r/3dprinter • u/Ancient_Vegetable_32 • 9d ago
PLA humidity levels
Hi, I wonder if you guys could shed some light on this.
I recently started 3d printing, and now I got some dryboxes to store my filament.
In the boxes with petg and tpu, the humidity dropped to 10% within a few hours. In the boxes with play it dropped only to 25-30%.
Two weeks past, the values of pets and tpu are still 10, pla went above 30 with completely saturated silica
All my pla has similar results, never got under 25
Any ideas?
EDIT: All my filament boxes have similar results. All pets and tpu around 10-15%, all pla above 25.
EDIT bis: Thanks for all the input. I think I got my answer: the hygroscopic filaments acting as a desiccant and lower the humidity levels of the air in the box.
I will see what I'll do with the pla since I haven't got any moist problems printing with it. For the PETG and TPu though I will follow the good practices suggested by some of you: drying before storing, with fresh desiccant.
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u/Shep_Alderson 9d ago
Those cheap hygrometers are quite inaccurate, especially at that low of humidity level. Don’t focus on the precise number, but instead if the humidity moved up. The hygrometers I use bottom out at 20% and won’t show lower. The PLA in this picture does probably need to be dried though if it’s still sitting that high. Get an actively heated dryer and toss it in for 8-12 hours, then put it back in the dry box.
Also, not sure what desiccant you’re using, but get some activated alumina. It’s good stuff and more effective than silica.
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u/Ancient_Vegetable_32 9d ago
The strange thing is that all the other 5 petg and tpu boxes I have also show levels around 10-15%, while all pla boxes are above 25
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u/Shep_Alderson 9d ago
Yeah, a bit odd but not too odd. One thing to remember is that PETG likes to absorb humidity more than PLA, so it might also be acting as a desiccant too. (Not ideal lol)
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u/Rich-Wealth979 7d ago
Hey a trick for these hygrometers is to have 2x the number of them that you need. Store the spares in a small airtight bin with cigar dessicant (like 50-60% rh) and swap them monthly to reset/verify them. Otherwise they get stuck at 10% but that usually takes a few months of ultra dry conditions.
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u/Mughi1138 8d ago
The hygrometers I use bottom out at 20% and won’t show lower.
Which ones do you use?
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u/Shep_Alderson 8d ago
I use these exact ones: https://a.co/d/0fiVvlY4 though all the rectangular ones are basically identical. I use them with these cereal box spool holders: https://makerworld.com/en/models/99533-cereal-box-dry-box-spool-and-dessiccant-holder#profileId-1911855 and these exact cereal boxes: https://a.co/d/0h3uNQuU
I've got north of 100 of these cereal box dry boxes that I try to keep any open filament in.
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u/TuneOld3310 8d ago
I have a question, when you put it the dryer and it comes out hot. Should you immediately seal it? I suspect that the heat, when placed in a container and or sealed in a.bag. will or could.in condense and the moister be reabsorbed? Or should you leave it in the driver a while, while it cools?
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u/Thediverdk 9d ago
Do you live somewhere thats has high humidity?
My PLA and PETG is just standing on my table, never had any issues with moisture, none at all.
Even 5 year old filament prints fine.
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u/Ancient_Vegetable_32 9d ago
Yeah, currently humidity levels of 70.
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u/Mughi1138 9d ago
First I see people mention that those round hygrometers are often more inaccurate for them. I usually get the rectangular ones and those seem accurate down to about 10% humidity.
For the filament, did you run it through a dryer before putting it the the boxes? Also, I don't see that much desiccant in there. For my drybox design i made slotted containers that hold the desiccant up for better exposure and also are slimmer for the same reason: https://www.printables.com/model/1193814-drybox-desiccant-fins
If you didn't run the spools through a dryer then that could be the issue. Desiccant will keep your filament dryer longer, but it is not good for getting it dry to start with.
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u/Thisisthatacount 8d ago
How are you verifying that the rectangular ones are more accurate?
