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Does PLA Filament Need To Be Dried Before Use?

Polylactic acid or PLA is a popular type of filament in 3D printing, but unfortunately, it’s also prone to absorbing moisture. If that happens, the filament will likely expand, affecting the sensitive measurements of a 3D print. With that in mind, is it necessary to dry the filament, or can you rely on the heat of the machine to make things right?

PLA filament needs to be dried before use, as does all 3D printing filament. Of course, it’s best to keep the filament dry at all times, but if it gets wet somehow, you will need to dry or cure it before you can use it again. The reason is that moist PLA filament will swell and change in texture.

This article will go over why you need to keep PLA filament dry. We’ll also discuss how to keep your filament dry, including the best storage methods.

Why It’s So Important That You Keep PLA Filament Dry

PLA is both cheap and easy to work with, making it a very popular choice for professionals and hobbyists alike. Unfortunately, it’s also hygroscopic, meaning it draws in any moisture from its surroundings. 

Excess Moisture Can Lead to Stringing

If this happens, not only will the texture of the filament change to something much more rough, but you may even notice bubbles coming out of the nozzle as it extrudes. These bubbles can lead to stringing and uneven prints.

This can happen simply because it’s not stored correctly in many cases. If your storage area has excess moisture, such as near a kitchen, chances are you’ll see a rough texture, and you’ll need to dry the filament completely before use.

Excess Moisture Can Shorten the Shelf Life of the Filament

Other filaments have the same problem. PLA, ABS, polyesters, nylon, acrylics, and polycarbonates all absorb moisture. 

When this happens, they can cease to function within 48 hours. They swell, and even if it’s only by micrometers like the width of human hair, it’s enough to mess up a printing job relying on precise microlayers.

That shows how much a little humidity can mess with printing and why you need to make sure the filament is dry. Any long-term exposure to ambient conditions isn’t good for filaments. 

So, look for storage in cool, dry, and dark locations. 

How To Dry a PLA Filament Before Printing

There are a few ways to dry an already moistened PLA filament. Common methods involve food dehydrators, filament dehydrators, and a convection oven.

Use a Food Dehydrator

Food dehydrators work at a low temperature compared to ovens, but they’re meant to dry materials.

Set it between 104 and 113 °F or 40-45 °C for between four and six hours. PLA structural degrades at around 160 °F (71.11 °C), so you’ll want to stay below that with some buffer.

Use a Convection Oven

If you must, sometimes the simplest solution is to put the filament in a convection oven. 

Convection distributes the dry air evenly and doesn’t typically use moisture for cooking foods. On the other hand, propane and methane ovens often create water vapors. 

So, if you don’t have a convection oven, this method is not for you.

Like with food dehydrators, set the oven between 104 and 113 °F or 40-45 °C for anytime between four and six hours. Also, preheating sometimes goes over your dialed temperature, so don’t place the filament inside before the oven finishes preheating.

Use a Filament Dehydrator

If your printer came with one or you’re willing to invest in an additional specialized product, filament dehydrators are ideal. As their name indicates, manufacturers designed them for printing filaments. Sometimes they even operate during the printing process.

This Sunlu Filament Dryer from Amazon.com is very affordable and offers fast heating with proper air circulation. It even has a default setting for specific types of filament.

How Not To Dry a PLA Filament

One of the key things to remember when drying PLA filament is keeping the temperature low. That means you can use any of the methods described above, but leaving the filament to dry in the sun is a big no-no.

Not only can the heat be too much and damage the filament, but UV rays will destroy it. They’ll alter the color and the strength of the material. This degradation applies to printed items as well as raw filaments.

On top of that, you cannot control the humidity in the air, which might be why your PLA got moist in the first place. Adding the sun doesn’t change that.

How To Store PLA Filament 

There are several approaches to storing PLA filaments safe from excess moisture. 

You can:

  • Add dehumidifiers in open-air storage, like a garage or office. 
  • Place silica packs in enclosed storage areas, like drawers and boxes.
  • Wrap plastic bags around the filaments and seal tightly with duct tape.
  • Use a specialized climate-controlled cabinet or dry box.
  • Create a combination of any of the above.

PLA filaments tend to last about a year. So, however you choose to store them, keeping track of the dates you bought them will tell you what quality you can expect as time goes by. 

Also, silica packs will need to be refreshed, either with new packets or by dehydrating old ones in the oven.

Another terrific option is to use this YOOPAI Filament Storage Bag Vacuum Kit from Amazon.com. It comes with 20 sealable bags that are big enough for standard filament spools, plus a simple hand pump to remove any air from the bag. 

Avoid Moisture by Using Proper Storage Advice

The best way to dry filaments is never to have them moisten in the first place. In other words, store them properly.

As a thermal plastic monomer, PLA has double bonds that make water extra inclined to hydrogen bonds. Once the filament has moisture through these hydrogen bonds, it becomes hard to remove. 

However, at least PLA isn’t as difficult about this as other filaments.

Water creates bubbles in PLA filaments, leading to a rougher texture and abnormal forms. That texture, blobs or stringing can tell you if your storage environment is too humid. 

These may become more obvious during the printing process and you might even hear hissing.

Note: When you actively dry the filament, you need to not over-dry it. The plastic can overheat and dry up to the point that it becomes too brittle.

Final Thoughts

PLA filament needs to be dry to ensure a smooth 3D printing process. Ideally, this would mean that your storage area is dry enough to not let enough humidity in for the PLA to absorb

With plastic bags, silica packs, and dry boxes, you can achieve this. But if you must, you can dry filaments using a convection oven, a food dehydrator, or a filament dehydrator.