Rockwell Automation 5370-CBPK Color CVIM BLISTER-PAK Option - Manual (Page 23)

Chapter 5
Auto Setup
5–3
Minimum Position Tolerance
The minimum position tolerance parameter sets the minimum value to which
the position tolerance will be set during the “teach–in” process, even if the
observed position variation is less. The default value is 10%.
During inspection, the system attempts to match the camera image of objects
with the stored image of those objects. In an ideal world, every object in
every pocket of every blister would appear in exactly the same position.
However, in the real world of production inspection, at least some variation
in position is almost certain to occur. This variation is known as positional
offset.
During the auto setup process, the Color CVIM BLISTER-PAK option
accommodates positional offset by evaluating variations in the positions of
the sample objects and, on the basis of that evaluation, automatically
calculating X and Y position tolerance values for each blister. These are
expressed as percentages.
It is possible, however, that very little positional offset may occur during the
carefully controlled conditions of an application “teach-in.” This could result
in calculated tolerance values that are be much lower than the actual
positional offsets expected during production inspection operations.
If you expect that the values calculated by the auto setup process are likely to
be too low, you can use the
Min. Pos. Tolerance menu item (before starting
the auto setup process) to enter higher minimum values that will override
any calculated values that are lower. These higher minimum values can be
based on the known mechanical characteristics of your own installation, on
experience, or on other criteria.
When you select the Min. Pos. Tolerance menu item, an onscreen
calculator appears, on which you can enter a minimum position tolerance
value between 0% and 100%. The value that you enter determines the
minimum acceptable positional offset range for each axis.
For example, if you enter a value of 12, it establishes a minimum acceptable
offset range of
12% for both the X–axis and the Y–axis. If the auto setup
process then calculates a position tolerance of 7% for the X–axis and 14%
for the Y–axis, the position tolerance for the X–axis would be forced to 12%
(the minimum value), while the position tolerance for the Y–axis would
change to 14%, since it is higher than the minimum position tolerance.
NOTE: Changing the minimum position tolerance after completing the auto
setup process will have no effect on the current position tolerance values.
You can, however, alter the current position tolerance as explained on page
6–9 under the Position Tolerance heading.