Calibrating The Rmp400; Why Calibrate A Probe; Calibrating In A Bored Hole Or On A Turned Diameter; Calibrating In A Ring Gauge Or On A Datum Sphere - Renishaw RMP400 Installation Manual

Calibrating the
RMP400

Why calibrate a probe?

A spindle probe is just one component of the
measurement system which communicates with
the machine tool. Each part of the system can
introduce a constant difference between the
position that the stylus touches and the position
that is reported to the machine. If the probe is
not calibrated, this difference will appear as an
inaccuracy in the measurement. Calibration of the
probe allows the probing software to compensate
for this difference.
During normal use, the difference between the
touch position and the reported position does
not change, but it is important that the probe is
calibrated in the following circumstances:
•
when a probe system is to be used for the first
time;
•
when the enhanced trigger filter delay is
changed;
•
when a new stylus is fitted to the probe;
•
when it is suspected that the stylus has
become distorted or that the probe has been
crashed;
•
at regular intervals to compensate for
mechanical changes of your machine tool;
•
if repeatability of relocation of the probe shank
is poor. In this case, the probe may need to be
recalibrated each time it is selected.
It is good practice to set the tip of the stylus on-
centre, because this reduces the effect of any
variation in spindle and tool orientation (see page
3.6, "Stylus on-centre adjustment"). A small
amount of run-out is acceptable, and can be
compensated for as part of the normal calibration
process.
Three different operations are to be used when
calibrating a probe. They are:
•
calibrating either in a bored hole or on a turned
diameter of known position;
•
calibrating either in a ring gauge or on a datum
sphere;
Draft 5 16/04/18
•

calibrating the probe length.

Calibrating in a bored hole or on a
turned diameter
Calibrating a probe, either in a bored hole or on
a turned diameter of known size, automatically
stores values for the offset of the stylus ball to
the spindle centre line. The stored values are
then used automatically in the measuring cycles.
Measured values are compensated by these
values so that they are relative to the true spindle
centre line.
Calibrating in a ring gauge or on a
datum sphere
Calibrating a probe either in a ring gauge or
on a datum sphere with a known diameter
automatically stores one or more value for the
radius of the stylus ball. The stored values are
then used automatically by the measuring cycles
to give the true size of the feature. The values are
also used to give true positions of single surface
features.
NOTE: The stored radius values are based on the
true electronic trigger points. These values are
different from the physical sizes.
Calibrating the probe length
Calibrating a probe on a known reference surface
determines the length of the probe, based on
the electronic trigger point. The stored value for
length is different from the physical length of the
probe assembly. Additionally, the operation can
automatically compensate for machine and fixture
height errors by adjusting the probe length value
that is stored.
3.7