Axis Monitoring Functions; Contour Monitoring; Contour Error; Following-Error Monitoring - Siemens SINUMERIK 840D sl Function Manual

A3: Axis Monitoring, Protection Zones

3.2 Axis monitoring functions

3.2 Axis monitoring functions
3.2.1

Contour monitoring

3.2.1.1

Contour error

Contour errors are caused by signal distortions in the position control loop.
Signal distortions can be linear or non-linear.
Linear signal distortions
Linear signal distortions are caused by:
● Speed and position controller not being set optimally
● Different servo gain factors (K
With the same servo gain factor (K
follows the set position along the same path but with a time delay. With different servo gain
factors (K
● 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.
Non-linear signal distortions
Non-linear signal distortions are caused by:
● Activation of the current limitation within the machining area
● Activation of the limitation of the speed setpoint
● 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 motion 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
3.2.1.2

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.
80
) of the feed axes involved in creating the path
V
), a parallel offset arises between the set and actual path.
V
) for two linear-interpolated axes, the actual position
V
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions