Introduction

Though the nature of order picking has changed considerably in recent years, the demands made on order picking systems within logistics operations continue to grow. Guided by a number of different factors, including the dramatic increase in online shopping and the constant desire to reduce inventories, companies are facing new challenges to pick items more frequently and in smaller quantities. This means that the process of picking orders has become an increasingly cost-intensive function. Order picking is estimated to account for as much as 55% of total warehouse operating expense, and the need to improve efficiencies within this area continues to be one of the biggest challenges facing supply chain managers.

Various factors must be considered when deciding upon the layout. These include taking into account the results of an initial data analysis of the current operations’ overall volume of orders, stock size, desired pick speed and product range. Some picking systems also work better than others depending upon the industry sector. For example, in a perfect world, multi-channel retailers would benefit from the capability to juggle order picking systems, combining the picking of many single item, internet orders with a few large bulk orders for stores replenishment. Trying to pick both types of order in the same warehouse can be hugely challenging and many retailers have chosen to separate the two. The ability to pick many small orders at the lowest possible cost has become especially crucial for them, as online customers have high expectations. Accurate, efficient picking is essential to ensure that their orders arrive on time, especially considering the recent surge in next day delivery demands.

'Person to Goods'

There are a number of different picking layouts available. The first, and most commonly used in warehouses today, is the ‘person to goods’ method. This can be set-up in one of two ways. The first would contain a large bulk storage area and a small picking area with pick face stock being replenished from the bulk store as required. This is most suited to small volume, large orders because the operator wastes less time moving around to pick each order- a shorter ‘pick walk’. This system also works best where stock levels are high, as can be the case with the picking of directly imported goods, because the small pick area keeps pick walks short whilst the bulk storage can be, for example, narrow aisle – a type of racking that provides dense storage but is generally unsuitable for picking from. The second way to set-up this kind of system would be to have one large picking area with no separate bulk storage. This works best for retailers such as grocers, where the orders are large and in big volumes, and picks are generally at case rather than item level and stock turnover is fast. The operator walks further to pick each item required to complete the order, but replenishment from bulk is reduced by holding more stock in the pick face and close by in reserve locations.

Zone Picking

Another type of layout is the  ‘Zone Pick’ system. This is most beneficial for companies dealing with very small orders picked from a large range, for example online retailers. Picking these types of orders in a conventional layout results in very long pick walks even if multiple orders are being picked at the same time. In a zone pick solution, each operator is designated a pick zone, or section of the racking, and only picks those items on the order that are located in their zone. Instead of the picker moving from zone to zone the order moves on a conveyor, usually with automatic routing, so that the carton or tote visits only those zones with stock for the order. The potential drawback of this solution is that it can be difficult to balance the workload between the pickers.  As with armies marching at the speed of the slowest person, here orders may be picked at the speed of the slowest picker. Some may work faster and more effectively than others, or may simply have more or less work to do. Pick face profiling (making sure each product is located in the best pick position based on its throughput) becomes critical in a zone pick operation, as does operator training and assignment to the right zone. Nevertheless with a well managed order launch process and careful and regular attention to pick face profiling, this can be a very effective type of layout.

'Goods to Person'

A quite different option is the ‘goods to person’ solution. This is where an automated machine is used to move along a rail between rack faces to store and retrieve pallets, or bins of stock, which are brought out to fixed pick positions. Because the goods are being brought to the picker, and taken away again, this is the most efficient type of pick. The picker does not have to move and can concentrate solely on picking at rates not achievable by any other method – in some cases up to 1000 picks per hour. In the past pallet stacker cranes and miniload cranes have been the most common types of retrieval machine to be used for this application, but more recently shuttles are being introduced (small devices running on rails attached to the racking or shelving and typically with one machine per level per aisle). However, the initial capital outlay needed is very high and so can only usually be justified in certain situations. The best application of this technology is for situations where a company holds tens of thousands of slow moving lines which would be very labour intensive to pick in a conventional operation, particularly where very high service levels and short reaction times are needed. Spare parts and pharmaceuticals are both good examples but there are also applications of this for on-line retail where, again, ranges tend to be much greater than in store.

Sortation

Yet another picking option is to use sortation. Here, in contrast to picking in one step, the orders are combined. The items on orders are picked in bulk and then sorted into separate orders.This can be particularly efficient where many orders contain similar products. Simple versions of this can use pigeon hole shelving for the sortation, whereby each customer order is allocated a pigeon hole, whereas more advanced versions use high speed sorters. Like goods to person picking, investment levels can be high, but in this case because products have to be touched several times (once to pick it in bulk, once to load it on to the sorter, and once to take it off the sorter) net productivity rates are not always particularly attractive. This approach therefore needs to be very carefully evaluated and specified.

Technology

Within all of these different types of picking, many new technologies and techniques have also been integrated over the years, with varying degrees of success. From the old pen and paper method of ticking a box when picking an item, through remote, handheld terminals, to voice picking and beyond. ‘Voice-picking’ can be particularly effective. Here, staff will wear a small, belt-mounted terminal and a headset with a microphone. They receive directions and confirm tasks verbally. This means that their hands are left free at all times, so that they can pick more accurately and spend all of their time focussing on product handling. This is in contrast to the use of handheld solutions, where the operator has to constantly juggle the device when picking more than one product, leading to wasted time and inefficiencies. It also compares favourably to a physical paper-picking list, which requires constant switching between product handling and recording.

When implementing technological picking solutions, it must be remembered that the physical layout is still critical. Solutions must be integrated carefully to ensure that they do have a positive impact on picking performance and are not simply gimmicks that in fact offer little benefit to overall efficiency.

Conclusion

In conclusion, for any warehouse operation to be considered efficient it is important that order picking is optimised. A poorly designed picking system will see costs spiral and service levels suffer, while the cost of dealing with returned goods due to inaccurate picking could be crippling. It is therefore important to review existing layouts and processes, and integrate new technology where needed, to ensure efficiency, accuracy and cost-effectiveness is achieved. As the UK moves towards economic recovery, a well devised order picking profile has the potential to improve the overall supply chain and pay dividends in the long term. It may well be time to ask yourself the question: how efficient is your system?