It’s not just automotive companies in Detroit—who seem to be garnering
substantial attention from mass media. It’s the same in food production,
too. Improvements in food production require closer integration of the
many machines employed on the line.Not all processing or packaging machines are designed with identical
throughput specifications. And even if they were, variations from
machine to machine would inevitably skew the relative rates. Control
systems of the various machines must receive feedback from other parts
of the line in order for operations in world-class plants to tune the
line to its optimum operating effectiveness.
Product tracking has become another key operating function given
requirements both from agencies such as the U.S. Food and Drug
Administration (FDA) and from the need to conduct a fast and efficient
product recall should that ever be required. Tracking requires
information coordination among all the machines on the line.
Allpax Products, a division of Pro Mach Inc., manufactures a number of
retorts for low-acid food production along with associated automation. A
retort, or pressure cooker, is one of the machines on a process line
that often must be taught, so to speak, to communicate directly with
packaging machines, too.
Jonny Watkins, director of software engineering at Allpax, describes a
typical production line producing microwavable bowls of soup. “These are
now highly integrated lines. We have to interface to the packaging
parts that a lot of times are not Pro Mach machines. They may be German
or from other countries.”
In one recent line, upstream machines filled and sealed microwavable
bowls of soup. The bowls were fed from the sealing machine onto a
conveyor in single file with the first-filled, that is oldest, bowl
first. The first bowl filled is used in a destructive test to determine
the temperature of the product in the center of the package. Bowls are
tracked using 2D bar code read by a Cognex vision system. The oldest
bowl is flagged as it proceeds down the line. Operations people pull it
off the conveyor, check it again with the vision bar code reading
system, and conduct the destructive test.
Meanwhile the rest of the bowls move from the conveyor to baskets that
will convey products to the retort. When four baskets are filled, a
shuttle transports them to the retorts for processing. The retort door
is closed and the operator must enter information derived from the test
into the control system in order to set the parameters of the process
and to start the system. Temperature and pressure are critical process
parameters that must be measured and logged. “We’re tracking the
products and the process so that we know how many products were
processed, the number of each basket, where it has been, how long it has
sat, all in a database program [All Trax] that we have developed,” says
Watkins.
Tracking is accomplished using a variety of sensors and the bar code
reading vision systems. “At that point, we have basically assured that
the product has undergone the proper processes, moved around the system
properly and that no unprocessed food has made it to the end of the
line,” Watkins says. “In the event of a deviation, the product is moved
to a separate queue.”
When the processing system is finished, the shuttle unloads the product
to a conveyor unload line and returns for another load of product to be
processed. Product now heads to the labeler and case packer. “We update
all the logs by capturing data and tracking through the system. Once
it’s sent to the labeler, we no longer track it. We just send
information to the plant database for reporting purposes,” continues
Watkins.
Aside from tracking products, the customer had another request for
Allpax on this line. It wanted Allpax to make its lines more efficient.
They needed to make the system speed fluctuate based on the output from
the filler machines and backup at the case packer. So Allpax set up its
control system to synchronize its loading and unloading system with the
speed of the packaging line machines. Watkins relates, “A number of
networks were involved between the packaging machine supplier and us. We
use ControlNet (a networking standard promulgated by ODVA) because you
can schedule data packets and know exactly the data transfer rate. It’s a
deterministic network on data rate, so we can match efficiencies and
machine speeds. The only thing that doesn’t change speed is the retort
process itself because of food safety.”
The customer was able to satisfy quality and regulatory concerns as well
as improve its overall equipment efficiency through intelligent linking
of processing and packaging.
