Siemens SINUMERIK 840D sl Programming Manual page 220

Measuring variants
3.3 Measure workpiece (milling)
Defining the rotary axis positions
Three measuring points (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 calculated inside angle of the rotary axis angle segment is monitored in the TVL parameter.
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 position 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 position selected directly above the
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calibration ball
Rotary axis positions poorly selected; clamped
triangle is too small
Starting position selected laterally above the cal‐
ibration ball
Programming Manual, 12/2017, 6FC5398-4BP40-6BA1
Measuring cycles