Thanks, that is a good implementation of adding dehumidified air to the dryer process, which is what injection molders use. One caveat though, color changing desiccant loses it’s effectiveness long before the color changes. Ideally it would be great to bring that airstream up to the drying temperature so that the air movement isn’t cooling the dryer container.
ah very nice… probably overkill for PETG, but that could be really nice for Nylons etc. Then again, this BBL PETG-HF does seem really sensitive to being dry and the stated 65Deg C for 8 hours in a proper blast oven is actually pretty onerous. Think my little FixDry is fine for maintaining it during printing, but actually drying it out is another thing altogether. Thanks for the info., will definitely explore your hack if I end-up using this HF material.
It’s not really regretfully, if it’s removing moisture from the spool(doubt that given the hardness of that plastic and the low temps) and cardboard spool center(probably), it all benefits the filament moisture content. I dry until I show no more weight loss. Just so happens that that’s generally 12 hours increments for me due to daytime job and night time sleep.
That makes sense to me. PET is semi-crystalline, whereas my understanding is PETG is almost entirely amorphous - ie is degraded for 3D filament use. Then stirring the secret sauce a little to make it high speed / High Flow is then knocking down all the properties even more. Damn, I just bought 4 rolls of the stuff as prints really nice, but I am finding the properties pretty pants (durability and inter-layer adhesion especially) - I am adding an extra wall to see if I can recover some strength, but at the moment my tricky ASA prints are just so much more durable. To be fair, its mostly all in the BBL TDS. Thanks for injecting some realism!! (hey, see what I did there!!?? 
)
Dried mine yesterday 12 hours on print bed 88C bed temp and 80c box temp… there isn’t any filament that should melt at 65. Something is up with your dryer.
The glass transition temperature is the point at which filament will warp and deform. It takes much higher temperatures to actually melt it to a liquid-type state for printing, but warping and deforming happen at lower temps. If you print something out of the PETG-HF and then put it onto that bed in that box at that temperature, it will warp.
Bambu themselves says as much in the TDS. They say 66 is the glass transition temperature.
You are talking BBL PETG-HF? I doubt it, as the TDS is pretty clear… if you bake it at 80Deg C is gonna turn into a bowl of mushy soup.
ce12d65176a94f1086e6aefa238e62e2.pdf
I worried about that too. When I first was looking into it, I did calculations based on the whole silica gel reservoir having a uniform distribution and what exit humidity would be as it picked up more and more water. Turns out it’s not a concern.
The reason why is the moist ambient air starts dropping its water as soon as it hits beads. The air has progressively less water the further it moves along the column and there’s less water to use up the silica gel.
The process of pulling the water out of the air is pretty fast and exothermic. Those who have poured water on dry silica gel beads have them crack and pop because they grab the water so fast. I got an IR imager and was blown away that I could see the heat being generated where the air was first entering my test reservoir.
As the column gets used, a gradient sets up with indicator changing hard right at the air entrance with less and less color change along the column. You only see breakthrough of water when the beads at the exit start losing their ability to grab and hold water. But a whole lot of water gets dropped and held by the beads at the ambient air ainlet. Here’s an example…
At the time I switched from the column on the right to the one on the left in a revised base as I refined the design, I had dried 26 spools and run some other tests. Drying times were starting to get a little longer because the humidity was probably starting to rise as the gradient not going full dry at the top like the new reservoir. But they weren’t much longer. Exit hygrometer was still pegged at 10%. I was hoping to see the exit humidity start coming up off pegged, but needed to switch over to do more testing. But that’s why I estimate 30 or so spools worth of drying on a fresh charge. That’s also going to vary based on local ambient humidity. The higher the humidity, the faster you’ll use up the silica gel. If I just threw the silica gel away and bought fresh 2 lbs at a time, it would cost about $0.50 per spool to just replace it. I regenerate.
Last point is the aquarium pump flow is fairly low. I don’t notice much if any effect on the heater duty cycle. It’s probably better than using those door props but I have no numbers to back that up. Just a guess.
