Expert Insight: Sorting it Out
By Cliff Holste
Date: July 31, 2008

Logistics News: Developing Optimal Order Picking Strategies


The Central Question In Order Picking Strategy Is Whether To Move The Picker To The Part, Or Move The Part To The Picker

When it comes to improving order picking strategies and technologies, many companies are not sure where to start. Here’s one smart place: I think the central question in order picking strategy is whether to move the picker to the part, or move the part to the picker.

As stated in the recently published SCDigest Letter - Advanced Order Picking Systems, order picking and replenishment activities can represent more than 50% of distribution center labor costs.  For most DC operations, selection of orders is the single most expensive part of the order fulfillment process.  It is therefore appropriate that consideration be given to choosing the picking strategy before deciding on the equipment technology and system design.  The evaluation of alternative pick strategies demands a thorough analysis and rational business case.  It’s not a matter of what has the most bells and whistles.  Depending on the application, the right solution may also be the simplest solution and the one with the lowest cost. 

The typical conveyor and sorting system approach involves bolt-to-the-floor stationary equipment and pickers that are mobile.  The exception is where carousels are utilized to bring the product to the picker.  Carousels can be effective when there are sufficient numbers of items of appropriate size and weight with relatively modest demand profiles.

A recent development by Kiva Systems (as demonstrated at NA08) utilizes robots (small wheeled AGVs) to deliver a constant stream of items to stationary pickers.  With Kiva’s Mobile Fulfillment Solution, products are stored on small sets of shelves known as inventory pods.  When a particular SKU is needed, the management control system dispatches a robot (guided by optical markers placed on the floor) to pick up the required inventory pod and deliver it to the appropriate picking station.  Here, a picker selects items from slots in the inventory pod, and places the item in the appropriate customer container, as directed by the computer screen and a laser light.  When the picker is finished with a particular inventory pod, the robot takes it back to storage, or to another picking station, while at the same time another inventory pod is moved into the pick station and the pick cycle continues.

Choosing the Best Order Picking Strategies

So, how do you choose the best order picking strategy?

A good start would involve answering the following questions:

  • How many SKUs are maintained and what is the distribution of demand among them?
  • Number of lines per order?
  • Number of orders picked per shift, and per day?
  • Average order size and weight?
  • Are there multiple order profiles that impact on system design?
  • Is batch picking practical?  What are the pick wave options?
  • How critical is order cycle time?  What are the mission-critical time cut-offs?
  • How are current customer products, order profiles, and service requirements likely to change over the next five years?

Upon analyzing this data, in addition to a host of other special requirements, it will be possible to develop conceptual plans and budget costs that will then lead to the appropriate picking strategy for your operation.  It may be that for your operation, the optimal solution is a “multi-modal” blend of picking strategies and automation technologies, as referenced in the SCDigest Letter.

Powerful and impressive as today’s automated systems can be, their planning and implementation demands that they not be made too sophisticated and rigid. The pace of change in the supply chain world requires operational flexibility.

Agree or disgree with our expert's perspective? What would you add? Let us know your thoughts for publication in the SCDigest newsletter Feedback section, and on the web site. Upon request, comments will be posted with the respondents name or company withheld.

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profile About the Author
Cliff Holste is Supply Chain Digest's Materials Handling Editor. With more than 30 years experience in designing and implementing material handling and order picking systems in distribution, Holste has worked with dozens of large and smaller companies to improve distribution performance.

Holste Says:

Powerful and impressive as today’s automated systems can be, their planning and implementation demands that they not be made too sophisticated and rigid.

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