Sounds good! I’ll have to keep an eye out
I fully agree. When you can feed dried air into the dryer, that makes much more sense and is easier with a filament dryer than a food dehydrator.
In an unmodified setup, the filament dryer will also start from the ambient air, so there is no difference to the food dehydrator. If both do their job, they extract additional moisture from the filament into the air. So the air will become even wetter than the ambient (absolute humidity rises). exchanging the extra wet air for fresh ambient air is better than just letting the water accumulate.
I think that is exactly what you say too, right?
So if you don’t apply modifications, I can’t see any reason to buy a filament dryer over a capable food dehydrator. (I don’t talk about those transparent barrels). The food dehydrator reaching 10°C higher ( or more, depending on the type of each) is quite an advantage in my opinion, Especially for filament like PA.
Then I either had defective ones or all cheap ones are not the same quality. The 18% spread was after more than 24h sitting next to each other. I also put them all together in a bag with desiccant for a night with the same outcome. Seems like I shouldn’t generalise that.
Regarding different types of desiccants: Have you tried molecular sieves? Also known as Zeolite. I was able to grab 1,5l of type 3A from work and it is really amazing stuff.
It has some great advantages over silica gel:
First, it doesn’t slow down taking up water from the air if humidity is already quite low. When I used silica gel in the AMS, humidity never dropped below 10%. With molecular sieves, it goes down from 20% to 0…1% within an hour.
Secondly, it still works at 100°C and more where silica gel already releases the water.
Third: it typically extracts water more aggressively than most silica gels.
It also has two disadvantages:
- It can hold less water: while silica gel takes up to 50% of its dry weight, molecular sieves saturate at ±20% depending on the type. So you have to regenerate it more often or need bigger amounts.
- To regenerate, you have to heat it to 300°C, which is a bit more cumbersome. I put it in an empty paint can and use an Aoyue hot air desoldering station for electronics, that blows into the bottom of the can.
You could just add a box holding the molecular sieve and a fan to a dryer, keeping the system closed. The molecular sieve then could extract the water that was released by the filament from the hot air. That way you don’t exchange air at all, so that you don’t have to extract the ambient humidity from fresh air and you don’t have to heat it up. The molecular sieve only has to take up the humidity released by the filament and therefore should last longer than silica gel that has to continuously generate new dried air despite the lower capacity.
Yep. Exchanging moist air from inside the dryer with lower humidity ambient air is better than letting the moist air find its own way out.
If you make no modifications and run them at the same temperature, they are about equal though a dehydrator would have an edge with lots of air exchange. And if you need to hit higher temperatures for some filament types that a regular filament dryer can’t hit, even more of an argument for food dehydrators.
On the hygrometers, I can’t really speak to yours. I just know based on what others have said here that I was expecting lots of variability and disagreement. Didn’t really see any of that here. They all agreed amazingly well with none defective or reading far off from others. Only thing I saw was relatively long settling times that could be improved by doing things to direct air flows (where applicable) into the hygrometer air port above the sensors.
I haven’t tried molecular sieves but have tried Drierite. The way I dry my filament dryer purge air is with the desiccant totally away and outside the dryer heat. That keeps silica gel on the table. I tend to think silica gel IN a filament dryer where it can heat up is a mistake. Sieves and Drierite are fine with the heat.
Since I’m doing purge air for my filament dryer I don’t need molecular sieves or Drierite. I don’t need to dry the air super dry because there’s lots of water waiting for it from the filament. The difference between absolutely dry air used as purge vs a small RH% is so small I don’t see it. As my beads get hydrated up, the purge air humidity will climb but it’s always overwhelmed with filament moisture.
Even with very dry air it’s still a diminishing returns kind of thing. Air mixing in the filament dryer messes with getting the water out and those last percents of humidity take longer and longer to hit. Plus there is also the aspect of how dry is dry enough? Is there any advantage to keep drying to super low humidity/moisture content if prints stop showing moisture effects?
Putting a strong desiccant like sieves or Drierite (calcium sulphate) inside a filament dryer does have merit. The desiccant only has to remove the water that leaves the filament plus whatever was already there or leaks in. For that, though, a food dehydrator isn’t appropriate because of the air exchange. Food dehydrators are really only good for filament drying if you are in a low humidity environment. But absolutely, if you want to put desiccant in the filament dryer it can be more efficient and some have that capability. As long as you are generating a dry environment and removing water, that’s what it’s all about.
