tures that may exist. Several algorithms are
required to detect hairs. One for dark hair,
one for blond hair, and another for gray hair.
After image analysis is complete, the master
iPC communicates the result to the PLC,
which in turn actuates one of two air cylinders required to pass the package, or divert it
to the reject bin.
Another challenge was illumination. Due to
the shape of the package itself, and because
the seal areas are recessed in lanes between
the eight cuboid-shaped pouches, engineers
had to develop a compact, custom illumination system that fit up inside the lanes between
the pouches, very close to the seal areas.
The highly-specialized strobe lighting solution is an integral part of each camera/lens
stack and light assembly, and provides the contrast required for the machine vision software
to detect the required seal defects.
Detecting 50-micron defects requires a resolution of 10 or 12 microns per pixel, the material handling system had to achieve tight axis
control in terms of positioning tolerances to
maintain a +/-1-mm depth of field when presenting the seal areas to the cameras.
Package handling challenges
During ASI development, the engineering
teams tasked with specifying the part-handling
and machine vision system had to address several design challenges. First, the fact that each
eight-pouch package may contain numerous
items of varying sizes and weights, which,
when combined with the non-rigid nature of
the package, make the packaging tend to flop
around during handling.
Another design challenge is the breathable
nature of the Tyvek lidding, which makes it
difficult to pick up with vacuum. Plus, the flexible material’s wavy and uneven surfaces challenge part presentation by the gripper to the
machine vision cameras for inspection.
Despite the flexible nature of the packages and the fact that they may contain various medical devices and supplies of different weights and sizes, the material handling
system must maintain package flatness due to
depth of field requirements of +/- 1 mm over
a 1-ft, y-axis stroke and a 2-foot, x-axis stroke.
Because this required the use of a rela-
tively heavy vacuum chuck that was power-
ful enough to hold flat the porous packaging
despite the weight of its contents, engineers
chose a three-axis gantry system over a wristed
robot because it provided the smooth, precise
and repeatable movement required.
Besides minimizing the risk of sterile Class
II and III medical device and supply product contamination, the ASI could potentially impact the packaging of food, military
supplies, consumer products or virtually any
other application that relies on flexible packaging with intact hermetic seals.
Figure3: The low-profile and highly-specialized strobe lighting solution is an integral part of each camera/lens stack and light assembly, and provides the contrast required for the machine vision software to detect seal defects.
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