Robot positions do not change, unless someone or an instruction changes them.
If a robot goes to a different location other than programmed, this would be very dangerous.
Therefore, the robot checks throughout it's path where it is in relation to the processed path and target.
If there is deviation, the robot should stop and produce an error, from what you are describing then mechanically the robot appears in a different location.
This suggests the feedback of the motors is still functioning correctly and tracking therefore the robot is not producing errors.
Slow the robot down through the cycle, does this reduce the shift amount, if it does, then check the following:
- Backlash in gearbox(es) - Check this in T1, energise motors, zero speed and have someone push/pull on joint to check if there is motion.
- You mentioned remastering due to 'slipping', this suggests possible motor shaft wear/belt wear/pulley wear, requires investigation for integrity.
- Check Tooling mounting bolts, alignment.
- Check Robot mounting bolts.
- Check pedestal mounting bolts.
- Check target peripherals are secured and are not moving.
- If you are re-teaching and find those positions are not staying the same, check the program is not loading default positions.
- Often a programmer will use master locations and re-prime these at some point, reversing any change an operator does with touchups.
What you are describing suggest overall, this is mechanical in nature and will only get worse, but remastering inaccurately can cause deviation over long distances too.