Nice. Here’s two more graphs I’ve posted here before too. They are more appropriate to this discussion.
All your graph shows is equilibrium water capacity at a range of temperatures. It is basically how much water the desiccant will/can absorb sitting in a hot box with a container of liquid water. Pretty unrelated to conditions drying filament.
your graph shows silica’s ability to absorb at a percentage of relative humidity for a given temp. What this graph is showing is how much water can be absorbed as humidity decreases.
It should be obvious that less less humidity in the air, the less effective the desiccant is at absorbing it.
My graph does not indicate the desiccant is in a box of water lol, it shows the total absorption ability for temperature.
As temp goes up, the ability to absorb decreases, but at 140F, it is still quite capable of absorbing moisture from the air, until it is saturated for that temperature.
My graph shows saturation level per 100grams of dessicant
This describes the ability to absorb at 150F, and regeneration at 300F
I’m done arguing with you. Look up what saturation level is and how you would measure that. Your graph is how much water the different desiccants hold as a function of temperature. The only way to measure that is by not limiting how much water there is to absorb. Either that or they specify the humidity level used to derive those graphs which wasn’t considered when lifting that graph. lol
Edit - the humidity level does look like it was specified in clipped off text in the upper left corner of your graph. “P(H20) = 0.407 in. Hg” IF I read the remaining text correctly. So not at 100%. It was at some specific humidity level. Regardless, it is only a measure of how much water those desiccants hold at whatever humidity as a function of temperature.
yeah, exactly. At 140F 100grams will absorb 5-7 grams of water from the air. The more water you can absorb from the air, the lower the relative humidity is
Relative humidity is just a function of how much moisture air can hold based on temp.
If I have a box at 77f with 50% humidity and raise temp to 140F, relative humidity drops to 7.9%
This allows the filament to release it’s moisture.
As the box cools, the desiccant absorbs moisture faster, although it begins absorbing at 140 because the moisture from the filament increases relative humidity.
Here is some empirical evidence from my dry box.
Starting temp and humidity = 75F and 50% on hygrometer
at 140F with three fresh spools PETG =75%
after 24hours = 16%
after 24hours with heat off = 10%
Here are some equations to calculate relative humidity based on temp change:
you can use the magnus-tetens equation to calculate saturation pressure vapor and then relative humidity change for a given temp assuming an airtight container to verify my calculations for relative humidity
Saturation pressure = 6.1094 exp((17.7*T)/(T+233.04)
do this for both temps
Now you can calculate relative humidity, which is just the ratio of actual vapor pressure to saturation;
RH1 =E1/(Es(T1), or rearranged E1=RH1xEs(T1)
then calculate RH2 using the same equation since you now know E1, except use T2 or 140F in this case.
No. Maybe you are just saying things imprecisely but that statement is incorrect. Desiccant doesn’t just start absorbing moisture at some arbitrary temperature. Maybe you mean that’s when it really gets going?
These are processes pushed away from equilibrium by conditions. Put a fresh pack of desiccant in a dryer with a spool of filament at room temperature and watch what happens. The RH falls because the desiccant is scavenging moisture to its ability. That water is from the air, stuck to the surfaces of everything in the dryer, and from the filament. If you did nothing but let it sit and do that for however long it takes to reach equilibrium, the dryer would settle at some non-zero humidity and desiccant and filament will both move to some non-zero moisture content as water equilibrates with all sources and sinks in the dryer.
What moisture content and humidity is set by how much each player wants the water. It’s actually very simple. People say desiccant cannot dry filament on its own and that is incorrect. You can dry it bone dry if you keep the desiccant itself dryer than that equilibrium point and don’t mind waiting a very long time. And before anyone else says that’s wrong, no, it’s absolutely correct. It’s an equilibrium thing. It’s just slower than most consider practical. And evaporation and condensation are happening at the same time on the same surface right next to each other. What we see is the bulk process. The net gain or loss of water.
Heating just supplies extra energy to everything in the dryer including the water. That energy (heat) is vibration, translation, and rotation. Water molecules get more and more “wiggly” as they get hotter. Some have more energy than others and the distribution of energies is described by a Boltzmann distribution. The higher the temperature, the more water molecules will be wiggly enough to break away from the surface of whatever and bounce away in the vapor phase - evaporation/sublimation.
