(This is the third in a series of deeper dives into the 8 lean wastes.)
We’ve all seen operators of a concession stand or sales associates on the floor of a retail store standing around doing nothing when there are no customers to service.
We’ve also quite possibly seen operators on a manufacturing floor standing around doing nothing because they aren’t able to move on to the next step in their process.
Both of these are examples of the lean waste of waiting. It’s wasteful because the time you or your company has paid for (or is paying you for) is being underutilized due to not doing anything and simply waiting on something else to happen first.
Waiting can be caused by a few things. First, an operator may be part of an unbalanced process. For example, if a two-operator process has one operator complete their steps in 60 seconds and the second operator complete their steps in 40 seconds, that second operator will be waiting 20 seconds for the first operator to get done. This is unbalanced, and if the standard work time was balanced (i.e. 50 seconds each) there would be less time wasted waiting.
(Sidebar: balancing workloads and removing waiting time can help in overall productivity as well. In the above example, each unit produced by this process requires 60 seconds of effort by operator one and 4o seconds of effort by operator two. If the labor and process steps stay divided as such, the greatest number of parts this process can make in an hour is 60. However, if you are able to balance the labor between the two operators and each one takes 50 seconds to complete their steps, you’ve eliminated the waiting time and now your production rate is one part every 50 seconds. Over the course of an hour you are now producing 72 parts instead of 60, an improvement of 12 parts per hour.)
Waiting can also be caused by a lack of raw materials. Maybe in the two-person process from above, the raw materials have run out and the process cannot continue. Until the raw materials are replenished the operators are forced to wait.
Machine downtime can also cause waiting. If a machine that is critical to a process goes down, the process cannot continue until the machine is back up and producing good parts. Until that happens, the operators are again forced to wait.
Also a lack of downstream customers can cause waiting. During the middle-to-late innings of a baseball game, fans don’t spend as much time hitting the concession stands so concessions operators spend their time waiting for customers to arrive if there is nothing else to do. Sales associate on a store floor would also spend their time waiting for customers. Because of the ebb and flow of downstream customers it would be hard to have any even demand across multiple hours because customers drive the process.
So how can waiting be combated? For starters, identify unbalanced work loads. In the two-operator example, conduct time studies to see if some labor can be transferred from the first operator to the second in order to balance the effort and time required.
Implementing a simple kanban material replenishment system can help prevent stockouts, thereby preventing waiting caused by lack of parts available. The kanban system would be like a supermarket, with reorder points and replenishment of parts consumed by the process.
The best and easiest way to prevent machine downtime is to implement a standard basic preventive maintenance program for machine upkeep. Keeping machines clean and functioning at their optimal level through elimination of functional abnormalities (broken parts, cracked glass, split wires, dirty fixtures, worn out parts) will minimize wastes due to machine downtime.
With concession stands and sales floors, make sure there are downstream activities available to complete when there are no customers to service. For example, a concession stand must be cleaned at the end of the night. In the event there are few customers to service in the late innings of a baseball game, start deploying the concession stand operators to initiate nightly cleaning chores. By using this time wisely and completing end-of-shift tasks, the full gamut of tasks remaining at the end of the shift will be smaller by having started them earlier.
Reducing waiting through time studies, optimal machine efficiency, and task planning will make a big impact on productivity and cost savings. This list is by no means exhaustive, but more illustrative of where waiting waste can occur.