Owner's manual

Programming Basics and Setup 5-35
36. Using the position controls, move the dispensing head to the upper right-hand corner
(URHC) of the tutorial board, center the crosshairs on the dot in the URHC, and repeat the
above steps to teach the second fiducial.
37. Once you have completed teaching the second fiducial, you will have successfully taught
the workpiece fiducials.
5.4.3.3 Corner Fiducials
In some cases, accuracy is greatly improved by identifying the corner of the part to be dispensed on as a
fiducial, especially if there are no good fiducials on the workpiece. Corner Finder is a method to identify
fiducials that are part edges or lines or edge pairs, such as the edge of a die. Corner Finder uses a vision
tool called a Caliper (see below) designed to find edges or pairs of edges.
The position of parts can be slightly rotated by automatic placement systems, or the parts can be
dislodged during the transfer process. By using corner fiducials, you can ensure that the orientation of the
die is determined before dispensing. The Corner Finder method assumes that edge images are a change in
gray value from light to dark or from dark to light. Edges are identified by locating these types of gray
changes and analyzing them statistically to see if they meet a given criterion.
Using Caliper Tool
The caliper tool has a caliper window overlay on the image of the edge. The tool is placed over the edges
to be identified and can be sized in 2-dimensions. See Figure 5-21.
• The Search Length is the longer dimension of the caliper tool and crosses the edge to define
the length of the area to be searched for the gray transitions. It is important not to include
more than one transition or edge along this length.
• The Projection Length is the shorter dimension; the distance that the application will
average gray-scale values down the edge in order to reduce noise and enhance the
transition.
Figure 5-21 Caliper Window Overlay
Application Point
Search Length
Caliper