Are we kidding ourselves about desiccant?  

RE: Are we kidding ourselves about desiccant?

@bad-raven-2

Any chance of a photo of a PETG or TPU print?

RE: Are we kidding ourselves about desiccant?

Yes, "10 years" is a long time. Probably I'd get 2016-era results with my 2026 printer for a wide selection of materials even if the filament is in equilibrium with room humidity. But the 2026 printer can do better and an A/B comparison is like night and day.

And, filament generally does not come dry out of the bag. Taking a freshly opened bag as reference, then yes I agree - I don't have to dry filament, it won't get significantly worse. But - as said - the printer can do better.

The drier was the most important improvement to print quality for me. And curiously, I don't see much need to tune filament over generic presets. It just works -as long as it's dry. If not, no attempts at tuning will do any good.

RE: Are we kidding ourselves about desiccant?

Here are 2 examples (PC and TPU) of filament that was printed straight from a factory vacuum sealed bag on the left and after drying on the right. Main point is never assume filament fresh out-of-the-box.... is fresh...

RE: Are we kidding ourselves about desiccant?

Absolutely true.  It is amazing how many will argue with you on this.  

Posted by: @hyiger

Here are 2 examples (PC and TPU) of filament that was printed straight from a factory vacuum sealed bag on the left and after drying on the right. Main point is never assume filament fresh out-of-the-box.... is fresh...

RE: Are we kidding ourselves about desiccant?

When you live in a temperate maritime climate, you quickly realize how much moisture affects filament, even PLA. I”m constantly drying desiccant in a microwave while also occasionally redrying both PLA and PETG in my PrintDryer. I’ve gotten several of the Polymaker dryer units which are more convenient, but I find my PrintDryer works better. 

The one thing I’m more concerned with, and no one addresses, is cardboard spools. Eventually filament will absorb moisture, but I’d think the cardboard spools would absorb it at least as fast. Once this happens, if you just dry the desiccant, you’ll be drying the cardboard more than the filament. I only buy plastic, reusable spools now. Since Prusa is 3x the price in Canada, my go to filament right now is from Bambu because of cost and spools.

RE: Are we kidding ourselves about desiccant?

I can see your point.

Posted by: @crab

When you live in a temperate maritime climate, you quickly realize how much moisture affects filament, even PLA. I”m constantly drying desiccant in a microwave while also occasionally redrying both PLA and PETG in my PrintDryer. I’ve gotten several of the Polymaker dryer units which are more convenient, but I find my PrintDryer works better. 

The one thing I’m more concerned with, and no one addresses, is cardboard spools. Eventually filament will absorb moisture, but I’d think the cardboard spools would absorb it at least as fast. Once this happens, if you just dry the desiccant, you’ll be drying the cardboard more than the filament. I only buy plastic, reusable spools now. Since Prusa is 3x the price in Canada, my go to filament right now is from Bambu because of cost and spools.

RE: Are we kidding ourselves about desiccant?

Posted by: @conrad-2

As a metrology geek, I tend to trust nothing! I have various humidity measuring devices that all agree closely, including a chilled mirror device of my own design, but there are many pitfalls when you get to the signal digit numbers. 5% is a dewpoint of about -9 degrees F and I don't know if my chilled mirror can get down that low. What I can say is that as things dry out, the response seems to be linear, so I doubt the readings are way off. Fortunately, we're not so interested in the high humidity end. We have to subject our products to that where I work and the humidity sensors we use don't have a great lifetime under high temp and high humidity conditions. I'm still of the opinion that keeping a large amount of filament dry with a small amount of silica gel is a big ask.

Good points about readings.  I just purchased some sensors that make a promise of accuracy and I still need to test them.  I created a chart to calculate RH% based on the dew point to judge what I need to think about and when I should be concerned.

As for meters, I have experienced the issue of a so called good meter to find that between 5 of of them, I found over 10% RH difference when all were placed in the same bin.  Useless.  At least the ones I am using were within 2% under the same test, they don't read below 10%RH.  Of course, for 99% of our usage, 10% RH at 22 degrees is more than dry enough.

Silica is not that efficient for moisture absorption so I agree that it would be a challenge.  One reason I moved to activated alumina.

RE: Are we kidding ourselves about desiccant?

My little datalogging Switchbot devices supposedly use this- https://sensirion.com/media/documents/33FD6951/67EB9032/HT_DS_Datasheet_SHT4x_5.pdf

I think it's probably the best consumer grade sensor available and the datasheet shows the typical and maximum tolerance limits. I wish it were a bit better but I also wish for world peace. Placed in a bag of freshly dried (600+ F kiln) 4A molecular sieve, which should be down at 1% or less, it reads about 6%.

My Creality SpacePi X4 supposedly uses- https://eleparts.co.kr/data/goods_attach/202306/good-pdf-12751003-1.pdf

I've seen it read 11%, but the sensor is located in a different place than the filament and it doesn't agree closely with a Switchbot placed in the middle of a filament spool. The Switchbot is also limited to a maximum of 60 C.

IMO, bottom line is we can get a general idea of the humidity below 10%, but not with any great accuracy/certainty. Still, should be plenty good enough for any 3D printing.

RE: Are we kidding ourselves about desiccant?

Posted by: @conrad-2

IMO, bottom line is we can get a general idea of the humidity below 10%, but not with any great accuracy/certainty. Still, should be plenty good enough for any 3D printing.

Unless it's PA6 or PPA, generally < 15% is good enough in my experience. And anything cut with CF goes in the drier regardless before a print. 

RE: Are we kidding ourselves about desiccant?

