Fair enough. I won’t argue your test. I’ve managed engineering test facilities, and am aware of just how hard it is to get accurate results by controlling every conceivable variable. The RH calculations are solid, and I stand by my statement based solely upon that factor.
No offense intended, and I’m certainly not saying you’re wrong. “Diminishing returns” does not mean “no improvement”. It’s a question of bang for the buck, is all.
To address your results, maybe it’s important to get the heated air much drier than 5% to fully extract moisture from the filament? I’ve never heard of that, but perhaps that’s true. If a drier is really well sealed, airtight, the liberated moisture couldn’t exit the machine? Some amount of air circulation seems necessary. Or, some quantity of silica gel in the drier to absorb the liberated moisture could be important in the absence of air exchange.
I have a simple Creality filament drier, and have had much success drying filament in it. It is has a heater with circulating air flow, and is definitely not air tight. So, there’s opportunity for moisture to escape with heated air, and it definitely does dry filament.
In any case, I’m glad you found a method that gives you good results.
I don’t question those at all. The RH calculations by temperature will be accurate.
The test I did was weigh a spool of filament, put it in my S2, started the dry, and turned on an ambient air purge. I recorded the change in weight and the change in indicated RH% in the filament dryer as a function of time. I waited for the weight and RH% to essentially stop changing which I took to mean the spool was as dry as it was going to get. At that point I put the drying column in the line where what was being purged was essentially dry air. Humidity started dropping again and so did the weight. Data is in the other thread here already referenced.
You tell me. The step difference was significant. The only difference was the air being dried or not. If anything the purge was reduced slightly by the additional backpressure on the pump.
As for diminishing returns, that’s a value judgement. My ambient humidity generally runs 40-50%. I started having moisture issues with PLA so I bought a Sunlu S2. It wasn’t doing the job so I looked into why. Drying the air and purging the S2 has made a huge difference in the prints. I just changed the desiccant packs in my AMS units after changing them last August now that my filament wasn’t pulling the indication below 2. Until now, replacing a spool of filament would pull it back to being 1. After I dry filament it goes into sealed poly containers with hygrometers. Every last one is pegged at 10% which is as low as those read. The cost if I threw the silica gel away after it absorbed too much water to continue instead of regenerating it is about 50 cents/spool but I haven’t pushed that as far as it can go so it could be lower and maybe much lower. I regenerate it.
Anyone who wants to test it for themselves can do it easily. You may not have the same water issues I was. That’s something many forget - just because they may not have water issues doesn’t mean that nobody else does.
But I don’t have water issues now. Except for one spool that had to be put in an AMS before it was ready and carried excess moisture because of that, I don’t have water issues now. Not with PLA, PETG HF, ASA, and even the silk PLA that got discontinued because people had a hard time getting good prints. That stuff prints beautiful for me. I’ve posted photos in other threads of before and after drying prints with PETG HF. Even straight from the shipping bag within a day or two of receiving the shipping box PETG HF was showing moisture. After drying the same print was perfect.
It may be diminishing returns for you but it’s the difference between high quality prints or not for me.
You may not need dry air to dry your filament but I keep asking people to do this test and nobody takes me up on it. Throw one of your dried spools in a sealed impermeable container with a hygrometer than can reach at least 10% RH on the low end and read the humidity after 10-12 hours. No desiccant. Just a full spool of filament and a hygrometer.
I have done for multiple spools of PETG-HF. Each time I got a RH reading of between 40-50% at ~70F (~21C). I don’t have any trouble with PLA in my environment. Right now, with forced-air natural gas heating running, I am running under 20% RH in my house (even with a whole house humidifier!). Even late last summer when I got my first printer, I was typically in the 30-40% RH range, so I clearly don’t have the same level of issue that @MZip has. But I really like MZip’s scientific approach to the problem and believe his results.
Also, I think the entire absolute humidity (AH) vs relative humidity (RH) question is a red herring. If you look at the equation for calculating AH, the only variables (for a standard air mixture and pressure) are RH and temperature. So if looking at RH over time, as long as the temperature is relatively constant, RH can be used as an equivalent to AH. It just isn’t fair to compare RH of 20C air to the RH at 60C, but if you are drying to a particular RH level at 60C, that is reaching a given AH level each time.
Hi all,
Could I step in here and ask a similar Q. I got the X1C over Christmas. LOVE IT!!! I just bought 10 refill rolls of the Bambu new Petg-HF Filament. I was just starting a print to print a spool for this filament. ;X1C gave me the error message. I can’t print this filament flat on my build sheet. I have the new textured gold sheet. Love it so far. What build sheet do I need to buy. Thank You. P.S. I read most of the comments here. It looks like I will not be buying any more of this filament. I Have been using Matterhacker MH Build Series Petg running in sport mode and prints great. So I will probably use something like that from know on. Until things sort themselves out. I need the higher temp resistance in the sun than PLA provides and I don’t like printing ABS with all the extra fumes, etc.
Any of Bambu build plates that are labeled for use with petg should work, though you may want to consider using a glue as a release agent to prevent it sticking too well.
As for non-Bambu build plates, a lot of people get good results with garolite/g10 as a build plate for PETG. It sticks well enough if you get it hot enough, and auto releases when it cools down.
For what it’s worth, I also dry my PETG HF at 70. This makes one side of the spool about 74-76 deg C measured with a cheap “laser” temp gun (where the hot air comes out) and about 65 on the opposite side (so I need to rotate the spool a few times). No issues. My only issue is it’s hard to get the inside of the spool dry and a spool needs like 5 trips to the dryer at least (or print from a dryer - but then I can’t do multi colour…)
Yeah they probably use degraded low MW PETG, but I think there is a fine filler that increases viscosity when the PETG is melted, gives the matte texture, and doesn’t need much energy itself to “melt” because it’s not going through any phase changes. And that filler itself is probably very hydroscopic.
Yeah this is PET! Super cheap but super expensive once in a filament form…