Types of Waste

Although the elimination of waste may seem like a simple and clear subject, it is noticeable that waste is often very conservatively identified. This then hugely reduces the potential of such an aim. The elimination of waste is the goal of lean, and Toyota defined three broad types of waste: muda, muri, and mura; for many lean implementations this list shrinks to the first waste type only with reduced corresponding benefits.

To illustrate the state of this thinking, Shigeo Shingo observed that only the last turn of a bolt tightens it – the rest is just movement. This ever finer clarification of waste is key to establishing distinctions between value‐adding activity, waste, and non‐value‐adding work (Ohno 1988). Non‐value adding work is waste that must be done under the present work conditions. One key is to measure, or estimate, the size of these wastes, to demonstrate the effect of the changes achieved and therefore the movement toward the goal.

The “flow” (or smoothness) based approach aims to achieve JIT, by removing the variation caused by work scheduling and thereby provide a driver, rationale, or target and priorities for implementation, using a variety of techniques. The effort to achieve JIT exposes many quality problems that are hidden by buffer stocks; by forcing smooth flow of only value‐adding steps, these problems become visible and must be dealt with explicitly.

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. Unreasonable work is almost always a cause of multiple variations.

To link these three concepts is simple in TPS and thus lean. Firstly, muri focuses on the preparation and planning of the process, or what work can be avoided proactively by design. Next, mura then 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 then 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.

A typical example of the interplay of these wastes is the corporate behavior of “making the numbers” as the end of a reporting period approaches. Demand is raised to “make plan,” increasing (mura), when the “numbers” are low, which causes production to try to squeeze extra capacity from the process, which causes routines and standards to be modified or stretched. This stretch and improvisation leads to muri‐style waste, which leads to downtime, mistakes and back flows, and waiting, thus the muda of waiting, correction, and movement.

The original seven mudas (TIM WOOD) are as follows:

• Transport (moving products that are not actually required to perform the processing)
• Inventory (all components, work in process, and finished product not being processed)
• Motion (people or equipment moving or walking more than is required to perform the processing)
• Waiting (waiting for the next production step, interruptions of production during shift change)
• Overproduction (production ahead of demand)
• Over processing (resulting from poor tool or product design creating activity)
• Defects (the effort involved in inspecting for and fixing defects) (Womack and Jones 2003).

Eventually, an eighth “muda” was defined by Womack et al. (1990); it was described as manufacturing goods or services that do not meet customer demand or specifications. Many others have added the “waste of unused human talent” to the original seven wastes. For example, six sigma includes the waste of skills, referred to as “under‐utilizing capabilities and delegating tasks with inadequate training.” Other additional wastes added were, for example, “space.” These wastes were not originally a part of the seven deadly wastes defined by Taiichi Ohno in TPS, but they were found to be useful additions in practice. In 1999 Geoffrey Mika in his book, “Kaizen Event Implementation Manual” added three more forms of waste that are now universally accepted: the waste associated with working to the wrong metrics or no metrics, the waste associated with not utilizing a complete worker by not allowing them to contribute ideas and suggestions and be part of Participative Management, and lastly the waste attributable to improper use of computers; not having the proper software, training on use, and time spent surfing, playing games, or just wasting time. For a complete listing of the “old” and “new” wastes, see Bicheno and Holweg (2009).

The identification of non‐value‐adding work, as distinct from wasted work, is critical to identifying the assumptions behind the current work process and to challenging them in due course (Ohno 1988). Breakthroughs in SMED and other process changing techniques rely upon clear identification of where untapped opportunities may lie if the processing assumptions are challenged.