Prusa Mini Adjustable Y-Rails

The center distance between the Y-Axis Rails should be 120mm.

I measured the STL-Files from Prusa (R7), they are 120.53mm in distance.

So there's the Problem:

If you lay down your Y-Carriage on the bushings and fasten it to the left side (marked in red) with the bearing clips, maybe you can see a little gap on the right side, between the bushing and the Y-Carriage (marked in green). 

This Gap should not be present, if your Rails aligned correctly to 120mm center to center distance.

The problem will also mean that when you slide your bed back and forth, the force required will be higher in the rear and front areas than in the center of the rails, because the rails tend to bent.

Another problem is that this will skew the print bed, and many people tend to print models to compensate for the squareness between the print bed and the Z axis.

I decided to fix this with an adjustable Y-Axis 

What you need:

• 4x M3 Nut
• 4x M3x16 (can also be 20mm long)