In recent contributions to this series we have looked at how different physical picking methodologies are appropriate to different warehouse operations. We have tried to show how selection of a methodology that meets your unique operational factors is important in achieving high level warehouse performance. And we have suggested that choosing the right methodology before you select and deploy technology to improve it is probably the correct way to approach things.
Many companies are familiar with the concept of ‘wave picking’. And in case anyone defines it differently, for most people this usually means the ability to create a ‘wave’ (group) of orders based on chosen criteria. These criteria are typically things like date or delivery time, geographical factors such as region, city or postcode, product or product type factors like specific picking or transport requirements, and order profile, for example the average number of items per order.
So typical examples of a ‘wave pick’ might be a wave of all orders for delivery before 10.00am, one based on the London E17 postcode, or one of orders containing foodstuffs requiring an ambient temperature regime. However once the wave has been created there may be nothing clever about the way orders are dealt with at the picking stage. They have simply been grouped together for operational simplicity, or convenience of delivery, rather than for reasons of picking performance. They will then be picked as single orders in the manner we’ve previously discussed.
However, and this explains our qualified definition, some people’s understanding of wave picking can be something slightly different. Namely, the grouping together of orders for simultaneous execution by a single picker. Forgive the semantics, but we would prefer to call this ‘Cluster Picking’ as it involves a ‘cluster’ of orders being picked by one operative. The wave pick is what usually precedes it as, in line with the description above, a cluster of orders has probably formed part of a wave for a particular reason, for example because it may consist of five or fewer items.
The initial wave selection can be based on any factor that makes the orders suitable for picking in clusters. This may be related to the number of order items, as above. Size is a factor too, as it is clearly easier to pick multiple orders containing items which are smaller and easier to handle. It may relate to the physical size of the storage area, for example where specific products are kept in a dedicated zone, making it feasible to complete a full wave of order picking in a smaller area.
But it is with the picking methodology itself, not the wave selection that efficiency gains can be realised. Using a trolley containing despatch boxes, or other media (dependent on size) to assemble orders, the picker follows a designated walk sequence, visiting each location where stock is required to meet one or more orders. The walk sequence continues until all relevant locations have been visited, and all orders are complete. They can then be taken directly to a packing station, or, where picking and packing are a combined activity, directly to a despatch area for loading.
There is lots more detail to examine in terms of this process. There are questions about how to identify picking media used and the reasons for doing so. There are issues around discrepancies and the way to deal with these as part of the overall process, and both areas are connected with overall pick and despatch methodology. But we can be reasonably certain that by using the right technology this will be significantly easier and boost productivity further. We’ll take a look at the technology for this as well as other picking methods in our next article.
You may also be interested in: Warehouse Performance Part Six: Picking #3