Lean manufacturing, the production system pioneered by Toyota, is predicated on the elimination of waste from industrial processes. One of the fundamental causes of waste is workload imbalance, or mura in Japanese.
Remedies typically aim to stabilize factory throughput. For example, standardized customer order sizes (heijunka) or smaller batch sizes in assembly lines (just-in-time) can help level output. The problem is that these methods are hard to apply in a reactive maintenance environment with unpredictable equipment breakdowns. To fully leverage Lean, traditional concepts like mura need to be interpreted to fit the maintenance context.
One way the workload of a maintenance organization can be unevenly distributed is vertically. Technicians, leads, supervisors, planners and schedulers all must work together as a team. If too much is asked of one group and not enough of another, then the load is unbalanced and waste is inherent, as those in the overloaded category will fail to deliver while underloaded resources end up underproducing. Management must define each role so that the workload is as even as possible in order to achieve optimal performance.
Mura can be present horizontally, as well. First shift is often overstaffed to align the workforce with a typical management 9-to-5 schedule. Second and third shifts then are more lightly loaded, just enough to handle emergencies and keep the plant afloat until first shift comes back. For around-the-clock operations, this imbalance can be very wasteful. Spreading resources evenly can result in a nimbler maintenance department that can better handle breakdowns at any time. It may also be easier to schedule planned work over 24 hours instead first shift only.
A third potential source of mura is if maintenance teams are organized by plant area. Some production lines may perform better than others at a given moment, which can again result in over- and underutilized technicians. Team performance can improve by floating resources toward areas that need the help.
Make no mistake, redistributing work can be tough. People don’t readily accept additional roles or move to areas of the plant they may not be familiar with, and training is required for a smooth transition. Reassigning workers from high to low-performing areas may be interpreted as unfair or “punishment” for success. If shift changes are involved, then load leveling may even generate turnover. Ultimately, the costs associated are inevitable and short-lived, while eliminating mura yields long-term savings.
Maintenance and reliability best practices include many tools from Lean manufacturing. For example, most departments have standard operating procedures or a 5S program – or at least strive to. But as Jeffrey Liker explains in his seminal work "The Toyota Way", Lean methods as standalone tools typically fail to achieve sustained results. Rather, the essential element is not the tools themselves but an understanding of the philosophy behind them, in order to overcome challenges such as mura. As the Toyota Production System was designed with operations in mind and not maintenance, interpretation is required.
