Conventional, and most times correct, wisdom dictates that slotting a storage or pick area in a distribution center will yield increases in productivity and throughput. In a vast number of instances, it certainly does. Placing slower moving product, which is accessed infrequently, furthest away from the main activity area of your facility will avoid the wasted time of pickers or lift truck operators constantly walking past that product on their way to access the product or goods that are in demand. Consolidating faster moving, more frequently accessed product closer to the points of receipt or shipment, will reduce the travel time spent accessing those items. So far, so good. But, there's always a "but", blindly doing so, without consideration of how dense the activity in the velocity zoned pick area may become, or ignoring the physical characteristics of the zoned product, may actually reduce productivity and throughput.
If you perform velocity slotting. without consideration of product characteristics in a conventional pick area, where product is picked to pallets or even into totes in a less than case pick line, results can be problematic. In a pick to pallet environment if velocity zoning ends up driving pickers to pick light bulbs before cases of hammers, the results could be disastrous. In the worst case, with an inattentive picker, the order end up being topped off with hammers atop crushed light bulbs. In the best case, the picker will need to reorganize the pallet by moving the light bulbs, and using heavier, denser cases of hammers a base and then placing the light bulbs atop them. Even if the light bulbs were among the fastest moving product, they should be sequenced in the pick after heavier, less fragile product. Considering the varied characteristics of the picked product along with velocity when slotting product will yield the most productive and throughput possible without sacrifices such as damage or re-handling of picked product.
Another potential pitfall of velocity zoning is contention or “too much of a good thing.” Sometimes velocity zoning can be so successful that it will drive too much activity into too small an area. This could result in too many pickers trying to access too few pick locations or too many forklift operators trying to put away and pull product from the same aisle. If the demand in a high velocity pick or storage area is too high, the workers will constantly get in each other's way or need to wait for the picker or lift truck driver in front of them to complete their task before the waiting worker can get on with theirs. Multiply that by many workers waiting to get to the same place and you create a virtual conga line of lost productivity. Ensure the density created by a velocity zoning approach is not too dense, and if it is, spread out the volume to some degree to allow for unfettered access to work task demands in your high velocity area. Too much velocity zoning density can be worse than no zoning at all.
Velocity zoning will always increase productivity and throughput to some degree. If zoning is done with an understanding of the pragmatics of your product characteristics and with an eye on avoiding contentious congestion akin to a morning traffic commute, then velocity zoning will never slow you down.