Tech Briefs Magazine - October 2022 - 16

Vision Systems
With this assembly cell, the manufacturer
of the pneumatic valves meets their
need to produce high-quality, defect-free
parts while minimizing waste. From the
design perspective of the vision inspection
station, rigidly mounting the smart
camera in place and presenting parts
into the field of view with precision fixturing
enables reliable vision inspections
with accurate measurements. This kind
of vision system set-up is ideal in most applications
because the position of the
camera relative to the part under inspection
is the same over time. As we'll see in
the next application, sometimes it is better
to move the camera into position for
each visual inspection task.
Moving Camera, Fixed Part
Position
Figure 2. Some of the electric and pneumatic handling systems used in the automated assembly cell
are shown here. The vision inspection station is visible in the upper-left corner. (Image: Festo)
rigidly mounted in a stationary position
above the field of view.
It is important to inspect each valve
body at this point so that a defective valve
body can be rejected at this early stage,
which minimizes waste because no additional
components have been installed
yet. During the vision inspection process
the vision system counts the number of
holes in the valve body and measures the
dimensions and locations of the holes.
After the vision inspection, each accepted
valve body is indexed to the next
station where pneumatic fittings are
threaded into pre-drilled and tapped
holes in the valve body and a small,
printed circuit board is pressed into a
slot on the side of the valve body. Finally,
each fully assembled valve body is indexed
to an exit position where another
dedicated handling system transfers it to
an outbound conveyor.
The handling and threading of the
pneumatic fittings, the insertion of the
printed circuit boards, and the handling
of the assembled valve bodies through
the cell are accomplished by numerous
handling systems, as partially shown in
Figure 2. The various handling systems
are comprised of both pneumatic and
electric variants of different rotary actuators,
linear actuators, and grippers.
Quality control requirements during
the assembly of fuel pump control
boards in the automotive industry dictate
that critical steps of the assembly
process are well documented and traceable.
This second application is for the
pressing of fuses into printed circuit
boards. The assembly process requires
accurate motion control with multiple
points of visual inspection using a machine
vision system. The manufacturer
of the fuel pumps must not only determine
whether a fuse has been properly
pressed into the control circuit board
and provide a simple OK/NOK (Not
OK) result to downstream steps in the
process, but also must document the verification
of all parts and the results of
each assembly step to comply with traceability
requirements.
Ballscrew-driven
servo-press actuator
Vision system with
lens and lighting
Pneumatic gripper
and actuator
Figure 3. The handling system used for picking and placing each fuse into a waiting PC board is shown. Multiple functions reside on the Z-axis: pneumatic
gripper and actuator for picking the fuses, camera with lens and ring light for visual inspection tasks, and ballscrew-driven servo-press actuator.
(Image: Festo)
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