Update 2019-05-04: Thanks to IsmaelPR1 for confirming that the "Commercial Chef CCD100W6" is the same as what was being sold as "Westinghouse WFD100W" when I bought it.
Many comments on a dominant e-tailer's site suggested this was a good food dehydrator to use for drying filament, but most also pointed out that you had to cut apart the racks, preventing its intended use for drying food, and Westinghouse doesn't seem to sell spare racks.
These extensions fit between existing racks to separate the racks enough to fit a filament spool in-between. NOTE that this is ONLY for the model WFD100W ... if you have the "101" model, see @mgg4's remix instead!
The 73mm high extension -- along with the height of the rack you put it on -- allows the widest spool I have (Taulman Bridge... just over 80mm) to fit with a filament clip still attached to the side. If you print just one set, this would probably be the most useful. This one is white in the photos.
If you have a big printer and don't need it in such small pieces, see the remixes from @alanerickson (2-3 parts) and @andreq (1 part).
I printed the 88mm extension set (yellow in the photos) before noting that I would get extra vertical space from the tray onto which I place the extensions.
The 28mm version was just to test fit; I never printed a full set. I think it would accommodate spools about 35mm thick, roughly 1-3/8" --- I've never seen any that skinny. I included it only because I had the file already, Maybe it would be useful if you print the 73mm version and find you really need just a bit more after all?
N.B., I don't think the "version 2" clips are really sturdy enough. Honestly, I keep using the set I taped together most often.
Version 2? (2019-06-25): One thing I've not been happy with is the flop and wobble at the top end, especially if/as the snap pins start to loosen a little over time. The v2segment88mm.stl file has a couple of square holes near each outer edge near the top and the v2clip.stl holds them together. The photos with purple filament show this version. Not sure how useful this is, but it made me happy :-) Let me know if you need a different height or the rather disorganized FreeCAD file.
Edit 2018-10-22: My wife has commandeered the dehydrator for the past few days to dry "hen-of-the-woods" mushrooms that grow wild around here. The pieces are too tall for the usual trays, so she's using these extensions. That 28mm version I never printed would have been perfect.
Support on BUILD PLATE ONLY. You do need to support the curved wall, but you do not want to clog up the pin holes. If you're printing the pin pegs separately (or your slicer supports it), they probably don't really need support. June 26 '19: I forgot to turn on supports and was printing at 0.35mm. Had some cleanup to do under the unsupported curved wall, but it held together!.
Print six (6) of the extension pieces and at least six (6) of the pin pegs. I went with 8 pin pegs to have spares. On one run I lost one in the mess of my "office;" on the other, one came unstuck from the bed about halfway through. (Fortunately, I saw it and was able to remove it and the air-print string of its remaining layers before damage was done to the rest.)
Because PLA will soften at drying temperatures, you should probably stick with ABS/ASA; PETG should be okay, too. The square "feet" that hold the pin holes seem to be adequate to help prevent ABS warping without a brim, but I did print them in an enclosure (the white ones).
Assemble the six pieces in a circle with one peg in-between each adjacent pair. (In the holes; push together firmly.) Version 2: insert the clips into square holes near the top. I disliked the hot air sneaking out the sides, so I sealed them with that aluminum tape used for HVAC ducts. This also made the rack above fit more securely.
Place at least one rack below and one rack above the extension ring (with aluminum tape holding the sides together, I could use just the lid). No need to modify the racks.
Update 2018-10-20: If you print it in ABS, you might want to do what NielsJL did and glue the parts together with ABS+Acetone. See his build: https://www.thingiverse.com/make:552342
If you would like a size I didn't include, my apologies that the FreeCAD file is not very well organized. Expand the tree from MainArc-ExportWithPinHoleBlocks > Fusion002 > MainShape > Fusion > UpperArc-Controls Height > Cylinder
This Cylinder controls the total height... presently it's 78mm high and 10mm up which gives the 88mm total height of the largest version I needed. If you need is smaller, reduce the height; larger, increase it and also increase the height of the Cylinder001 next to it that cuts it out.
You will also want to adjust the z position of the upper_pin and upper_pin_support inside Fusion002 by the same amount you change the height of the cylinder.
Make sure select all three of the "MainArc-ExportWithPinHoleBlocks" along with the "PinHoleBlock" and "PinHoleBlock001" when exporting your STL.
Emmett's Parametric Pins
I'd just made a few of Emmett's heart gears for Valentine's Day (https://www.thingiverse.com/thing:243278), so it seemed natural to use those pegs to hold the segments together.
I also checked with Emmett who agreed it would be easier to just include the file I used, so recognizing that it's not my OpenSCAD program, that tweaked file is here too (pin2-10x5.scad). Thanks again, Emmet!
If you'd rather start with his original pin2.scad, the parameters I changed are
To make my life a little easier in combining the elements in FreeCAD, I added a translate and rotate to the pin hole, inserting a translate and rotate into line 24 of his .scad as follows:
You need to set object=0 to generate the pin peg, export that STL, and then set object=1 to generate the solid for the hole which then is subtracted as Boolean cut (for example) from some other object.