Your robot starts leaving parts slightly off, fails on insertion or the program 'no longer lands' where it used to. Before thinking of a serious fault, the most likely thing is that it has lost its reference: it needs mastering and, possibly, axis calibration.
What mastering (robot zero) is
Mastering —or zeroing— defines the reference position of each axis: the position the robot considers its 'zero'. All movements are calculated on that zero. If it's lost, the robot doesn't really know where each axis is and everything it runs ends up offset.
What fine calibration is
Absolute-accuracy calibration goes one step further: it adjusts the robot's mathematical model so that the real coordinates in space match the programmed ones. It's what lets you, for example, exchange programs between robots or work with absolute coordinates accurately.
Symptoms of accuracy loss
- Parts mispositioned or programs systematically 'offset'.
- Insertion failures, welds off-point or minor collisions.
- The problem appears after a specific event: battery change, crash, motor/encoder replacement.
Common causes
- Battery loss and loss of position counters.
- Collision that shifts the mechanical reference.
- Replacement of a motor, encoder or gearbox on an axis.
- Mechanical wear accumulated on high-hour robots.
How exactness is recovered
Each manufacturer has its procedure and tools: fine calibration on ABB, mastering with EMD on KUKA and mastering on FANUC. The technician returns each axis to its reference position and, if needed, redoes the precision calibration. Doing it well is what gives the robot back its repeatability and accuracy.
It's a common intervention within ABB, KUKA and FANUC maintenance, especially after a component change or a collision.
Frequently asked questions
What is mastering?
The zeroing of each axis, the reference position on which all movements are calculated.
Why does it suddenly lose accuracy?
Battery loss, collision, motor/encoder/gearbox change or wear. After those events the mastering must be redone.
Are mastering and calibration the same?
No: mastering sets the zero; fine calibration adjusts the model so real coordinates match the programmed ones.