3dP Filament: Drying

[last updated: 2022-11-20]
3d printing home page
filament home page

filament drying specs
See Reference Links below

Quick ref:

Dry at:
PET: 65 - 80C

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• Why dry filament:
  Many filaments are hygroscopic ("water loving"). They will absorb moisture out of the air.
  This can mess up your print - adhesion, stringing, globbing, etc.
  • If you store your filament in a "dry box," with dessicant and/or heat, you may be just fine printing with it.
  • But if you store it in normal living environment, which has normal air humidity, you should consider drying it before printing.
  • PET and especially Nylon are improved by drying if they haven't been stored in a low-humidity environment.
• Drying Procedure:
  • This is JWID. It's different than some things recommended online, but it works for me.
    Broadly:
    put filament into the oven,
    heat up the oven,
    monitor/control the temperature,
    wait bake/soak time,
    turn off the oven,
    wait cool-down time,
    remove the filament.

  • Warning: Many online sites recommend you don't do this in a gas-fired oven. Filaments may outgas volatile organics that may be flammable.

  • Use a digital temperature gauge.
  • I'm currently using a digital LCD gauge (from China), sold as a refrigerator/freezer temperature monitor
  • Decide on your target temperature - some value less than "glass transition temperature" for the filament:
  • Higher drying temperature will dry your filament quicker. Anything above 120F or so(?) will get the water out, but the higher you can go, the quicker it will dry. You must of course avoid melting or even significantly softening your filament. See filament specs link above.
  • Beware that your chosen temperature, which may be well below glass transition temperature of the filament, may still be hot enough to soften the spool plastic.
  • Put a baking sheet onto center shelf of oven, with a layer of tinfoil.
  • Insert temperature probe into oven, on top of the baking sheet.
  • Put filament spool on baking sheet.
  • Heat oven:
  • Turn on oven to your target temperature, as best you can with the limited resolution of your oven temperature control.
  • Monitor temperature with your digital readout to see how your oven responds.
  • It will likely take a few minutes. Wait for the temperature to peak.
  • Adjust your oven temperature control as needed up or down so that the actual temperature measured by your digital probe
    is close to your target temperature.
  • Bake/soak your filament:
    • When the oven reaches your target temperature, wait for desired bake/soak time, then...
    • Turn off oven.
  • Remove filament from oven:
    Online sites suggest allowing filament to cool to room temperature before removing.
    I take mine out as soon as it's cool enough to handle

  • Note:
  • Online tips suggest turning off the oven and leaving the spool in the oven until it's cooled to room temperature, saying this will avoid "generating thermal stresses" in the filament from rapid temperature change. It occurs to me that as far as affecting the print itself, this is a non-issue, since the extruder melts the filament to deposit it, so no stresses will remain. OTOH if there are high stresses, breakage on the spool might be an issue. Frankly have not done any test of actual stress in filament, so I just let it cool enough to handle the spool without burning my hands. It's JWID.

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• Reference links:
  (link to:) all3dp.com
  (link to:) matterHackers.com
  (link to:) rigid.ink
  (link to:) forum.seemecnc.com

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