RE: Filament humidity range
just FYI, most of you already have a functional dryer in your kitchen. Your oven light will warm the interior to 85 - 90°F which should help dry out anything you put in there. Might take some time but someone with a hygrometer can do some testing.
RE: Filament humidity range
Actually, all of us in on this site have one; your heated print bed.
There are plenty of articles about using the bed to warm and dry your filament. Plus you are usually heating the bed anyway. I won't use my oven for non-food stuff. That is my personal feeling and action, and I'm not telling others to follow suite, do what you want with what you have. I'm sure we breathe in more plastic just walking around anyway (but makes you wonder if we are adding to it - we are).
RE: Filament humidity range
One comment. RH% is dependent on temperature. If you have 30% at 25 degrees, at 20 degrees it will be higher at over 40%. There are tools on the net to compare between them.
Drying with desiccant is a slow process and not the best but for storage it helps if you don't have a dryer.
I have about 1.5kg in both bins with 6 or 7 rolls of filament. I have 21% at 19 degrees right now. Drying the silica gel is the biggest headache but it helps to heat the workshop in the winter time.
RE:
Good catch. I always overlook dew point, wet-bulb temp, and the like.
I don't dry with silica gel. It is, like you say, much too slow.
I use heat, moving/forced air, and activated alumina. Much quicker. And I tend to dry then store in a vacuum bag with a jar of desiccant in there. I'm an old cable dawg, so anything like a cable air dryer works for me.
I only need to get sub 30%.
RE: Filament humidity range
Just read a paper on the differences between Activated Alumina and Silica Gel. I was about to order more Silica but that is now going to be changed. They are about the same price from what I see.
From the paper, Activated Alumina was 100% effective and Silica Gel is 77.9% Activated Alumina took the RH% down to 0.0 while Silica Gel stuck at 9.7% in the closed test.
RE: Filament humidity range
I don't have the ability to test that, precisely, but my anecdotal evidence (professionally and as a hobbyist) has seen a vast difference.
I do, however, use silica to store with the filament, as it is cheap (meaning I have a ton that has accumulated over the years) and I don't need it super-dry.
RE: Filament humidity range
Just a note. I ordered some Activated Alumina from AliExpress. C$ 19.95 /kg. Will have to test it.
A test I have tried with silica gel. 2 hrs in an oven then sealed in a jar with a temperature/RH sensor and it won't go below 25% at 19° More testing.
RE:
I know the thread is old, but I am rather new to 3D printing and came across this thread, because I was wondering what I am doing wrong.
No matter what I do, the relative humidity in my storage boxes is between 15-20%. I have never been able to get it down to 10% or even less like some people seem be able to achieve. So I am wondering what I am doing wrong.
For each of my filament spooles I bought an air-tight cereal box which is nearly the same size asthe spool itself. (The volume of the cereal box is approximately 4l.) I bought a couple of re-usable tea bags. Those bags are nylon meshws with a zippers. I use them to fill in color-changing silicia gel. I bought a couple of digital temperature/humidity meters to throw them into the cereal boxes. Their rated measurement range is from 5%–95% with 2% tolerance. I assume they work, because if I put them next to each other they show identical values (within the rated error range). My ambient environment is 21-23°C with 40-50% relative humidity.
First I dry the spool in a dedicated filament dryer (depending on the material between 50°C and 70°C for 4-8 hours). Then I put them into the cereal boxes with 100g of silica gel and the digital hygrometer. The hygrometers settle down at 15-20% humidity and remain there for weeks.
I read that people seem easily to get 10% relative humidity. I even see posts where people write they swap the silica gel when the humidity goes above 10%. I have never been able to get below 10%. So what am I doing wrong?
RE: Filament humidity range
Ordinary hygrometers aren't much good below 15-20%. You need expensive instruments to measure accurately very low levels of humidity.
I don't keep hygrometers inside the filament bags, just silica gel balls. I put them inside 3D printed containers with a threaded lid, so it's easy to check the color and, if needed, remove the balls and put them on a heat-proof glass tray inside the microwave to dry them. It takes only a couple of minutes with the microwave at max. power setting.
When new and totally dry those balls are orange/amber. As soon as they start turning into greenish yellow, probably the level the humidity inside that bag has risen too much already. Don’t wait until they turn into deep blue, it’s time to dry the balls AND the filament. That applies for the more hygroscopic filaments (PA. PC. TPU) PLA is more forgiving in this matter, even PETG and ASA aren't that bad. Instead, some PA filaments are so water-hungry that, if you want to avoid stringing, blobs and other artifacts. you must dry them every time you want to print, even if you dried that spool only a couple of days ago.
RE: Filament humidity range
I have learned so much about water vapour, humidity and temperature issues since I got into 3D printing. This is a topic that causes so many issues for people using 3D printers, as one of the first comments in many cases, is to dry your filament.