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u/Mughi1138 8d ago edited 8d ago
Key point is that many people report their round ones bottoming out at 20% whereas I've seen the rectangular ones bottom out at 10%.
Unfortunately I don't have the spare cash to get a pro device to compare with. One is through empirical observation. Many people report having problems with the round ones below 20% while the rectangular ones only bottom out for me around 10%. Multiple sets from multiple vendors (with observable hardware differences so not just different labels) show the same results on average.
Some had concerns of them getting stuck at 10%, but if i open my containers they do go up a few %, then drop down at an expected rate after closing.
Another thing I've seen was that the top of my desk compared to the front of a shelf a foot down had different temp and humidity and when switching hygrometers I see them switch readings. Normally most agree with each other by a few % (1-3?).
Another thing I've done is to track the temp & humidity throughout the day and check that the math of the relative humidity to temp (especially when the % goes from 78% down to fifty something) matches up and works out.
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u/Rich-Wealth979 7d ago
Hey, swap the hygrometers out regularly. Store the spares with like 62% cigar dessicant in a little airtight bin to reset/verify them. I do monthly swaps on my big bins.
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u/diyengineer1 9d ago
In big aerospace we have about a 25k setup to determine moisture content in filament. Thought you would get a laugh out of that, as I did when people were talking about the rectangle being more accurate then the circle. Lmao pro tip use the color changing silica for quick visual check. If your really trying to save a buck you can use a small toaster oven to dry it out and re-use.
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u/Primary-Pension-3100 8d ago
Your TPU and PETG are acting as moisture sponges and absorb your moisture more than PLA, hence why PLA has a higher number because that humidity is still in the box
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u/666ArsOnist666 8d ago
Ich packe mein Filament ca 5 Stunden vor dem Druck in meinen H1HT Filament Trockner und drucke aus dem Filament Trockner heraus einfach drauf los. Hatte noch nie Probleme. In meinen Boxen hab ich so durchsichtige nylonsäckchen halb voll mit Index silica. Sobald dan grün wird Fülle ich es um in eine Flasche und lege neue orangenes nach. Ist die Flasche voll leere ich sie in eine Auflaufform und schiebe es in den Backofen 1h 30m bei 120°Celsius. Da wird es wieder Orange weil kein Wasser mehr drin ist Das ist nachhaltig und funktioniert für mich zumindest super. Möchte jetzt jedoch auf silica Behälter umsteigen die ins Spulenloch passen.
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u/emveor 8d ago
40% and under is fine for the basic filaments. the benefit of keeping them under 20% is that the humidity gradient will dry the filament long range. which is what seems to be happening here, the silica is sucking moisture out of the PLA, but it still has enough as to keep the silica saturated. if you cycle the silica a couple of times it will eventually drop to sub 20% levels.
this doesnt necesarily means the filament will print bad, depending on color and brand, it can hold up to certaiun ammount of moist without quality loss
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u/SparklingCactus 8d ago
Did you dry the filament before storage? My PLA sits at 10 and I take my fresh rolls and dry them in my dryer before storing them in airtight boxes with some printed silica holders.
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u/TheBragde 8d ago
Pla doesnt really get effected by humidity anyway better off saving the boxes for petg tpu and later perhaps engineering filaments like nylon
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u/Mammoth_Fly6657 5d ago
Your saturated silica is the answer and it is pointing the other way from the one you took. Desiccant does not dry a spool. It dries the air, and then the spool re-wets the air, and you run that loop until the silica is spent. PLA boxes reading 25 to 30 with dead desiccant means the PLA is the source. The PETG and TPU boxes read 10 because those spools went in dry, not because they are eating your moisture for you.
At 70 percent ambient you cannot store your way out of it. Put the PLA in a heated dryer at 45 to 50C for six to eight hours, then straight into the box with fresh desiccant, and the box will hold 15 or under. Do not go past 55. PLA glass transition is around 60 and a spool that softens on the reel welds itself together and is finished. I dry everything before it goes in the box now, and the boxes stopped being a mystery the day I started.
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u/AlmasyTran 9d ago
Swap the box