This model is an air dryer - not a filament dryer. It supplies dry air to a filament dryer to make the drying process more reliable, repeatable, and faster.

A modification to your filament dryer is probably needed to be able to plumb the dry air into your filament dryer. There could be safety issues if you don’t do that properly.

This air dryer may not have enough flow volume for multi-bay filament dryers like the S4. If it works it will essentially be a slower purge because of the larger volume. Until someone tries it and reports good results, I can’t recommend it as it is untested.

This air dryer won't work with a food dehydrator. Those are designed to exchange lots of ambient air that will swamp the effect of adding dry air.

Do not pressurize the model with compressed or canned air. The glass bottle can shatter and cause injury. Small pressures over large areas develop significant force.

Do not operate the air dryer with a cracked or chipped reservoir. That can weaken the glass leading to breakage and injury.

Do not leave air and filament dryers running unattended. The air dryer is pretty benign but filament dryers are not. They have fairly powerful heaters and some have fans.

Do enjoy 3D printing with dry filaments and kiss clumping, stringing, and (at least some) failed prints goodbye. A few examples at the end.

Hopefully the instructions are clear and easy to follow but please read them through if you are considering this. I won’t know how good these instructions are until someone tries to follow them so fair warning.

This work had helpful suggestions from and credit is also due to NeverDie, IslandBill, and others.

Jump to the end if you want to see some prints using dried filament. I’ve only got before/after examples for PETG HF but you can see some after with PLA too.

How to test your filament to determine if moisture content might be an issue is also at the end.

If you need a way to dry your silica gel beads, here’s a way: https://makerworld.com/en/models/685210. When changing out beads, do the microwave thing to get the bulk water out, but if you finish them off drying in dry air, you can get them really dry. One charge in use and one charge out.

Introduction:

This print supplies a low pressure, moderate flow of dry air to filament dryers. It significantly shortens time to dry to a certain humidity, or reaches lower humidity at fixed drying time than using ambient air. Preliminary results are that less than 800g of silica gel beads are enough to dry 20-30 spools of filament with an ambient humidity between 40 and 60% while supplying “dry” air of 10% or less relative humidity. Starting from cold, it dries a kg spool of Bambu PLA to a 19% filament dryer chamber humidity in 8 to 10 hours for an average weight loss of slightly more than 2 grams. I saw this with spools of PLA I had stored in Ziplock bags in non-gasketed bins as well as with new spools of PLA fresh from their shipping bags give or take a little.

I tried printing with a fresh spool of Bambu white PETG-HF, got minor stringing with a little corner lift in one place, dried the spool to 21% RH (took it off when going to bed) in a Sunlu S2+ filament dryer being fed dry air from a fresh column of beads, and this morning got a perfect print with no stringing or lifting on a smooth PEI plate with glue stick.

Using the air dryer, time to dry a spool depends on starting water content in the filament but not on ambient humidity since this air dryer removes most of the water from the air it pumps. All high ambient RH does with this is cause you to use desiccant faster but doesn't affect drying time.

The desiccant reservoir is clear glass and allows seeing the indicator change color. Ambient air enters the threaded end of the reservoir (top of the water bottle) and flows up to the fitting on the end of the straw. As the desiccant dries the air flowing through the reservoir, the silica gel at the bottom is the first to see the moist ambient air and gets the most water fastest so the color change starts at the bottom and moves up. As the color change moves up, eventually the bead layers above it becomes less able to grab remaining water in the air and water “breaks through”. What happens is during use the exit air is gradually increasing in humidity.

When the exit air goes above 10% RH the exit air hygrometer will start showing the real humidity level and you can decide then when to regenerate the desiccant. (Note - the hygrometers I used can only display down to 10% RH. If the exit humidity is 1% the display will still show 10%. This isn't that important unless you need really dry air. You can always put a housing inline with the exit air that holds a hygrometer that can see lower.) Even with the exit air above 10% RH, you can still dry filament. It just dries slower.

