hmm, that's odd. Prusa is generally regarded one of the better brands....I guess it just goes to show you anyone can have a "clunker" slip through from time to time.

Was the filament "brittle" when you were manipulating it? Filament with too much moisture content will go brittle and will usually snap when you try to bend it in your fingers....
 
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RJSakowski said:
I was doing some reading as to what the equilibrium RH vale vs. moisture content in the silica gel. I wasn't able to pin it down but it appears that you won't be able to remove all the moisture. I would suggest baking the filament at a temperature shy of your melt temperature and storing in a well sealed environment. Silica gel is dried at a temperature of around 130 to 140ºC so any temperature above that would be an improvement on using silica gel to remove water.

The drying temperature could be reduced if you are using a vacuum. About 12 years ago, I acquired a vacuum oven. The only problem was the silicone seal was missing and although it is available, the cost is prohibitive. I tried an adhesive backed EDPM gasket but the combination of the vacuum and heat just sucked it in. However, if restored to working condition, it would be ideal for the purpose.
Click to expand...
I agree the silica gel is not the best for this. I believe one needs to use molecular sieve material to get out more moisture. But molecular sieve stuff is difficult to regenerate.

PLA material is pretty low melting point stuff in the pantheon of 3d printing. Elevating the temperature over 70C may result in a spool of material that is hard to unwind. But any increase in temperature, or reduction in pressure helps.

It would be great to have a vacuum oven, or for that matter a good vacuum chamber. Maybe 45-50 years ago I acquired a great glass bell jar with a ground seal, but I had it at my parents' house and somewhere, somehow, it disappeared. To replace it these days would cost a fortune. It was about 14" ID and maybe 28-30" high. Found it in an industrial surplus place. Got all sorts of parts and vacuum pumps for it. But that bell jar has vanished. I have a mechanical vacuum pump, a diffusion pump and even some vacuum gauges, but no chamber. One of those projects that slipped away from me.
 
WobblyHand said:
I agree the silica gel is not the best for this. I believe one needs to use molecular sieve material to get out more moisture. But molecular sieve stuff is difficult to regenerate.

PLA material is pretty low melting point stuff in the pantheon of 3d printing. Elevating the temperature over 70C may result in a spool of material that is hard to unwind. But any increase in temperature, or reduction in pressure helps.

It would be great to have a vacuum oven, or for that matter a good vacuum chamber. Maybe 45-50 years ago I acquired a great glass bell jar with a ground seal, but I had it at my parents' house and somewhere, somehow, it disappeared. To replace it these days would cost a fortune. It was about 14" ID and maybe 28-30" high. Found it in an industrial surplus place. Got all sorts of parts and vacuum pumps for it. But that bell jar has vanished. I have a mechanical vacuum pump, a diffusion pump and even some vacuum gauges, but no chamber. One of those projects that slipped away from me.
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Just an fyi: the food saver brand has containers that it will suck down as well as toppers that can be put over jars and such to turn any container into a vacuum canister. I use a smaller one to store my unused desiccant bags under vacuum. If nothing else, it keeps the desiccant out of the ambient air moisture.

I'm sure other brands likely have the same type of things.

Worth a look....
 
great white said:
Hmm, that's odd. Prusa is generally regarded one of the better brands....I guess it just goes to show you anyone can have a "clunker" slip through from time to time.

Was the filament "brittle" when you were manipulating it? Filament with too much moisture content will go brittle and will usually snap when you try to bend it in your fingers....
Click to expand...
Yeah. It was a bit brittle. Was quite astonishing to me because the other material I had, shipped at the same time printed great. When I changed spools it was like being on another planet where the rules didn't apply. The original spool worked fine with their recommendations, but the new spool just didn't want to print. The old stuff was PLA, the new was PETG. I know the settings and materials are different, and used the recommendations for PETG, but it just didn't print well at all. Definitely heard popping in the extruder on that spool.

