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Humidity... A Silent killer of PLA 3D Printer Filament

Updated: Apr 18, 2023

Plastic including the 3D printing thermoplastics used in FDM 3D printers is a polymer. Some polymers are hygroscopic in nature, which means if they are exposed to the atmosphere it will absorb the moisture in the air. PLA (Polylactic acid), a biopolymer made generally from corn starch is a hygroscopic material. It absorbs moisture if kept unprotected. This means, simply leaving your filament out in the open result in poor-quality of prints.

What problem arise from moisture-absorbed PLA filament?

3D Printer Damage– Absorbing moisture makes the PLA filament to swell. This increases the diameter of the filament. Feeding the filament with increased diameter will jam your printer extruder and sometimes replacement of your extruder.

Poor 3D Print Quality– The moisture trapped in the filament, when heated will escape as steam. This bubble of steam will interfere with the flow of plastic resulting in the poor quality of 3D prints. It will also decrease the layer-to-layer adhesion resulting in a poor look

Weaker 3D Prints

Moisture-absorbed filament shows lower tensile strength by 6%.

I run a 3D printer filament manufacturing company Tråd3D Technologies, we conducted the experiment is keeping the PLA filament open to the atmosphere during the peak monsoon (humidity level around 85%). I checked the diameter before exposure to moisture and after 6 days of exposure to moisture. The initial diameter was 1.767 mm and after 6 days the diameter increased to 1.807 mm, an increase of 0.04 mm.

I have tried the same filament for printing without drying, dried at room temperature, and forced drying in the oven. The conclusion is:

  1. The result was bad (Pic 1).

  2. I kept the filament in a dry place Or in the sun and tried printing (Pic 2). Better.

  3. I have dried the filament in my oven ( if you don't have the drier keep it in the SUN for a longer time) @ 60 deg C for 3 Hrs and tried printing (Pic 3)

How do you know if the filament is wet and needs to be dried?

  • The easiest way is to extrude some filament and watch it come out of the nozzle. If you see any bubbles, hear any hissing/popping/cracking, or see steam coming off the filament, then it’s definitely wet and needs to be dried out.

  • The filament will not adhere to the print bed

  • Repeated builds seem inconsistent or fail with no changes in variables

  • The Extruder motor stops but the filament keeps coming out

  • The extruder motor starts but filament extrusion is delayed

  • Parts become soft, fragile, and break easily

  • Extruder jams

What is the best way to prevent PLA from absorbing moisture?

Keep filament in an airtight container- Keeping filament immediately after use in an airtight container with desiccant will reduce the risk of moisture absorption. In India, rice is used as a safe desiccant. This will not work if the moisture content is high.

Use Vacuum bags with desiccant Not the Ziploc bags (the bag that you simply lock from the top). Buy vacuum bags that can be used along with your vacuum cleaner and place the silica get pocket inside the bag before the vacuum seal.

Use storage box with silica gel-

The most effective desiccant for keeping filament dry is silica gel. These are the small packets of moisture-absorbing gel you find in your shoe boxes and vitamin bottles. You can buy silica beads that will change color as an indicator that the beads have exceeded a certain amount of water. Once the beads change color, you can put them in the oven for 3 hours at 120°C and they will turn back to their original color for you to re-use. You can 3D print a small container with holes and keep it inside the 3D filament storage box.

Dehumidifier cabinet/ Dry cabinets– This is an expensive solution. If you use a huge quantity of filament you can buy this. This is the best solution for keeping your filament dry.

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1 Comment

swami Sundaram
swami Sundaram
May 14, 2023

Very informative.

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