The Boltzmann distribution is why desiccants don’t just turn on and turn off.
I’m really done. I have other things to do and it’s obvious this is just wasting everyone’s time. If this doesn’t make sense to you, it gives you enough to find out where your misconceptions are coming from.
i didn’t mean to say it STARTs absorbing at 140, just that it will absorb slowly there. the desiccant will not absorb water from the filament without added heat, because as you point out, there is simply not enough random kinetic energy at standard temp and pressure to allow the water to break the bond it formed in the filament. If it could, we wouldn’t have wet filament from the bag.
desiccant works because it is is more hydroscopic than the filament at both STP and 140F. This is also why the desiccant must be heated to a much higher temp to be regenerated.
Once the water molecules have enough energy to move from the filament, it can be absorbed by the desiccant at a faster rate than the filament.
You are not being precise in what you say when the topic demands it.
What you said was
Technically you didn’t say it starts at 140. You said it begins at 140 but both mean the same thing to the best of my understanding.
No. Completely backwards from what I said. What I said specifically is that there is enough energy for water to break free from the surface, just that there aren’t many molecules with enough energy to do it. That was the whole discussion of the Boltzmann distribution and how filament can dry at room temperature just very, very slowly.
The part about wet filament from the bag is a completely different issue / set of issues.
I’ve got things to do today and this is just as productive as banging my head with a brick. Seriously, either you are misusing the terminology or don’t understand the processes. Either way, this is my last post on this and I’m muting this thread.
I calibrated pressure advance and flow rate in orca slicer. General surface quality is great, but those holes are there. Now, I am still drying that exact spool for 8h again and it lost around .6g. So there is moisture in there, I guess. Its just weird to me, people dry their filament for 4h and are fine, i have to dry it 48h?
I love my A1 Mini but that moisture problem is super frustrating.
If you have calibrated the filament correctly, the result is correct. So why is the result obviously not correct? Orca Slicer is not a panacea. Just something to consider. You can learn to understand the interrelationships in 3D printing. Every calibration tool is just a tool to make certain things easier. But the question remains: why is the result apparently not correct despite calibration?
First, the filament must be dried. Whether and how long you need to dry a filament depends on how it is processed and what material it is (whether it absorbs more or less moisture in a given time). With brass nozzles, low temperatures and slow print speeds, I never had any problems with moisture in the filament. My filament was always lying around open and was therefore certainly damp. And yet I was able to print with printers like “Ender” “without any problems”. I cannot process PAHT-CF on an X1C cleanly until I have dried a supposedly dry spool of filament for about 24 hours. With PAHT-CF, I found this out by test printing every few hours of drying in the dryer, so now that the filament has finally dried, it can be calibrated somehow. If the printing temperature is correct, the print will also be correct.
I have recently set up temperature towers where I can see for a filament at different printing temperatures in conjunction with different speeds where the printing result is best and the colour fidelity is greatest. Perhaps something like this would be a measure for you to get to the bottom of the matter.
What I have seen in the pictures, my assessment is already given.
Best regards!
Thanks for your answer. I will try to calibrate it even further later today.
But what I noticed on my prints is, that all the holes always appear in small groups and not all over the print. Could that be an indicator that only sections are wet and some dry, like if I have to twist the spool in the drier ever 2 hours or so. What do you guys think?
Rotate your model an arbitrary amount on the build plate (not the usual 15,30,45,90) and then reprint. I had this issue on a few models, one even being a flat faced box, with few triangles. You may be running in to a slicer issue, which is why it is only happening on one side. I’ve also had some quality differences on a few sides due to cooling, or breezes from the AC. If your unit is close to an AC vent, one side may be cooling differently than the other. An easy check is to grab a cardboard box, throw it over the whole assembly, print and see if it helps. Also what type of seaming are you using? Play with different seam positions/painting and see if this helps I really, really doubt you’re running in to moisture issues. Generally, humidity won’t lead to specific repeatable issues like pin holing in the same spot. Stringing, and surface quality can be affected by humidity, but if you’re having repeatable holes on only one side, try my thoughts above. Good luck
