Siemens SINUMERIK 840D sl Programming Manual page 164

Measuring variants
2.3 Measure workpiece (milling)
Defining the rotary axis positions
Three measuring positions (ball position) must be defined for each rotary axis. Please note
that the positions of the ball in space (resulting from the three defined rotary axis positions)
should lead to as large a triangle as possible being clamped.
Rotary axis positions sufficiently far away from
one another; large triangle clamped
The resulting angle of the measured triangle is monitored in parameterTVL . Angle values of
< 20 degrees can cause inaccuracies when calculating the kinematics.
Approaching the ball position
First of all, the probe must be positioned above the calibration ball at each of the three rotary
axis positions defined by the user. The position must only be approached by traversing the
linear axes (X, Y, Z). The positions themselves must be entered (set up) by the user. They
should be determined manually using an active probe.
When selecting approach positions, please bear in mind that, within the context of automatic
calibration ball scanning, the probe always moves in its preferred direction. Particularly
where head and mixed kinematics are concerned, the starting point should be selected in a
way that ensures alignment of the probe with the center point of the calibration ball in the
approach position.
Starting point selected directly above the
164
calibration ball
Rotary axis positions poorly selected;
clamped triangle is too small
Starting point selected laterally above the
calibration ball
Programming Manual, 02/2011, 6FC5398-4BP40-0BA0
Measuring cycles