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By Bob Sperber, Plant Operations Editor | 05/07/2010
Conveyors are no longer mere material handlers. Modular, flexible units wired for the computer age can connect to a plant's network, talk to machinery in front and in back of the conveyors, flip switches to turn themselves off and wake up when a signal comes down that dinner's coming -- and needs to be sent to the wrapper.
Both the mechanical and the electrical worlds collide in modern conveyors. They're no longer passive chunks of steel, but active participants in productivity, quality and compliance with management initiatives, standards and regulations.
Mechanically, conveyors are always getting better at shuttling around and manipulating products so Machine B can use Machine A's output. They're getting better at conserving floor space and energy, too. And when traditional conveyors won't work, robots are also coming of age as a significant product-handling solution. Controls become more miniaturized and capable, ushering-in "smart" conveyors for integrated automation.
The first step in any decision, of course, is to figure out what kind of machinery is needed to keep product flowing and organized at high speeds.
Some of the most challenging applications involve products whose sanitary guidelines prevent conveyors from direct product contact. That was the challenge a Wisconsin meat plant issued to Dorner Manufacturing (www.dornerconveyors.com), Hartland, Wis., when four lanes of unwrapped sausage in trays needed to be transferred into a single packaging machine's infeed conveyor.
Hytrol conveyors form a sortation and accumulation loop in a large meat processing facility.
"We used a system of servomotors, conveyors and other control system elements to gently accelerate and decelerate the trays to keep the line moving, without jarring product out of the tray," says Mike Hosch, director of product development. To keep high-speed plastic chain-belting running smoothly, nose-rollers were used. Nose rollers help reduce the gap at product transfer points, and are especially useful on curves, which helped to "transfer the product gently from one conveyor to the next without jostling the product," he adds.
Additionally, sensors, vision technology and stainless steel-enclosed servomotor and control equipment provided the tools to monitor the line and control speed, spacing and other parameters. "On this line, the conveyor looks like one, but actually it uses four individual belts on one conveyor, with each controlled by an independent servomotor control loop," Hosch says.
Elsewhere, processors have a hard time getting loose, processed products into the infeed line of equipment that will put them in trays, packages or lugs used for intermediate steps. Examples include frozen meat patties, breakfast foods and products in the sandwich category, including pocket-type products.
What looks like one conveyor is actually five. Successively faster conveyor modules from Kleenline divert and "chicane" a random product flow from processing into a higher-speed, singulated flow for packaging.
For example, it's a challenge to handle 900 pieces of a product coming off a spiral freezer belt, spread 10 or 20 pieces across. But by splitting that flow into five smaller conveyors running 180 pieces/min. gives a processor a chance. A series of smaller belts can split the flow into separate, successive conveyors that put the product into single-file for delivery to the packaging machine infeed. Such a "smart-belt distribution chicaning system" has been implemented by Kleenline (www.kleenline.com), Newburyport, Mass.
How smart are today's conveyors? Kleenline is now installing a system in a major processor's frozen meals plant that automatically changes configurations -- down to the servomotor-controlled rails that change their width based on product recipes stored in plant computers.
"You press a button for the meal you want to pack, and the rails across the plant -- it could be a mile's worth of conveyors elevated 25 ft. -- will all start changing," says Jim Laverdiere, CEO of Kleenline. Additionally, standard automation hardware and software monitors equipment to track a machine's hours of operation, scheduled maintenance needs and the full range of data needed for Optimal Equipment Effectiveness, continuous improvement, Lean Manufacturing and other programs.Rise of the robots
Once a stream is split into a manageable and organized flow, it can be handed-off to robots as well as conveyors feeding directly into wrappers, cartons or just bulk packs. Robots have proven reliable for decades, mainly in downstream material handling and palletizing applications. But "some processed foods are very difficult to handle with robots," continues Laverdiere. "It's all depends on the end-of-arm tooling."
Just like conveyors, robots are getting faster, smarter and more robust for upstream processes. One or more well-positioned small robots, for example, can transfer products from one conveyor to another when traditional conveyor transfers can't. This is sometimes the case for products or packages with odd shapes or loose components (meats and cheeses) that are likely to topple over in handling.