When you save a job to external memory the values of those global position variables that are used in that job get stored in the .jbi file. But the values are whatever they are at the time on saving (not from when you last ran that job). So the values in the job backup file may have nothing to do with that specific job.
Use global variables wherever you want. Just keep in mind that when using the same variables in different jobs (which is totaly ok) you need to think of them as something not permanent. So before each time you use the variable in a job something should define it's value (SET instruction, touch sence etc).
BTW when you load a backup job from external memory the position variable values in the controller will be overwritten with whatever values the backup file has, so be careful when you load a backup. Choose a time when it's ok to overwrite position variable values.
Since we are a high mix low volume facility, we have more programs than the teach pendant can retain. To work around this we move programs onto USBs back and forth from the pendant whenever required.
Sometimes when we transfer the program back into the pendant from the USB, the positioner/skyhook positional values associated with the weld lines only become affected. For example the original set point may be…