Manual

5-20 Programming Basics and Setup
Teaching Fiducials
Fiducials are used to define the position and orientation of the workpiece, or to identify the location of
parts on a workpiece. Part of the programming process is to determine which fiducials should be defined
to achieve the accuracy and speed required for your dispensing process.
Fiducial Detection Methods
The Vision System is capable of automatically locating features on the workpiece so that patterns can be
placed accurately. Defining workpiece origin and fiducials is the crucial first step in creating accurate
dispensing programs. The Vision System has three tools or methods to find fiducials.
Model Finder – This method uses pattern recognition to find a previously defined gray-scale
model, which is the defined fiducial in the field of view.
Corner Finder – This method uses edge detection algorithms to find the corner of a previously
defined part in the field of view.
Manual Finder – This method is primarily used on dispensing systems equipped with the
AV-7000 Vision System. Manual Finder prompts the operator to manually target the fiducial
location every time a fiducial search is performed.
Model Fiducials
Model fiducials are usually letters, dots, or silk-screened marks on the board. You have the option of
selecting one or two fiducials. Selecting two fiducials helps determine the workpiece angle. Two
fiducials are recommended if the fiducials are round.
In order to be effective indicators of workpiece location, fiducials must be unique and easily distinguished
from all other features on the workpiece. They must also be repeatable and consistently placed in the
same location from one workpiece to another. Fiducials are selected according to shape, size, uniqueness,
and contrast.
Shape
The shape of a fiducial determines whether the fiducial is recognizable under translation or rotation
(See Table 5-4). Fiducials should be recognizable as the same shape, even if rotated or translated.
Table 5-4 Model Fiducial Ratings and Characteristics
Shape Rating Characteristics
} Donut Excellent
Immune to rotation. Inner and outer diameters allow for
further definition.
# Pound
Good Uniqueness maintained under rotations.
z 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.