Slotting: The secret to optimized picking

Too many companies take a once-and-done approach to slotting. But done right, slotting can add years to the investment you’ve already made in your materials handling system.

By Bob Trebilcock, Editor at Large -- Modern Materials Handling, 9/17/2008 7:07:00 AM

Warehouse and distribution center managers spend a lot of time looking for new processes and technologies to improve picking efficiency. The one they most often overlook is the one they might be staring at every time they look at their pick faces and storage locations: Slotting.

Put simply, slotting is the science behind determining where to store individual products in a facility to enable the most efficient picking. The general rule is that the fastest movers should be located closest to the shipping area and in the golden zone that is easiest to pick from within that picking locale. Slow movers, meanwhile, are located further away, in reserve storage.

Sounds simple.

And, truth be told, a lot of thought goes into slotting when a DC is first set up. And, that’s the problem: Too many DC’s take a once-and-done approach to slotting, never taking the time to ask if their order profiles has changed. Maybe the fast movers are now the slow movers; maybe items now located in pick faces up front ought to be in reserve storage in the back.

“Over time, companies don’t manage their total picking process,” says Bill Casey, president and COO of SI Systems. “The best companies are constantly looking at where their products are stored, and at what is the best technology for picking each SKU. It could be that an item in a pick-to-light area is more popular and ought to be in a carousel or an A-frame.”

Slotting software tools, which are available in most warehouse management system packages and as stand-alone applications, look at a map of the warehouse along with the velocity of orders and order mixes to calculate which items will be picked most frequently and should be in the most advantageous position in the warehouse. In addition, the tool will make recommendations like putting the heaviest items at chest height to avoid back injuries or to separate similar parts to avoid picking errors. “You’re trying to reduce the amount of travel a picker does to move the orders,” says Jim Le Tart, director of marketing, RedPrairie.

To make the most out of slotting, Le Tart adds, the system should be integrated with a labor management program. “Slotting can determine the moves to make to improve picking,” says Le Tart. “A labor management program, on the other hand, will calculate the cost of moving the material from one location to another, along with the potential labor savings from more efficient picking. That way, you can determine whether the cost benefit from more efficient picking outweighs the labor cost associated with moving product from one location to another,”

In addition to licensed applications, there are also Web-based slotting tools, adds Casey. “All a user needs to do is to enter their warehouse data on the Web and the tool will do the work,” says Casey. “They can get a report in a matter of minutes, along with the economic benefit. They may find that 20% of their SKUs will deliver 80% of the economic benefit.”

The most important benefit from slotting, however, may be that it extends the life of existing systems. “By reslotting, the value of your automated system will be as good five years from now as when it was first implemented,” says Casey.