To a layman a picking process can seem chaotic. The orderpickers drive like busy bees in an apparently chaotic way through the warehouse. However, like with bees, behind the tasks of each orderpicker lies a mature strategy. Only the shortest possible route can reduce picking costs to a minimum.
The simplest orderpick strategy is called the S-shape approach.
The orderpicker starts its route in the most left or right aisle where a pick needs to be done. After the first pick is executed, it runs completely through the aisle and then into the next one as listed on the route. Also this aisle is completely driven through, and eventually the driver is creating an S-shape through the warehouse.
A disadvantage of this strategy is that the picker drives completely through every aisle, regardless of the actual pick location in that aisle. The chance that a lot of unnecessary mileage is covered, is thus relatively large.
This is different when we examine the so-called 'Largest gap' strategy.
This strategy is based on the largest distance between two locations in a pick aisle. That largest distance is the part of the aisle that will not be visited.
Once the order picker reaches that largest gap, the truck turns back and goes into the next aisle on its route. After all the aisles are approached from the backside, the order picker does the same from the front side. This time to visit the pick locations on the other side of the largest gap.
This strategy provides mainly short routes when the number of locations to be visited per aisle is low.
Combined or Optimal
The Combined routing strategy uses the best of both above-mentioned methods.
In this case we look only one aisle ahead. Every time all goods are collected in one aisle, it is determined whether to proceed towards the end or whether to turn around to the beginning. Broadly speaking, this is similar for the Optimal routing strategy. This one calculates the shortest picking route, regardless of layout or locations where items have to be retrieved.
The actual choice for a strategy also depends on the desired performance. Good advice seems indispensable. As it is a smart WMS. Because for the driver it is obviously impossible to constantly determine the quickest and most efficient route by himself.