One desicant question: Can you microwave Alumina desiccant?  I see conflicting info on the internet.  

RE:

Posted by: @cwbullet

One desicant question: Can you microwave Alumina desiccant?  I see conflicting info on the internet.  

Alumina is used in microwave windows and as substrate inside microwave equipment. So it's safe.  However, I've read (somewhere) that it's not very tolerant of thermal shock, if it goes through a fast temperature swing it could crack. I generally just pop it in the convection oven and allow it to preheat. It's non-toxic. 

RE:

Thanks.  I will keep an eye out for a small convection oven at Goodwill or on sale at Walmart.  

Posted by: @hyiger

 

Posted by: @cwbullet

One desicant question: Can you microwave Alumina desiccant?  I see conflicting info on the internet.  

Alumina is used in microwave windows and as substrate inside microwave equipment. So it's safe.  However, I've read (somewhere) that it's not very tolerant of thermal shock, if it goes through a fast temperature swing it could crack. I generally just pop it in the convection oven and allow it to preheat. It's non-toxic. 

RE: Are we kidding ourselves about desiccant?

Posted by: @cwbullet

Thanks.  I will keep an eye out for a small convection oven at Goodwill or on sale at Walmart.  

I spread them out on a baking sheet and set my oven to air fryer mode at 200° (400F) for 2 hrs. 

RE: Are we kidding ourselves about desiccant?

Microwaves are very good at heating water and a few other things, things with high RF losses, at the frequency they operate at. They also need a load to remain healthy and trying to heat things with little RF loss, like ceramics, is probably bad. No doubt they're designed for some amount of abuse, but I wouldn't make a habit of it. I see lots of advice on heating silica gel in the microwave but I think it's a bad idea. Heating will be uneven and there's a risk of overheating. Heat it in a suitable oven at a controlled temperature. It needs 120 C for 1-2 hours. Alumina needs 250 C, give or take. Toaster oven seems reasonable, but never unattended. IMO, don't trust any desiccant advice found on a 3D printing site. Go to the people who make it and sell it!

The part I'm not confident in is getting the hot dry desiccant converted to cold dry packaged desiccant, without degrading it.

RE: Are we kidding ourselves about desiccant?

Activated alumina is used in industrial equipment so there is lots of information on how to rejuvenate it.  Since mine is in stainless steel containers, I put in a K thermocouple and heat until the inside is over 200 degrees and leave it for at least an hour in a cheap secondhand convection oven.  Then put it into a sealed pot until it cools enough to put into my containers.

I saw an interesting video about a dry cabinet the other day and they kept doing tests with silica gel and couldn't get below 18% RH without stating the temperature.   They did a mod that circulated the air in the chamber through the desiccant and it lowered the humidity even more.  I am thinking of designing a fan to circulate the air in my storage containers.

RE: Are we kidding ourselves about desiccant?

Will have to look at what the sensors are on the different I2C sensors I have purchased.   Both are supposed to be accurate, just haven't had the time to test them.  Since they are I2C, may put one in each storage container and connect them to a monitor.  Still better than the cheap RH% meters I am presently using that don't indicate anything less than 10%.   

RE: Are we kidding ourselves about desiccant?

Just looked at the last sensors I purchased.  AM2302.  Also called the DHT22.  RH is +/- 2% accuracy at 25 degrees.  From the data sheet, is showing a graph with a bigger error than the data sheet.  For filament, this is more than accurate enough.  I can use the AD2302 to calculate dew point and what the RH% is at 22 degrees and display that number for filament monitoring.  I also have a BME280, pressure, temp and humidity for testing.  This may be the general workshop sensor for reference.

Oh, for some more spare time.  🙂

RE: Are we kidding ourselves about desiccant?

Posted by: @conrad-2

The part I'm not confident in is getting the hot dry desiccant converted to cold dry packaged desiccant, without degrading it.

I have an old pressure cooker that I use.  Take hot desiccant out of oven at 200+ degrees.  Put it into the pressure cooker and close the lid until cool.  Limited air space to hold moisture.  This works for me since my activated alumina is in stainless steel containers.   I can fit three containers in the bench top convection oven.  Check goodwill for one.  Old Instant Pot type pot will work if you have the seal.  I feel that an old pot with a heavy lid will also work.  I just happened to have the pressure cooker from an old project.  Stainless steel bowl with a sealing lid is another idea while cooling.

I went with containers when I was still testing silica for ease of use, after spilling so much silica on the floor.  If you don't have containers, take the hot desiccant and put it in an old jar that you saved from pickles or something like that.  That is what a friend of mine does with his activated alumina.

RE: Are we kidding ourselves about desiccant?

Posted by: @robin_13

I learned what CNC Kitchen showed.  Desiccant doesn't dry filament.  You do need a dryer.  

For most filaments like PETG, PCTG, ASA it can keep them from collecting enough moisture to cause problems with printing for maybe a few months. For other types, especially PA's and TPU's it only really keeps the filaments from getting too damp which will prolong the drying time. PA6 in particular is unprintable even after a few days at < 10% RH. For PA's and PC-CF regardless of how it's stored, it goes into the dryer before a print and PAs I dry while printing. 

RE: Are we kidding ourselves about desiccant?

Thank you for the suggestion.  I bought a convection oven to dry it, and that works well.  Although desiccant typically will not dry filament, it sure does limit hydration.  I would nto call it worthless.  

Posted by: @hyiger

 

Posted by: @cwbullet

Thanks.  I will keep an eye out for a small convection oven at Goodwill or on sale at Walmart.  

I spread them out on a baking sheet and set my oven to air fryer mode at 200° (400F) for 2 hrs.