How are people keeping their filament dry?

[MZip]

I hadn’t considered an aquarium pump but that would work great in the setup I’m building! For recirculating air in an aquarium-style tank with desiccant to create a dry air reservoir, I think I’d go with a fan instead though. More air flow would help get past dead air around and in between desiccant beads/chunks. Aquarium pumps do move significant air but I think for fastest equilibration you want more air movement. I might be thinking about what you are proposing wrong, though.

I’m going the other way - I was going to use a fan to push air through a tube of desiccant and then into a Sunlu dryer, but in a first run it didn’t have enough pressure to push much air. So was adding another fan (when you only have a hammer…) But an aquarium pump is pretty much positive displacement so can develop a fair pressure if needed. They certainly can get at least about 10-20” water column pressure - that’s perfect!

Certainly with a reservoir of dry air you’ll have a better functioning dryer. I’m not sure if my residence times will be good enough but with a low flow rate they might be fine. But that aquarium pump idea is brilliant. I was thinking I could print a peristaltic pump. I’ve got one of the USB gearmotors from Bambu and their USB speed controller. It would have worked and given more pressure, but an aquarium pump is perfect. Skipping the 2 fan approach and going straight to aquarium pump. Thanks!

[NeverDie]

@MZip

For recirculating air in an aquarium-style tank with desiccant to create a dry air reservoir, I think I’d go with a fan instead though.

I believeI understand your goal for creating a “dry air reservoir.” It may not be to your taste, but if you don’t mind a suggestion, I’m fairly sure that at least one dead simple way to quickly put together such a thing for a proof of concept would be to 1. place one or more of these Eva-Dry high speed desiccant regenerators inside your reservoir,

Amazon.com: Eva-dry Bundle Air Dry System, White Sand : Toys & Games

2. disable the heating elements in it/them (either permanently, or with a switch), 3. plug them in and turn them on, such that the air inside your reservoir will be continually circulated through the replaceable desiccant column. Although the blower system was designed by Eva-Dry to regenerate the desiccant by heating up ambient air and blowing it through the desiccant column, in this altered configuration there would be no heat so it would instead dry the air inside your reservoir. Then, later on, after a filament drying cycle was completed in the way you had envisioned (namely, by heating up the air around the desiccant and pumping in make-up air from your dry-air reservoir), you could simply remove the desiccant column from inside the reservoir and replace it with an identical one that was either new or had already been regenerated (perhaps from using an additional, non-crippled eva-dry unit located outside of the reservoir, but this time as an actual desiccant regenerator, in the manner that Eva-Dry had designed and intended for it to be used ).

You could, of course, devise your own, but this seems like it would work with very little modification straight off the shelf. Easy peasy. I may even give it a try myself. If nothing else, it’s food for further brainstorming.

[MZip]

It’s @IslandBill who is going with a reservoir. What I’m doing is a bit closer to the Eva Dry system. I’m looking for small footprint and am circulating air through a clear Nalgene plastic bottle where the desiccant beads are located. Air pump will be here Saturday. The Nalgene bottle seals up nicely so makes a great bead holder for this I think.

Where the question comes is kinetics of the beads absorbing water. The way I’m approaching it is a forced air flow through the desiccant beads. If the beads absorb the water quickly compared to the air movement there should be a red band form at the bottom of the bottle and get larger/taller as it removes water. If that mechanism is slow, the beads in the whole bottle will change color more or less at the same time and water will be carried out in the not-so-dry air.

With the approach Bill is taking, he’ll start with “dry” air assuming it has had most of its water removed, but if the kinetics are slow, his dry air will be diluted by wet makeup air but with small flows, he should still be fine. His method should work either way while if kinetics are slow, more bottles would need to be added in series for mine not unlike that filament dryer made from cans.

That reservoir is a good idea and those Eva Dry units would make a handy system for keeping it “dry”. For me, I just don’t have the space to have a reservoir.

[MZip]

Hey @NeverDie - this is essentially what I decided to go with and something like that image is what I hope to see - the red/blue (or orange/blue) color change. That is showing two things - that the kinetics are quick and the water sticks right down, and that the sticking is possibly pretty robust or else the color would blur out just sitting there. We don’t know how long that column was sitting, though, but that is very hopeful! If the beads I got don’t work, I’ll try Drierite!

Edit - Indicating Drierite is calcium sulphate, a little carcinogenic possibly from the cobalt indicator compound, and fairly expensive. But not terribly so especially since it can be regenerated. Amazon has it in a 5 pound bottle for about $150 but it’s much cheaper direct from the Drierite company: Drierite - Indicating Drierite

That drying column has some impressive numbers for how much air can be pushed through it how fast - 300l/hr and it will hold 25g/25cc of water. But the important number is 300l/hr - that’s way more flow than a filament dryer needs. And they also sell plastic tubes preloaded with Drierite.

