Giova's Extruder

The goal of this project, started in Spring 2015, was to create a cheap and lightweight extruder, the first choose was "24BYJ48", substituted with "28BYJ-48" (Fig.1) because stronger, cheaper and easy to find.
This stepper motor is unipolar and it needs to be modified to become bipolar, there are 2 methods: the first method consists by unmounting the case (Fig.2). the second consists, in a faster and less invasive method, by cutting the plastic case and PCB, i suggest this method (Fig.3).

You need:
x2 - 28BYJ-48
x2 - 40mm fans
x4 - M3 screws + nuts
x4 - M4 30mm screws + nuts
x5 - M4 20mm screws + nuts
x2 - MK8 drive gear for 1,75 mm filament
x2 - 605 2RS 5X14X5 bearings
x? - M4 washers
The connection to RAMP 1.4 must be modified (Fig.4), the connector of second extruder is inverted connected

Assembly: (Fig.5)
(Tolerance is always 0,5mm excluding Hot-Ends connectors)
Idlers are different and they are marked with L or R letters visible in the model, the washer is use