Chicken is big business. The U.S. produced nearly 37 billion lb of commercial chicken in 2010, and the average American consumes more than 80 lb each year. Getting that much meat from farm to table relies heavily on advanced automation, where reliability is critical, and pneumatics often plays a central role.
For instance, an important step in preparing fresh chicken for the supermarket involves weighing, sizing, and sorting the fillets, wings, thighs, and drums from processed birds and packaging them quickly in a sanitary environment. The new Flexible Sizing & Packaging System for Poultry (FSPS-P) from Baader North America Corp., Kansas City, Kan., performs all these tasks, combining the functions of several individual machines into one all-encompassing system.
Conveyor belts on either side of the 60-ft long FSPS-P each handle about 180 pieces per minute, explains Doug Barnett, a senior design engineer with Baader. The chicken pieces travel across a moving conveyor scale, where they are weighed on the fly, then move on to one of eight stations along each conveyor, where they are automatically sorted per customer requirements and placed into various-size tray packs commonly found in grocery stores.
Beyond the tray-pack area, the remaining pieces on the two conveyors are discharged to the center of the FSPS-P, creating larger batches that are boxed for shipment, freezer storage, or future processing. Finally, conveyors carry the trays and boxes away.
Getting a handle on processing
Much of the sorting and handling is pneumatically powered. For instance, custom pneumatic rotary actuators — designed and built by Baader — drive paddles that shuttle products from the conveyors to the packing stations. The rack-and-pinion actuators are constructed of oil-impregnated nylon and stainless steel and are approved for food-handling applications.
Virtually all the remaining pneumatics on the machine, from actuators and valves to fittings and filters, are supplied by Festo Corp., Hauppauge, N.Y. For example, at the tray-pack stations, sorted batches drop into metal drawers. Festo’s DSNU air cylinders push the drawers out to operators, who pack the contents into trays, and retract them when the process is complete.
Twenty-six of the corrosion-resistant DSNU round cylinders, in several sizes and strokes, are used throughout the machine, according to Kevin Ost, Festo’s Kansas City area senior sales engineer. They have stainless-steel cylinder barrels and piston rods, and anodized aluminum bearings and end caps. Those handling small-to-medium loads feature Festo’s PPS internal cushioning, a self-adjusting end-position cushion that requires no adjustment. Units handling larger loads use adjustable end-position cushioning. Both types of cushions minimize impact and shock loads that could potentially damage the machine and cause premature cylinder wear.
In the large-box packing section, the FSPS-P makes similar use of rotary actuators and the corrosion-resistant DSNU cylinders with Viton seals (designed to withstand severe washdown environments) to sort and move the product. But here, chicken accumulates in center drawers that are alternately shuttled to packing stations on either side of the machine. This created an engineering challenge for Barnett because the FSPS-P is more than eight feet wide, and available space is constricted by conveyors running over and under the drawers’ travel paths. Here, he opted for Festo DGC rodless cylinders because of the long length, low profile, and structural support they offer.
The linear drives have a 1.2-m stroke with an 18-mm piston. The DGC’s sealing system consists of an outer cover strip and an internal sealing band that offers excellent contamination resistance with virtually no leakage, says Ost. Loads mount directly to the slides, which run on plain-bearing guides, and the units have adjustable end-of-stroke positioning and cushioning. Twenty of the DGC linear drives are used on the machine.
Flow controls govern actuator speeds, and 72 Festo MPA-S directional valves control cylinder movements. A PLC handles overall motion and pneumatic control in conjunction with proprietary electronics for weighing and sizing.
The valves are mounted in groups of eight throughout the machine in individual stainless-steel enclosures. “That puts the valves in close proximity to the actuators they are driving,” explains Barnett. “It gives us the benefit of not having lots of compressed air in long tubing lengths, which saves air and energy. Plus, we’re not introducing delays in the timing of movements — and timing is critical at the rates we’re talking about,” he emphasizes.
“It also gives us some modularity,” adds Barnett. Although this machine was custom built, the intent is to produce similar versions for other customers. “A large part of the variations in these types of machines is in the number of positions, which directly affects the number of actuators. So housing the valves in modules makes it easy and straightforward to scale the design to whatever the project demands,” he says.