To drive the shredder i used the gearbox i mentionned above. Project can be found here: https://hackaday.io/project/173854-3d-printed-high-torque-servogearbox-version-2
The gearbox was powered by a 3S 2200mah LIPO battery with the help of the Universal Motion Controller i made (project: https://hackaday.io/project/170604-umc-universal-motion-controller). It's possible to run the gearbox on a 6S LIPO but this would destroy the gears almost immediately in this application.
The components listed are the ones only for the shredder. The components for the gearbox can be found on the project page of the gearbox: https://hackaday.io/project/173854-3d-printed-high-torque-servogearbox-version-2
For the dimensions of the 2 shafts see the drawing that's located in the files section on this page.
It's recommended to use at least 25 percent infill for the structural parts. Use up to 5 outer perimeters and layer heights of at least 0.2mm (when printing with a 0.4mm nozzle). top and bottom layers should be around 1mm.
Video can be found here: