Oh, I forgot about that. My printer is a BQ Hephestos 2, which is a Prusa based printer. The firmware is updated.
The X and Y axis move the print table from the step motors transmitted by rubber belts and the Z axis has 2 step motors that move each a long screw that makes the the extruder go up and down. (I guess this is standard in a prusa printer)
This printer specifically has autocalibration, where a magnetic sensor detects the distance of the extruder to the glass (not heated) bed, which has beneath the glass a metal sheet, so the sensor can know the distance and thus autocalibrate the bed slope.
I love this printer that makes very high quality looking objects BUT when having to make parts to fit, like now with that part I've told above, it's pretty bad. Everytime I download such kind of object from thingiverse I have to adapt it or things wont fit usually for being to tight.
Thanks again for your help, I appreciate it.