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Required Humidity % for printing Hygroscopic materials (PVA, NYLON)

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Hello Everyone:)


My NYLON and PVA are showing signs of moisture absorption (crackling sound when printing and bubbles)
My current room humidity measures 45- 50%


One thing still not clear is what is the Humidity % required to print PVA and Nylon (hygroscopic materials) without absorbing humidity ?
On ultimaker website it seems to be written upto 50% is okay.
but polymaker seems to say less than 15% humidity is required to print.
I store both my materials in airtight box with lots of silica.
I have attached photos of the same.



What is the best option to print with my current humidity % (45-50%): ?

Option1: Bake Nylon and PVA on the ultimaker 3 heatbed at 55 deg for few hours before hand when printing. and later keep it in the airtight box with silica.

Option2: Make a carboard box with a lots of silica in it and put it on the ultimaker spools and stick it leaving 2 holes for material to feed into the feeder. ( I have made this for time being for some urgent prints.


Option3: cover the whole printer with a huge box so that minimum air goes inside and put  lot of silica inside.

Option 4: Buy Poly box (drybox) for Nylon and PVA, But it will disable NFC feature and create other extrusion problems because of travel from poly box to feeder.( i read in posts)

Please suggest best solution to this problem.

Edited by KamalDahiya

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You will have to bake the filament from time to time regardless of where you store it. Storing dry is very important, but not always to only way to keep the spools dry. So option 1 is something to do when your prints are not nice or you hear a sizzling sound.


Option 2 or 4 is a must-have in my opinion to have a consistent quality also for a longer print job. I prefer the Polybox, it is nice, small and keeps 2 spools in a dry environment. But it is nothing more than any other box you modify. I don't care about the NFC reader it does nothing else than select the material for you, so I can select it manually too. (But be careful, because then you have to choose the generic material in Cura and not the UM one, otherwise the printer thinks you have the wrong material loaded.) I also have no extrusion problems with the Polybox, you should just place the box in a way, that the filament goes in a "natural" way into the Bowden tube to avoid too much friction. I have mine on the floor beside the printer, without any problems.


Option 3 is not good. Without good ventilation, the air will get too hot inside and can cause problems with the material and stepper motors get too hot.


The Polybox is also nice to store the filament, so normally I don't put the spool back in an airtight container after printing, I just rewind the filament back and that's it.


But your drybox is also ok, so just use it, it fits perfectly behind the printer and you can use the NFC reader too.

  • Thanks 1

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Thank you so much Smithy for your consideration 😄
A little clarity on...

1. Can I Bake my Nylon spool on my ultimaker3 heat bed. (like Ultimaker website suggested for PVA). If yes, then what temperature and time for nylon?

2. Yes, I agree the Polybox would be better. But it will take few days to ship to my country and till then i have imp prints to give, So made this hack myself. But my question is the polybox claims to maintain humidity % below 10% and claims hygroscopic materials requires humdity% below 15 %. I am pretty sure my hack box is not keeping humidity% below 15%. it somewhere between 40-45%.

and on ultimaker website it says Hygroscopic materials can print upto 50 % humidity,
So what should be the humidity% maintained for prinitng Nylon an Pva ?

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You can bake it on the heated bed or in an oven, both are possible. The time depends on how wet your filament is, overnight is a good starting point and then you will see if it was enough or not. I don't know the temperature for UM Nylon, but you should always stay below the glass temperature, otherwise, the filament gets soft and you can ruin the spool. As far as I know, the UM nylon has a lower glass temperature than other brands, round about 50°C, so I would start at 40°C for the drying process, but with lower temperature, it will take longer. 


There also commercial solutions available like the DryBox, but it is nothing more than a normal food dryer which is much cheaper than the Drybox solution. But a heated bed and covered with a towel or an oven is also a way to go. When you use an oven, be careful and heat up the oven without the spool, because ovens mostly overshoot the target temperature when heating up.


My Polybox has humidity inside between 11% and 20% and that is fine. I also think that humidity below 50% is a way too high, especially for storing. I guess UM means that you print the material when below 50% but for sure not for storing. And when you have a long-running job, 50% can be too much. There is no other general rule how much humidity is acceptable, but keep it as low as possible.


Your hack box has maybe also too few silica packs, so you could give it a try to put 2 500g or 2x 250g packs in the box. The very small ones are not working fast enough and due to the reason your box is not airtight enough, too much air comes in and the packs cannot absorb the humidity quick enough.


Every box which is more less airtight and which contains enough or big packs of silica packs are ok and useable. The Polybox is just a commercial solution, which works well, but you can also make a box on your own to achieve the same result.

  • Thanks 2

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I think your cardboard box is a really great idea: it is very compact, and "part of the printer", sort of. But being of cardboard, it will absorb moisture by itself. It might be better to make it out of transparent plastic (and then you can see what is going on). And add little pieces of teflon tubing from the exit of the box to the feeder-entry. To close the seams between box and printer, maybe you could add soft foam like on window and door seals? I think it is worth developing this further.


As Smithy says above, you should add *lots* of silica gel. I use 500 gram packs sold in car shops to de-humidify car interiors. These have a blue indicator turning to pink when saturated. Also, regularly regenerate the silica gel: once saturated it not only loses its function, but makes things worse. Also put dry silica gel in the box/oven while drying the filament.


This silica gel bags are clean, easy, and can be regenerated on the central heating, or in a micro-wave.




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