A3: Axis Monitoring, Protection Zones
2.2 Axis monitoring
Basic Functions
78 Function Manual, 09/2011, 6FC5397-0BP40-2BA0
2.2 Axis monitoring
2.2.1 Contour monitoring
2.2.1.1 Contour error
Contour errors are caused by signal distortions in the position control loop.
Signal distortions can be linear or nonlinear.
Linear signal distortions
Linear signal distortions are caused by:
• Speed and position controller not being set optimally
• Different servo gain factors of the feed axes involved in creating the path
With the same servo gain factor for two linear-interpolated axes, the actual position follows the set position
along the same path but with a time delay. With different servo gain factors, a parallel offset arises between
the set and actual path.
• Unequal dynamic response of the feed drives
Unequal drive dynamic responses lead to path deviations especially on contour changes. Circles are distorted
into ellipses by unequal dynamic responses of the two feed drives.
Nonlinear signal distortions
Nonlinear signal distortions are caused by:
• Activation of the current limitation within the machining area
• Activation of the limitation of the set speed
• Backlash within and/or outside the position control loop
When traversing a circular path, contour errors occur primarily due to the reversal error and friction.
During movement along straight lines, a contour error arises due to a reversal error outside the position
control loop, e.g. due to a tilting milling spindle. This causes a parallel offset between the actual and the set
contour. The shallower the gradient of the straight line, the larger the offset.
• Nonlinear friction behavior of slide guides
2.2.1.2 Following Error Monitoring
Function
In control engineering terms, traversing along a machine axis always produces a certain following error, i.e., a
difference between the set and actual position.
The following error that arises depends on:
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