Does filament moisture matter as much as relative humidity?  

RE: Does filament moisture matter as much as relative humidity?

Well you know the filament is too moist when the steam makes bubbles in the extruded filament...

I can't see any direct connection to RH and stringing though.

Any swings in your room temp - or drafts? I can see warmer == more stringing.

RE: Does filament moisture matter as much as relative humidity?

Posted by: @robert-rmm200

Well you know the filament is too moist when the steam makes bubbles in the extruded filament...

Saturation is definitely an issue. Just didn't expect RH to make it worse and then better in a single cycle.

I can't see any direct connection to RH and stringing though.

I was surprised. Thought I'd toss the spool in the dryer after the big print, only to be surprised that it stopped one day. Back again today.

Any swings in your room temp - or drafts? I can see warmer == more stringing.

It's in a 3/4 walled cabinet. Enough to block drafts, and the temp in the enclosure stays about 5-6C/10F warmer than the surrounding room. Around 23C most of the time in both cases.

RE: Does filament moisture matter as much as relative humidity?

I've noticed a correlation between changes in the RH% in my Room and the weights of my test samples.  I'll see if I can pull the data out of Netatmo / Domoticz and graph it vs the daily measurements from the samples.

RE: Does filament moisture matter as much as relative humidity?

Posted by: @jmone

I've noticed a correlation between changes in the RH% in my Room and the weights of my test samples.  I'll see if I can pull the data out of Netatmo / Domoticz and graph it vs the daily measurements from the samples.

I was fully expecting weight to go up due to moisture absorption, no matter how small the amount. I will be very surprised (but interested) if it varies both up and down over the course of a few days. That would certainly explain the high degree in variability in the results people see!

RE: Does filament moisture matter as much as relative humidity?

Here you go - this plots the average of my PLA samples weight as they change vs the RH and Temp in the room.

RE: Does filament moisture matter as much as relative humidity?

I'm running another test on my samples of how the weight changes putting them in a freezer bag with a few desiccant packets.  It's only been going for a couple of days but within 24hrs they all lost a heap of weight.  From what I'm seeing, the filaments both gain and lose weight based on the RH of the environment they are it, and react to the RH of their environment remarkably quickly.  They don't "hold" onto the extra weight but shed it as well.

RE: Does filament moisture matter as much as relative humidity?

Here you go - this is how various Filaments "dry" out when just placed in a bag with some desiccant satchels 

RE: Does filament moisture matter as much as relative humidity?

Posted by: @jmone

Here you go - this plots the average of my PLA samples weight as they change vs the RH and Temp in the room.

Could you elaborate on this one a bit? I'm having a hard time understanding the values represented in the graph. What is the actual percentage and value of the weight change?

RE: Does filament moisture matter as much as relative humidity?

These are the print samples I made a month ago, and the % represent the change from straight off the printer.  So after been in the "Air" for a couple of weeks, the ePA-CF on the 24th @ 7:30am had gained 2.71% in Weight, 0.3% for PLA, etc.  They all then went into the same freezer bag with some desiccant satchels.  24hrs later the ePA-CF had dropped to 1.54% (eg lost almost half the weight it had gained), the PLA down to 0.3% (eg lost 2/3rds of the weight it had gained).  The PLA had reached it's original weight after 48hrs in the bag (and has even got a bit ligter since but that could be measurement error as I only have one sample for these so no averaging over multiple samples).  

My other experiment on using the 50g raw filament samples (instead of these printed samples) after being in the 80% humidity chamber is still weeks away from the drying part so we will know more than.  Anyway, what I think it shows, is just keeping filament in a low Humidity Environment (even a freezer bag with Desiccant) will quickly make significant changes in the absorbed moisture.  Techniques like driers, vac chambers etc my do nothing but speed up the process..... we will see in a month I guess.

RE: Does filament moisture matter as much as relative humidity?

Posted by: @bobstro

Posted by: @jmone

Here you go - this plots the average of my PLA samples weight as they change vs the RH and Temp in the room.

Could you elaborate on this one a bit? I'm having a hard time understanding the values represented in the graph. What is the actual percentage and value of the weight change?

This first graph, shows the change in weight of the PLA samples VS the RH and Temp in the same room.  You can see the PLA weight go Up and Down (the Column as I only have one measurement each day vs 3hrs measurement for RH and Temp).  

RE: Does filament moisture matter as much as relative humidity?

Posted by: @jmone

This first graph, shows the change in weight of the PLA samples VS the RH and Temp in the same room.  You can see the PLA weight go Up and Down (the Column as I only have one measurement each day vs 3hrs measurement for RH and Temp).  

So if I'm understanding this correctly: The weight of PLA will go up and down on a daily basis in response to changes in relative humidity, but the total amount of variation is within 1% and does not accumulate beyond that level. Is that correct?

What I'm not sure I'm interpreting is the rate of change relative to RH. Is there a linear increase or decrease, or might it vary at particularly low RH levels? At 25-30% RH, I see the usual fine stringing but I was surprised that it disappeared on the days when RH went below 20%.

I store all my filament in a ziploc freezer bag with a packet of desiccant. I don't usually dry PLA but do when it gets stringy. I'm hoping to understand exactly what changes to be a bit more scientific in my approach. I'm beginning to wonder if a dehumidifier in the cabinet might be as effective as toasting and/or desiccant. 

RE: Does filament moisture matter as much as relative humidity?

Keep in mind these are just my observations so far as I wait for the Test Filaments to fully saturate in the 80% RH Box, then I will start on various drying methods (but this will not be till late January). 

