Answered Robo R1 - Z not moving up during print

Sounds like the Z axis steps/mm is off. This can happen if you accidentally load the wrong firmware.
The Z steps are wildly different on the various flavors of Robo 'R1' style machines. The Beta and R1 are both different and so is the R1+

What Z steps did you use and which machine specifically do you have?

 

So this line is the key one:

#define DEFAULT_AXIS_STEPS_PER_UNIT {80,80,800,723.38} // default steps per unit for RoBo 3D R1+ (leadscrews)
#define DEFAULT_AXIS_STEPS_PER_UNIT {80,80,2560,723.38} // default steps per unit for RoBo 3D R1 (8mm threaded rods)
#define DEFAULT_AXIS_STEPS_PER_UNIT {80,80,2267.72,723.38} // default steps per unit for RoBo 3D R1 beta (5/16 inch threaded rods)

 

If you have an R1+ then that is correct.

Maybe your stepper driver is getting weak. The R1+ has two actually (one for each Z rod -- which is not normal for this style printer) but regardless if one of them is not working as it should the attached stepper could drop steps and that will make it not get high enough for the next layer.

 

I mean there is always the possibility that a stepper itself is going, but they are pretty sturdy

If you have not calibrated the extruder you might want to give that a go. If it is over extruding that can give you issues where too much plastic is put down and your extruder will crash into it next layer. ..

 

I don't normally look at that as a first step since the default numbers Robo used in their firmware tends towards under (not over) extrusion.