When i was a child i did love playing (and reading) "YPS mit Gimmick". One of the things i still remember, is the Gimmick "Die Maschine die eckige Eier macht", as it was one of the things that did work great and impressed me. First i did try to create the machine as a straight 1:1 copy, but this did not work very well. So i did a complete new design just using the same mechanics.

I uploaded one chassis with added text "EggCuber" and one without.
If you like you can add some mirrored text to the ground plate to have it on the egg afterward :-)

Only hard boiled egg should be used. Let them cool down a little bit to not deform the PLA, because of the heat, and then put it in the fridge for around 1 hour. Enjoy your cubic egg :-) 

This is a redesigned version of my old model which is available on Thingiverse