The Elimination of Waste, Increasing efficiency, and Achieving Cost Reduction through Interleaving of Tasks

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Interleaving

Task interleaving is designed to reduce deadheading, or waste in movements through the warehouse—a Lean doctrine, i.e., when a worker, for example, picks products and drops them off at a dock and then returns to the picking area without performing any useful tasks along the way. In most operations, some workers are dedicated to picking, while others are dedicated to put-away. Task interleaving is most common in operations with workers that have permission to do both. So instead of a warehouse associate returning all the way across a warehouse to a pick zone, they may stop at a nearby receiving dock, pick up a pallet for put-away, and then store it in a location near where their next pick occurs.

 

Drivers on forklift trucks can use this system, as can associates on foot. At times, forklifts are underutilized. They go to the dock and pick up pallets, park the lift truck and wait for what has to be done next. They hop back on the lift truck for their next assignment instead of staying on the truck and interleaving tasks.

 

A Lean Kaizen Blitz team could come up with some good ideas zeroing in on task interleaving.

 

This eliminates labor waste and increases efficiency. It also increases through put to the customer. It’s like the truck who drops a load at a customer, and returns with an empty trailer. The truck is only 50 % utilized. This is also called deadheading and it is a Lean waste. The goal is to eliminate all wastes, and bring value to all activities in a warehouse, or any facility for that matter.

 

Task interleaving does not just change the way floor-level employees do their job, it also changes things for managers, particularly shipping coordinators. Prior to interleaving, the associates at the dock knew that once a truck was loaded they needed to bring their paperwork to a manager, and get new work to do.  If there was no immediate work to do, these associates would take a break. If it is an unscheduled break, this is also a waste. The manager should have the tasks ready by priority after a truck is unloaded. Shipping coordinators need to monitor the docks more proactively than they did in the past. Time is money. Associates standing around waiting for their next task is a waste.

 

It is similar to routings in manufacturing. These routings tell you what steps to take to finish all tasks, in priority sequence, so no time is wasted and all labor steps are accounted for on the shop floor. Task interleaving can be used in manufacturing as well. If an Industrial Engineer does a time study on a job, they can review the job and make recommendation for more efficient movements by the manufacturing associate.

A warehouse layout that has receiving docks on one side and shipping docks on the other (which is recommended by many warehouse professionals) is not as conducive to productivity gains from interleaving as a layout that has a few dedicated receiving docks next to a few dedicated shipping docks. Some have dock doors only on one side of the warehouse, and any dock can be used for receiving or shipping.  This layout brings more flexibility for efficient movements.

Interleaving tasks has been talked about for more than a decade, but only in the past few year, warehouses that have actually implemented it. Task interleaving can be a great way to improve productivity, particularly for pallet moves, but change management must be addressed carefully.

Some Warehouse Management Systems (WMS) have task interleaving as part of the software. It is up to management to implement it, and use it effectively. A good warehouse management system should maintain an on-going to-do list of required transactions based on event triggers.  The system should assign efficient batches of multiple transactions of work to warehouse resources.  With task interleaving, the WMS looks to combine different types of tasks to reduce this deadheading, and drive productivity gains that can be as high as 20%. The best decision is to turn a new WMS system on without including interleaving. First, get users acclimated to the new environment and system before adding this additional element of change. WMS vendors and consultants need to develop better tools to really understand the flow and real labor savings expected from interleaving. Avoid too much guesswork by managing interleaving later.

Task interleaving is certainly worth investigating.

What are your thoughts on task interleaving? Any additions to our basic overview? Let us know your thoughts. Thank you.

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