filament dryer  

RE: filament dryer

Do you use incandescent lamps which act as heaters, and control them via a thermostat (not just thermometer)? In my understanding you need to heat the air inside the box, to ensure that the filament releases the water that has already bound to its matrix. Just surrounding the filament with dry but cool air is not effective. 

RE: filament dryer

The lamp in the overhead box is a led corn roll type screw in bulb, the two vertical bulbs are just  fluorescents,  I think there is no appreciable heat coming from the bulbs, i set the dehydrator to its lowest setting and that's where  the 119 Fahrenheit and the 10% humidity is coming from 

RE: filament dryer

I still have a question, where does the moisture go? The cabinet is closed afaik wine fridges?

RE: filament dryer

Desiccant type dryers (like silica gel units): They absorb water from the air, holding it inside the desiccant. You need to “regenerate” the desiccant later (by heating it to drive off the absorbed water). In this case, the humidity doesn’t “leave” the closed box — it’s stored in the desiccant. 

Active dehydrators like mine These usually use heated air + airflow to remove moisture. In their normal use, they blow moist air out into the room, so the water vapor leaves the system. 

If the fridge is truly airtight, then moisture has nowhere to go. The dehydrator will heat the filament, the water in the filament will evaporate into the chamber, and humidity will just rise until it reaches equilibrium — not effective for drying. If the fridge has vents or small leaks, then when the dehydrator fan pushes air around, some humid air may be expelled and replaced with drier air — allowing drying to occur. Some people modify the fridge by adding a vent hole or exhaust port so the moist air can escape, while the dehydrator continues circulating drier air inside.  in my case the wine fridge has an imperfect seal, so I did not have to install a vent.

 couple of practical notes for a setup: 

Check airflow direction: If your dehydrator has a fan, make sure it’s pushing air toward the vent so moisture has a path out. Monitor humidity: A cheap hygrometer inside the fridge will tell you whether the humidity is really dropping. Insulation vs. venting balance: Since wine fridges are well insulated, they’ll hold heat nicely, but you still need that slight “leak” so moisture doesn’t just cycle around. 

Drying Settings by Filament 

PLA Temp: 40–45 °C (104–113 °F) Time: 4–6 hours Notes: PLA softens around 55–60 °C, so don’t go hotter or you’ll get brittle or warped filament. PETG Temp: 60–65 °C (140–150 °F) Time: 4–6 hours Notes: PETG is very hygroscopic — dries well at this range without softening. ABS Temp: 65–70 °C (150–160 °F) Time: 2–4 hours Notes: ABS doesn’t absorb as much water, but still benefits from drying for consistent extrusion. TPU (flexible) Temp: 45–55 °C (113–130 °F) Time: 6–8 hours Notes: Very sensitive to heat — keep it cooler and give it more time. Nylon (PA6, PA12, blends) Temp: 70–80 °C (160–175 °F) Time: 8–12 hours Notes: Nylon is extremely hygroscopic. Needs longer drying, sometimes best stored in a dry box with desiccant afterward. Polycarbonate (PC) Temp: 80–90 °C (175–195 °F) Time: 6–8 hours Notes: Tough material — can handle higher heat. Needs thorough drying for best layer adhesion. 

so just use a small  fan to vent the air so you will evacuate the air along with the moisture.

i hope that answers your question  

RE: filament dryer

Fillamentum doesn't agrees with those drying temperatures fpr TPU. They recommend 80C for their TPU92 and as much as 100C  for TPU98. According to them, drying these filaments at 50C is useless, even worse than no drying them at all.

https://fillamentum.com/wp-content/uploads/2023/10/Recommendation-for-filament-processing_drying_EN_12102023.pdf

I tested drying TPU95 in my Sunlu E2 at 80C for two hours and I saw no ill effects afterwards ( i.e. the strands didn't deform or stick together ).