Order picking – Pick your strategy carefully says Gavin Parnell, Director of Go Supply Chain Consulting Limited.
Order picking is often one of the most labour intensive operations in the warehouse. For this reason a review of the picking operation can offer the greatest opportunities for productivity gain. Furthermore, inaccurate picking is a source of errors that are highly visible to customers and result in costly and inconvenient returns. Time invested in designing cost effective picking operations is time well spent.
Even ignoring full pallet picking, order picking remains a diverse activity, ranging from picking half a pallet or more worth of heavy cases, as might be common in the food and beverage sector, to small parts picking from totes. Sometimes, for example in automotive after-market spares warehouses, there can be a wide range of picking profiles under the same roof. For all of this diversity, we can typically understand order picking as made up of a number of component activities:
• Pre-pick activity (e.g. pick up an empty pallet, log on to hand held terminal etc.)
• Travel time to first pick-face
• Travel time between pick-faces
• Time spent per visit to the pick-face
• Time spent per item retrieved from the pick-face
• Travel time to marshalling area
• Drop-off at marshalling area
Strategies for improving usually productivity focus on reducing the time spent in one or more of the above areas. Some examples of these are:
• Automatic task allocation by WMS
• Zone picking or goods-to-man systems to reduce travel distance and time
• Picking more than one order per pick walk, either into separate containers / pallets, or into a common container followed by a sortation step
• Use of conveyor to take away picked orders
• Smaller, denser pick-face configurations
• Ergonomic pick-face design
• Hands free scanners or voice picking to speed up handling at pick-face
• Automatic or semi-automatic layer picking
Like any aspect of warehouse design, this often comes down to a trade-off between capital costs and operating cost reduction. Furthermore the choice of picking strategy will have an effect on the frequency and time devoted to pick-face replenishment and this must be taken into account.
Strategies for improving accuracy include:
• Barcode scanning of pick-face location and / or goods
• Voice picking with use of check digit to confirm location
• Post-pick checking of some or all picked orders
Designing an order picking operation is a mixture of analysis, experience and options cost modelling. Two businesses that are superficially similar may not in fact have the same optimal picking solution if their order profiles are different e.g. fewer items per line or lines per order. We have seen this with multinational companies that have tried to impose a ‘blueprint’ solution across different markets. It is always worth doing the analysis to segment the range, understand the order profile and design the optimal picking solution.
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