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Measuring with Multiple Styli |
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Definition |
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During the inspection process, access to a feature is
often limited to the feature's relationship to the
current stylus. For example, if measuring a through bore
that is parallel to the surface plate you will need
either a long probe whose shaft is parallel to the bore
and can reach the length of the bore, or the ability to
use multiple styli where you can capture data points
entering the bore from both ends.
Using a styli with a long shaft is not the preferred
method due to the degradation in repeatable accuracy and
just the fact that it is harder to capture data points
inside a feature where visibility is often obscured.
By using multiple styli that are positioned to access
much of the feature from different entry points, you can
spread the data points over the entire feature assuring
the highest possible confidence on the reported results.
The ideal condition is where you have an articulating
probe, such as the Renishaw
MH8
or
PH10T. These probe heads provide repeatable
positioning of the styli without the need to requalify.
The alternative method is the use of a star cluster that
has up to 5 fixed styli attached to a common center. The
star configuration can be positioned in the probe head
mount to align the styli to the inspection fixture .
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Using Multiple Styli on Measured Feature |
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In this example, we will measure a through bore that
lies parallel to the surface plate and its axis is
parallel to the X-Axis of the CMM. To setup the styli
that will be needed, use the Stylus Manager to
qualify the required positions. We will us two
styli, one pointing in the -X direction, the other in
the +X direction. |
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Step 1 |
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Activate the
Stylus Manager and
Activate the qualified styli that is
orientated toward the -X direction.
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Step 2 |
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Select the proper feature to be measured. Here we will
use the
cylinder with 16 points. Capture data points by
entering the cylinder from the right side of the
cylinder opening. Spread 8 data points around the full
inside surface of the cylinder to a depth allowed by
your sylus length. When these 8 data points have been
captured, pull the stylus out of the cylinder an
activate the Stylus Manager.
NOTE: If you are using a DCC style CMM, make sure
you have included the necessary IPs between styli
changes to provide safe movement during automatic
inspections. |
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Step 3 |
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The Geomet prompt will still show a cylinder is in
progress and that there are 8 data points still
required. When the Stylus Manager is opened during a
feature measurement, you can choose a new stylus and set
it active. Choose the stylus whose orientation is the +X
direction and press the <+ Set Active> button. Geomet
will not place a program statement in the report, but
the Current Status banner will update to show the stylus
change.
NOTE: You can use as many qualified styli as
needed to measure a single position. The styli being
chosen must be the same probe diameter. |
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Step 4 |
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Capture the remaining 8 data points on the cylinder from
the left opening. When all data points have been
captured, Geomet will report the cylinder as a single
feature. |
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Stylus Manager, Features, Menus and Support Tools |
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