I have a question about mastering a homemade external axis with a KUKA motor.
Robot type: KR150 L150
Software Version: KR C V4.1.6 SP 3
Control cabinet: KR C2
Our goal is to mathematically couple the external axis and the robot. We've built a 1-axis positioner external axis. We took a motor for an A2 axis off of a KR150 L 150 and are using it for the motor of the external and then built our own mechanics around it (photo attached). For mastering, we have not installed any mechanical zero or consistent home position: we simply go under Setup > Master > Dial > External Axis 1 > *move the external axis a little in the negative direction* > softkey "Master". So, every time that we master the external axis, it has a different home position then it had the last time it was mastered.
I think it's because of this process that we're getting a huge error (around 700 mm) every time we try to do a Root Point calibration. To bypass this, we've just been calibrating with "Root Point (numeric)" by placing the TCP of a calibrated reference tool at the Root Frame of the external axis and displaying TCP position with the $POS_ACT variable, but I've read that that's not very accurate. Our programs are not running per the simulation supplied by offline programming (Rhino and KUKA|prc), and I think it's because we're not mastering the external correctly.
So, I'm wondering what to do next on creating a home position for the external. Since it's an A2 motor, does that mean the home position can't just be anywhere (i.e., does it have to be the same as the home position of the robot A2 axis relative to the motor)? Since, it's a KUKA motor, is it better to remove a mastering gauge cartridge from a stock robot and then install that onto our external axis, so that it can be mastered with an EMT tool?
Please let me know thoughts, thank you.