Drying Times and Temps in Dehydrator  

5 week double zip lock bag PETG storage results

Five weeks later I have results for PETG storage in double bagged gallon zip-lock freezer bags + silica packs. They were then put back into their cardboard boxes and left undisturbed for the entire 5 weeks. RH in room runs 30 to 40% with room at 18.5 to 24.0C during that time.

Scale was recalibrated with 1.000 kg standards prior to use.

Sorry about formatting. This forum makes tables  near impossible.

spool gm0 gm5wk delta indicator

A 1132.07 1132.34 0.27 blue

B 1136.24 1136.95 0.71 purple

C 1163.56 1163.96 0.40 blue

D 1122.95 1123.53 0.58 blue

E 1140.91 1141.42 0.51 blue

Double bagging definitely makes a big improvement. Half a gram of water gain over five weeks storage means all the test spools are in usable condition. Even the one whose indicator had changed to purple is still acceptable. I can expect prints with up to 1 gm of water gain / kg spool. This is great news for those of us who find single bagging fails in about a week.

RE: Drying Times and Temps in Dehydrator

I should emphasize these were actual Zip-Lock brand freezer bags, not clones. 

I did not measure the silica packs initial masses. I do not known how much they changed. Only the spools themselves were weighed.

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Great test.  I will have to try double bagging.  

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@guy-k2

Great work! Thanks. Looks like I’m off to Costco to get some more ziplock bags  

cheers

 Rick 

RE: Drying Times and Temps in Dehydrator

Posted by: @aureumlocus

@guy-k2

Great work! Thanks. Looks like I’m off to Costco to get some more ziplock bags  

cheers

 Rick 

 

I have found th double zippers work better.

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Posted by: @charles-h13

I have found th double zippers work better.

I've been using the ZipLoc 2 gallon bags with a double seal at the top. I still find the desiccant packets change colors after a week or two, so double-bagging is still probably necessary. The size is a bit too large but should accommodate double-bagging easily.

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As an idea, if you are double bagging, put some desiccant between the bags as well.  Should help stop the moisture penetrating the inner bag.

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Has Anyone try the thicker Commerical bags?

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I use such vaccuum storage bags: Amazon link

(and desiccant packets of course)

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Posted by: @charles-h13

Has Anyone try the thicker Commerical bags?

I have read that mylar bags are more effective, but haven't done any testing myself.

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@bobstro

The Mylar works pretty well.  It is not double zippered, but they work.  

RE: Drying Times and Temps in Dehydrator

How's this for a summary???

Overview:  MatterHackers has a good article "Beat Moisture Before it Kills Your 3D Printing Filament".  In summary, 3D Printing Filaments will all absorb atmospheric water over time.  The more hydrophilic the filament type is (such as Nylon, PVA) the quicker the filament will absorb water.  Once a filament has become "wet", it will impact the quality of the prints but this process can be both prevented and reversed.

New Spools:  There is no guarantee that your brand new spools will be Dry out of the bag!  Even though they are Shrink Wrapped with Desiccant the more hydrophilic the filament type is (such as Nylon, PVA) the higher the chance your filament will need to be dried before use.

Drying Filament:  Filament can be dried by using a combination of Heat, Time, and Airflow.  The amount of Time and Heat you need is determined by the Filament Type (brand, colour).  Here is the Recommended Drying Time from PrintDry:

You can use your Oven to Dry Filament, though many have now moved to inexpensive (approx US$100) Food Dehydrators as they can not only be used to Dry the filament but also used as a heated Print Box as well ensuring that your heated filament stays dry during your prints.  

Another Option for Drying Filament is to use a Vacuum Chamber.   As a Vacuum increases the Boiling Point of water decreases.  So at 1000mbar/10,000Micron/29.5Hg/750Torr water boils at 0c.  I have a 2 Stage / 9CFM / 1HP cheap pump and chamber (similar to the picture below and can be purchased as kits for about US$100) that can exceed this.  You can get chambers of various sizes and mine will hold 4 spools comfortably.  I've been combining both drying / heating my filament in the Dehydrator then playing the spools in the Vacuum chamber and giving it a few "hits" to boil and draw off the water.

Storing Filament: The simplest and cheapest option to keep your filament dry is to use 1gallon Zip Lock bags.  Double bag your spool with desiccant packets in each bag.   guy-k2's tests in the previous posts show that this will keep moisture absorption down to about 1/2 gram per month (pending your environment, filament type etc).  

Other variations to the theme use "air tight" plastic tubs with desiccant, though given the volume of air and that the top will be opened all the time to access spools, this method is less likely to be as good as individually packaging each spool.  There are also commercial products like PrintDry's Vacuum Sealed Containers.  These should work better than Zip Lock bags but they are much more expensive (and keep in mind while the "vacuum" will be relatively weak it should be pretty good at preventing moisture ingress). 

Regardless of the method, your spools are still absorbing moisture, and hence at some point in time you may still need to dry your filament.

