Need help with the electronics and Hot end

Hello, im a student mechanical engineering and I am making a 3d printer out off knex like this, [imgur.com]
Now i need help with controlling the motors and which hot end do i need to use?

Whatever you like. All electronics have the same basic feature set, can all drive the same extruders and all extruders/hotends are compatible with all electronics. Also, you likely want not only a hotend (which is where the filament is melted), but a whole extruder (which also has some mechanism to feed that filament into the hotend). Not every hotend fits into every extruder, they can differ in their way of mounting.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Okay i have now read some things, but i cant decide witch extruder i need. What are points to pay attention too? Im not that rich

Are you going to use a heated bed? If not, then PLA is really you only option (and the only thing I print with). As for the hotend: [forums.reprap.org]