Introduction:

There's been a lot of discussion in the forum here and probably most 3D print forums on the need to dry filament for best prints but people report drying results all over the place. Some are good. Some are bad. The reason is probably that some are trying to dry with high humidity ambient air and others may have pretty dry air to work with already. Filament dryers heat the air and that lowers the relative humidity, but as the ambient humidity goes up, drying slows and even stops.

Standard / cheap filament dryers just bake filament in a mostly closed low temperature oven. Some dryers have fans to help circulate air in the dryer which can help. There's a number of models you can 3D print that prop open the doors of various filament dryers. These help more than I had thought but still are handicapped by ambient humidity.

What filament dryers really need to dry filament effectively and more uniformly is a source of dry air to sweep the moist air out and keep the dryer operating at low relative humidity levels - a dry heat. To make sure it wasn’t just the pump sweeping moist air out giving quick and deep drying, I tried drying a spool with just the aquarium pump. Results were very similar to propping the door open and the dry stalled out at 34% RH. When I connected the desiccant reservoir back in line again, it finished drying to my target of 19% RH. Filament dryers need a flow of dry air for most effective filament drying.

This model attempts to address the air exchange issue with basic filament dryers. All it is is an aquarium pump and a bottle of silica gel desiccant plumbed together in the print. (You don't have to use silica gel, though. If you need really dry air you can use other desiccants like Drierite, molecular sieves, etc.) The print just gives it all a home and makes it presentable while causing minimum restriction to flow. It's meant to be plumbed into a filament dryer to supply it with dry air but it can supply dry air for other uses at aquarium pump flow rates.

Best way to plumb the dry air into a filament dryer in is a hole near the bottom of the filament drying chamber with a hole or holes near the top for the moist air to escape. I use a Sunlu S2+ which already has holes near the top for filament to be able to use the dryer while printing.

A right angle air fitting would be better but this is just an illustration of how you might plumb air into a filament dryer. All I had were straight couplings so that's why it looks like it does and took such a low angle hole. If you get the kit of fittings called out in the parts you will have enough right angle fittings and straight fittings to connect the dry air into your dryer.

I used a plastic material that hardens up like a one-part epoxy called Sugru (not Sugaru as I misspelled in the photo text). However you secure the fitting, you want it air tight. The entrance hole into the dryer isn't too important except if you need to miss a fan, etc, as long as the air entrance is low in the dryer. When you reinstall the base, use a sealant like silicone seal to seal all around where the base attaches to the Sunlu dryer. Get a good solid bead all the way around the baseplate. Any air that leaks out and isn't pushed into the dryer wastes desiccant and dry air and there’s no good way to verify you got a good seal without taking it back off.

Hygrometers/thermometers are in the dryer air flow to monitor the humidity level of ambient/incoming air and most importantly, the humidity of the outgoing air headed to the filament dryer (except we just know when the RH is above 10%). It's been optimized for low pressure drop so you get a mighty wind from the aquarium pump. Or a light flow. It's an aquarium pump. Keep the tubing connecting this dryer to your filament dryer short. Not crazy short, but not much more than a foot or two long if possible. The less restrictions to the flow the better since aquarium pumps are low pressure and “high” flow. Restrictions and back pressure cut into the flow volume pretty hard.

You don't want too high of a flow, though. The specified aquarium pump has a throttle valve on it so you can set whatever flow you want within its capability. It's looking like this setup's silica gel beads have enough water capacity to dry 30 rolls of filament at an ambient humidity in the 40-60% range.

With fresh silica gel the exit hygrometer should peg at a display value of 10% - that's as low as it can indicate so the actual relative humidity (to the accuracy of these cheap hygrometers) is 10% or less. As the exit humidity value rises, you're feeding your filament dryer “wetter” and “wetter” air. So when the exit hygrometer starts indicating, might be a good time to regenerate the silica gel.

Cost just for parts to build this is about $90 (minus glue, silicone, screws, 24ga or finer wire, vibration absorbing pads, and filament).

