The Importance of keeping the filament dry and how to do It
When we face the printing of a new piece, we configure the slicer with the most optimal parameters, prepare the printing surface and make sure to choose the most suitable filament for the job. We may have been very meticulous in getting the gcode and have our machine set up.
Once the impression is finished we may return and find that the result is not the same as other times: layers detached, superficial defects ...
Then we ask ourselves: How is it possible that with parameters that have always worked, it has ended in disaster?
For the most likely cause is humidity, an enemy of 3D printing that we seldom blame and affects all thermoplastics.
In this article we are going to see why moisture affects both thermoplastics and how we can prevent it from affecting our filaments.
Why does moisture affect thermoplastics?
We have to start by understanding how the structure of a plastic is, we do not intend to give a class of chemistry so we will try to simplify explanations as much as possible. Basically a plastic is a polymer, this means that they are substances that are made up of the union of many very long molecular chains called monomers.
For example polystyrene is a polymer formed from the repeating unit known as styrene.
The fact that these compounds are formed by chains attached to each other causes them also to break under certain external conditions or agents and one of the most affecting them is water.
The water is positioned between the chains of the polymer causing it to lose some of its properties. To this capacity of materials to absorb water we call hygroscopicity.
How to prevent moisture from affecting the filaments for printing?
Although the percentage of humidity in the environment is minimal, a tiny amount of water can already damage the plastic and make it not behave as it should.
In 3Dfils we extrude our filaments after a long process of drying the virgin material and once winded they spend a day in special containers that help to eliminate the remaining moisture that has been able to absorb during the manufacturing process. Afterwards they are packaged including in each container a sachet of desiccant gel to keep them dry until they reach the consumer.
Once opened the filament is when we must make sure to store it properly to prevent the material from absorbing moisture.
The first thing to consider is that our workspace contains a minimum level of ambient humidity. Although we know that this is not always possible. But there are storage alternatives such as keeping our filaments in a closed container with desiccant gel. A good example of how to create a storage box is as follows:
How long does the 3D filament hold until moisture is affected?
This depends on the material we are talking about. We also have to take into account that plastic materials can behave in two different ways in the presence of water:
- Materials with low hygroscopicity only accumulate moisture on their surface and it is very difficult to absorb moisture within their molecular structure. This means that with simple storage we can prevent problems. These materials are for example polyethylene, polypropylene, polystyrene or PVC.
- The materials with high hygroscopicity if they accumulate water within its molecular structure and are very affected by its presence. These are for example ABS, PET, nylon, TPU or TPE.
Taking into account this we will take some measures or other conservation depending on the material that we are going to use.
How can we realize that a filament has absorbed moisture?
The first thing is to observe the diameter of the filament. When a polymer absorbs water, it can increase its size by more than 10%. In high quality filaments such as eFil or eFil where the diametrical tolerance is taken care of, it is very easy to determine if it has absorbed moisture by looking if its diameter is larger than the one marked by its tolerance.
We would like to make a paragraph here, when measuring the diameter of flexible materials with a caliber, it is very easy to be mistaken because with the caliber we can chafar the filament and get a wrong measurement of the diameter and less to the real one. Therefore we can use the weight to measure the percentage of moisture, comparing the weight of a few meters of open filament, with those of a dry and freshly opened coil. For this we must weigh at least 5 meters to eliminate errors due to tolerance. So we can see if the difference in weight exceeds 10%.
Another way to check the moisture content is to extrude a few meters in our printer and stick the ear if we hear a sizzle as the filament comes out through the nozzle, then there has been absorption of moisture.
There are scientific methods that are used in the laboratory to measure this, but with these two will be more than enough to determine if the 3D filament has absorbed enough water to affect the quality of the piece.
What do I do if the filament has absorbed moisture?
If you suspect the filament has absorbed moisture, you do not have to throw it away. It will be enough to dry it before printing so that it is like new. To carry out the drying process, an oven will suffice.
The best thing for this is a convection oven and use hot air to dry the material. The temperature and drying time depend on the material. To have clear values we must consult the glass transition temperature of the material to be dried and always put the oven at a lower temperature.
To dry eFil and eFil+ we must put the oven at a temperature of about 60ºC and once reached leave the filament in between 3 and 6 hours, depending on the moisture that has absorbed.
After the time has passed remove the coil from the oven and let it cool to room temperature before printing or introduce the filament into a storage container prepared for it.
There are certain materials like nylon that we will almost always dry before printing if we have stored it incorrectly.
We hope this article has been useful to you and if you have any doubts put it in the comments.
See you printing.