rugged but sensitive

Until science figures out a way to beam products from one point to another, a la Star Trek, distribution centers will rely on conveyors for transport. But no one's waiting around for the teleportation revolution. In the meantime, conveyor makers are introducing design improvements that make their systems more efficient and versatile than ever before. You might even say that modern conveyor technology is on a roll.

Compared to their predecessors, today's conveyors are faster and more flexible, thanks to their modular designs. They're smarter too, owing to advances in the sensors used to control starts and stops, and relay critical information to their human overseers. New materials used in the manufacture of rollers, bearings and conveying surfaces have reduced noise and wear. And at a time of spiking energy costs, they're drawing less juice through the use of DC drives and improved sensor design.

Sense-sational
Among the most significant changes in conveyor design is the move from mechanical sensors to electronic sensors. Electronic sensing has many advantages. It allows for higher speeds, reduces noise and lessens the need for maintenance because there are no moving parts to wear out. It also extends the range of items that can be handled via conveyor. With mechanical systems, cartons need a certain amount of heft to depress a sensor. The new electronic sensors, by contrast, can be tripped by cartons weighing less than one pound.

And electronic sensors can be made with a brain. "Sensors now have microprocessors that make them 'smart sensors,'" says Boyce Bonham of Hytrol Conveyor Co. "Because you can put as much intelligence in them as you want, you can make them very efficient."

Bonham reports that electronic sensors are replacing mechanicalstyle sensors to accumulate small cartons. Accumulation zone lengths are no longer based on how far apart the sensors are, but are instead determined by the size of the cartons conveyed. That allows for smaller gaps and means that more cartons can occupy a given footprint.

Smarter sensors, like the 32-bit variety commonly used today, can also provide diagnostic information. They can indicate exactly where a jam has occurred, for example, or identify which drives have failed.

"Intelligence can provide diagnostic feedback on the health of the system that allows maintenance crews to do more accurate repairs," adds Bonham. Even schematics can be stored within the system, so that a maintenance technician with a laptop can call up repair information directly from the facility floor.

Other maintenance tasks have become easier as well. Belts that used to take an hour to change out can now be turned around in 5 to 10 minutes.

"We are also seeing more snap-in components, as opposed to those that had required nuts and bolts before," adds John O'Brien of equipment supplier HK Systems.

Conveyor speeds have also increased. Some conveyors are approaching rates of 500 feet a minute, with sorters actually attaining blazing-fast speeds of up to 700 feet per minute. Of course, that's not an advantage if the rest of the operation is unable to keep up. If you can't pack and load at those rates, ultra-fast conveying and sortation will create bottlenecks that offset any gains achieved through greater velocity. Speed can have other drawbacks as well. "The faster you run, the quicker components wear out and the more noise levels increase," cautions Tim Kraus of system supplier FKI Logistex.

Roll on
Not only are they speedy, but new conveyors are also versatile, designed to handle a wide range of products. Placing rollers that are 1.9 inches wide a mere two inches apart gives the rollers greater surface contact with products and allows them to carry an unprecedented variety of items. Being able to put lightweight and oddly shaped items on a conveyor reduces the need for relying on other means of moving those products, humans included.

That's good news for DCs in regions where labor is in short supply. "The problems of finding labor for distribution centers is not going away," says Susan Rider of conveyor manufacturer Intelligrated. "There is a need to reduce the amount of non-conveyables to eliminate additional manual handling."

Beyond their spacing, the rollers themselves offer advancements. Powered roller designs, in which small motors for driving product are actually contained within individual rollers, are gaining favor. They are easier to maintain and allow for a good deal of design flexibility, as the power and intelligence are self-contained within small conveyor sections. And they're getting better all the time. "As we move forward with this technology, we should expect to see costs go down and roller capabilities go up," says Bob Barnes of HK Systems.

Though power rollers can cost up to 30 percent more than shaft and belt drives, their lower energy consumption can lead to long-term savings. But that's not always an easy sell. "Many people look at only those initial costs," says Don Kloosterhouse of conveyor manufacturer TGW-ERMANCO, "but these rollers can save energy, maintenance and preventative maintenance. It is best to look at costs over the life of the system. There could be real savings."

Powered rollers achieve these savings by operating only when product is available for transport. As a carton or tote approaches the zone, the roller kicks on to carry it forward to the next zone. If no other cartons are present, it turns off. For this reason, powered rollers tend to be used for applications that feed specific work zones like picking areas, value-added work zones and packing stations—areas where the conveyor is not constantly running. But that same feature makes them less than ideal for transporting items long distances, such as to and from docks or storage, where product is nearly always present on the conveyor.

Powered rollers are also less costly to install in the field than shaft and belt drives. That's largely a reflection of their modular design. The more pre-wiring that can be done in the factory, the faster these systems can be up and running when they reach the DC.

Modular design also means that it's no longer necessary to tear out the conveyors when requirements change. Technicians can simply rearrange the modules in a different path. "Conveyors then become reusable assets," explains Ken Ruehrdanz of Dematic (formerly Siemens Logistics & Assembly Systems). "Modular 'plug and convey' designs allow conveyor sections to be moved and reconfigured to another location or building and into a different application."

Today's conveyors even look better than their predecessors. Newer systems that hide all of their components from view have been popular in Europe and are now showing up on this side of the Atlantic as well. Wiring, drives, controls and pneumatics are mounted within the conveyor frame or hidden behind shrouds or plastic windows. Not only does this present a more attractive appearance, but it also reduces noise and fluid leaks. And although the components may not be visible, conveyor manufacturers say, they're still highly accessible for repair purposes.

One word: plastic
Where is conveyor design headed in the future? Most experts agree that systems will continue to get faster, smarter and more efficient. We may see a greater reliance on composite materials not only for bearings and drives, but possibly for the conveyor structures themselves. Escalating steel prices may eventually result in plastic conveyors that will also be quieter to operate.

Designs will also be simpler, with greater emphasis on making the conveyor part of an integrated system. "We are going to see more modularity that will allow a designer to build from building blocks using standard components," predicts FKI's Kraus. But the focus will continue to be on integration. Future conveyor systems will not simply connect pieces of equipment; they'll be the glue that holds them all together.