HEIDENHAIN ND 1300 CNC Setup - Manual (Page 43)

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Oscillates during move?
CNC moves should be smooth in mechanically sound systems. Vibration, roughness or oscillation during
a move is an indication of PID loop instability.
NOTE
Confirm that your system components can move smoothly and are free of mechanical
problems before attempting to tune PID loops.
Axis vibration can be observed visually or heard as a buzzing or whining sound. However, low levels of
vibration can often not be detected without lightly touching an axis component while the axis completes a
CNC test move.
WARNING
Be extremely careful while touching an axis in motion. Stay clear of the axis path.
Do not attempt to touch an axis in motion at all if it represents any risk of personal
injury.
Increase derivative
The derivative factor reduces loop gain for the rapidly changing following error signals caused by under-
damped axis motion or by axis oscillation. If axis vibration is observed during a CNC test move, increase
the derivative factor a small amount and perform a new CNC test move. Continue increasing the derivative
factor in small increments and retesting a CNC motion until the vibration disappears. A small number of
systems might oscillate when add-
ing integral to a loop that already
contains derivative. In these cases
it might be necessary to reduce the
derivative factor to stabilize the
axis, or to find a different mixture of
proportional, derivative and integral
terms altogether.
While small to moderate amounts of derivative can eliminate vibration due to PID loop instability, excess
derivative can cause oscillation. Be careful to increase the derivative factor in small increments.
CNC Setup and PID Loop Tuning Guide