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Touch-trigger probe systems - TP1, TP2, TP6, TP6A, PH1, PH5, PH6, PH6M
http://www.renishaw.com
Applications guide
Stylus selection
In the majority of probing applications, to maximise accuracy we recommend that you:
Keep styli short and stiff
The more the stylus bends or deflects, the lower the accuracy. Probing with the minimum stylus length for your application is
recommended and where possible the use of one piece styli is suggested. Probing with excessive styli / extension combinations
should therefore be avoided.
Keep the stylus ball as large as possible
This will ensure maximum ball / stem clearance whilst providing a greater yet rigid effective working length (EWL). Using larger ruby
balls also reduces the effect of surface finish of the component being inspected.
EWL is the penetration that can be achieved by any ruby ball before its stem fouls against the feature. Generally, the larger the ball
diameter, the greater the EWL (see figure below).
EWL can also be affected by assembly tolerances. For this reason, Renishaw styli are assembled to exacting standards in controlled
conditions.
Trigger force
Trigger force is the amount of pressure applied by the helical compression spring onto the pivotal plate and bearing points to hold the stylus
mount in place.
The trigger force is preset by Renishaw but can be altered for any of the following reasons:
to permit the use of longer styli on the probe
to permit the use of heavier styli on the probe
if the preset trigger force has decreased due to probe use
if the acceleration of the CMM is causing illegal triggers
NOTE: Changing the probe trigger force will affect the probe's measurement performance. It is important to requalify the probe
configuration and check the measurement performance of the probe system after any adjustment has been made to the trigger force.
Issued 11 2014
A
Overall working length
B
EWL
C
Ball / stem clearance
12
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