I agree with Artur5 about most hygrometers. I have some that were cheap and when compared to my "good ones" and a Arduino based sensor, they didn't read close. So, are relegated to just thermometers. My "good ones" are cheap but I have compared them over a range of temperatures and humidity and I am happy with them for filament and have many around my house. They do read down to 10% and then show LL. My "good ones" are about $6 each at AliExpress.
I agree with the comment about re-drying colour changing silica, as soon as you start to see a colour change. Most I have looked into are designed to register when they have absorbed enough water to represent about 20% RH. But RH is a very bad reference, I have found out in my research. Dew Point is a better reference since it doesn't depend on air temperature. When talking about RH, you have to reference the temperature that you are at. I made this mistake in the beginning. Hot days, under 30% RH but when it cooled off, the RH shot up in the sealed containers with desiccant. This is why it is easier to dry warm filament compared to cool filament. Even with desiccant. In my experience, TPU filament will absorb water from the air at 35 degrees and 30% RH but print good at 30% RH at 22 degrees. Higher temperature has a higher amount of water vapour at 30% RH.
From my experience, under 20% RH at 22 degrees, even with TPU, I don't have issues. TPU is the first material that I found I need to use a dry box with. It has been a strange, humid summer this year. Reading the bin RH is dependent on when the bin was last opened and when new filament has been added. I just started the procedure to put the more hygroscopic filaments into their own bin and keep the RH lower.
Colour indicating silica can be damaged if it is over heated and I did make that mistake early in my experience, as the toaster oven I used didn't regulate the heat well and over heated it. Activated alumina drying requires the toaster over to be at the maximum temperature.
My wife won't allow me to put anything "shop" related into any kitchen appliance due to chemical outgassing. Good for her. If I do, I replace it, bad for me. 🙂
One thing to be careful about. Some plastics degrade if they are too dry and can become brittle and permanently damaged. There is chemistry behind this from what I have read.
I am happy to keep my filament below 20% at 20 degrees. I do calculations for when to dry my desiccant based on the Dew Point. I have only started printing with TPU and have not tried Nylon yet. Until this week, I have never had to dry any filament and in hindsight, I know that the filament that forced me to by a dehydrator wasn't having water issues but a different profile than any ASA filament I have ever printed. Of course, until this year, any RH above 40% was on a very rainy day. I would purchase filament, put it into my storage box for a couple of weeks before printing. Even CNC Kitchen has shown that this will dry your filament at a slow pace.
Sorry for the rant.
RE: Filament humidity range
I agree with the comment about re-drying colour changing silica, as soon as you start to see a colour change. Most I have looked into are designed to register when they have absorbed enough water to represent about 20% RH. But RH is a very bad reference. You have to reference the temperature that you are at.
And which temperature would this be? My understanding is that for the color changing the absolute amount of water which is absorbed by the silica is relevant. The color indicates how many water molecules are integrated into the crystal lattice. (I hope I use the correct, technical English terms.)
Dew Point is a better reference since it doesn't depend on air temperature.
[...]
I do calculations for when to dry my desiccant based on the Dew Point.
And those calculations look exactly how? Sorry, but you are talking so much about RH, Dew point, etc. and how RH depends on the temperature. However, I believe everybody in this forum knows that. It is called relative humidity for a reason at last. But you never say anything specific or go into details.
Nonetheless, the discussion let me think about another point. Most filament dryers are not real dryers but just heaters and one need to put silica gel into them to do the actual drying. When I take a spool out of the "dryer" and into their final stoeage box, I wonder whether one should move them while they are still hot and then let them cool off inside the storage box or whether one should let them cool off first and then put them into the storage box. The former reduces the risk that they gather moisture from the environment again, but the latter gives them the chance to steam off some more water into the environment while cooling down. I am unsure what is more effective.
RE: Filament humidity range
I’m referring again to the document released by Fillamentum on this matter :
After drying the filament, the spools must be removed at once from the drier and put inside a vacuum container or sealed bag with desiccant. If you leave these spools inside the drier after it has been switched off, waiting for the temperature to go down, the moisture might be reabsorbed back into the filament in a few minutes,
I don't quite agree with you about the absolute necessity of putting silica gel in the drier. It helps, but basically what removes moisture from the filament is the heat. Of course the drier should have vent holes for allowing the warm water vapor to escape outside.
RE: Filament humidity range
Hi Matthias Nagel and Artur5
My colour changing desiccant started to change colour at about 20% to 30% RH at 22 degrees, where I keep my workshop most of the time. I bought the silica and after some time, purchased hygrometers to put into the storage bins. I found that I couldn't count on the colour change to be an indicator with the silica that I had. My searches have recommended hygrometers or reference RH cards instead of the colour changing aspect. I spent about a year searching for the ideal RH to store filament at but never found an answer. Of course, most what I saw would give an RH but no temperature.