At the top end of the market are commercial Dry Cabinets.  These come in a range of dehumidification specs, and some models can go down towards 0%RH but they can run over US$1,000 pending on the size and RH floor limit.   I've tested a few models, and find it hard to recommend the Mid range ones that only get down to 40%RH, though the ones that run down to 0%RH are fantastic (if you don't mind the cost).  At near 0%RH, these cabinets not only prevent moisture absorption, but will also dry out material (though slowly).  I tested putting some wet colour changing desiccant in the cabinet and over a week it turned back to orange.   These cabinets are also good at quickly "recovering" a low RH environment after opening the door (something desiccant in a storage tub will not do).

Moisture is not the only issue, filament should also be stored away from direct sunlight as UV will degrade many filaments.

Thanks

Nathan

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It should also be noted, that the time, effort, and costs of doing all of this Vs the benefit is important.  If I was living in a low RH city, printing PLA and getting through my spools every couple of weeks then it most likely overkill.  Unfortunately (or Fortunately), I live in Sydney where the RH is rarely below 60%, and I have some 60+ spools of which many are a year old.

Also, I have one unanswered question I can find no info on... Can some filament types be "too" dry?  I've set both my dry cabinets to 0%RH but can chose any ceiling.  I have no idea if PLA, Wood Filled, Metal Filled, TPU, etc etc should be stored at 0%RH or something higher.

Also there can be unintended consequences of some of these recommendations, eg I do know that printing PLA from my heated box increases the likelihood from skipping due to heat creep from my stock extruder (on longer prints).  To combat this, it is best to print PLA "cold" or in my case I added some heat sinks to my Extruder Motor.

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I do have one printdry container.  I like it but they are costly.  

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The Gourmia 9 tray unit is back in stock at $99 Amazon https://www.amazon.com/gp/product/B01M6AZ863

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I pulled out an older role of Nylon (Dupont Zytel) and Flex (Dupont Hytrel) from my Dry Cabinet that I had not dried in either with heat or vacuum and compared it to my initial test prints and they were far better.  It is obviously much slower and a lot more expensive but storing filament at around 0%RH is they way to go.  

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RE: Drying Times and Temps in Dehydrator

@tim-m30.

I initially did not think to use my vaccuum pump but I got a fresh spool of ePA-GF and was having all sorts of issues printing it even after backing it in an oven (see - https://forum.prusa3d.com/forum/original-prusa-i3-mmu2s-mmu2-how-do-i-print-this-printing-help/esun-epa-gf-weird-hue-changes-on-layers/ ).  It was better, but still not great.  In googling "drying filament in vacuum chamber", I found a heap of info saying this works and interestingly, this site - https://amtechniques.com/ about a vacuum filament dryer (that is now on Kickstarter for big $$) so I thought I'd try it.  I then did a couple of cycles of warmed up the ePA-GF and putting it in the vacuum dryer and it worked for me in drying out the spool.  I wish I had the forethought of taking some measurements to see how the weight changed over time with each of the methods I used on the spool.

I've also asked the makers of the vacuum filament drying the following:

- How long does it take to dry a spool of filament (eg is there a table like print dry with recommended times)?

- Does the pump need to run all the time during the dry phase or does it just turn on/off to keep the pressure under 50mbar?

- 50mbar is not that strong, did you consider a stronger pump that could get to around 5mbar (at which point water boils at 0c)

- What sort of pump is used and is there any maintenance requirements (eg change oil etc).

Their reply was:

Thanks the for questions I will answer them below:

 

Drying times:

It is hard to state exact drying times, they are depending on multiple factors like moisture content and how many filament is left on the spool.

The moisture content in the spool itself is a factor as well. The spools get moist and get dried as well.

However, we noticed 3 hours to be sufficient for most materials.

 

Run time pump:

Drying goes in cycles, so the pump runs a couple time per hour.

Drying is done with a program which includes venting.

Vacuum will be applied after pre-heat. After that the drying cycles starts, which includes venting with air from the other side to dilute the moisture so it can be removed.

 

 

Pump pressure:

The minimum pressure is 20mbar, the video showed 50mbar as set point. The Switch-of-pressure during drying is 30mbar below set point. So it ends up at 20mbar.

Lower pressures will decrease drying times a little. This lower pressure is not possible with a membrane pump, so in that case we couldn't use a maintenance free pump. The lower pressure would have no effect on final part quality.

Therefore we decided to go with this pump.

 

Pump type:

It is an oil free membrane pump which doesn't require maintenance. We picked this type so we are able to use a build-in pump.

The build-in condenser protects the pump against water.

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...and I did test my vacuum that it was strong enough to boil water.  I just put a cup of water in the chamber and it was boiling off within a minute under vacuum.  I did not run it for long like this as the water will contaminate the oil as I don't have a vapor trap (but did see a video about how to separate the water out of the oil.... but I just purchased more oil for when it goes cloudy).  One important thing I did notice (and hence one of the questions above), is that you need to either keep running the pump (either continuously or in cycles) as if you turn off the pump and close the valves the water  stopped boiling.

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that's expected , the evaporating water will raise the chamber pressure toward equilibrium