Drying desiccant  

RE: Drying desiccant

I got this one:
https://www.amazon.com/gp/product/B008H2OEKK

I did a video on the modifications here:

What I like about it is the ability to modify the temperature and also set the time (some of them just have a timer.)

It also collapses down pretty small for storage (once you figure out how to stack the trays. I don't know how it compares to others, but it's fairly loud.

RE: Drying desiccant

Height: Make sure the height when all the trays are used will accommodate your widest reel.  Some have a small raised center section in the bottom and a hand grip in the lid that take up usable  vertical height.

Temp Control: Temp control is a must in order to accommodate various types of material.  Be sure the temp range covers all the materials you plan to use.

Timer:  A timer is nice but no a necessity.

Heat Element: Not critical, but some of the lower cost units use a light bulb vs an actual heating element.

Grids: If possible try to keep one small opening grid intact to use for drying desiccant.

RE: Drying desiccant

I also purchased 2 kg of loose silica gel with indicator color and distributed it in my filament containers. But loose silica gel is a mess, these small balls roll everywhere... particularly when trying to dry the stuff.

Drying takes around 130 °C, so I am not sure if a filament dryer or nylon bag works.

https://www.giebel-adsorber.de/images/unternehmen/neue-produkte/GIEBEL_Regeneration%20of%20silica%20gel_EN.pdf

I went to a drapery store, bought the thinnest cotton fabric I could get and made flat pouches the size of the printer bed. The first idea was to put them on the printer heat plate for drying, but this did not work. So I put them in the oven at 130°C for drying.

I wouldn't buy silica gel with indicator color again - according to Wikipedia, the indicators are all more or less toxic and they are of little use anyway. The level where it changes color is much higher than what PETG would tolerate, so you need a humidity meter and change according to the humidity reading. Silica gel without indicator also tolerates much higher temperatures, so you don't have to worry "burning" the indicator by too high temperatures.

RE: Drying desiccant

All,

I pulled the trigger and received this one today:

https://www.amazon.com/gp/product/B07J5G6T6Q/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1

It has the added advantage that it's digital, fairly accurate and I got a really dry 500gm spool of PETG in 3 hours.  It seems to be able to hold 3 (1kg spools), at a time as well.  And the flour strainer for desiccant.

YMMV

RAH

RE: Drying desiccant

Additionally,

I went with a larger square dehydrator with shelves.  For the following reasons:

1) No modification necessary though a little more costly, ($90 vs $70).  So I could return it should it not work out.

2) Shelves are removable so I didn't have to void any warranty.

3) Round spools in larger square space leaves room for desiccant bags and extra airflow.

Thankfully my spool of eSun PETG, that started printing fine and went to MUSH in under a week in the open on the printer, came back to life in about 3 hours.  So I guess I'm keeping it.

I plan on using dry boxes for filament storage.  I was in the midst of printing the desiccant boxes when it all went to mush.

RAH

P.S. I am thinking of rejuvenating my open spools like this all the time.  Especially in the muggy wet summer we are having.

RE: Drying desiccant

(I'm replying to a couple messages here...)

@big-bird

I like the round flour strainers as a desiccant drying holder.  I would only fill them to about one layer deep to dry out desiccant.  They would dry so much faster.

Another batch of silica drying using the flour sifter I dried even more silica gel and having a depth of a couple centimeters. The depth didn't seem to affect drying time, probably enough warm air was able to blow up through the mesh of the sifter and up through the gaps between silica beads. Dried out in a few hours.

I pulled the trigger and received this one today:

https://www.amazon.com/gp/product/B07J5G6T6Q/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1

Nice looking dehydrator. I kinda wish I had gone that route instead of the ElCheapo brand round dehydrator for only about $30 less. Not that mine doesn't work, I just still don't trust it's thermostat and yours looks better. 😉

@martin-m25

Drying takes around 130 °C, so I am not sure if a filament dryer or nylon bag works.

I'm only drying my silica at about 65°C, not sure where you got 130°C from. Maybe you meant 130°F (which is 54.4°C)?

RE: Drying desiccant

Posted by: Sembazuru

I'm only drying my silica at about 65°C, not sure where you got 130°C from. Maybe you meant 130°F (which is 54.4°C)?

Sorry, I missed that the original question was about drying silica gel in a food dehydrator.

This does not work. Drying silica gel requires about 130 °C (not °F). Giebel has an excellent blog page about it, https://blog.giebel-adsorber.de/trockenmittel/ unfortunately german only, you might want to fire up google translate or so. It's also on Wikipedia.

Have a look at the graph on page two in this document: https://blog.giebel-adsorber.de/wp-content/uploads/2019/05/Silicagel_Grundlagen-Regeneration-von-Silicagel_DE.pdf

It shows the equilibrium loading of silica gel vs. temperature. You can see that with 65 °C, you get from 0.37 down to maybe 0.35, while at 130 °C you get to 0.01. So drying at 65°C has nearly no effect.

This document https://blog.giebel-adsorber.de/wp-content/uploads/2019/05/Silicagel_Regeneration-von-Silicagel_DE.pdf (german also, but lots of pictures) describes how to dry silica gel in a household oven.

RE: Drying desiccant

Posted by: RAHRAH

[...] My question is which dehydrator would you recommend? Or at least which features are important for a dehydrator?

I'm quite pleased with the PrintDry I was gifted last Christmas, but if I were doing it over again, I'd opt for the Gourmia GFD1650 style linked earlier in this thread. I had looked at those online but had no real sense for the interior dimensions. Having a timer would be very welcome. Noise is a factor, but may be hard to compare.

RE: Drying desiccant

Posted by: bobstro

Posted by: RAHRAH

[...] My question is which dehydrator would you recommend? Or at least which features are important for a dehydrator?

I'm quite pleased with the PrintDry I was gifted last Christmas, but if I were doing it over again, I'd opt for the Gourmia GFD1650 style linked earlier in this thread. I had looked at those online but had no real sense for the interior dimensions. Having a timer would be very welcome. Noise is a factor, but may be hard to compare.

Bob,

It's quieter than the Prusa i3 MK3s .  It has a fairly quiet fan and real heating element.  Air in from back and out the top.  Fits 3 spools nicely and has already dried several open spools.  Room for desiccant.  See picture.

Robin

RE: Drying desiccant

Looks like it would be easier to integrate into a cabinet as well. Ah well.

Thanks for the info.

RE: Drying desiccant

Bob/All,

Even better news.  I put a 4th spool in front vertically.  😉  If ever you need to replace yours...

According to MatterHackers and the PrintDry Literature silica should dry well in about 3+ hours at 65C/149F.  this dehydrator can do that easily.  I have seen instructions for putting desiccant in the oven but don't have the temp/time handy.

I attached Matter Hackers chart for reference.