Needed Parts:

Kodrine Glass Water Bottle 32 oz Water Bottle with Plastic/Metal Straws / Amazon - ASIN B0CXP7TBDW - $26

KEDSUM Quietest Aquarium Air Pump, Adjustable Oxygen Aerator Pump with One Outlet / Amazon - ASIN B08FJ1HRTP - $21

TANOMA Aquarium Air Pump Accessories / Amazon - ASIN B0CXTP8R3S - $9 (Just need the 2 right angle air fittings so if you can find them elsewhere or substitute smooth bent tubing or something else you can save some money)

JEDEW 2-Pack Mini Hygrometer Thermometer Digital LCD / Amazon - ASIN B07GR65CNT - $9

FOXTIP 8Pcs AA Battery Holders with Wire Includes 2 each of 1 AA Holder, 2 AA Holder, 3 AA Holder, and 4 AA Holder / Amazon - ASIN B0C5ZVMPL1 - $7.50 (Just need the single cell holder out of this pack. Probably any single AA cell holder would work but not sure where you can buy just one. There are also 6-packs of single cell holders for a little less. Needs a center mounting hole or drill one for an M.4 flathead screw.)

"Dry & Dry" [3.6 LBS] Premium Orange Indicating Silica Gel Desiccant Beads (Industry Standard 3-5 mm) (or equivalent) / Amazon - ASIN B0C3311JMQ - $25 – 3.6 pounds is enough for two complete fills of the reservoir (about 800g) with a little left over.

2 each M4x8 screws to hold the battery door and an M4x6 flat head screw to hold the battery holder

Thick cyanoacrylate/superglue, silicone seal, some self-adhesive 1/8” thick neoprene, and some fine color-coded wire are needed to complete this project.

Assembly:

Note - some photos show “IN” and “OUT” text on the model. That text was deleted to get a more air tight base. There is no version that has that text on the base now even though there are photos of both in the build instructions. The bottle mount was also reworked and is now part of the model instead of gluing in the water bottle lid.

The print of the Arid Air base is critical because air leaks cripple performance and can result in using desiccant faster than you should. Air leaks also will reduce flow and can compromise the ability of your filament dryer to see full or even any benefit. The walls, floors, and ceilings are all set to 4 layers to make Arid Air as air tight as it can be without curling like a potato chip. Each print of the base always got a build plate cleaning and fresh glue stick. I used Bambu matte latte brown PLA because superglue paints it well and sticks well so it can seal up any leaks. I tried to get it to not need sealing (I used thick superglue) but even at 4 walls and layers, during a pressure test it would still bubble along wall to floor joins, etc. Now that I painted mine it is tight as a drum. The model settings as they are probably are tight enough that you can omit the painting/sealing without too much air loss if you are sensitive to cyanoacrylates but it really can make a difference if your printing has layer adhesion issues, etc. Glossy filaments may not seal well.

[1] Print the parts and remove all support from the inlet and outlet air filters. The smaller outlet takes a bit more patience to get it all out but it can be done. I used Bambu Matte PLA and that looks good and superglue seems to stick well to it to use as a sealant. 

[2] I have yet to get a base to print that was fully sealed just from printing. The entire base inside and out unfortunately needs a coat of thick superglue or other favorite sealant (thick superglue worked really well for me) that you know will seal up pinholes in whatever filament you use. Next best is to seal just the air channels inside the base without sealing the outside. (You can always paint the outside later if it leaks too much.) Not a thick pooling coat either. You want to just brush it out making sure you wet the entire surface and brush it or squeegee it into holes/pores. The wet look will also highlight imperfections.

Make sure any excess glue/sealant drains out. Also, leaks in the small screw threads are negligible. Don't paint glue or sealant into those or if you do, chase the threads with a tap after it dries. The bottle threads are a significant amount of surface but too much cyano can make it too tight. With 4 walls, the threads will be pretty air tight anyway. If you dare paint them, I’d use a thin coat of thin cyanoacrylate. There is a bottle thread tester that only needs to be enabled to print it. It’s just the bottle mount so if you want to paint the bottle threads, might want to print that to test the application doesn’t make them too tight. And again, this is exterior of the model. You can always paint it later if it leaks too much.

Best time to paint the base is before you begin any assembly but you won't really be able to leak test until it's all assembled. With 4 walls, ceilings and floors using matte Bambu PLA, one coating was enough to seal it completely but YMMV. If you don't get it fully sealed up now, you'll get to touchup or repaint the outside at the end. Also note only the big base needs this. The other parts don't matter.

