Your Filament Dryer Is Lying to You — Push Plastic Plant Manager Speaks

Main ideas / concepts

• Moisture effects are real but often overestimated. The episode argues that online advice about filament drying is “not false,” but usually incomplete and oversimplified.
• The key concept is hygroscopicity (how polymers absorb moisture) and how absorbed moisture changes material behavior.
• For most common FDM plastics (especially PLA-family), drying often isn’t necessary for the typical problems people attribute to moisture.
• Some “stringing/brittleness” issues are better explained by other causes, especially:
  • Incorrect printing temperature / tuning (especially for PETG).
  • Annealing and mechanical “memory” of filament on the spool, which can lead to crazing/cracking that a dryer can mask by annealing.
  • Irreversible chemical damage (hydrolysis) is mentioned as a true moisture mechanism, but the dryer cannot reverse it.

Practical conclusions given

• Drying doesn’t hurt in general, but it may not be doing what users think it is doing (often it’s annealing/softening-relaxation rather than “fixing moisture damage”).
• Be more selective about drying, prioritizing it for materials where moisture absorption is truly significant—notably nylon—while tuning temperature and process for others.

Methodology / “how to think about drying”

1) Identify the main moisture-related mechanism

• Hygroscopy: filament absorbs moisture to some degree.
• Hydrolysis (hydrarolysis): moisture can break polymer chains (chemical/irreversible damage).
  • If hydrolysis occurred, a dryer cannot reverse it.
  • True hydrolysis would require adding agents to rebuild molecular bonds—not something a home dryer does.

2) Understand “brittle filament after sitting”

If filament becomes brittle and breaks after being loaded/left for a week or two, the cause may be:

• Annealing + spool “memory” leading to cracks/crazing, not moisture.

Mechanism described:

• Filament conforms to the spool over time (especially PLA), becoming slightly ductal/“remembering” its curved shape.
• When moved into the printer tubing, it gets bent/reshaped.
• Micro cracks form along the inside of the bend.
• Disturbing/removing can let cracks grow; leaving it in the tube lets cracks worsen.
• This is referred to as filament crazing.

Implication:

• Avoid leaving filament loaded in machines (example concerns include jams in AMS-like systems).

3) Recognize what drying can actually change

A dryer can anneal filament:

• Heating toward the material’s glass transition temperature allows molecular relaxation.
• Slow cooling helps lock the structure tighter.

Effects of annealing:

• Can increase toughness and reduce crazing likelihood.
• Can increase heat resistance, so some filaments print better at higher temperatures.

4) Evaluate PLA / “PLA” products critically

• PLA base resin is claimed to be low hygroscopic, so it likely doesn’t absorb enough moisture during typical FDM usage to ruin prints.
• Marketing confusion exists:
  • Some materials are labeled “PLA” but may be different polymers/additives (e.g., “flexible PLA”).
  • If the printed material isn’t truly PLA, drying needs may differ.
• If users see problems, they may need to verify:
  • Correct printing temperatures and whether the material is actually PLA-like.
  • Manufacturers may not disclose full compositions (e.g., no safety/technical data sheet), making proof difficult.

5) For PETG: treat “drying fixes stringing” as conditional

• Drying PETG can improve clarity and may help slightly by reducing moisture.
• But the video emphasizes stringing is often dominated by the temperature sweet spot / retraction behavior, especially because PETG is more prone to stringing.

Temperature argument given:

• Too cold → retraction causes filament to ooze/curl/string due to pressure/flow behavior.
• Too hot → retraction doesn’t stop flow; filament dribbles.
• Therefore, aim for the right hot/cold range for minimal stringing.

Moisture vs surface moisture:

• Surface moisture can “cook off” quickly in the hotend before it fully mixes into the polymer.
• Unlike resin processes with mixing, FDM extrusion is described as mostly laminar flow, so surface moisture is less likely to disperse throughout.

6) Nylon: drying is strongly recommended

• Nylon is described as a major offender due to strong water absorption (sponge-like behavior).
• Failure mode:
  • Moisture causes steam popping during extrusion (vapor expansion creates bubbles/foamy appearance).
  • “Bacon-like” sounds are attributed to steam/porosity effects.
• Recommendation:
  • Dry nylon before printing, with storage in a dry room/dry environment.

7) ABS / ASA: can absorb moisture but effects may be minor for FDM

• Claims:
  • ABS and ASA can absorb moisture, but slower than nylon.
  • Drying doesn’t hurt; printing may still be fine without it depending on conditions.
• Also emphasized:
  • Some “looks like moisture” problems can actually be overheating/frying chemistry and not moisture.

8) TPU and “frying” vs moisture

• TPU is described as already near/past glass transition (because it’s flexible), making it susceptible to overheating (“frying”).
• “Frying” can be mistaken for moisture-related issues.
• Fix suggested:
  • Lower temperature incrementally and re-test.
• Extra note:
  • Annealing can raise temperature resistance, potentially helping in some cases.

9) If drying is used, weigh benefit vs cost

• Dryers use substantial electricity, especially for multi-printer setups.
• The video frames dryers as potentially unnecessary if temperature/process tuning can solve the dominant issues.

10) Don’t ignore contamination

• Even if moisture is uncertain, dust/contaminants are a practical printing risk.
• Storage/handling to reduce dust is presented as a legitimate reason to use dry boxes/dry storage.

Speakers / sources featured

• Joshua Van Vleet — plant manager at Push Plastic (primary source/expert).
• “Where Nerdy is Cool” host — the narrator/interviewer (name not stated in the subtitles).
• Push Plastic — sponsor and subject of the referenced factory tour.