bigger columns, center holes of screw, although I haven´t modified the x-carriage I have added it to make everything easily only for coherence holes.
Based on Mk8 Extruder mount for Prusa i3 Rework by inornate - on http://www.thingiverse.com/thing:835475,
Thins is most hard, and the support has robust hole for inductive sensor:
NEMA 17 stepper motor is a stepper motor with a 1.7 x 1.7 inch (43.2 x 43.2 mm) faceplate.
Inductive Sensor 18mm ( DC 6-36V NPN NC 5mm Inductive Proximity Sensor Detection Switch LJ18A3-5-Z/AX ) like
MK8 Aluminum Extruder Kit With NEMA 17 Stepper Motor 1.75MM For 3D Printer RepRap Prusa i3
I have done enfasis on robust, and add fan support
I have Added a copy of 4 bearing x carriage with high holes, by Joe558, published Jan 20, 2016 on this url, (For make coherence)
I used catia for this design
I have added catial files for do easy modification