The reason I went with silica gel beads is all the above plus you can regenerate them at lower temperature. It doesn’t take a hot oven to do it. By having them outside the filament dryer the dryer temperature doesn’t matter. Plus the water capacity is really high and costs are very low. And my Sunlu had no provision to put desiccant inside unless I went with spool core holders. I wanted something that would run for long periods without having to change stuff out all the time or worry about ceramic dust getting on filament.
But dehydrators can work fine as evidenced by all the people who use them. And filament dryers can work fine too. There’s just caveats with both of those. Using other desiccants in the filament dryer also seems to be viable. It’s really whatever floats your boat.
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Just buy a SUNLU S4 dryer. It’s $30 more than the dehydrator and it designed for filament, holds 4 spools, and can feed directly to the printer.
The Graef DA2042 costs 60€, the S4 is 150€. And the S4 only reaches 70°C instead of 80°C of the Graef. For drying PA, I think the Graef is the better choice.
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When reading the initial post again, I’m not sure if I would use a filament with carbon fiber for climbing grips. The CF is really abrasive. When climbing, the fibers might hurt the hands and fiber fragments could get stuck in the skin. Or is that intentional for extra grip? I know those climbing grips to get really worn after some time.
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I’ve never used a CF filament before so I wasn’t sure if that would be any kind of a concern.
I may look at some other options then, what all would you suggest?
Typically you would use CF filament for increased temperature resistance, more stiffness and better dimensional accuracy. The last point often makes engineering material easier to print when they contain CF because it warps less. This makes it especially interesting for PA, which naturally is quite soft and notoriously warps.
Often, the tensile strength is even decreased in filaments, because the fibers are so short and weaken the base material.
If PETG doesn’t do the trick, a recommendation depends on how it falls short in your application. I love PC for its great combination of properties. ABS could also be interesting. But it really depends on how you need an improvement over PETG.
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I think impact resistance is the issue. Basically, if I stomp on it really hard, it starts falling apart. I’ve played a little bit with print orientation and the number of outer walls, and that does affect it, But I basically just want something where you can print a hold in any orientation and still be strong enough to not break if someone stomped on it.
Here’s a picture of it on the wall, I’m using a washer bolt, as well as a wood screw. The failure point seems to be around the wood screw, if you just stomp on the corners even with 6 walls the screw just cuts through the plastic and it rotates.
Try making the handholds with 2 or 4 screw holes, 4 is better. That should stop the rotation and the failure.
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Yeah it’s worth looking at some more. But stronger material is more of what I am looking at.
I think I would try PC first. No idea how BambuLab compares to other brands. I have only seen tests that suggest very similar (outstanding) behaviour between Polymaker Polymax PC and Prusa PC blend. Polymaker Polylite PC on the other hand isn’t so much better than PETG. So it really depends on the make.
Another filament that is almost indestructible is TPU. It is known as flex filament but there are also quite hard recipes available. that is all just from reading, no first hand experience.
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I can give construction advice, as far as which filament is stronger, I haven’t got a clue as I am fairly new to printing.
If you were using wood, concrete or stone pieces, I would still advise at least 2 screws per piece and 4 would be better. 1 screw = rotation and failure of the piece to stay attached.
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Good stuff, I’ll look into picking some of that stuff up. TPU seems like it would be perfect if I can find a less squishy version.
Good stuff, to clarify there is both a bolt and a wood screw holding it. But I will definitely look at adding an additional screw, thank you!
This is very interesting. To keep a simpler setup, could I just run a food dehydrator inside a sealed box with desiccant? I imagine it would be less efficient but the desiccant should eventually lower the humidity inside the box, lowering the humidity of the air going into the dehydrator.
You could but there would be some drawbacks but maybe not bad? During the first part of a dry, a lot of water comes off and it spikes the humidity. For that part of the dry the dehydrator would be better off with free air exchange to get rid of water without wasting desiccant. That’s the thing that makes dehydrators good for many people. The lower their ambient humidity, the better dehydrators work.
You might want a way to add and remove the desiccant and vent the dehydrator or not to be more efficient. Start the dry in open air and when the air in the dehydrator drops to match ambient humidity, put it in the box with desiccant.
That should work I think. You’d need to protect the desiccant from air when not in use, monitor humidity and whatnot, but it sounds doable.