SFP1 laser engraving misalignment explanation

Description

SFP error diagram 1 

Prior to initial calibration the sytem requires SFP1 to be manually positioned in the C-axis to 0° on the laser engraved scale.  As a result the intial calibration is carried out with the measurement direction at the tip correctly aligned to the surface normal.  The laser engraved scale will appear correct until the head repositions.

SFP error diagram 2 

Subsequent measurements rely on the position of the end stop in the housing and a move away from this stop.  Due to the incorrect marking of the 0° position with respect to the end stop the result is a misalignment of the tips measurement direction by 3°.  This may result in metrology errors.

If a further calibration is performed, the system will again move with respect to the end stop and  give a different calibration.  This calibration may be more representative as it will be misaligned to the measurement direction by the same amount.  It may however still result in metrology errors as it is still nominally misaligned by 3°. 

In all cases of head positioning the laser engraved scales will read 'incorrectly'.

Requirements

See also