[3] Once the parts are cleaned up and ready to assemble, start by cutting the plastic straw that came with the water bottle to 265mm long and glue the small air outlet fitting onto the straw using cyanoacrylate. Make sure it is/can be fully seated before gluing. 

[4] Cut four 1 foot lengths 24 gauge or finer insulated color coded wire and twist one red and and black (or whatever colors) together into a cable and make sure the wire will fit down the tubes for the wires. You must insert from the front to test and make sure you can navigate the bend in the wire tube for the inlet air hygrometer. I use wire wrap wire but it's pretty delicate. Once you know the wire can fit, solder the wires to the hygrometer battery terminals and test with an AA cell to make sure they still work. The center terminal is negative (-) and the side terminal is positive (+). Be sure to use color coded wire and note polarity because polarity is important.

[5] Once soldered, use hot glue or silicone strain relief to support the wires so the leads don't break free. When cooled/cured, insert the wires most of the way into the respective wire tube and lay a smooth continuous bead of silicone seal around the rim of each hygrometer and push into position (help the battery wire by gently pulling on the end sticking out in the back) and set them firmly. Silicone should squish out all the way around the hygrometer rim. Doesn't need to be a lot but you want to know you sealed continuously around the rim. Hold the wire ends on a AA battery or LR44 coin cell that came with the hygrometer to test the hygrometers again before the silicone sets. Let that cure and when cured, you can carefully cut around the hygrometer rims with a sharp blade to free the squished out silicone. One more step with the hygrometers themselves - the display glass also needs to be sealed. Just rub silicone seal around the display glass with a slight pressure to force silicone into the space that creates between the housing and the glass. Clean up the excess before it cures using a Kleenex or similar tissue and buff the glass shiny. It's messy at first but the uncured silicone wipes away pretty clean and completely seals the hygrometer faces. Keep silicone off the rest of the Arid Air base though. If you need more sealing of the outer housing, it could make that difficult.

[6] Locate the black plastic lid to the water bottle and carefully remove the pliable sealing gasket.

[7] You don’t need to seal the bead filter disk into the base but it will reduce the amount of air that just leaks across from inlet to outlet without passing through the desiccant. If you’re drying PLA, probably not important. If drying more hygroscopic stuff, it could help. I’d only do it if you really need it. The bottle clamps it down so it won’t be too leaky. If you do seal the disk into the base, You might want to use a really thin bead to allow removal. Or use some sealant that doesn’t really cure and just gap fills.

[8]  The raised C shaped and straight areas on the disk fit into the C-shaped and straight channel in the base and assure proper orientation of the air passages. The filter disk gets oriented with the largely flat surface up.

[9]  Press the gasket from the water bottle lid into the groove formed by the filter disk and the bottle recess in the base making sure it’s properly seated and no part is twisted or rolled.

[10] Insert the straw fully into the center hole and push it down intil it hits the bottom stop. Screw the bottle on and note the clearance between the exit air fitting you glued to the straw in Step [3] and the inside surface of the bottle when you secure the bottle with the same tightness you would to get the gasket to seal. You want around two bead diameters of clearance. If you don’t quite have that clearance, cut the free end of the straw back until you do. The reason is you don’t want beads caught between that fitting and the glass to capture a bead and put point pressure on the glass to crack it.

[11] Glue the In and Out air fittings into place with thick cyanoacrylate at whatever angles you prefer. The inlet air fitting should point to where the tube from the pump makes a smooth curve to it. The outlet fitting can point however is most useful but keep accessibility in mind with the reservoir bottle in place. Make sure they are both sealed into place.

[12] Mount the AA battery holder using an m6x4 flat head screw and connect up the battery holder wires to the twisted wire pigtails from the hygrometers. Test the wiring by installing a AA battery and make sure the hygrometers both are working. If all is good, force silicone seal into the wire tubes the wires exit out of into the battery compartment and wiggle the wires a little in the fresh silicone to make sure they are well coated and sealed.