You are correct about my comments on RH, dew point and temp. What I disagree with is many talk about RH without talking about temperature. This is very important since 20% RH at 15 degrees will be lower at 20 degrees. I am still working out how to explain the Dew Point, RH and temperature combination and have slowly learned more about it over the year since I started to look at it. I have a spreadsheet that will calculate the RH at different temperatures based on the dew point. I am refining that to create a simple graph. that I will sharie that shows, if the RH at X degrees is this, at Y degrees it will be this for the same dew point. I have been testing the process and my results are very positive. Example, yesterday, outside dew point was a few degrees lower than in my workshop. Opened the overhead door, turned on the big fan, and the RH in the workshop dropped by 10% with no temperature change within a few minutes.
Silica in the dryer might help, but what works is the higher temperature can hold more moisture, so the vented air flow helps to remove moisture. If the air temperature is high enough, the drier will remove moisture from the desiccant at the same time. Moisture is sucked out of the filament due to the moving air and the heat due to the difference. There is a physics equation to calculate this process.
Again, you are correct about moving spools to storage (different options) or it will absorb moisture from the air. Same when you dry desiccant. This is why the drier must vent the moist air out of it. I use activated alumina and the reactivating temperature is over 200 degrees. I now have an old pressure cooker that I put it into and seal the lid. I am working on drawing a vacuum on the vessel while the desiccant cools. I use sealed storage bins with lots of desiccant in each bin. Tried vacuum bags but they were more of an issue than the bins. Only issue with the bins is their mass. 10 - 20 kg of filament make for a heavy bin. 🙂
RE:
My totes where I keep open filament are kept below 10% RH at 23C using basic silica gel desiccant. As for dryers, part of why they work is the plastic will release more moisture as it heats up (or depending on schools of thought can't hold as much moisture when warm). Its why a dry vacuum alone won't dry filament, you need the heat, too. Think vapor pressure.
RE: Filament humidity range
After drying the filament, the spools must be removed at once from the drier and put inside a [...] sealed bag with desiccant. If you leave these spools inside the drier after it has been switched off, waiting for the temperature to go down, the moisture might be reabsorbed back into the filament in a few minutes.
Thans for the clarification. I did it right intuitively and that is in line with the next aspect.
[Silica gel in the drier] helps, but [...] what removes moisture from the filament is the heat. Of course the drier should have vent holes for allowing the warm water vapor to escape outside.
Unfortunately, most "driers" seem to miss those vent holes. While the dryers are not actually air-tight, they still mostly circulate the same air. So the dryers are actually only "heaters". They heat up the air within the dryer which decreases the relative humidity so that the hot air can absorb more water. But after that, the hot, water-pervaded air is just swirled around. I performed a test with my dryer, put in a small shot glass with 10ml of water, let it run for 4h at 60°C and I could actually see how the water condensed on the cooler surface of the dryer's lid. I believe 10ml or 10g of water is an amount one could reasonably expect to be inside a spool as well. That's why I decided to put in some silica into the dryer as well. That also probably explains why Filamentum recommends to take the spool out of the dryer immediately. Because, if one waits until everything has cooled down again, the hot air will cool down as well and the water will condense.
I spent about a year searching for the ideal RH to store filament at but never found an answer.
I guess the answer is quite easy: the lower the better. As far as I understand it, filament won't be harmed due to RH being too low. The only problem is that at some point the effort is not worth the result.
Of course, most what I saw would give an RH but no temperature. [...] many talk about RH without talking about temperature. This is very important since 20% RH at 15 degress will be lower at 20 degrees. [...] I am still working out how to explain the Dew Point, RH and temperature combination and have slowly learned more about it over the year since I started to look at it.
I don't know why you bother to write so elaborate posts about well-known physical principles. It is a well known fact how relative humidity, temperature and absolute amount of water in the air relate to each other. I don't know what you mean when you say you are still working out how to explain the Dew point. There is nothing to explain about the Dew point. If one assumes normal environment conditions and if you have two of the three quantities one can calculate the third. The formulas are well-known and there are even website which provide online calculators if you don't want to do the math by hand. But you give the impression as if you were unraveling one of the huge mysteries of mankind.
I have a spreadsheet that will calculate the RH at different temperatures based on the dew point. I am refining that to create a simple graph. that I will share that shows, if the RH at X degrees is this, at Y degrees it will be this for the same dew point.
Again, I don't know what you dry to achieve there. You don't need to create such a graph on your own through experiments. You can just google it. Or use a formula, type it into your spreadsheet editor and create a graph if you want one. The mutual dependency between temperature, RH and Dew point is no rocket science, but well understood by physicist and engineer since centuries.
I believe the simple reason why most people do not explicitly state the ambient temperature when they talk about the RH is, because they assume normal room temperatures for storage, i.e. something between 19°C and 23°C.