Super impressive… very nice little project to improve any workflow using a dryer. Is the column completely airtight? Looking at your Printables instructions very quickly think it is, so the silica beads could potentially sit for a few months. It’s not likely that I’d ever be drying 30 spools consecutively tbh, more like 2 or 3 a week maybe, so far easier to load once and change when indicated, even if 3 or 4 months later??
Dang. Of course the answer to that isn’t completely straightforward.
The column is air tight. My first prints using non-dried filament were more porous than later prints using dried filament. I still have painted them with thick cyanoacrylate to seal them though. You’d be surprised how porous 3d prints can be though. I increased walls/ceilings/floors layers and went with honeycomb infill (gyroid is very open) to help with leaks as well. My last print was very tight but not perfect. Leaking a little ok but easy enough to make it totally tight.
About those beads…That’s another area that’s luckily not terrible in practice. Because the water sticks down pretty hard to the silica gel bead surface area, it tends to stay where it sticks - mostly. As more water lays down, additional water is held less tight. As more water collects at the reservoir entrance it gets more mobile. As it uses its new-found mobility to move down the column it gets to drier and drier beads until it sticks down again. It’s just in its new home it’s held tighter and is less likely to get up and move. This is the process that sets up that gradient you saw in the photo.
That process continues whether the pump is running or not. It’s just with the pump off there is no bulk flow to move the water through the column. It’s all random walk. But the process continues. All those beads with a range of indicator colors in the nice gradient pattern got dumped back into the desiccant container to be regenerated later. All these bright orange beads next to dark green. It was definitely easy to see who held water and who didn’t.
I looked back in after a couple of weeks and they were all an intermediate darkish green. The water had equilibrated to an average value over all the beads.
The path was short. It was just bead to adjacent bead for the most part with no gradient to hold moisture at bay. It shows what happens over time, though. If the column just sits, how bad that sitting is depends on how much water it’s holding. If it’s mostly dry there won’t be much effect. If it’s got a lot of water the dark band at the entrance will gradually blur out during long storage and if if reaches the end of the column, you’ll start having exit humidity start rising prematurely. I have little data to know how fast it happens but I’m still using that then new column in the photo. That’s the one I tested and saw a 2% RH reading still a couple of weeks ago after I’ve been using it off and on since that photo dated September 2.
There’s another user here who built a small version of his own design with a 200g reservoir. His is working great last I heard. He just needed less spools dried and I think he said he is getting 5 or 6 spools dry using his. But again, how long the desiccant will last depends on your ambient humidity.
One other thing is I’ve started using my filament dryer with dry air purge to re-dry my beads. One charge in and one charge out. Anyway, I brute forced it first run and did all the drying in the filament dryer. The amount of water they give off is huge. Next batch will get microwave pretreatment to drive off a fair amount of water from the start and dry air to take them back as close as I can get them to new. There is overhead.
My first batch of beads did 26 spools, could probably have done at least 30, and drying the beads in the dryer was the equivalent of about 5 spools hand waving. So you do lose a little drying capacity regenerating the beads. Microwave pretreatment should get it down a few spools but no numbers yet.
Not sure about other brands, but the glass transition temperature of Bambu’s Basic PETG is 68°C, not the 80 to 85 you quote. So PETG-HF is only 2 degrees lower than that, and about 6°C higher than PLA. My guess is that the heating in your dryer is not even, and the side of the spool that melted was closer to the heat source and experienced temperatures considerably higher than the 65° you set it at.
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I never used Bambu brand PETG Basic. I’ve only had my printer about 4 months and since their PETG Basic has been discontinued my only experience in their lineup is with the HF and translucent variants. I’ve been using Sunlu PETG (glass transition of 85) for Basic and am currently experimenting with Inland (glass transition of 80). Most brands seem to be in the 80 to 85 range, so I’m not sure what was different about the Bambu Basic that made it so low.
