A while ago I purchased a EHEIM Twin Fish Feeder to tend to my hungry fishes while I am away for extended period of time.
This automatic fish feeder is different from most other automatic feeders on the market, because it utilizes augers to propel food forward into the tank, as opposed to a rotating drum mechanism that most fish feeders use.
In theory the auger should allow for better control of food proportioning than a rotating drum. However in practice I encountered problems with the auger jamming.
I find that the auger works great with larger grain size pallet and flake food. However for micro pallets (even worse yet, ground pallets), the auger is rendered almost inoperable due to jamming and power requirement.
Several variations of the auger designs were 3D printed and tested, with different pitch, shape, and, tolerances; but none could handle the super fine ground pallets with the existing motor. Eventually I resorted to an entirely different approach - instead of having an open spring like auger, I made the auger inside of a rotating drum.
The entire auger and drum assembly rotate together, therefore there is no grain size clearance issue to begin with. This design combines the simplicity of a rotating drum feeder and the accuracy and consistency of an auger feeder.
Below is a video of the improved feeder in action dispensing very small amount of very fine grain pallets consistently.
The 3D printed auger can be purchased here.
The design files are available upon request.