How long should you dry a brand-new unopened roll of PLA?
Would you keep it in the dryer while printing a 13 hour print?
Richard
Most times I don’t dry out of the box filament, unless I think there is an issue.
When I do use a dryer, I dry for a least 6 hours.
95% of the time, I will print straight from the dryer, I’ve done 72 hours print like this.
I always print ASA, TPU & PETG from a dryer…PLA if it’s a overnight or longer print.
Thanks for your thoughts!
PLA is not very hydrophilic. Amongst all the filament types, it’s about the best. The problem with PLA and humidity is more that it makes the filament brittle and prone to breakage as it passes through the printer’s filament path. If it still feels good and flexible, that’s a good indication you don’t need to dry it. If it snaps like uncooked spaghetti, it definitely needs drying.
There is no one answer to “how long”. I put my rolls in the dryer the day before I expect to print, so they get a minimum of 12 hours and usually closer to 24. Filament can’t be “over dried” so it’s no big deal to go longer, it’s added insurance.
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Thanks… I plan on using a brand new roll of Voxel PLA+ for a 13 hour print. My plan is to dry it today for about 6 hours, then keep it in the dryer while I am printing.
Thank again for all your ideas.
Best… Richard
My method of controlling filament moisture is based on weight, detailed here. I’ve now have an Eibos dryer, but the only time I print directly from the dryer is with TPU and PC, or maybe PETG if I expect to be using the same spool over several days.
I tend to be a bit obsessive about printing with dry filament, but PLA is slow to absorb moisture and the material I worry about the least. Though I’m in a humid climate, I can leave PLA out for at least a week or so (no AMS) without moisture problems. (In that case, I do dry it again before storage.). I don’t worry about one or two grams of moisture weight gain, six grams or more definitely calls for dryer time.
You’ll get the vast majority out of PLA fairly fast, 3-4 hours at ~45-50c with airflow will take probably 90% of absorbed moisture out
I do now have hyrgrometers but I do not know what defines dry. What is a good number? At what point are problems going to occur?
With a brand new spool of Bambu PLA, the RH inside the AMS settled to 11-12% fairly quickly and the print quality was excellent. I decided it was time to dry an old spool of Polymaker PLA that felt fine and had printed ok recently. So I put it in the Sunlu heated dryer for 4.5 hours at 50C. After transferring it to the AMS, I gave it 30 minutes to settle down and the RH was 21%. So the 8 hour recommendation from Bambu is warranted at least for a spool that’s not been well-maintained. Elsewhere I’ve read that 6 hours is enough (though many YT are much more stringent and go for a lot more). I think an empirical approach like measuring settled RH or water loss is more reliable.
The AMS while sealed reasonably well suffers from that big rush of air when you open the lid, I have a govee digital hygrometer parked inside mine and its a sawtooth jump with a gradual gain of humidity over days of this. I dry my desiccant weekly and see 20g of weight loss from a 15min microwave boost (30% power). I think thats mostly my lid opening and not from my spools as there is no heat/vacuum involved to evaporate it from the filament. I think monitoring RH is ok for desiccant condition but not a good measurement of filament moisture content as too many variables exist (length of filament, no. of spools, etc). Weighing individual spools is my method as you can see controlled data at any stage.
PLA is pretty boring and I get lazy on my A1Mini to the extent of leaving spools out for a week if i’m using a set of colours, my room floats anywhere between 40-50% humidity normally and I’ve yet to suffer brittle or print issues from this time in the open. I have had a few spools go brittle but generally its from new and before I put it through a heat/vacuum cycle.
Drying PLA is recommended, I think it’s most important to do it at the start but after that is probably dependent on the individuals environment (ie. if you live in the tropics or a desert). Heat is necessary, but in my case I combine it with a period of vacuum in a pot so I reduce my heat cycle. If I purely use the heat method, I’d aim for 4hrs as anything over that is possibly overkill and damaging to any additives (not scientific proof, just my thoughts).
Video lost me at the start, TLDW as it felt like a sales-pitch.
As I’ve said, I keep the heat to a minimum as I don’t think the moisture is going to essentially kill the PLA in limited amounts. Getting rid of excess moisture is the key, and for the most part we have no way of effectively knowing how much of the Kilogram spool we have freshly opened has inside. For all we know its like the kilo of mince from the supermarket, the before and after weights are a good indication. Say 10g of something akin to moisture has gone, I’d say this would be better out than in if it is going to cause brittleness or print quality issues.
As far as recovering a brittle spool, yes in my experience the heat/vacuum cycle does work. I’ve had two from memory that were bad, a PLA-CF and PLA basic spool, both left remnants inside my feed and hence needed some love. Afterwards, no issue and I’ve gone to use them onwards without any further drama.
Indeed the RH shoots up when you open/close the lid but the the Bambu calcium chloride desiccant (which absorbs more and faster than rechargeable silica) restores the RH from the wet air in about 15 minutes for me and goes from 25% back to 12% in a room with an ambient RH of 30-35%. As for overkill in heat-drying, I’ve read from various sources that it’s the temp and not the time that ruins the filament. In other words, stick with 50C and a long time and not try to rush it with 60C and less time. Using accurate RH over time to double-check the dryness of a filament in addition to weighing (drying) is something I picked up from Stefan of CNCKitchen. He has a video where he dries with different methods and shows the weight loss. While he uses weight loss, it is only via a no-further-gain approach that he decides it’s dry and explains why a stabilized RH can also show that it’s dry because the water content in the filament will adjust to the point that it equalizes. RH does not directly measure water content of the filament but does tell you whether it’s wetter than a target goal if you let it reach equilibrium.
That video is a bit hard to watch… My takeaway is that there is some damage that is irreversible but this did not seem quantified to an extent applicable to the end user. So by itself partial hydrolysis of the polymer does not contradict the effectiveness of heat-drying of PLA spools. The slightly modified advice might be that while dry-heating works, the number of wetting cycles is limited so be vigilant with your desiccants.
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While I’m certain there is some truth to the fact that drying PLA doesn’t repair the polymer, it does still remove the water. That’s half the battle. Passing boiling water through your print job doesn’t do anything good for your print quality.
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And about desiccants, it gets even more complicated. They can be water sinks (which you want them to be) but also water sources (which you don’t want them to be).
If they are reversible (which desiccants that can be regenerated are), as they collect more water and the humidity in the chamber starts to rise, put a dry roll in and that water can be absorbed by the filament with a fairly large reservoir of water in the desiccant. It will absorb that water until they both “want” water the same amount and they are in equilibrium.
It’s all about equilibrium and what “wants” the water more and what is in a position to give it up. In a chamber without desiccant, put a dry roll in with a “wet” one and the dry roll will act like a desiccant to pull water from the wet roll.
Best way to avoid this is by changing/regenerating desiccant before it starts letting chamber humidity rise too much. Waiting until it tells you it’s humid is probably too long if you want maximum drying.
No numbers to help guide decisions when to change, though. This is just what will happen. The when is fuzzy without numbers to know exactly when desiccant turns from sink to source but that depends on how wet/dry the desiccant is and how wet/dry the rolls are.