Essentially, a warehouse delivers four kinds of activities: goods reception, storage, order picking and shipping. Developments in recent decades (e-commerce being the most influential) have turned order picking into the costliest and most labour-intensive of those. Gian Schiava explores the choices you must make when designing or redesigning your order picking process.

In this article we consider the various methods, technological tools and other factors influencing the order picking design process. These ultimately determine whether you will be able to gain productivity improvements.

Static versus dynamic

Order picking is the process of retrieving products from storage or buffer areas to fulfil a specific order. When beginning with a blank sheet, the warehouse manager can opt for static or dynamic order picking, and this choice has a huge impact on overall warehouse layout.

With static order picking, the operator must go to the goods. It involves transportation to the location, picking the item/pallet and then transporting it to the delivery location. Both efficiency and effectiveness are influenced by the choices made, which may involve:

• Minimising walking/driving distances
• Optimising route sequences
• Arranging storage locations according to types of goods
• Shortening processing time and/or pick time (with hands-free approaches)
• Selecting the method of collection

In addition, various tools are available to boost performance further.
Dynamic order picking is all about getting the goods to the operator. This can be done with conveyors, mini-load systems, vertical carousels or even robots. The main considerations here are ergonomics, the reduction of actions and fault control.
In making the complex decision between these two basics, your company should consider return on investment (ROI), maintenance, scalability, flexibility and speed. Unless there are large and almost continuous incoming and outgoing flows, most warehousing companies will operate a static order picking process, in some cases supported by a degree of mechanisation.

Methodology

We talked to René de Koster from the Erasmus University in Rotterdam who believes that there are two basic choices to make in static order picking.
The first is between sequential and parallel. With sequential order picking, one or more orders are picked and completed by one person, or possibly by several persons, and then the order is passed on. In parallel order picking, several people work on these orders simultaneously. The advantage of this is that one person does not have to go through the entire warehouse, so walking distances are limited.

The second choice is whether to collect per order or collect per item. In the first case, one or more people complete one order before they start with the next. In the second case, all order lines within the orders are rearranged in batches of orders per item or per zone. Each person picks one batch and therefore only a limited part of the full order. This also has the advantage that walking distances are limited.
The method most suited to your business will depend on these four factors:

• The number of orders per day
• The number of order lines per order
• The product assortment
• The characteristics of the goods

Sequential picking works well if the number of order lines per order is limited. It is simple and the chance of errors is very limited. However, if the number of orders grows and the assortment remains limited, batch picking is worth investigating.
The characteristics of the goods also play a role because they often have consequences for the storage method. Voluminous articles will be in pallet racks or even on floor locations. Smaller goods tend to be stored in shelving systems. In warehouses with different storage systems, parallel picking may well be the most practical solution.

Independent companies which test warehouse forklift trucks, like the Dutch agency Andersom, have pointed out that most gains on the lower level can be expected from working with forklifts offering good acceleration, flying start and walk-beside features, and great ergonomics. The warehouse manager must then deliver a routing process that reduces wasted time and optimise picking distances.

The ideal order picking process…?

It simply does not exist. Each situation will turn out to be unique. Too many factors are involved and it therefore pays to work with experts when designing your optimal order picking process.

If you would like to read the unabridged article by Gian Schiava please visit Eureka, the online magazine for the materials handling professional.