This is really good.

[NeverDie]

@MZip

the Drierite company: Drierite - Indicating Drierite

Their website has a wealth of really interesting information. Assuming I’m understanding it correctly, they’re saying that air which is dried with Drierite will have a dewpoint of -100F! That’s -73C.

As I had referenced on one of the other threads, Vision Miner appears to recommend that make-up air that is sent into a blast oven used for drying their high performance engineering filaments should have a dewpoint of -40C. I took that as the goal, even though I wasn’t entirely confident how to reach it, but now, leveraging Drierite as the desiccant, it seems we may have a relatively straightforward way to get there: on its face, -73C would be ample headroom for achieving the Vision Miner spec.

As you note above:

@MZip

Drierite is calcium sulphate

and for the non-color indicating version, this seems more or less confirmed in the SDS:

Setting aside the Limestone and Silicon Dioxide content, which I’m guessing are simply impurities, would it be correct to say that Drierite is nothing more than gypsum which has been sieved to a particular mesh size and then baked completely bone dry in an industrial oven? Or was that just the feedstock, and they did something beyond that to make it perform in the outstanding manner which they claim?

If the former and not the latter, then do a google search for pelletized gypsum. You will immediately find that pelletized gypsum is widely available from all manner of sources, in all manner of shapes and sizes, and it is literally dirt cheap. Without barely lifting a finger, here’s a simple for-instance: you can buy 40 pounds of pelletized gypsum at Lowes for a mere $16.48:

Maybe it’s not as pure, and fresh out of the sack it certainly would be nowhere near as dry as the Drierite, but to its advantage the Lowes gypsum pellets are more spherical in shape, which might facilitate airflow through a column packed with it, as compared to the Drierite granules. A more thorough search would, I’m guessing, turn up even better prospects.

The key question then: would baking gypsum pellets of a suitable mesh size until they’re bone dry produce a desiccant that’s either as good as or nearly as good as Drierite, or is there some kind of as-yet-un-revealed non-obvious production method used in the manufacture of Drierite which greatly elevates it to a much higher performance category than is attainable from relatively ordinary bone dry gypsum pellets?

[MZip]

I don’t know a lot of those answers but did see where they cautioned on how to dry - too hot and they say you can ruin it but that could be true of the Lowes gypsum as well.

I’d bet you’re right across the board - likely the same thing (minus indicator) and that is very cheap! Sieve it out to size and get rid of the dust and it may be cheaper than desiccant beads while drying air like a bandit. I was looking for similar information on silica gel and everything I find is big capacity for water but as soon as it starts absorbing water the effective humidity climbs fast. It also fits with silica gel being regenerated at a lower temperature than Drierite.

All About Silica Gel Desiccants

Anyway, already ordered some indicating Drierite but my silica gel won’t go to waste. I can run a bottle of silica gel in front of a bottle of Drierite. The silica gel can remove “excess” water first before the Drierite to help it last longer. It’s getting more complicated but not by much. And if we get truly dry air out the end and into a dryer, it should work much better.

[NeverDie]

It seems we are collectively compiling a nice collation of relevant facts and useful information, which in turn is giving rise to some meaningful forward steps and plans for action. I bet before long we’ll be in need of a method for measuring whether the dew point of the air coming out the end of your stacked column or buffering within @IslandBill 's dry air reservoir is truly as low as this work is leading us to hope for. Wrestling with how to measure/validate an ultra low dewpoint will be a very nice quality of problem to have!

[IslandBill]

One could always also include a Peltier chip mechanism to cool the air to the point that all the moisture condenses as ice on a chip heat sink (cold sink). Think of the desert that Antarctica is. A large enough cold sink could prevent most ice formation and just drip condensate till there is no more to drip.

A bit expensive in energy consumption but absolutely doable from the DIY perspective. I’ve considered this but don’t think it’s necessary until I can actually test what I believe will work short of extravagant solutions.

The other side of the Peltier chip is hot, very hot and could be used as the or a heat source for the heated filament spool chamber to get air molecules excited. If the Peltier chips were embedded in a dividing wall between the air and filament cambers, the heat and cold both get used as positive, no waste, solutions.

For the air chamber, circulating air past Peltier modules to build up a crust of ice and then melting it by just turning the unit off and allowing ambient temperature to drip the condensation to a drain. Repeat as necessary till no or little ice forms. Make up air could be passed over Peltier modules on its way in to grab ambient moisture early on when it’s still in a concentrated form before it gets mixed in with the already somewhat ‘dried’ air.

