I’ve occasionally seen posts and videos about how to dry 3D printing filament using a food dehydrator, but never felt the need for one… until recently. I had a failed print that looked like wet filament was to blame, so I decided it was time to make my filament dryer. This post is about my experience – mostly good – with that dryer.
Disclaimer
This post is about my experience. Yours may be different. In particular, don’t blame me if you melt a reel of filament – it’s easy to accidentally do that. And be sure to follow all the safety information that comes with your dehydrator.
How I Made My Filament Dryer
Let’s get right to it:
- I bought a Rosewill Countertop Portable Electric Machine Food Fruit Dehydrator from Amazon for about $45 USD. I chose that one because Angus at Maker’s Muse had linked to it in his video on drying filament, it was large enough for a reel of filament, and had the temperature marked in Fahrenheit and Celsius.
- I used a pair of flush cutters (any cutters or scissors will likely work) to cut a large, circular hole out of each (but one) of the dehydrator’s drying trays to make room for a spool of filament. NOTE: I left one tray un-cut, to use at the bottom of the dehydrator.
- I checked the stability of the dehydrator’s thermostat by watching the temperature for a few minutes with a meat thermometer. It’s probably not the best monitor, but it covered the right range: 40° C to 150° C.
- Based on several recommendations I’d found, I dehydrated my wet PLA at 50° C for about 8 hours, depending on how bad the filament was. I’ve read you shouldn’t heat PLA higher than about 55° C, or it will melt into an unusable blob on the reel.
- Once my filament is dry, I store it in a watertight storage bin, with desiccant. I’ve described my filament storage in detail in another post.
![Cutting the trays. Two rings stay, for support](https://bluepapertech.com/wp-content/uploads/2020/10/20201022_115303wiki.jpg)
![One cut tray](https://bluepapertech.com/wp-content/uploads/2020/10/20201022_115338wiki.jpg)
![The assembled dehydrator, with an un-cut tray on the bottom](https://bluepapertech.com/wp-content/uploads/2020/10/20201022_115151wiki.jpg)
![The temperature control, in Celsius and Fahrenheit](https://bluepapertech.com/wp-content/uploads/2020/10/20201010_142538wiki.jpg)
![Checking the thermostat's accuracy with a meat thermometer](https://bluepapertech.com/wp-content/uploads/2020/10/20201010_192148wiki.jpg)
![My waterproof reel bin, with a box of desiccant](https://bluepapertech.com/wp-content/uploads/2020/10/20201022_121755wiki.jpg)
Drying a Yellow PLA
As part of moving from Fusion 360 to FreeCAD (that’s another story), I found myself doing more printing than I had in a few years, using filament that was several years old. Some of that filament showed signs of being wet.
On two occasions, while I was printing using a yellow PolyLite PLA, the filament snapped off in the extruder, stopping the print and leaving a chunk of filament in the extruder that was hard to remove. The second time the filament snapped convinced me to try drying the reel – because brittle filament is one symptom of wet filament.
By the way, removing the broken filament from the extruder was a bit of a pain: the first time it snapped, I heated the hot end to extrusion temperature while I pulled on the end of the filament with a pair of hemostats (big tweezers). The second snap happened lower in the extruder, so I heated the hot end to extrusion temperature and this time pushed the filament down into the extruder. That didn’t work so well; I had to push it much further down, using a piece of smaller-diameter filament. I imagine I could have used any < 3 mm diameter needle or filament.
![PLA filament snapped off in the extruder](https://bluepapertech.com/wp-content/uploads/2020/10/20201006_151401wiki.jpg)
So I bought the Rosewill food dehydrator, cut reel-sized holes out of all but one of the trays, stuck a meat thermometer into it, and set the dehydrator for 45° C. After a few minutes I saw that the thermometer showed a temperature close to 45° C, and varied only one or two degrees C up or down, proving this dehydrator would suit my needs.
After reading a few posts on filament drying temperatures and times, I set the dehydrator for 50° C, popped the yellow PLA reel in, and left it for about 4 hours. I then stored the filament in my watertight storage bin.
