Order picking can be defined as follows:
Order picking is the process by which products are retrieved from specified storage locations on the basis of customer orders. In general, the order picking process is the most laborious of alle warehouse processes. It may consume as much as 60% of all labour activities in the warehouse (cf. Drury, 1988).
Improving order picking efficiency generally means minimizing the total expected order picking time, which includes four components (Caron, F. et al. 1998).
- Travel time incurred in picking an order which corresponds to the length of a picking tour starting and ending at a depot. Travel time can be seen as the sum of the 'within aisle' travel time, i.e. time spent travelling within stocking aisles, and the 'across aisles' travel time, i.e. time spent moving along cross-aisles from one stocking aisle to another.
- Processing time at the location points, i.e. the time required to execute tasks such as searching for pick locations, extracting items, documenting picking activity.
- Administrative time incurred at the start and finish of a picking tour, i.e. the time spent on administrative and start-up tasks, e.g. collecting or depositing a pick device (cart, roll cage, etc.), obtaining a pick list, etc.
- A fourth component of the total order picking time is the waiting time for the next job. If one job is finished and the next can not be executed yet, then the picker has to wait.