Rockwell Automation 5370-CBPK Color CVIM BLISTER-PAK Option - Manual (Page 24)

Chapter 5
Auto Setup
5–4
Minimum Area Tolerance
The minimum area tolerance parameter sets the minimum value to which the
area tolerance will be set during the “teach–in” process, even if the observed
area 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 to have exactly the same area.
However, in the real world of production inspection, at least some variation
in area is almost certain to occur.
For purposes of the Color CVIM BLISTER-PAK option, the area of a
previously learned color (along with its shape and relative position)
determines the definition of an object or blister. Area is determined by
counting the number of contiguous pixels covered by a color.
During the auto setup process, the Color CVIM BLISTER-PAK option
accommodates area fluctuations by evaluating the variations in the area of
the sample objects and, on the basis of that evaluation, automatically
calculating area tolerance values for each blister. These are expressed as
percentages.
It is possible, however, that a very small range of area values may be
encountered during the carefully controlled conditions of an application
“teach-in.” This could result in calculated tolerance values that are much
lower than the actual area variations 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. Area Tolerance menu item (before 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. Area Tolerance menu item, an onscreen
calculator appears, on which you can enter minimum area tolerance values
between 0% and 100%. The value that you enter determines the minimum
acceptable range of area variation.
For example, if you enter a value of 15, it establishes a minimum acceptable
area range of
15%. If the auto setup process then calculates an area
tolerance of +12% and –17%, the plus (+) value would be forced to 15% (the
minimum value), while the minus (–) value would remain at 17%, since it is
higher than the minimum area tolerance.