In the mean time I've been playing with how my printed samples react to various conditions and they seem to indicate:

- Weight changes based on the RH% of the environment (both up and down)

- The higher the RH% of the environment the quicker it gains weight

- The lower the RH% of the environment the quicker it loses weight

- In a stable 80%RH environment common filaments will gain 0.10% in a few hours, 0.20% in under a day and reach their peak saturation in a week

- In my room (varying between 40-70% RH) common filaments hit 0.10% in a day (ish), 0.20% in a couple of days (ish), and reach their peak saturation in a week (ish) but will fluctuate both up and down in line with the RH of the environment.

- ePA-CF is an exception, taking up weight much faster and taking much longer to reach a much higher weight gain.

On thing we need to find an answer to is:  What is the best Moisture Content Range for printing? 

- Max:  I've seen some specs say under 0.10% and others 0.20% but that was for injection moulding with PA. 

- Min: I know that my PLA filament stored in my 0% RH cabinet after months is now fairly brittle.  No so brittle that it is unworkable but when I was making my tightly would test spools it did crack on a few of the turns.  

I'm starting to wonder if:

- Just storing common Filament like PLA & PETG in something as simple as a Freezer Bag (or box) with desiccant or a common dehumidifier is good enough to both keep and dry filaments..... and there is no need to use other drying techniques at all (oven, filament dryers, vac etc) unless you want to speed up the process.

- My expensive 0%RH cabinets are really only needed for more exotic filaments like ePA-CF and that I could be over drying?

- That Heated Print boxes may only be be necessary for longer prints (PLA/PETG) in a humid environment or for filaments like ePA-CF

Anyway, this are just the observations so far.  Will know more when we get to the drying part of the Test Filament test and I'm using these mini tests while I wait to work out what drying tests (and conditions) to use.

RE: Does filament moisture matter as much as relative humidity?

Quick update on the observations:

- Desiccant will only dry items out so much.  Looks good for PLA, PETG, and ePC but not for ePA-CF which has now stabilised at 0.35% (much higher than the sub 0.1% for the others).  

- I've also seen some samples start to regain some weight.  So what I've done is replaced the silica gel packets with "fresh" ones, put them in the sample bag and I'll see how both the samples and the silica gel packets change weight on the next few weeks while I am away.

RE: Does filament moisture matter as much as relative humidity?

I have read the posts in this thread avidly. I remain unconvinced by statements from heated dryer box manufacturers that it’s only possible to dry filament using heat.

When moisture from the air is adsorbed into pores in the filament it makes sense that this would be a two way equilibrium phenomena. I suggest that, by presenting an environment having low RH even at room temperature, it should be possible to reduce moisture level in filament even at room temperature. It may take longer to dry damp filament this way but observations tendered by previous posts on this thread indicate it can work.

At least, that’s my bet. But I have a heated dryer standing by if it’s needed 😉 🤣 

RE: Does filament moisture matter as much as relative humidity?

Posted by: @bryn51

I have read the posts in this thread avidly. I remain unconvinced by statements from heated dryer box manufacturers that it’s only possible to dry filament using heat.

When moisture from the air is adsorbed into pores in the filament it makes sense that this would be a two way equilibrium phenomena. I suggest that, by presenting an environment having low RH even at room temperature, it should be possible to reduce moisture level in filament even at room temperature. It may take longer to dry damp filament this way but observations tendered by previous posts on this thread indicate it can work.

At least, that’s my bet. But I have a heated dryer standing by if it’s needed 😉 🤣 

I think the filament is very dry as a result of manufacture and way dryer than the  environment hence to reach a steady state with the environment must absorb moisture and not give it away. 

RE: Does filament moisture matter as much as relative humidity?

Hmm yeah if it’s prusament you can be sure it’s properly dry in the box. But there is plenty of evidence not every manufacturer has the same quality standards.

RE: Does filament moisture matter as much as relative humidity?

Thanks for such a helpful information here!

RE: Does filament moisture matter as much as relative humidity?

I have had a roll of questionable filament from multiple manufacturers.  It amazes me that filament can get "wet" when vacuum packed.  

RE:

I still do not understand all of the factors that go into damp filament.

I can't remember getting a spool from the factory that was damp, but I very recently changed a spool of PVA from the Ultimaker name brand to the Dynamism house brand, and the Ultimaker spool was in place, exposed to room air (20s to 30s percent RH) from shortly after the first of the year until a couple of weeks ago with no issues, and then after about two weeks the Dynamism brand spool showed the tell-tale signs of being damp, with the stringing and snap-crackle-pop upon extrusion.  Overnight in the Ninja Cooker on dehydrate cured it, for now.

I also recently had a spool of RepRappers yellow PLA that started the snap-crackle-pop thing after being exposed to room air no longer than spools of other brands that have not shown the symptoms of being damp.  Again, Ninja Cooker overnight cured it, for now, that is.

Now this morning, I started printing the bracket for the pool alarm that I spoke of in another thread.  This is the piece that will hang over the pool and hold the sensor and tube.  I'm using white RepRappers ABS for this, and the spool has been on the spool rack, exposed to room air, since before the first of the year.  Before I started the print I bent it to be sure it was still supple, and it was, and it's now printing, 3+ hours into a five hour print, with absolutely no snap-crackle-pop.

I've only seen one spool of filament that I could not render usable by using heat to dry it.  This was the remains of a spool of FilamentPM silver-gray, which appears to be the same stuff as what comes with the Prusa kits.  I had forgotten about it and it sat in the corner of the spare bedroom, exposed to room air, for over a year.  I tried drying it and using it, but it kept snapping.

Inspection showed many hairline cracks (see photo below, look closely).

The RH in the house typically is in the high 20s in the winter and in the 30s in summer.  I do have three dryboxes for storage, each with a humidity gauge, and I will bake the dry-packs in those when the humidity starts creeping up into the high 20s.