DC Velocity - May 2009

Carton flow racks and shelving aren’t the only storage media that are good candidates for pick to light, however. For medium-velocity SKUs that might not warrant carton-flow racks, Remstar’s Romaine recommends using AS/RS pod technology (which incorporates pick to light). These systems bring the items to the pickers, instead of requiring the pickers to travel to the pick location. For example, a pod may consist of two horizontal carousels that are integrated into a pick-to-light system. The carousels automatically turn so that the correct item is in a position for picking, and the light tree indicates what carousel to pick from, what shelf to pick from, which cell on the shelf, and the number of items to be picked.

Whatever the type of storage used, however, it’s important to take travel distances into account. For pick to light to make sense, pick locations must be relatively close to one another; lengthy travel distances will offset the technology’s speed. “Even though you may have a very high-velocity item, if you’ve got to travel six feet in between picking locations, then pick to light may not provide the best payback,” says Reese.

The non-starters

Just as there are characteristics that make a zone a good candidate for pick to light, there are others that essentially rule it out. What’s not a good fit? To begin with, zones with bulky items and items that are being picked from a pallet. “Any place where you have a worker aboard a forklift truck picking pallet quantities, pick to light does not make sense; it’s almost impossible to get off a forklift truck and push a light,” says Broadfoot.

The same goes for zones where throughput volume is extremely low or extremely high. David Remsing, system sales manager for Innovative Picking Technologies Inc. (IPTI), says IPTI receives many inquiries about the technology from companies that only have two pickers. “In those cases, you just don’t have enough volume to justify it,” he says. To be a good candidate, he says, the operation needs at least 10 pickers.

At the same time, Remsing warns against using pick to light for extremely high-volume operations. For those applications, he says, a mechanized solution like a mechanical sorter or an A-frame would probably be a better choice.

Other non-starters include what

Broadfoot calls “grocery store setups” that contain 10,000 to 100,000 SKUs and where travel distances between picking locations can be several pallet-lengths long.