Function
Compensation of thread pitch errors of the ball screw or errors of the measuring system, e.g. due to inaccuracies of the code disk/code ruler.
On SINUMERIK CNCs, interpolating compensation is divided into two categories:
- Leadscrew error compensation (LEC) and measuring system error compensation (MSEC) as axial compensation (basic axis and compensating axis are always identical) and
- Sag error and angularity error compensation as cross-axis compensation (basic axis affects other compensation axis)
The principle of "indirect measuring" on CNC-controlled machines is based on the assumption that the leadscrew pitch is constant at every point within the traversing range. This means that the actual position of the axis can be derived from the position of the drive spindle (ideal situation).
Manufacturing tolerances in ball screw production, however, result in large dimensional deviations to a lesser or greater extent (referred to as leadscrew pitch errors). Added to this are dimensional deviations caused by the measuring system as well as its installation tolerances on the machine (measuring system errors), plus any machine-dependent error sources. Since these dimensional deviations directly affect the accuracy of the workpiece machining, they must be compensated for by appropriate position-dependent compensation values.
The compensation values are derived from measured error curves and entered in the SINUMERIK CNC in the form of compensation tables during commissioning. The relevant axis is then compensated using linear interpolation between the intermediate points.
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