BASE video
 

I love YouTube because it allows us to access the readings and perspectives of other technicians in the additive manufacturing field. There are many convictions that we, as professionals, share in practice but rarely manage to scientifically validate due to time constraints. After all, we are not academic scientists; our commercial focus is on solving problems and keeping machines running. Sometimes, it is more practical to find a solution than to deeply understand the physical-chemical phenomenon that originated it.

The video I am sharing today, while I find it incorrect in some points, brings up interesting ideas that I would like to debate. I don’t claim to be the owner of the truth, as I haven't developed this in a lab. However, as I have studied materials and am an area I constantly research, I share the logic that seems to make the most sense to me.

Basic Facts

• PLA Hygroscopy: Although less hygroscopic than other polymers, PLA absorbs enough moisture to compromise print quality. Furthermore, most brands today sell "PLA+," which is highly additive-rich.
• Structure: PLA is a polymer with semi-crystalline tendencies.
• PETG and Nylon: These are highly hygroscopic materials.
• Hydrolytic Degradation: Wet PLA, PETG, or Nylon result in more brittle parts. The water present in the hotend, under high temperature, causes the breakdown of ester bonds (in PLA and PETG) and amide bonds (in Nylon) through hydrolysis, degrading the polymer.

The Myth of "Absolute" Filament Drying

This is one of the most complex topics I have analyzed. In our print farm at Evolt, practical experience dictates that if we want to print fast and with quality, we must dry all filaments.

PLA has a low Glass Transition Temperature (Tg), around 50°C to 55°C. As a semi-crystalline material, it comes from the factory predominantly in its amorphous state (coiled on the spool). By drying it in a conventional convection oven (like standard office dryers, Polydryer, or the AMS 2 Pro), the high temperature above Tg induces "cold crystallization" of the material. The filament crystallizes and "keeps the memory" of that curved shape from the spool.

For this reason, at Evolt, we dry filaments in vacuum ovens. With reduced atmospheric pressure, water boils at just 40°C. This allows us to dry the filament at mild temperatures, below its Tg, removing moisture without altering the polymer structure from amorphous to crystalline.

When drying filament with hot air above the Tg, it crystallizes in a curved state. Since modern filament transport systems are complex and full of tight curves in PTFE tubes, trying to straighten a filament that has stabilized its structure in a curved way causes it to break due to the rigidity of the crystals.

In the video, Joshua Van Vleet mentions at 5:57 that the filament breaks due to the hydrolysis process, and he suggests it has to do with manufacturing. As far as I know, this is impossible to happen during manufacturing because no one I know industrially extrudes plastics without drying them first; the machines are designed so that this does not happen! I truly believe the problem lies elsewhere, and the issue of hydrolysis is much more problematic at the moment of printing on the machine.

The Impact of Maritime Transport and Cardboard Spools

This theory extends to imported filaments. During a sea voyage, the thermal amplitude inside a shipping container can fluctuate by about 30°C between day and night. These daily thermal cycles, over the course of weeks, affect the stability of the material (in my opinion).

A curious detail: PLA on cardboard spools usually appears less hydrated. This happens because cardboard is extremely hygroscopic; when the filament heats up during transport, it releases moisture which is absorbed by the cardboard (my theory based on what I have seen in our FARM tests).

Manufacturing Process and Print Speed

During the filament manufacturing process, the extruded polymer passes through water baths to undergo rapid cooling (ensuring it remains amorphous and perfectly round). In this process, it absorbs some superficial moisture. In older printers (like the early Ender 3s), which printed at very low volumetric flow rates (e.g., 2.3 mm³/s), the moisture had time to escape passively.

Today, with sharper and more efficient thermal transitions in the heatbreak of high-speed machines, this surface moisture cannot escape and boils directly in the nozzle, causing micro-hydrolysis. That is why reducing speed helps mitigate residual moisture issues.

The Duality: Aesthetics vs. Mechanical Resistance

Finally, I defend that filaments should be printed at the highest possible temperature (within the polymer's thermal degradation limit) to ensure maximum interlayer adhesion. In semi-crystalline polymers, cooling should be the minimum necessary to allow the material time to form crystals, which provide greater thermal and mechanical resistance to the part.

However, we hit the eternal duality of FDM: to avoid curling and ensure a perfect aesthetic, PLA requires maximum cooling (keeping it amorphous). If we want mechanical performance, we sacrifice the visual aspect; if we want aesthetics, we sacrifice strength.