Rockwell Automation 5370-CVIM2 Module - Manual (Page 419)

5 Chapter Chapter 7
Inspection Tools
7–181
As Figure 7.146 shows, the CVIM2 system provides two sets of range limits:
Warning range limits, and fail range limits. Warning range limits must
always lie within fail range limits or must be equal to them, as shown below:
Fail Low <= Warn Low <= Warn High <= Fail High
NOTE: A tool can also “fail” if it is unable to perform its inspection. For
example, a gage will fail if its operation is Linear Measure and it finds no
edges.
Here is an example of ranges:
•
The Fail Low limit is set to 14.6.
•
The Warn Low limit is set to 14.8.
•
The Warn High limit is set to 15.2.
•
The Fail High limit is set to 15.4.
With the range limits set as shown above, if an inspection result is outside
either warning limit (above 15.2 or below 14.8), the CVIM2 system will
generate a warning signal only. If an inspection result is outside either fail
limit (above 15.4 or below 14.6), the CVIM2 system will generate a fail
signal only.
In a practical application, the warning range limits could be used to indicate a
deteriorating condition, such as a part that is very close to a tolerance limit
because of wear in a cutting tool or die. The fail range limits could be used to
indicate a failure condition, such as a part that has exceeded a tolerance limit
because of a broken cutting tool or die.
Here are some methods for determining the appropriate warning and fail
range limits:
•
For measurements or counting operations using pixels, use the Nominal
function to determine the pixel values of workpieces at the upper and
lower tolerance limits. Use the nominal value as the basis for determining
the appropriate fail and warning limits.
•
For any measurements, run a series of trial inspections, using a
representative sample of workpieces, in order to accumulate a statistical
basis for setting the appropriate fail and warning limits.
After you determine the appropriate range limits for your application, you
can enter them in the
Ranges selection panel (see Figure 7.145, page 7–179).
To enter each of the range limits, as may be required for your application,
pick the field alongside the limit. When you do, the calculator pad appears on
the screen. Enter the value for each limit as required for your application.