Instruction Manual

7-6 Programming Basics
Table 7 -1 Fiducial Ratings
Shape Characteristics
£ donut Excellent. Immune to rotation. Inner and outer diameters allow for further
definition.
# pound
Good. Uniqueness maintained under rotations.
l circle Good. Immune to rotations.
❍
❍❍
❍ hole/gap
Poor. Requires machining accuracy to match definition. Not repeatable
between different workpieces.
: cross Poor. Single axis identification does not allow for poor quality printing of the
shape.
Uniqueness: While a fiducial must be a unique feature on the workpiece, the fiducial must appear the
same on all similar workpieces. The fiducial includes the feature and the background. This means that the
same shape on two workpieces with different backgrounds will not be identified as the same. See
Figure 7 -3 for examples of good fiducials.
The uniqueness of a fiducial is often defined by its proximity to other elements on the workpiece. A
circle might be a repeated pattern on a workpiece, but a circle next to a rectangle might be unique to the
location you are trying to define. This type of identification is more common when defining nested
pattern fiducials, rather than workpiece alignment fiducials.
Contrast: The ability to enhance the contrast of the fiducial to the background can be optimized by
Vision System parameters. However, you should choose a fiducial that has good natural contrast from the
background.
While the selection of a fiducial is dependent on the workpiece, the following figures show good
fiducials as far as shape, background, size and contrast.