The next day, after the filament had cooled completely, I did a print, with impressive results: not only did the filament not snap (even when I tried bending it), but the print was noticeably smoother. I regret I didn’t take a before and after photo for this reel.
Drying a Silver PLA
Later I tried to print my redesigned Mainspring Clamps Box in a very old silver Village Plastics PLA. That PLA was the oldest I have, and it likely absorbed a lot of moisture from the air before I bought watertight filament storage bins.
The print was a disaster; it was so bad that I sliced and printed it again to see whether I’d told the slicer the wrong filament… and again got a bad print.
![A failed silver PLA print, showing very bad layer adhesion](https://bluepapertech.com/wp-content/uploads/2020/10/20201002_162505wiki.jpg)
I had almost given up hope on this filament, until I found All3DP’s How to Dry Filament: PLA, ABS, & Nylon. That post showed a picture of a failed print made with wet filament, that looked nearly like my print.
After drying this filament at 50° C for 5 hours, I tried the print again. It still failed due to bad layer adhesion, but was promising.
![After 5 hours at 50 C, somewhat better results](https://bluepapertech.com/wp-content/uploads/2020/10/20201014_135500wiki.jpg)
At this point I decided to switch to an actual test print: a Benchy by CreativeTools… and the result was even worse: not much more than a ball of filament stuck to the hot end.
![The first Benchy - worse than the other print](https://bluepapertech.com/wp-content/uploads/2020/10/20201014_143742wiki.jpg)
So I lengthened the drying time: I put the reel in the dehydrator at 50° C for 12 hours and, after it cooled, tried another Benchy. Still no joy.
![After 12 hours at 50° C, still pretty bad](https://bluepapertech.com/wp-content/uploads/2020/10/20201017_171509wiki.jpg)
Since the longer time had improved things a little, I tried a little higher temperature: 52° C for 15 hours. Once it had cooled, I tried the Benchy again, and it was starting to look good…
![After 15 more hours at 52° C, very promising...](https://bluepapertech.com/wp-content/uploads/2020/10/20201021_165300wiki.jpg)
Then, frustratingly, the adhesion failed at the roof of the Benchy, after printing the rest of that test object just fine. Although looking closely, I did see a few slight adhesion problems in the hull and in the square in the back.
![...and yet the Benchy failed at the angled roof](https://bluepapertech.com/wp-content/uploads/2020/10/20201022_114857wiki.jpg)
Since the higher temperature (or lots longer drying?) seemed to help a lot, I decided to be daring and go for 55° C for 15 hours. I worried a bit, because this temperature is only 15° C below the PLA Glass Transition temperature of 70° C: the temperature at which the filament will turn into a solid blob of plastic.
Unfortunately, the higher temperature drying (or something else?) made the next Benchy test worse than before: there was serious delamination in the hull, and a fuzzy deck from poor adhesion. I canceled the print and have given up on the reel.
![Higher heat dehydrating made the prints worse](https://bluepapertech.com/wp-content/uploads/2020/10/20201024_171650wiki.jpg)
On the good side, since the reel was unusable to begin with I haven’t lost anything, and it was interesting to see the print improve with a little drying.
Conclusions
So the dehydrator definitely saved at least one reel, and improved – but didn’t save – another one. Based on my experience and the posts I’ve read, I think I’ve found a useful and inexpensive tool against overly-wet filament.
References
- Maker’s Muse’s Reviving 7yr old filament with a $20 Dehydrator.
- All3DP’s How to Dry Filament: PLA, ABS, & Nylon, which describes why filament absorbs moisture, various ways to address the problem, and gives a good list of temperatures for drying various types of filament.
- 3DInsider’s How to Dry Your PLA Filament, which gives a good list of symptoms of wet filament, and talks about the Glass Transition Temperature of PLA.
- CNC Kitchen’s very thorough Investigating Different Methods of Filament Drying compares several methods of drying filament, and presents lots of experimental data.