The last release of STL files was in October of 2018, and I have made many tweaks since then to improve the function of FED. I have just uploaded a new set of STL files. These parts result in better dispensing, better aesthetics, and they solve some unexpected problems (like mice stealing SD cards!)
These include tweaks to all of the parts, which I'll quickly review here:
1. Wall Mounts. The front now includes corner insets to hold 8mm magnets for wall mounting. This allows FED3 to be mounted externally on a cage or wall, or be placed inside of it:
Here are 8 FEDs mounted on plastic boxes in my lab. Wall mounting keeps the FEDs cleaner but it requires dedicated space to run them.
2. Option for a metal pellet well. I included 2 variants of the front file, one (above) that is printed in one piece, as before, and another (in the STL pack) that has the "nose" removed. This is so the nose can be printed as a separate part in metal to stop mice from chewing on it (I've been doing this commercially through Shapeways at $15 each for the metal part). Here it is in brass (nose-piece STL is in the files area too):
3. SD card door. The housing now has a sliding door for covering the SD card and USB port (take that, curious mice!)
It has a nice "click" to it too, see here.
4. Larger diameter pellet disk. The diameter of the pellet disk was increased by 2mm to reduce the chance of pellets getting in between the disk and the wall of the pellet hopper, creating a jam. During assembly, it is important to "center" the disk so it rotates freely.
5. More reliable hopper. Four significant changes were made to the hopper itself. First, the pellet "foot" was decreased in size to just cover the dispensing hole. I found this reduced pellet "grinding". (Fun fact, this was like this in the FED1 design!)
Second, I removed the inner "ring" inside the pellet disk. This was designed to stop pellets from becoming jammed between the pellet disk and the wall of the pellet hopper, but it ended up creating a new place where pellets could become jammed if the hopper was not seated perfectly. With the wider diameter pellet disk this is no longer necessary. New (left) vs. old (right):
Third, I added "feet" to secure the orientation of the hopper correctly. When screwing the hopper on, the feet should align like this:
Fourth, I reduced the height of the hopper by ~1cm, which will allow FED to fit in even more caging (we had some caging that the old design was just barely too tall to fit in with the lid comfortably closed. In terms of capacity, the hopper previously fit ~2000 pellets, and now holds ~1500. This is an estimated drop from ~13 to ~10 days of dispensing, which I think is worth it for the decrease in height. FED3 needs to be checked more often than that anyway so it's sort of a moot point.
Old (left) vs new (right):
6. Tessellated lid text! (Update 11-16-19 - while awesome looking, I found that this tessellated text design wasn't ideal as it got dirty really easily and was hard to clean inside the text, I've removed the text in the most recent version in the files area).
7. Tweaked back cover. Very minor tweaks to improve how it slides, and update the label to FED3 version 1.1!
If you made it this far here are photos of completed FED3 with the new parts: