DIY Filament Dry Box: 5-Step Guide To Follow

Most 3D print filaments should be kept as dry as possible to ensure that it doesn’t degrade and weaken. Unfortunately, that’s true with almost any 3D print filament you might have. 

However, for some filament types, you’ll have to store it in a dry box even if you use it within a few weeks. Importantly, if your filament arrives vacuum-packed, leave it in the packaging until you’re ready to use it – you shouldn’t need any other dry storage. 

A DIY filament dry box will allow you to keep your 3D filament safe from moisture. However, the best filament dry box depends on the filament you’re working with. This means that a good dry box may be a simple sealing box or it might require heating and moisture management. 

How To Make A Filament Dry Box

A good filament dry box prevents your filament from absorbing moisture, so that you don’t have to dry it out.

That can help to prolong the lifespan of your filament, because it means that you won’t have to finick with heat, potentially over-drying, or potentially annealing your filament while drying it. 

It’s important to check what kind of filament you are storing because it can dramatically impact your dry storage. 

For example, if you’re storing PLA, the best dry box might be: 

• A sealable Tupperware or similar container 
• A vacuum bag, e.g., the kind you get from Ikea that connects to a household vacuum will work just fine, as will any food storage solutions that are large enough for spools of filament. 
• A Rubbermaid or similar sealable bin (with silicone sealing) with silica gel inside

Any of these three options will protect most filament from moisture in the air. However, they won’t dry your filament out, especially if you’ve already stored it in the open or in a cupboard without sealing it.

If you need to dry filament, you can also:

• Use a dehydrator (set to less than half of the melting temperature of the filament)
• Use an oven with a fan (also set to less than half the temperature of the filament)

You can also create your own 3D print filament drying box. 

1. Buy Materials

In most cases, you can build a simple drying box for less than $50, depending on the size you want it. 

Here, you’ll want to assess the following:

• Heating mat, such as one sold for reptiles, with a thermostat, sized to the container you buy 
• Plastic storage container with a seal large enough to hold the filament reels you want 
• Small fan (e.g. 120 mm electronics fan) with mounting bracket 
• Electric drill with 2-inch Forstner bit 
• Small screws 
• 2” cable hole cover (with rubber sealing, not a lift cover)
• Silicone + caulk gun 
• Cabling for your electronics 
• Black electricians’ tape 
• Hygrometer 
• Threaded steel rods sized to cross the distance of the container to hold a filament spool + two nuts per (e.g., if you have a 24” wide container, you’ll need a 26” long rod per filament spool you intend to store) 
• Drill bit sized to the rods 

2. Drill Holes 

Flip your rubber container upside down and pick a corner, close to the bottom. Use a Forstner bit to drill a 2-inch hole in the bottom of the container.

If you’ve chosen a thin container, use something to support the plastic so it doesn’t crack. And, make sure you don’t put too much pressure on the plastic, or it will crack. 

Use a measuring tape and a marker to mark where the filament spools should hang. Ideally, they are off the floor and spaced far enough apart that you can easily get the spools in and out. Mark placement with a marker and then drill the holes. 

Use gloves or sandpaper to remove the sharp bits of plastic around the hole. 

3. Install The Plug 

Run a bead of silicone around the cord hole cover and insert it into the hole in the container you’ve just made. Make sure it fits well.

Fill any gaps with more silicone. 

4. Install The Electronics 

Place the heat mat in the bottom of the container and run the cable out through the plug cover. Install the rods by inserting them through the holes and then putting a nut on each side to prevent them from falling out. 

Then, place the fan in an upper area of the box, where it doesn’t interfere with the lid closing or the filament being placed in the box. Use a screwdriver to place small screws to hold the bracket in place. 

You can run these into the plastic until they just start to exit through the other side. If they aren’t stable enough, use smaller screws. 

Run the cabling for the fan down the box and through the cable port. You can take the cables to the side to keep them out of the way. 

Place your hygrometer in the box. Most can be stuck to the sides. If you have cabling, run that through the cable port as well. 

5. Test Your Setup 

Plug your electronics in and turn them on.

The heat mat should normally be set to about 60° Celsius – which will heat the box enough to keep it dry. The fan will move air, ensuring moisture evaporates instead of condensation on the top of the box. 

You can then undo a nut on one side of a rod, pull the rod most of the way out, insert it onto a rod, and hang the reel of filament in the box. 

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Benefits Of A Filament Dry Box

In most cases, it’s important to store 3D printing filament in a dry place. Having a dry box has a lot of advantages. 

However, it’s often not better than using vacuum packaging unless your filament is already damp. 