The spool was properly packaged in a vacuumed bag with a packet of desiccant. But behaved as if it had a lot of moisture present.
 
great white said:
Just an fyi: the food saver brand has containers that it will suck down as well as toppers that can be put over jars and such to turn any container into a vacuum canister. I use a smaller one to store my unused desiccant bags under vacuum. If nothing else, it keeps the desiccant out of the ambient air moisture.

I'm sure other brands likely have the same type of things.

Worth a look....
Click to expand...
Will check it out. Been keeping bulk desiccant in glass mason jars. No vacuum, but not leaky either. Glass is vacuum tight to a certain level, rubber is worse, but for low vacuum pretty darned good. The desiccant had been stored for well over 5 years and was bright blue, so not soggy inside the jar!
 
Had to replace a battery in my sensor. The LiPoly battery has seen better days. It appears slightly puffier than a different LiPoly (lower capacity) that I have, so I replaced it with a standard LiIon battery 18650 cell. The bag is quite collapsed due to the exterior air pressure still. I suppose I ought to safely dispose of the LiPoly battery somehow, although burning it seems like it would be a lot more amusing. I could set up some fire brick and torch it... Still a kid, I guess.

Initially the RH in the bag (with the filament) went to zero before evacuation, and then shot up to 6% or so after evacuation. After a couple of days, it is now 9%. The cloth bags I have for the silica gel are a bit opaque, but I don't see any evidence of much color change. There's clearly a different behavior due to the partial vacuum vs just a closed air tight bag. I'm not complaining about 9% RH under partial vacuum. If it stays there it will be fine. If it goes up more, I will just regenerate the gel.

For anyone wondering, as a result of 2-1/2 days of cold, cold rain, the inside house RH was 29%. How accurate that is, I don't know. Hope to find that sling psychrometer some day.
 
WobblyHand said:
I tried out some of those vacuum bags and filament, with my home made RH meter. The meter is powered by a single 18650 battery. Putting the meter in the bag with silica gel and sealing it, but not pumping it down, you could see the RH plummet downwards from the initial room RH = 17%. The RH in the bag was below 6% within a couple of minutes.

However, when the bag is evacuated, the RH went up. It went up to 14%. Eventually, over 24 hours it declined back down to 6%. I think this is telling me that evacuating is a good idea as it is pulling moisture not just out of the air, but the filament. I think under vacuum conditions the filament is finally out-gassing the absorbed water. And the silica gel is slowly absorbing it. So simply putting your filament in dry air doesn't really pull the moisture out, you need to lower the ambient air pressure as well.

Anyways, thought it was an interesting experiment.
Click to expand...
I use 12v dual dryer boxes in which I have ripped out the electronics. I mount egg controllers which can regulate temperature an humidity in the boxes. I set the two relays in the controllers in series to power the heater. I set heat to a maximum temperature with no minimum and %RH to 15%.. One spool of filament is feeding the printer with RH% maintained the other spool is being dried in preparation of use. When I put a spool on it is used until empty. This negates the need for any special storage, the spool is dried before use.
 
weston1968 said:
I use 12v dual dryer boxes in which I have ripped out the electronics. I mount egg controllers which can regulate temperature an humidity in the boxes. I set the two relays in the controllers in series to power the heater. I set heat to a maximum temperature with no minimum and %RH to 15%.. One spool of filament is feeding the printer with RH% maintained the other spool is being dried in preparation of use. When I put a spool on it is used until empty. This negates the need for any special storage, the spool is dried before use.
Click to expand...
Sounds like an interesting set up. What kind of sensor is used for humidity? I'm finding there's a huge variation in their outputs, at least for RH below 20%. Having 3 sensors reading so far apart isn't comforting. To be fair none of them are industrial grade, but when one says 20%, the other 16%, the third says 11%, all one can say is that it's dry, sort of. From my reading of the sensor spec that I have, they simply don't read as accurately below 20%, which is the region of regulation.
 
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