HEIDENHAIN ND 1300 CNC Setup - Manual (Page 28)

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Max following error
Following errors are the differences between predicted and actual positions and are processed by PID control
terms, amplified and used to drive the axis motors.
Following errors occur naturally during CNC moves as
the machine is instructed to change position. Excessive following errors indicate that the required move is
beyond the capability of the system, or that the system has encountered an obstruction.
All CNC systems should include primary safeguards such as slip-clutches and limit switches to prevent
stage over-travel and collision damage. The maximum following error term is assigned only as an second-
ary safeguard that will halt motion if an obstruction is encountered.
The assignment of a maximum following error value is an empirical process and depends on the physical
system characteristics. Maximum following errors are displayed at the bottom of the CNC Setup screen
during CNC moves. Following errors will be shown in the Max following error field during PID loop
tuning and testing. The Max following error assigned in the Max following error field should be about
twice the maximum shown during test, and can be allowed to reach high
levels without degrading the performance of systems. Enter the desired maximum following error into the
Max following error field.
Following error = Predicted position - actual position
CNC Setup and PID Loop Tuning Guide