Prevent Moisture From Building Up 

A dry box prevents moisture from building up in your filament, which will prevent damage to the filament. This means that you’ll always preemptively protect your filament – which will increase the quality of your prints. 

Of course, if you normally use your reels of filament relatively quickly, this is unlikely to be an issue. 

Moisture buildup in filament can cause: 

• Brittle or fragile prints 
• Steam coming off filament 
• Filament not adhering to the print bed 
• Filament popping 
• Uneven extrusion 
• Bubbling or oozing 
• Artifacts in print 

Reduce Preparatory Steps To Print 

If you store filament in the open air, you’ll normally have to spend some time drying it out before you can print with it. That can add several hours to your pre-print process, each time you want to print. 

For example, it’s common practice to put PLA and other filaments in the oven or a dehydrator for 2-6 hours before printing.

At 60°C, that will remove any moisture that has built up in the filament, restoring the original strength of the filament. However, it does add a lot of prep time. 

With a dry box, you skip this step, because the filament will have been stored properly and will be dry when you go to use it. 

Dedicated Filament Storage 

If your filament storage bin is large enough, you’ll have a dedicated place to keep all of your spools of filament. 

That can help with organization and with ensuring you always know where supplies are and how much you have. 

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Which Filaments Need To Be Stored In A Dry Box?

Most filaments are at least somewhat hygroscopic (meaning it absorbs moisture). This means that almost all filament benefits from being kept dry – or in a low-humidity or humidity-controlled environment. 

That doesn’t mean you need a drying box. It just means you need a sealable container. 

PETG 

PETG is a very hygroscopic material that will absorb moisture from the air. This causes it to become more brittle – to the point where it may break when unrolled. 

However, even a small amount of moisture can cause structural problems with your prints – even if you don’t notice any changes in appearance. 

In most cases, PETG should be stored at as low humidity as possible, or at minimum, less than 50%.  

PC 

Polycarbonate or PC is a very strong filament, but it easily gets brittle if left out. In most cases, you can treat it exactly like PETG for good results. 

However, it is less hygroscopic, meaning you’ll have fewer issues. 

ABS 

ABS filament is almost identical to PC filament. It’s hygroscopic, meaning that, if left out, it will absorb moisture and get brittle. Therefore, you have to keep it in a dry box to ensure it doesn’t.

If you don’t have a dry box, it’s recommended to use low heat to dry your filament before using it. However, as ABS has a melting point of about 200°C, it’s important to stick to 40-60°C for drying temperatures. 

Nylon

Nylon is one of the most hygroscopic filaments. You’ll always have to seal nylon in a vacuum bag or a dry box or dry it before use. 

In addition, nylon can absorb moisture even if it’s left out during printing for a few days. This means you may see differences in print quality between spools of nylon even a few days after opening them. 

For this reason, some people make dry boxes with spool exits, so they can print from the reel in the dry box. 

PVA 

PVA is water-soluble, which is why people use it. It’s ideal for making easy-to-remove supports. 

Yet, if left in the open air, it can absorb too much water and start to dissolve. Therefore, you should always store PVA in a dry box, a vacuum bag, or in a drying box. 

Drying it out after it gets wet is not good enough to preserve this filament. 

PLA 

PLA is not as hygroscopic as the other filament on this list. However, it still has to be kept dry, especially if you live in a damp or humid area. 

Storing your filament in a sealed container or storing it in a vacuum bag is good enough to keep it dry. In addition, you can dry it out at 60°C in an oven if you’ve left it out too long. 

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Frequently Asked Questions

If you still have questions about using a dry box to store 3D print filament, these answers should help. 

What is the cheapest way to dry filament?

In your oven or in a food dehydrator. However, it’s important to ensure that your drying temperature is not too high. 

Why? Thermoplastics anneal at temperatures normally about half of their melting temperature. This means the plastic polymers start to crystalize.

The further this process goes, the less your thermoplastic will melt and the more brittle it will be.

For this reason, drying temperatures should almost always be between 40 and 60°C, although you can check specific melting and annealing temperatures for the filament you’re using. 

Can PLA filament be too dry?

PLA cannot be too dry. However, it can be left too warm for too long. 

Heat causes chemical reactions and changes to polymers, which can also make the filament brittle. For this reason, you shouldn’t use heat over about 60°C and you should not leave the filament in to dry for more than about 6 hours. 

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Final Thoughts

A dry box is a great way to store your filament and keep it dry in between use. On the other hand, if you’re storing filament for a longer period, a reusable vacuum bag should work just as well, without as much effort. In either case, it’s always better to prevent your filament from absorbing moisture by keeping it in a sealed container – so you don’t have brittle or bubbling prints.