I'm am new to the robot world so if I say something naive please forgive me.
I have an used Fanuc R2000iB 100P with a R-30iA controller. I have been working through some different issues and have found some useful info already on this forum. Currently I am trying to understand how the relationship between J2 and J3 works. I mastered and calibrated the system but when I jog J2, J3 moves as well but the position screen does not update the position of J3, only J2 updates. How does the robot know where J3 is ? As I jog the robot around I am setting both physical and software limits to the axis. I found that there is a magical number of -79 degrees for the combined values of J2 & J3. This doesn't allow me to move the head of the robot close to the base. Also I found that to transport the robot you need to move the J2 axis up to its max of -120 degrees and it shows the J3 axis down as far as it can go, which should be a large - degree but the table associated with the diagram says +41 degrees (J2+J3 = -79 degrees). What am I missing, do you master J3 to offset by 180 degrees ? If anyone can enlighten me on this J2 + J3 relationship I would greatly appreciate it.