Prusa I3 Hephestos improved Z axis brackets re-edited

An improved version of upper Z-axis bracket for Prusa I3 Hephestos.
Using ball bearing reduce swings of Z-axis jackscrew and improve printing precision.
I have changed the size of the original ball bearing of "Prusa I3 Hephestos improved Z axis brackets" created by "Boeing787" and I have improved the precision of the measures by checking the measures of the "Prusa i3 Hephestos".


Mejora del soporte superior del eje-Z para "Prusa i3 Hephestos". Se ha añadido un rodamiento de bolas para red