Pre-positioning

Attention

A collision-free measurement movement must be ensured for all three measurements. Please note here that the measurement movements co-rotate with the measured axis. This also applies to the probe angle and incremental angle.

Pre-position of the first measurement / cycle starting point

The pre-position of the first measurement is obtained from the cycle starting point. The touch probe must be positioned as centrally and vertically as possible above the calibration sphere. If the touch probe head cannot be positioned vertically at the start, an additional adaptation is required in the input parameters (for more details, see the Section Compensation for an inclined position).

Pre-positioning the second and third measurements

To pre-position the second and third measurements, the user must move measured rotary axis through any angle but which is as large as possible. Then the starting position for the next measurement must be selected so that the touch probe head is flush with the sphere centre point, i.e. points to the centre point of the calibration sphere.

During pre-positioning, only linear axes and rotary axes involved in a complete kinematic transformation may be moved. During the measurement, the measured rotary axis may not be involved in a kinematic transformation. The orientation of the touch probe head in the current coordinate system may only be changed during pre-positioning by the axis to be measured.

The measurement movement is co-rotated with the measured axis. The following rotation of the sphere measurement movement is obtained when the measured axis rotates, for example, about the Y axis in the current coordinate system and was turned through 35 degrees.

Co-rotation of measurement movements also applied to the probe angle. If the measured axis rotates about the Y axis and it was turned through 90° for pre-positioning, this rotation would place the X axis on the Z axis in a right-hand coordinate system In this case, the probe angle refers to the Z axis of the original coordinate system.

The rotation vector of the measured axis must be defined by the input parameters to adapt the measurement movement automatically. Minor deviations are insignificant here since these values are only relevant to the measurement movements. However, they have no direct influence on the measurement result. With manual pre-positioning, the traversed angle must also be defined.

Pre-positioning the second and third measurements with NC subroutines

If pre-positioning of the second and third measurement are to take place automatically, suitable NC subroutines can be saved here to execute the corresponding movements. It is recommended to pre-position the cycle in manual mode for the first application. Movements travelled in manual mode and resulting in successful execution of the cycle can then be integrated in the NC subroutines. This permits a completely automated execution of the cycle.

The input parameter @P90 must be set to 0 for automated pre-positioning. In addition, the files SysMeasRotAxPrePos2.nc and SysMeasRotAxPrePos3.nc must be saved. The file SysMeasRotAxPrePos2.nc is called after the first sphere measurement and describes the pre-positioning for the second measurement. The file SysMeasRotAxPrePos3.nc is called after the second sphere measurement and describes the pre-positioning for the third measurement.

Refer to the section Programming examples for an example of how these NC subroutines can look like.

Compensating an inclined position of the touch probe head at the start of the cycle.

If the touch probe head cannot be positioned vertically for the first measurement due to the machine design, the inclined position can be compensated by the parameters @P94-@P97. The inclined position of the touch probe head is defined here by defining a rotary axis and a rotation angle. This permits compensation of the measurement movement to the inclined axis. This adaptation is only required for the first measurement pass.

The inclined position of the touch probe in the graphic below can be described by a rotation of 20° about the Y axis. In this case, the following parameter definition should be transferred in order to execute the cycle successfully.

@P94 = 0, @P95 = 1, @P96 = 0, @P97 = 20

For pre-positioning, the touch probe head must still point to the centre point of the sphere.

The touch probe offsets in the X and Y directions determined by calibrating the touch probe are of no consequence here.