KRC2 will not master all of the sudden

[jschmidt]

Hello:

Im working with a KRC2 and trying to master it with an EMT. I've mastered it multiple times before with not much issue, but it won't master today.

Besides switching out the cable/emt (I've tried 3 different sets) do you know of other reasons why mastering would stop working all of the sudden?

I was thinking that maybe I'm plugging the cable into the X32 port on the KUKA wrong - because the cable can easily be removed and doesn't appear to be locking in - but the green lights on the EMT tool flash on when it's plugged in so I dont think thats the problem.

Any suggestions are appreciated - thank you!

[Johannes @ Robots in Architecture]

Hello,

Hmm.. That is strange - as you have mastered the robot before, I guess that the notches are properly aligned. Have you tried it with more axes, just to check that there is not e.g. something stuck with a single axis?
If you have made a backup of the robot before, I would load that, just to make sure that it's not a software issue. With KRC4 you could simply load an old project, but that doesn't exist for KRC2.
I'm pretty sure that the connection on the KUKA did lock, have you looked into the plug if any pins are bent?

Best,
Johannes

[jschmidt]

Hello:

Thanks for your reply.
I tried to move on to the 2nd axis to see if it was just the 1st that was wrong, but I got a message that said something like "incorrect mastering sequence" indicating that I couldnt do axis 2 before axis 1. Do you know if theres a way to override that?

yes I did look if the prongs were bent and they didn't appear to be. However the prongs on the connecting port on the robot are really old, so Im worrying if maybe there's a problem with those.

also, to be clear: the lights on the EMT are on and responding correctly, but when I click "axis 1 > master > start key" the robot moves like it's mastering, and then I watch the prong from the EMT tool go into the divet on the robot that it's supposed to line up with, and then move past it. Then the HMI has a message that  says "EMT mastering distances exceeded". Basically it looks like the EMT isn't sensing where the point on the robot is that it's supposed to line up with.

[Johannes @ Robots in Architecture]

Hello,

You can simply "fake-master" it by choosing the other calibration option. However I cannot quite remember its English name at the moment, in German it's (Mess)Uhr. But it's the option next to EMD/EMT and assumes that you screw on a dial gauge to manually find the deepest notch.
I've actually been OK by calibrating it "manually", simply by pushing with some piece of metal aligning edge and notch by sight - where possible - and where it is hidden by having someone else move the robot while you feel for the notch. Of course that's not ideal, but it gets the robot moving again if you do not need the highest accuracy.

Best,
Johannes

[jschmidt]

thanks for your reply! I ended up employing the time old tradition of turning it off and turning it back on, and then it mastered right away...

also, if I could tack on another question, to ensure that the robot is still mastered every time I turn it on, I go to setup > master > EMT > standard > set mastering, and then see if it prompts me to master the axises instead of saying "no axises to master" (meaning that mastering saved from the last time.
However, it ALWAYS prompts me to master all of the axises again instead of saying "no axises to master". So, I have to master the robot upon every start up. By doing the checking process of that I just described, am I unintentionally reseting the mastering?

I know there is a set process to actually check the mastering, but it seems so much easier to just hit "set mastering" and see if it prompts me to master or not. However, I will obviously switch to the cited "check mastering" process if my way is causing the mastering to constantly reset.

[Johannes @ Robots in Architecture]

The ancient solution to at least 25% of all problems ;)
An unmastered robot cannot move in Cartesian mode, so you do not have to worry about that. If the robot loses its calibration (e.g. if it is mishandled while shut down, and the axis position from before the shutdown do not match up with the current position) you will get an error message.
However it is strange that it forces you to master all axes, I believe that I always had to manually unmaster an axis, if I wanted to master an axis that the robot considered to be correctly mastered.
If your robot is always unmastered after you power it on for the first time, there is probably an issue with your RDW.

Best,
Johannes

[jschmidt]

all good information. Thank you! I will look into the RDW.

[jschmidt]

Update on this issue: the two 12 volt batteries in the robot controller were not fully charged and therefore not saving mastering data like they are supposed to. We replaced the batteries with two new ones that combined to output 24 volts and the robot has not lost mastering during power down / power up since.