I also disagree that the Dew point is more important than RH, if only a single value is given. Of course, it is always better to fully state all environmental conditions. However, if only a single value is given, RH is actually more relevant. For example, if someone says the Dew point is 18°C, you know nothing. If the temperature is 18°C as well, then RH is 100%. Obviously, you won't be able to dry anything, because the air is already fully saturated. However, the same air heated up to 60°C only has 12% RH and is able to dry filament.
Now, let's consider the inverse and someone states to use 12% RH. No matter, wether the temperature is 60°C or 18°C, in both cases the air can still absorb water and that is important. The only difference is that it will take longer at 18°C than at 60°C. Of course, you can still do the math: 12% RH @ 60°C implies 18°C Dew point (as before), and 12% RH @ 18°C implies -13°C Dew Point. But I don't see how it might help to know that.
Some more math for @robin_13:
- 12%RH @ 60°C means the air contains 16g/m³ water. 100%RH @ 60°C means 131g/m³ water. So theoretically, the air could absorb (131-16)g/m³ = 115g/m³ water before it becomes fully saturated.
- 12%RH @ 18°C means the air contains 1.8g/m³ water. 100%RH @ 18°C means 15.35g/m³ water. So theoretically, the air could absorb (15.6-1.8)g/m³ = 13.8g/m³ water before it becomes fully saturated.
This is also the reason why drying at the same RH but a lower temperature takes more time and the RH increases more quickly. The absolute amount of water which the air is able to absorb is lower. Still I don't see why you believe Dew point is so much more important than RH.
RE: Filament humidity range
I boiled it down to these key bullet points for me to understand it simply;
- Air can hold more water vapor at higher temperatures.
- Relative humidity is the percentage of water vapor the air is currently holding compared to its maximum capacity at that temperature.
- Dew point is the temperature at which the air becomes saturated (100% relative humidity) and water vapor begins to condense into liquid.
- A simple way to think about it: As air cools, its capacity to hold water vapor decreases. When it cools to the dew point temperature, the air can no longer hold all the water vapor, and dew forms.
RE: Filament humidity range
I my ramble since over the years, I have read many discussions and read web pages about RH and most mention that higher temperatures can hold more water and that RH% is dependent on temperature. I have also read where people are talking about using their printer in a cold workshop and concerned about the RH. Being able to compare how it affects your filament is important.
I built my own spreadsheet as a quick reference to put on my wall that doesn't include all the other info for RH. It also helps me to understand the relationships. As for searching, I am finding that AI is cluttering up searches and filling with what it thinks I want, not what I want. With my spreadsheet, I can enter what I measure for a dew point and get how it relates to what is in my workshop.
Over the years I have done searching for the ideal RH%. One site has numbers that I don't agree with but it is a reference point for those that are interested. 0-20% for Nylon, ASA, PETG, PVA, TPU. 20% to 40% for PLA, ABS, PE, PS and CPE, and 40% to 60% for PP, PC, PVC, PTFE, and HIPS. They don't mention temperature.
Here is the current draft of my RH chart, if people are interested. I adjusted the dew point number to give me the desired RH% number at 22 degrees.
RE: Filament humidity range
[Silica gel in the drier] helps, but [...] what removes moisture from the filament is the heat. Of course the drier should have vent holes for allowing the warm water vapor to escape outside.
Unfortunately, most "driers" seem to miss those vent holes. While the dryers are not actually air-tight, they still mostly circulate the same air. So the dryers are actually only "heaters". They heat up the air within the dryer which decreases the relative humidity so that the hot air can absorb more water. But after that, the hot, water-pervaded air is just swirled around. I performed a test with my dryer, put in a small shot glass with 10ml of water, let it run for 4h at 60°C and I could actually see how the water condensed on the cooler surface of the dryer's lid. I believe 10ml or 10g of water is an amount one could reasonably expect to be inside a spool as well. That's why I decided to put in some silica into the dryer as well. That also probably explains why Filamentum recommends to take the spool out of the dryer immediately. Because, if one waits until everything has cooled down again, the hot air will cool down as well and the water will condense.
I wanted to address this specifically, as early on, I got into this issue when looking at storage and filament feed boxes. There was a description on how to make dry boxes and to lower the RH, they put a reptile heater into the sealed dry box. I thought this was smart and started to build a large dry box based on this for use with my printer with MMU and purchased a large reptile heater for the box. As I learned more, this is a useless design concept. Now I am looking at a dehumidifier concept for this box to be tested in the future.
Your test with your dryer, is a good point that needed to be shared. I feel that there many that have purchased dryers that can be used to feed the filament as well, dry their filament as per the dryer instructions, no desiccant, leave their filament in the box and wonder why, a few days later they are having problems, come to the forums looking for help and swear that their filament is dry. Thanks for sharing this.