Printing issues related to humid filament

Why it happens, how to notice, avoid and deal with it

 

 


                                                                 

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Underextrusion, Stringing, Bubbles, and Oozing are issues related to the presence of moisture in your filament. If your spool is not dry, you can expect low print quality and weak prints. In this article, we're going to go through why this happens, how to spot the issue, and how to solve it and prevent it.

 

humidity-test-pva-01
From left to right: Dry PVA 10% humidity, PVA 30% humidity, PVA 70% humidity.

 

Know if your filaments are wet

The first thing you need to know when troubleshooting is knowing the symptoms of each problem. In this case, after reading this article, you'll be able to notice whether or not your filament is wet. 

 

The first and more obvious way is noticing the material is not smooth and there are tiny bubbles inside of it, these are formed by the moisture evaporation process, producing steam inside the filament. You can also notice if the filament is wet if the material keeps oozing out, even though the extruder motor has stopped pushing it through the hotend.

 

filament-humidity-2

The other one is more subtle but still noticeable: If you hear sizzling or popping noises coming out of the nozzle while the filament is extruded, it means the filament is wet, the spool needs to be dried up. 

 

What happens when moisture is absorbed by polymers

All the materials that are printed with BCN3D machines are polymers. These materials have a tendency to absorb moisture from their environment, some more than others, but they all do it. 

Having moisture in the filament can cause some issues in 3D printing, especially with more hygroscopic materials such as PA, TPU, PVA, or BVOH. Other materials like PLA,  PET-G, or ABS are also susceptible to catch moisture from the air, but at a lower rate. 

 

So, what exactly happens when the filament is wet? Why it has so much of an effect in 3D printing? There are two main reasons: Foaming and Hydrolysis. 

- Foaming is the phenomenon in which the caught moisture evaporates when the filament is heated. In this case, air bubbles are formed in the material, and the print comes out with strings and blobs, bad quality and weaker than desired. 

 

humid-filament-1* Foaming representation: When it happens, the filament has a bubbly appearance.

 

- Hydrolysis is the name of a reaction that takes part when there are water molecules present in the polymer structure. In short, when water is absorbed by the polymer, it breaks up all the secondary molecular bonds in the polymer, changing it to a much simpler form, monomers.

 

humid-filament-2

* Hydrolysis reaction schematic: Water molecules are placed in between each monomer and break down the polymer structure.

 

This makes the material composition and properties change, making it more hard and brittle. Furthermore, it is more propense to clog the hotend, as the fusion temperature increases.

How to dry filament and store it

So, how to fix these print quality issues? The answer is simple, you just need to dry up your filaments and know how to store them properly. To dry your spools you can use a regular oven preheated at the specified temperature.

If you don't want to mix up your cooking appliances with your 3D printing gear, our Smart Cabinet gives you the all-in-one solution for drying and storing your filaments in perfect condition while they are not in use. It is specifically designed for an extensive use and to improve the reliability of your printers.

 

store-filament-sc store-filament

 

You can also consider buying and modifying a food dehydrator, or getting an actual filament dryer, specifically designed for 3D printing materials, although the results might not be as good as when having the Smart Cabinet installed in your workspace.

 

Here's a drying chart that will help you along your 3D printing journey:

Warning! Always take into account the material of the spools, you'll see it normally specified in the same spool. If your spool is made out of recycled PLA, or a material that has a lower vitreous transition temperature than the actual filament, lower the drying temperature (for example, if you want to dry PA in a recycled PLA spool, you should dry it at 45ºC for a bit more time).

 

Filament type

How to dry it

How to store it

Before Printing...

PLA

45ºC for 6 hours

No special considerations

Just load it up!

 

TPLA

45ºC for 6 hours

No special considerations

Just load it up!

 

PVA

 

50-55ºC for 12 hours

 

Dry airtight container with desiccant sachet

 

Dry it a bit

 

BVOH

 

60ºC for 4 to 16 hours

 

Dry airtight container with desiccant sachet

 

Dry it a bit

 

TPU

 

50-55ºC for 12 hours

 

Dry airtight container with desiccant sachet

 

Dry it a bit

 

PET-G

 

65ºC for 6 hours

 

No special considerations

 

Just load it up!

 

ABS

 

80ºC for 6 hours

 

No special considerations

 

Just load it up!

 

PA

 

80ºC for 12 hours

 

Dry airtight container with desiccant sachet

 

Dry it a bit

 

PP

 

45ºC for 6 hours

 

No special considerations

 

Just load it up!

 

PAHT CF15

 

80ºC for 12 hours

 

Dry airtight container with desiccant sachet

 

Just load it up!

 

PP GF30

45º for 6 hours

No special considerations

Just load it up!

 

Conclusions:

If you want to know a bit more on this matter, check out this whitepaper:

The Importance of Optimal Filament Storage Conditions and an In-depth Comparison of Well-known Filament Drying Methods

Forum Community

Need more tips? Check out our forum community for more info about this. 

 

It's important to keep your printer in good shape to make the most out of it. In this chart you can find a list of the extruder maintenace procedures and how frequently these should be done. 

Maintenance Plan (Epsilon Series)

Maintenance Plan (Sigma Series)

Maintenance Plan (BCN3D Sigmax)

Maintenance Plan (BCN3D Sigma)

bcn3d-recycle  Take your e-waste to a certified recycler. Check how we do it in BCN3D.

 


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