Three Broad Types of Waste
The elimination of waste is the goal of
defined three broad types of waste: muri, mura and
The Toyota Way: 14 Principles
The words muri, mura
and muda are often used together and
referred to as the three MU's in Japan. "Just as muda offers a handy
handy checklist to start
the words mura and muri are used as a handy reminder to
start Kaizen in a workplace (gemba).
Mura means irregularity, and muri means strain. Anything
strenuous or irregular indicates a problem. Furthermore, both mura
and muri also constitute muda that needs to be eliminated,"
writes Masaaki Imai.1
Muri is all the unreasonable work that management imposes on
workers and machines because of poor organization, such as carrying heavy
weights, moving things around, dangerous tasks, even working significantly
faster than usual. It is pushing a person or a machine beyond its natural
limits. This may simply be asking a greater level of performance from a
process than it can handle without taking shortcuts and informally modifying
decision criteria. Muri also includes bad working conditions, and it will
often push a resource to work harder than its natural limits. Unreasonable work is almost always a cause of multiple
variations. Lean focuses on the planning of processes to avoid muri
and on the preparation and planning of the process, or what work can be
avoided proactively by design.
Mura is the variation and
inconsistency in quality and volume in both products and human conditions.
Lean focuses on how the work
design is implemented and the elimination of fluctuation at the scheduling
or operations level, such as quality and volume.
Muda is the Japanese word for
It specifies it specifies any human activity, which absorbs resources, but
does not directly add
activities and results are to be eliminated.
is, in its most basic form, the systematic
elimination of 7 wastes – overproduction,
waiting, transportation, inventory, motion, over-processing, defective units
– and the implementation of the concepts of continuous flow and customer
Muda is discovered after the
process is in place and is dealt with reactively. It is seen through
variation in output. It is the role of management to examine the muda
in the processes and eliminate the deeper causes by considering the
connections to the muri and mura of the system. The muda
and mura inconsistencies must be fed back to the muri, or
planning, stage for the next project.4