350W 4-spool rectangular filament dryer.

I wanted to buy a good filament dryer.
Unfortunately, at this moment (02.2024), nothing seems to be harder to buy in Europe than 3D printing accessories.
The Sunlu shop is sold out on most everything since december, while their products are offered on other platforms for high prices.

OK, here is my answer. A 4-spool filament dryer made from an 350W Ambiano Food Dehydrator, that is about 30€. Ambiano is afaik a trade brand of Aldi.
When I bought it, I did not have filament drying in mind, so it has not an ideal base shape.

The design consists of three parts: two cover parts (nearly identical, except that one part has a tongue to match into the other cover) and an inlay part, that has to be printed twice. You need some supports beneath the tongue of TrocknerRahmen2.stl

I am not very experienced with spool sizes. So let me have that very clear: This design will fit 4 Bambulab reusable spools.
It may, or may not fit other manufacturers spools. I included the OpenSCAD files for remix (You could also include a cutout for a hygrometer).
It took about 1000g PETG filament and about 25hours to print on my P1S.

With target 40°C, I measure 41°C-42°C inside the chamber at the bottom. I measure 34% humidity and 32°C on top of the chamber after a while.
Be aware: When you set this kind of dehydrator to i.e. 40°C, they do not put out 40°C. They give a pulse of air at their maximum temperature for a very short time.
The higher the target temperature you choose, the longer the output of air at maximum temperature will last. Over all, your chamber will go to the target temperature (more or less)
At the moment, I do not know, what this means to the spools in direct air flow. I am just testing. Please do not hold me responsible for any unwanted results. 
May be, that I will redesign the inlay, to hold only three spools, where none of them is in direct air flow (this is possible). 
Let me know, what you think.