Return To Zero - Renishaw SP600 Installation And User Manual

SP600 installation and user's guide
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Reorientation
The SP600M probe may be used in different orientations when mounted on a Renishaw PH10M PLUS motorised head. The design has
been optimised to allow this but it will have some effect on the distribution of the measuring ranges available in each axis.
NOTE: When using a SP600 with PH10MQ, a PEM25 extension bar is required to achieve A = 97.5° or A = 105° in all B­axis
positions.

Return to zero

The probe has a nominal absolute centre position where the functions of stylus configuration and probe orientation cause it to rest.
Because of small amounts of internal friction, when the probe is displaced from this zero point, the stylus will not return to exactly the same
point on the scale and the axis deflection readings will show a different value.
This characteristic of probe performance is called RETURN TO ZERO and is a feature of all analogue probes and is not a source of error
as the scale system continues to monitor position. Rather it is merely a factor which must be taken into account when designing control
software for using the probe. It can be given a value which represents the diameter of a sphere around the nominal zero position within
which the probe will return to reset after any displacement.
SP600M has a return to zero value of less than 5 microns after a deflection of 0.5 mm (typically 1 micron). It is important to take this into
account as it affects the minimum amount of deflection necessary before the stylus is considered to be in contact with the surface.
Because the stylus can return to a value other than the nominal zero, the CMM must recognise the fact that the range of rest positions of the
stylus must not cause the machine motion as the stylus is not necessarily in contact with a surface even though it is "deflected".
The CMM software should have a parameter for this minimum probe deflection and only deflections above this amount should be
considered as the stylus being in contact with a surface.
Issued 01 2018
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