Siemens SINUMERIK 840D sl Function Manual page 365

Figure 5-5
The error must be recorded in the form of a compensation table that contains a
compensation value for the Z1 axis for every actual value position in the Y1 axis. It is
sufficient to enter the compensation values for the interpolation points.
When the Y1 axis traverses, the control calculates the corresponding compensation value in
the Z1 axis in interpolation cycles performing linear interpolation for positions between the
interpolation points. This compensation is sent to the position control loop as an additional
setpoint. A positive compensation value causes the corresponding machine axis to move in
the negative direction.
Depending on the requirement, several compensation relations can be defined for one axis.
The total compensation value results from the sum of all the compensation values of this
axis.
Extended Functions
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
Example of sag caused by own weight
K3: Compensation
5.4 Interpolatory compensation
365