But either way if they’ve modified the formula (for the obsolete Basic or the new HF) so much from what would be expected for PETG and made it only slightly better than PLA, what’s its real purpose? What can it do that PLA can’t? From the TDS it looks like it maintains a slightly better flexibility, but otherwise it’s not any better than their PLA. HF has an impact strength in the XY that is just like PLA and greatly reduced from the PETG Basic. If it’s notched its XY impact is worse than PLA. In the Z its impact strength is substantially worse than PLA. And one of the big selling points for PETG is impact strength and flexibility, otherwise heat and UV stability is the key feature. It may have some better UV durability (I don’t know), but that won’t matter if it can’t stand up the heat of outdoors to even be exposed to UV.
For the life of me I still just cannot find a valid use for it (and I would love to because I have 10 spools of it). Right now I’m just using it interchangeably with PLA. Compared to regular PETG it looks pretty, but so does PLA. And if this stuff doesn’t really function any better than PLA, why does it exist?
For my 2 cents, I wouldn’t use PLA for any functional parts, while I would use PETG for those. PLA starts off somewhat brittle, but gets far worse over time as it absorbs humidity from the air and gets more brittle. Functional parts from PLA tend to fall apart over time. PETG doesn’t do that. And the fact that it’s a bit more flexible means it will handle stresses better without cracking.
But I don’t disagree with what you’re saying. In terms of the temperature specs, it’s not that much better than PLA. If I’m looking for something functional, that will hold up in higher temperature environments, I use ABS. If it’s going to be exposed to UV a lot outdoors, then I use ASA.
In fact, due to the crappy printability of normal PETG, I had pretty much moved away from it altogether. Based on prints I’ve made using PETG-HF, it now is back in the running. So I use:
PLA: non functional, decorative items, especially those that benefit from the huge array of colors and styles available.
PETG Basic: I now have no use for this at all.
PETG-HF: Lighter duty functional parts that won’t be exposed to high temperatures or UV. Doesn’t warp like ABS/ASA and no noxious fumes.
ABS/ASA: Functional parts that need to stand up to temperature or UV, are durable and long lasting. Needs extra care to avoid warping, and an enclosed chamber with outdoor venting.
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For the most part I agree with your comments. I have an A1, so ABS and ASA are not an option for me. That means my only functional option for heat/UV resistance is PETG (or Polymaker PA6, but that’s cost prohibitive unless absolutely critical).
Now, the part I’m not so sure I agree with:
Sentence 1 and 2, absolutely. But how do you validate sentence 3 in regards to Bambu’s PETG-HF, considering it hasn’t existed for long enough to know? Normal PETG doesn’t do that, but what makes you think Bambu’s PETG-HF won’t? In most regards it behaves far more like PLA than PETG Basic, and I’m certainly no expert but I see nothing obvious in the TDS that prevents me from believing that over time it will fall apart just as badly as PLA. Every aspect of the TDS makes it look more like PLA than PETG Basic, so why wouldn’t you expect its durability over time to also be more like PLA than PETG Basic?
I am not sure what kind of PLA y’all are using, but in my experience PLA is more than strong and durable enough for most use cases. Only for heat resistance I chose PetG. And my PetG prints, apart from maybe slight stringing, turn out just as pretty as PLA.
But let me show you my accidental PLA durability test:
I printed this keychain remote controller case 9 (!!!) years ago and it has been dangling and scraping in between those keys in pockets and bags for those 9 years. Yes, it’s beaten up, very slightly warped (most likely an afternoon in a hot car), but c’mon, this ain’t bad for 9 years of abuse right?
And that’s when PLA was considered bad and immature. So sometimes I think marketing tells us we need PetG, PLA, ASA, nylon, carbon fibre, filament dryers, whatever the next big thing might be, but for me PLA is still the best compromise of all of them without even being that much of a compromise. And if it gets hot, good old PetG
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PLA is definitely what I use most. Most of the things I print don’t need durability, really, so I go for looks. But my exceptions are not really forgiving.
I print a few things that are used in the car, like a clip for an external battery for my dash cam. The first one I printed was with PLA and it lasted less than 20 minutes after I put it in the car. Not sure how long, but about 20 minutes after I put it out there I went out to leave and it had already warped so badly that the battery dropped out and pulled the camera off the windshield. Now, I live in Atlanta, and this was right in the middle of the summer. At any rate, I picked up a spool of Sunlu PETG and reprinted it, and that one is still there and has zero warping.