Food for thought.

Getting to a low amount of moisture is probably sufficient for 3D printing purposes and I’m not sure the filament chemistry would actually like extremely low moisture content. Not being a chemist, I’d like someone who is to give an opinion.

[MZip]

I’m waiting on the parts to know sizing but am planning on putting the pump in a printed vented box with a socket for a hygrometer/thermometer so to within its accuracy should measure what air the pump is pumping. Another box for another hygrometer/thermometer will go on the outlet after just the silica gel bottle and then after the Drierite bottle for what the air is like going into the filament dryer. I have three left I can use to take measurements without disturbing anything and to monitor performance along the way. I’m thinking it will work but curious how often it might need desiccant recharge.

About water in the filament and if we can get it too dry, if this even works we can still control that through time, temperature, and flow rate. Also, since this may use two kinds of desiccant, that’s extra hassle to regenerate those since you do them a little differently. If this works, I’ll only be drying to whatever level is necessary out of pure laziness.

[IslandBill]

To limit hassle, I’m starting desiccant only, leaving more exotic ideas like Peltier modules for later after my initial Ideas show insufficient results. I think too dry could be as much a problem as too wet as brittleness might be the result. It may be wonderful at the nozzle, but may not get there in one piece as it cracks in the delivery path due to shaking.

I have a large air compressor with an 80 gallon tank. At the outlet, I have a desiccant dryer holding about a quart (liter) of beads and what looks like a roll of toilet paper as a particle filter. I set that up quite a while ago and have run lots of air through it and the desiccant is now starting to turn colors. Admittedly, I dump actual water at the bottom of the tank through a valve for that purpose after the tank cools off and water just condenses. That is the bulk of the water in the compressed air (150 PSI) and the desiccant is only supposed to take care of what’s left, an unknown quantity.

My use for that compressor is to fill tires but mostly for spray painting and the occasional air tool. Not heavy use but still it has many hours of use. Spray painting is sensitive to moisture in the stream and I have no issues. That tells me that the desiccant is fairly long lasting before it needs a recharge.

[SWElite]

I use the desiccant bags that come with Bambu filaments. I dry them in a special holder that fits a SUNLU S2 dryer.

Dryer Holder for Silica Bags (VIDEO) by SWElite

[MZip]

@IslandBill

That tells me that the desiccant is fairly long lasting before it needs a recharge.

It all depends since you are also draining the tank and we don’t know how much the compressor is used. The air pressure in that tank causes a lot of water to drop out so it’s kind of a prefilter of sorts but at least is going the right way. If you were having to constantly change the beads it would at least point to a possible capacity issue. Holding a lot of water is a selling point for silica gel but it takes relatively high RH to hold all that water.

I think @NeverDie nailed the last piece of all this with Drierite. Silica gel adsorbs water. It just sticks to the polymer surface but isn’t chemically bound. The water can come and go but in general a lot stays stuck. Drierite chemically bonds with water which is pretty much a one way trip until you heat the heck out of it to drive the water back off. That silica gel is regenerated at a fair lower temperature than Drierite also points to how effective they both are at taking water out of air. Drierite just holds the water far tighter.

[IslandBill]

I’m willing to try desiccant beads but not willing to try any other type of material dryer that requires rejuvenation periodically. If the desiccant beads don’t work sufficiently, I’d go with refrigeration via Peltier modules as a way to condense out the bulk of the water and then post process whatever air that produces with desiccant; essentially a two stage air dryer that then becomes the makeup air into the heating chamber as moist air is exhausted.

I’ve got plenty of micro controllers ($5 each), to allocate one to each function (stage) to have them run their individual functions as they see fit.

[NeverDie]

In regards to @IslandBill’s earlier idea, I’m open to using a Peltier to create a super cold reference temperature on some surface and then looking for condensation as evidence that a particular dewpoint has been reached. @IslandBill : Is that an accurate summary of the idea? If so, then what I don’t know is: is it easy to buy a not-too-expensive Peltier off-the-shelf that can reach, say, -70C without much effort, or is configuring that almost a project in itself?

Meanwhile, I have a couple of dumb-ass ideas that might work, but I’m not in love with either one.

1. Use a freeze-it can (e.g. I have one called 403 Super Cold manufactured by MG Chemicals, but there are dozens of similar ones on the market) to spray on a reference surface. According to their website:

403C Super Cold HFO-1234ZE is our best freeze spray with its advanced environmentally friendly formula. It quickly cools circuits to -50 °C (-60 °F) . It is made is 100% HFO-1234ze, which is non-flammable, non-conductive, moisture free, zero residue, and has a global warming potential of less than 1.