[13] The pump has to be modified to remove an air restrictor. There are four screws accessible from the bottom of the pump that hold the blue and black clamshells together. Remove those and lift off the top blue cover. Remove the metal outlet piece and the rubber tube that connects the actual pump nipple to the flow restrictor. Cut a piece of aquarium air tubing about two feet long and attach it to the internal pump being sure the silicone tube is well seated on the pump nipple. Replace the blue cover making sure not to pinch the silicone tube and reinstall the four screws that hold the pump housing together.

[14] Leak testing. If all went well with sealing and assembly the base should be air tight. If you were waiting to see how air tight your print is before painting with superglue, here you go. It's really easy. Install the glass reservoir bottle without desiccant beads - just the bottle and tighten it enough to get a good seal - but it doesn't need to be super tight. Get a 2 foot or so length of aquarium air tubing and connect it to either the air inlet or outlet fitting. You'll close off the other fitting with a finger.

The Arid Air base should be water tight but to be on the safe side, do not submerge the model under water. If there are holes you might get water leaking into the inside of the model and it could be very hard to remove. Only run water across it and only when the base has slight air pressure in it either from the pump or from blowing in a tube attached to the inlet or outlet. Do not pressurize the model and glass bottle with anything more than a light breath or a small aquarium pump worth of pressure. Do not pressurize the reservoir with compressed air or other high pressure sources.

Just use your breath or the air pump on the long tube to blow air into the base while holding a finger over the other air fitting. If blowing air manually you should feel it pressurize and hold that pressure as long as you keep pressure on the tube and a finger over the outlet fitting. That may miss small leaks though. Now hold the bottom of the base under a light stream of water where it flows like a sheet across the base while gently pressurizing it. (Again - light breath or aquarium pump on low ONLY) Any bubbles? Keep track of where they are.

Test by flowing water especially around the hygrometers, around the edges of the base, anywhere that walls join floors, the floor of the pump bay, etc. If you find any leaks, thoroughly dry the model and paint the leak locations with superglue or your favorite sealant.

When the base is properly sealed and the glass bottle is screwed in and sealed, with the aquarium pump set to its lowest flow rate and connected to the air inlet, you should be able to use the metal straw that came with the water bottle to see bubbles at a depth of 9 inches in water (9” of water column pressure). Pressure falls off rapidly if you have leaks. If you can’t get 9” WC pressure at the straw outlet and still see bubbles, you probably have leaks.

[15] Cut strips of self-adhesive neoprene or other soft 1/8" thick material to use as spacers to keep the pump off the walls of the pump bay. Put a couple of doubled up pieces on top of the pump and set it into the pump bay with the silicone tube extending through the hole in the front of the pump bay. Too hard and too tight of foam and you can turn the base into a sounding board for pump vibrations. Trim the tube to its final length and slip it onto the inlet air fitting. Fit the pump bay lid over the pump bay and hit it gently down to snap it into place. You do want soft foam for this.

[16] Fill the water bottle / desiccant reservoir with desiccant leaving about an inch of space. Turn the Arid Air base upside down and stab the straw down the center of the desiccant bottle with small turns back and forth to help the exit air fitting burrow down in the desiccant. If you use a different and more dense desiccant like Drierite it might be more difficult to get the air exit fitting to burrow down but it should. The exit air fitting has some facets on it to kind of drill through whatever desiccant you use. That's why the screwing/unscrewing, tightening/loosening motions - to help those faces push desiccant out of the way. Just know other desiccants may have smaller particle size where they can get through the existing bead filters. If you use small particle desiccants, you might want to lightly pack the air passages with some kind of filter material to help keep desiccant out of the air passages.

When you get the bottle and lid threads to mate, tighten the bottle with more screw and unscrew motions to help burrow the straw. When the glass rim hits the gasket seal, go ahead and turn it right side up, clear any beads on top of the exit fitting by more back and forth, tightening/loosening, and then give a firm but not too firm tightening.

You don’t want beads caught between the exit air fitting and the inside of the glass reservoir. This is why you need around two bead diameters clearance between the exit air fitting and the glass when the bottle is screwed on fairly firm. If the gap is too tight you’ll possibly trap a bead that can put point pressure on the inside of the glass reservoir and potentially crack or break it.

