Conveyor selection: It's all about throughput

Speed alone kills; maximum throughput for your line must acknowledge buffers and accumulators.

By Mike Pehanich, Plant Operations Editor

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When you’re planning conveyors, accumulators and buffers for your process or packaging system, focusing on throughput can carry you to the right solution.

Forget equipment that can run at the speed of light and conveyors that spiral and bend and pass through contraptions as if they were designed by Rube Goldberg. The key to manufacturing is getting more good product out the door while holding onto your pennies.

Higher throughput is everything. Nothing matters if you can’t make more product for less money.

Within that dictum is the key to selecting conveyors for processing or packaging lines. For the conveyors you choose are never more important than the product they carry or the equipment they connect.

Speed kills

Ask plant managers and manufacturing personnel about the most important equipment issues facing them today and you are likely to hear comments like faster changeover, more automation or greater line speed.

"People think that faster is better. But speed kills," says Patrick Helm, a former General Mills packaging engineer, now managing partner of The Manufacturing Systems Group Inc. (, Cincinnati, and adjunct professor at the University of Cincinnati’s school of applied science. Linking conveyor selection to throughput optimization is one of his major themes with students and packaging engineers. "The reality is that, without throughput, efficiency, line speed, changeover and automation are not important."

Nor is more automation necessarily the best solution.

"Eliminating bottlenecks is certainly key in improving productivity. But one of the biggest bottlenecks of all is lack of flexibility or adaptability on a line," says Bob Woelfling, vice president of manufacturing for Hershey Foods Corp., Hershey, Pa. "Adaptability is becoming a key factor in every part of our (manufacturing) system, especially packaging areas.

"Ten years ago, we were driving productivity at Hershey with automated case-packing and realized tremendous productivity in that fashion," Woelfling continues. "Then came display-ready cases, and most had a different configuration. We couldn’t get the hard automation we had installed to adapt.

"We have adapted since, but that was a five- to seven-year issue with us," he continues. "That was an early indicator. You automate something and think you have found a packaging configuration that is going to solve your situation. Then the marketplace changes everything!"

"Automation is expensive, and it requires higher-level skill sets for operations and maintenance personnel as well as increased planned downtime. It also reduces the flexibility of a system," echoes Helm. "With more automation, you have less opportunity to deviate. When you are designing a packaging system, you design it with a product family in mind. You have to know what those islands of automation will do. When designing a line today, you’re better off reducing its complexity."

Though the terms are often used interchangeably, Hershey’s Woelfling likes to differentiate between flexibility and adaptability.

"Flexibility for me means changing your line over on the fly [to run another product or size]," he says. "Adaptability is adjusting to a marketplace change, adapting your lines to a different product or package than you have run before. Conveyors play no small part in the adaptability/flexibility issue.

"In the overall picture, it’s how quickly you can follow the market trends that counts," he sums. "I’m looking for the kind of flexibility that can adapt in fractions of a shift, not fractions of a year."

Food manufacturers expect more from processing and packaging systems than ever before. Customers are demanding customized products and package sizes. That translates into large numbers of SKUs coming off production lines.

"You have to think what makes the system effective, and for most food manufacturers flexibility is an important requirement," says Helm. That means more planned downtime between product runs.

The first thing to consider when aiming to optimize the throughput of any production system is recognizing that it is a production system to begin with, and not just a concatenation of equipment.

"You have to look at the whole picture," says Mark Garvey, president of the Garvey Corp. (, Blue Anchor, N.J., a manufacturer of conveyors, accumulators and special food systems. "People generally manage a very specific area of a process. They may spend time and money improving ‘productivity’ in that area, but what they have done may have had no real effect on overall productivity."

Conveyors: the great supporting cast

Think of the production system as a line of movement through islands of transformation – where breading is applied, product is cooked and the product changes by entering a container; where the container is sealed, the product is checked for contaminants, safety or integrity and where it is packaged or multi-packed or palletized.

These machines are Helm's islands of automation. To bridge these islands, you use conveyors.

"Conveyors are transports or bridges, and they are as important as the islands of automation themselves," says Helm. "I call them the bridges of automation and compare the production line to the Florida Keys. You have all these islands connected by Highway 1. Think of the Keys as islands of automation and the causeways between them as the conveyors."

Effectiveness is process reliability, Helm explains, and only running time improves it. "It’s calculated as the difference between the time a line makes product and the unplanned downtime. But most lines have from 20- to 30-percent planned downtime built into their schedule." Cutting that planned downtime – not faster lines -- is the key to greater throughput, he says.
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