Assuming the reference surface is then -50C, I quickly insert it into the specially prepared gourmet dry air we have created (by whatever means) and I look for condensation. If I don’t see any, then that means the dew point is lower than -50C, and I declare victory because according to Vision Miner a worthy goal was -40C. i.e. it gives just a pass-fail result, and maybe that’s good enough.

2. Dry Ice has a temperature of -78C. That’s likely too cold for a dewpoint reference surface, but, all is not lost. If we can use it purely as a jumpstart to make a reference surface that cold and then remove it, stick a temperature probe in the reference surface and let it coast, then maybe we can just wait for the reference surface to gradually heat up to a temperature where the frost on it melts away? Then we’ve measured the dewpoint. I know, I know: it’s pretty janky, but it’s all I’ve got at the moment. But my defense is that this is brainstorming, so technically speaking no idea is a bad idea until somebody has a better idea. Right? So, I’m really hoping you guys have a better idea on how to get a good measurement. To manage something, you gotta measure it.

[NeverDie]

On the other hand, Drierite says their desiccant was verified by NIST, so maybe it’s its own reference standard? If we put a sample of fresh Drierite (or some other chemical desiccant) into the gourmet dry air and it doesn’t gain any weight, then we’re golden.

I’d much prefer there were a cheap sensor I could buy on Mouser that would give me a digital reading, but measuring ultra dry humidity maybe is beyond the scope of what’s in Mouser’s or Digikey’s catalog, without getting too expensive. I made only one quick pass at it, but I didn’t see anything. As near as I could gather, measuring dewpoint is where the action is at, mainly because humans have gotten really good at accurately measuring temperature.

[NeverDie]

Not sure how I missed it earlier, but I’m getting what seems to be favorable search results using “digital psychrometer”. At first all the ultra low dewpoint sensors seemed expensive AF, but here’s one that claims it can measure dewpoint down to -68C for $100:

Amazon.com: Extech - EXTRH300 EXTECH RH300 - HUMIDITY METER with DEW POINT :...

Not sure how accurate it is, but it seems like there’s now hope.

If we can find an equivalent sensor (usually for less money) on digikey or mouser then we can probably arduino measure it, and then we’d be golden for measuring/monitoring the dryness of the air as we generate it without having to get janky. What a relief.

[IslandBill]

My thinking is turning the Peltier module off as soon as the air falling down from the module (cold air sinks) gets to 0C. I don’t want a frozen chunk of ice because there’s no nice way to get rid of it. The fan(s) on the cold side of the module needs to be wired so that it is on full time even when the module is shut off to keep air moving on the cold side to try to take advantage of more condensation happening for a minute or two or five or ? as chamber temperature gradually increases due to fan heat and insulation inefficiency.

Condensation has to be allowed to exit the chamber where every drop allows an equal volume of ambient air to replace it. Can’t have a vacuum.

This assumes a well insulated container so that any cold produced isn’t rapidly destroyed. As the air temp increases turn the module on again, repeat as necessary to keep condensation happening while monitoring the humidity level until such time that no matter what you do, the humidity is no longer going down. You don’t determine what humidity level you get, the ambient conditions do.

This is interrupt driven, not time or anything else. When the humidity stops going down, that’s as good as it’s going to get given your starting conditions. It requires a micro controller and software to do the monitoring and control.

See https://www.amazon.com/dp/B07SM9LMLW and realize that it also requires a 12V DC power supply to run it.

[MZip]

@NeverDie

On the other hand, Drierite says their desiccant was verified by NIST, so maybe it’s its own reference standard?

In a way it is. Since it’s a chemical reaction that traps the water, material of certain standards of purity, etc, will all behave the same way under identical conditions and production materials can be compared against that.

@IslandBill - you’ll need to regenerate silica gel beads periodically too (or buy new). In the all about silica gel link above they show the water content in the beads vs ambient RH and the RH numbers are pretty high where the beads hold the most water. For low RH numbers the beads have to be really dry and have much less water holding capacity. The capacity is still there if you don’t mind the RH climbing. Not a big deal - just means you have to regenerate them more often to keep RH low.

[IslandBill]

I’m aware of the maintenance issue with the beads and am not too thrilled about it. I hate doing maintenance on anything where better materials or design can eliminate or reduce it.

The only reason I’m considering beads is because they’re cheap. If they work, I’ll put up with periodic dreaded maintenance. If not, I’ll go to refrigeration which may in and of itself provide adequate dry air to reduce filament moisture to some acceptable level.

Everything depends on actual testing once I get my 3D printer.

[NeverDie]

@IslandBill Wouldn’t that mean, by definition, that the dewpoint in your scheme never gets below 0C?