Use:

Use is trivial. Once you get it operational and plumbed into your filament dryer, plug in the pump and fire up the dryer. Set the pump throttle to about ¾ full scale. If you have a weighing scale, weigh the filament before it goes in the dryer and record that with the time and starting humidity in the filament dryer.

What you'll probably see first is relative humidity in the filament dryer drop some from ambient. That's the air heating and it's just a property of air that the RH drops as air gets heated.

Soon, though, the filament is going to start warming up and giving off water causing the RH in the filament dryer to rise. I see it climb to the 30-40% range the first few hours and then start dropping. The rate it drops slows as it gets to the 22-25% range but give it time and you can hit 19% in 8-10 hours depending on the water weight in the filament. If you weighed the filament before drying, be sure to note time, water loss, and the final humidity you hit in the filament dryer.

As it runs, the silica gel (if you use indicating - recommended) will start changing color at the bottom of the reservoir (the threads end of the bottle since it is upside down) because that is where the air enters. That color change will grow in over time and eventually the exit humidity will start to rise. The consequence is drying times will get longer. You can choose to regenerate the desiccant or just replace it when it isn't able to dry the air sufficiently and drying times get too long.

Do not shake the reservoir or remove it after it is put into use unless you are planning to replace the desiccant. As it runs, there is a water distribution that sets up which if you use indicating desiccant will become visible over time. What happens is the first beads are adsorbing most water and remaining water is being adsorbed by subsequent beads. The humidity of the air is decreasing as the air moves through the column and the beads near the exit remain “dry” for a long time. The dry beads near the exit are removing any water making it through the column. Shake the reservoir and you can move “wet” beads closer to the exit so there are fewer dry beads on the way out and you've compromised the ability of the reservoir to remove water.

Also, over long storage times, the water will redistribute in the do-nothing equivalent of shaking the reservoir. I'm about a month into my first bead charge, have dried 21 spools, and so far I'm not seeing any issues from water redistributing on it's own but over longer times, I'm pretty certain that I will. Warmer storage temperatures will make this process worse. That's why if you build one of these, try to use it as much as you can at first. Or, if you just use it as you need, you can regenerate silica gel beads as needed since that process is pretty quick. Long storage times won't be as much of a problem early in the life of the desiccant since it's all mostly dry. It's just with use when the indicator starts really changing at the air entrance because of all the trapped water, sitting unused and warm will help that water spread out and do a similar thing as shaking the beads without physically moving the beads.

On flow rates: this air dryer and pump can move a fair amount of air. Filament drying is a multi-hour process. You need flow but not wide open flow. All the air you pump through the filament dryer has to pass through the desiccant and if you use more flow than necessary you will hydrate and use up your desiccant faster.

When the desiccant is fresh and dry, high flow rates shouldn’t noticeably increase the exit air humidity but that changes as the beads get saturated. As the desiccant gets used up, water will start “breaking through”. Exit air humidity can be as high as 10% and the exit air hygrometer won’t tell you but the extra humidity will increase drying times and ultimately limit how dry you can dry. Keep an eye on the indicator state and how dark the desiccant is getting. Breakthrough will get more likely as the column traps more and more water. It's counterintuitive but if you have a dry being held back by water breakthrough, reducing the flow rate might help. Or replace the beads. They are easy to regenerate.

On the other side of that, more dry air flow will help sweep moist air out of the dryer faster. Filament might not dry much faster at high flows though because first the water has to leave the filament before it can be swept away. It will be diminishing returns to an extent and higher flow rates will hydrate your desiccant on the front end that much faster.
 

There’s a lot unknown about what conditions are best. People will just have to experiment to find what works best in their environment. But feeding a filament dryer with dry air eliminates the floor to drying caused by ambient humidity and greatly speeds up drying in general.

