When there are many orders to pick in the warehouse, one may see a large number of order pickers scurrying about, each one picking for a single order. This can involve a considerable amount of inefficiency, since each picker may travel throughout the warehouse to pick a single order. In addition, each one must enter an inventory relieving transaction to remove picked items from the inventory database, which introduces a high risk of transaction errors, simply based on the volume of entries being made.
A better approach is to use zone picking. Under this approach, an entire day’s picks are consolidated into a single master pick list, which is then sorted by warehouse location. Different pickers are then sent to specific sections of the warehouse with their portions of the master pick list, where they use much less travel time to pick their portions of all picks required for the day. All picked items are then consolidated in a central picking area, where they are broken down to fulfill individual orders. This approach represents a major reduction in travel time by pickers, while also eliminating many inventory transactions. If picking transactions are entered manually at a separate computer terminal, one can also assign the best data entry person to adjust inventory balances based on this smaller number of picks, thereby increasing inventory accuracy further. This best practice works best in very large warehouse environments where there are many orders to be filled.
There are several additional benefits to zone picking. One is that pickers can gain great familiarity with the items and locations in their assigned zones, thereby increasing both picking frequency and the accuracy of picks. Further, pickers can be given total responsibility for their areas, so they can slot inventory to increase picking efficiency based on their own picking experience. In addition, they can be kept on duty in their assigned areas, which tends to reduce socializing to some extent. Finally, there are virtually no traffic problems in the picking zones, because only one person is assigned to each zone.
The main downside is the need for an order breakdown area near the shipping part of the warehouse, where the consolidated picked orders are split into individual orders. Also, because people in every picking zone, as well as those manning the downstream operation must “touch” an order before it is shipped, zone picking makes it very difficult to assign responsibility for (or correct) order picking errors.
Another problem is that the picking volume by zone may change by day, depending on the contents of orders to be picked each day. When this happens, some pickers may find themselves overwhelmed with work, while pickers in other zones are not sufficiently utilized. To avoid this, one can periodically revise zone configurations based on long-term changes in transactions by zone. A more efficient approach to short-term variations in zone volumes is to have a computer system automatically reconfigure zones every day, though this requires a fully integrated (and expensive) warehouse management system.