One of the ways that newer material handling systems accommodate system stalls is variable speed drives, particularly in distribution supporting manufacturing. These controllers enable conveyors to run at variable speeds that can be increased or decreased at any time, allowing a system to catch up or decelerate in pace with potential upstream delays.
In many ways, the use of variable speed drives has required a change in thinking by material handling suppliers and DC engineers and managers, according to Bryan Boyce, product manager, case conveyor products, FKI Logistex North America.
“For example, if a packer is putting product into cardboard boxes, obviously the plant doesn’t want any equipment on the line to stop,” says Boyce. “When we design a conveyor system to take the boxes to a palletizer, the question used to be, if the palletizer goes down, how long can the packing operation continue to run until it has to stop to accommodate the delay in the palletizing area?
“What people neglected to consider was the time required to clear the resulting backed-up product through the palletizer. They were so focused on the upstream problem that they didn’t look at the downstream time needed to recover.
“In the past, the answer was to add more accumulation conveyor, increasing system costs. Now we see the prolific use of variable-speed drive controllers and more sophisticated controls on a reduced amount of accumulation conveyor. Manufacturing settings in which boxes are of a more consistent size through the line are more conducive to variable-speed drives and the variance in conveyor speeds that they allow. Generally, retail, e-commerce and other more conventional distribution settings still lean to accumulation as the solution,” notes Boyce.
Whatever the setting, supporting rapid and dynamic changes across the supply chain is the job of the material handling controls system. You can mechanically turn the chain faster or slower on a conveyor to vary its speed, but enabling the system to process additional information more quickly, more dynamically and more accurately is the function of the underlying controls.
Over the past decade, conveyor systems have gone through major changes in controls at the machine and system level. Onboard PLCs are much more sophisticated, as is the variety of PC-based control systems, wireless controls and other advanced systems that give DC managers the ability to supervise their equipment and make changes on the fly.
As systems grow in size and complexity, material handling vendors must build more sophistication and capacity into their control systems and networks. If a store in Atlanta needs an extra 25 boxes of goods, for example, is there adequate supply in the DC to satisfy that order? Building robustness into the controls system helps material handlers answer that question and deal with new situations quickly and accurately.
“The speeds we’re accomplishing today are faster than in the past,” says Cash. “We could always run faster by changing the gearing, but it’s the technology within the controls that enables us to see and move the boxes at a faster rate, much like your PC at home.
“Your PC gets faster and faster, doing the same things in less time. Likewise, the amount of real-time order and inventory information we can use and pass around the different distribution center networks allows us to make decisions faster and get more product out the door.”
RFID is the buzzword in material handling controls, and is slowly making headway as a way to increase visibility into the whole supply chain.
With lessons learned from RFID implementations in other markets, material handling vendors are increasingly adding RFID capabilities to their equipment. In conveying and sortation, RFID is still an adjunct, for the most part, with the capability for RFID tag reading and coding left at accessory readers, not built into the equipment. But, as the cost of RFID tags comes down and the technology further penetrates the market, material handling equipment will increasingly use the technology.
The Cost Factor
When all is said and done, the bottom line might be the ultimate factor that determines which direction to take in choosing a conveyor. With traditional belt- or chain-driven live roller conveyors costing as much as 75 percent less than sophisticated 24-volt motorized roller conveyors, traditional choices often trump more advanced offerings in many settings, particularly in slower manufacturing distribution lines.