Added Information: How dry is dry enough for filament? Apparently some filament may even get brittle if dried too much. I have no experience with that and can’t give any suggestions aside from a bit of sage advice someone mentioned in a thread here - ”it only needs to be dry enough to print well.” Anything more wastes time, energy, and adds excess water to the desiccant. I’ve been copying what others have mentioned as their technique - drying PLA to 20% RH in the filament dryer. Prints look great now so that works but maybe there is a better target humidity to dry to? What target humidity for other filament materials? I don’t know. What I do know is you should be able to dry to near whatever exit humidity you’re getting out of the air dryer even though you might not want to.

This is also a dynamic process that depends on how fast water can migrate out of the filament and then how fast that water gets swept out. If you dry with high flow rates you’ll dry the filament faster but at some point may be limited by how fast the water can leave the filament. Once you are going that fast, more flow won’t help. Too low of flow and drying will take longer. I’ve been setting the aquarium pump throttle to between half and ⅔ full scale - a compromise between fast drying and using up desiccant and that seems to work well but may not be ideal.

It takes 8-10 hours at 53C in my Sunlu S2+ to hit a target filament dryer chamber humidity of 20% with Bambu PLA. New spools fresh from the shipping bag lose around 2g of water in that time. A new spool of white Bambu PETG-HF that was left sitting out for a day (on purpose as a test) lost 2.38g of weight in the dryer in about 9 hours (using fresh desiccant). Where I was getting minor stringing and minor plate adhesion issues, it now is printing clean.

Results:

PETG HF is difficult for many to get to print well. To see how it behaves straight from the factory bag, I printed some netting clips to keep birds from nesting behind solar panels. Results were generally ok but had a number of issues. After drying, with no change in any settings, the prints have been beautiful with no defects.

PETG HF fresh from the factory bag showing lifting from the build plate, minor stringing (much more was there but not much visible in the photo), and a slightly doughy-looking surface.

PETG HF after drying using dry air. Note the smooth sides only showing layer lines, no corner or edge lifting, and almost no stringing.

After the PETG HF clips is an image showing how PLA prints now. Those white half moon parts are slip fits into the black housing.

On my X1C and the conditions I used to store my filament, too much moisture content would show up as scarring aligned with the extruder lines (photo below), then the base lifting in corners, and little zit-like things on sides. The photo shows prints to hold filament spools in the cereal boxes mentioned below. The “wet” part was part of what started this whole trip and shows moisture content issues. The dry print was one of the first prints after I started drying my filament. Not the same spool, but the same Bambu Basic black and same print settings.

Testing Your Filament:

How do you know what shape your filament is in? It’s a tough question with an easy answer. Just seal the spool of filament in a polyethylene cereal box (Amazon ASIN B08TWH2QHV or equivalent) with a hygrometer (Amazon ASIN B07GR65CNT or equivalent), BUT NO DESICCANT. Let it sit overnight to equilibrate and read the humidity. It’s an indirect measure of filament humidity. You’ll see a range of results depending on how you dry and store your filament. If your test humidity ends up settling above 20%, you are probably marginal. 30-40+%+ and water is probably an issue.

After drying, my Bambu PLA, ASA, and PETG HF spools all pull the relative humidity down to the lowest my hygrometers can read - 10%. The actual relative humidity in the cereal boxes is somewhere between 0 and 10%. This is where hygrometers that can read lower than 10% might be handy but in my experience so far, there just hasn’t been a need to even know. Printing quality is wonderful.

Moisture isn’t everyone’s print issue but it’s the root of a lot of people’s printing problems. This air dryer is a simple way to get arbitrarily low moisture contents in your filament but keep in mind you really only need to dry enough to get good results.

Important Safety and Disclaimers:

Build and use this model at your own risk. You need to modify a filament dryer to add dry air and I have no idea if there are hidden hazards or risks with other dryers or even the dryer I used. There’s a big glass water bottle involved that is fragile and needs to be handled carefully. Do not pressurize the model with the bottle in place. No compressed or canned air. You absolutely do not want an exploding glass bottle. I took the protective cover off it for the photos but it will help protect the glass if you leave it on, help contain the glass if you break it, and has a view port that allows seeing the desiccant to monitor status. It’s up to anyone building this model to determine suitability and safety for purpose and in operation. I tried to make it low risk but there are no guarantees.