I have a problem which is the same as you. I call KUKA service and tell them what happened. And then KUKA replace a mastering pin which solve the problem! Hope it's helpful!
Sorry, there is some thing I forget to tell you. After replacing the mastering pin, the robot can not calibrate tool correctly when the position have changed substantially. So please demount mastering pin carefully!
mastering cartridge can be ordered and replaced, it is not expensive either... you can lookup part numbers on Parts And Docs DVD or just talk to Kuka.
Another question regarding changing mastering pin:
I have a leak coming out of my 6th axis mastering pin on a KR150L130 (2004). I'm wondering what precautions/measures should be taken to get mastering pin back into same position?
The leak is very minor but annoying. Mostly because flies seem to love the smell of the oil :(. Is it something I should live with or is this an easy fix? I just have fears that the mastering is going to be thrown way off...
