Mura
斑·mura·"unevenness, irregularity"
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Mura refers to unevenness or inconsistency in processes that causes waste and makes work unpredictable.
Definition
Mura is the Japanese term for unevenness, irregularity, or inconsistency in processes. While muda focuses on waste, mura addresses the variation that causes waste. Uneven workloads create periods of overburden (muri) followed by periods of underutilization, both of which generate muda. Mura appears in demand patterns, production scheduling, work distribution, and process execution. Addressing mura through leveling (heijunka) creates stability that enables continuous improvement and reduces all forms of waste.
Examples
A manufacturer experienced wild swings in production—running overtime three days then having idle capacity two days. This mura resulted from processing orders in the sequence received rather than leveling the mix. Implementing heijunka smoothed production, reduced overtime 60%, and improved delivery reliability.
Key Points
- Mura often causes both muda (waste during slow periods) and muri (overburden during peak periods)
- Addressing mura at the source—through leveled scheduling—is more effective than reacting to peaks and valleys
- Variation in processes (inconsistent methods) is also mura and leads to quality and efficiency problems
- Stable, leveled operations provide the foundation for continuous improvement
Common Misconceptions
Mura is only about demand variation. While demand unevenness is common, mura also includes variation in how work is performed, equipment reliability, and supply consistency. All forms of unevenness create waste and should be addressed.
The solution to mura is more capacity. Adding capacity to handle peaks leaves resources idle during normal periods. The lean approach levels demand to match capacity rather than building capacity to handle worst-case peaks.