But my biggest planned use is outdoors. I take care of a colony of 30 feral cats. I’ve printed a significant number of braces to hold food dishes in place - all with Bambu PETG-HF. I’ve also been working on a “tunnel” that can be attached to their housing cubes to provide a bit more protection from wind and rain. Fortunately I haven’t printed any of those yet, but the plan was to use PETG-HF for those as well. As it stands now, those food dish braces will join the reusable spool when summer returns, because they will no doubt warp beyond the point of still working. At that point I’ll be out about $60 in lost prints, and I’ll have to reprint them all with real PETG.
Now for all that stuff appearance doesn’t matter (the cats don’t care what it looks like), but it is clear to me now that Bambu’s PETG-HF is not going to work in that scenario - whereas another brand of legitimate PETG should work with no problem.
As far as the durability of PLA, indoors I use it for several light-load type things. Probably the most it endures is for 40 brackets that are attached at the ceiling all the way around a room to hold my filament spools. As you can see in the picture, it’s just a basic frame type mount and each one holds 2 spools. They work perfectly fine for that. I did make a mounting bracket to attach my TV to the wall, but made it out of PETG-CF with the expectation that I may have to replace it with PA6 - but it’s not having any issues either.
But all that just cycles back around to my original point that the only real scenario that PETG-HF works for in my case is interchangeably with PLA. It looks as good, but it doesn’t seem to work any better at the end of the day.
Now as far as how you get your regular PETG to look as good as PLA - I wish I could pull that one off. In the picture below you can see a blue PLA benchy on the left beside the best I’ve managed to get from Sunlu PETG.
But I have fared a bit better with my experiments today with black Inland brand PETG. The left is PLA, center is Inland at default settings and the right is what I managed to get after printing an entire boatyard of the things over the last 2 days trying different setting.
I can only manage to reduce the glossy appearance at the top (the parts that print quick so don’t dry as well between layers) by manually slowing the printer down, decreasing the nozzle temp and increasing the fan when it starts into those areas - but that’s an unrealistic way to accomplish it. So the best I can get is an appearance that shifts as it goes - but that’s still better than the middle one, which just looks bad.
I would expect PETG-HF to behave more like PETG because it’s the same basic chemistry. PLA is a different material. Of course there’s no way to know for sure till it has some time under its belt. But I think it’s a good initial assumption is that a variant of PETG will behave similar to PETG.
Put the TDS for PLA, PETG and PETG-HF side by side and look at them.
I’m not denying that the basic chemistry of the underlying product is the same, but surely you realize that the modification to that underlying product can greatly affect how it performs - even to the point of making it perform more like a completely different product. And remember, the goal for Bambu PETG-HF is for it to print faster, easier and with better aesthetics. And what already prints faster, easier and with better aesthetics, yep, that’s right, PLA.
I don’t think, TDS aside, that it would be far leap to conclude that if they want it to print more like PLA they’ll modify its chemistry to make it behave more like PLA.
For my current needs the only aspect of PETG that is critical is how well it holds up to heat - both outdoor as well as in the parked car. My melted spool clearly indicated that Bambu’s PETG-HF does not hold up like normal PETG does. I compared it with Bambu PLA and Inland PETG in the oven. Both the PLA and the Bambu PETG-HF deformed and collapsed at 65C, while the Inland PETG showed no deformation whatsoever at 80C. I have a roll of Elegoo PETG on the way, and I’ll also see how it stands up under heat. But I know for a fact that if you put them in heat, the PLA and PETG-HF are both going to fail simultaneously, while regular PETG will still be going strong.
Now, everyone’s needs aren’t the same as mine and I’m not in any way saying Bambu’s PETG-HF shouldn’t exist. It very likely has a prominent place in 3d printing, but not for me in my current circumstances. And I don’t think they should be putting it out as a substitute for PETG Basic - it should be its own thing separate from PETG Basic.
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