Filament Dryer Temp Accuracy Test
My filament dryer is off by ~2°C. (Nice self portrait :) )

A lot has changed in the 15 years since I acquired my first 3D printer (a wooden Ultimaker Original).

In particular, filament drying is now considered standard procedure. And it really does make a huge difference, especially with very hygroscopic filaments like PETG.

But there is a lot of misinformation out there. Or incomplete information. For example: drying time. Drying time is impacted by too many variables for one to claim “this filament needs to dry for that long at that temperature” and have it be accurate. I’ve measured it by putting my filament dryer on a postal scale and writing down the weights over time. If you read online, PETG drying time will be 6-8+ hours. However, for my moderately damp filament:

Time Weight Total Loss
7:40 pm 4426g —
8:10 pm 4394g 32g
10:10 pm 4314g 112g
11:12 pm 4312g 114g

This is obviously a one-off and not terribly well designed, but ~3.5 hours sure ain’t 6-8.

Also, the critical part about drying is temperature. You don’t want to exceed the Tg (the glass transition temperature) of the filament or the spool it is on.

I compiled a list of Tg values and safe drying temperature ranges for a bunch of common (and some not so common) materials: Filament Dryer Temperatures. Also includes some resources for diving into material characteristics.