Siemens SINUMERIK 808D Function Manual page 120

Time constant too small
Too small a time constant (MD32540) in the circularity test is indicated by short-time compensation of the contour deviations
at the quadrant transitions which immediately increase thereafter.
Time constant too large
Too large a time constant (MD32540) in the circularity test compensates the contour deviations at the quadrant transitions.
(Requirement: The optimum compensation value has already been determined.) However, with too large a time constant,
the compensation value applies too long and results in an overcompensation at the next circular contour.
Optimization of the compensation parameters
To optimize the compensation parameters, the circularity test must be repeated several times and the values changed in
small increments. It is recommended that the optimization be performed with different values for radius and path velocity that
are typical for the machining operations performed on the machine.
Each effect of a parameter change should be checked with a subsequent circularity test and documented.
Function Manual
120
01/2017