Lean Methodology provides many approaches to classifying waste. In this respect, we have schemes like the eight Lean wastes, also called TIMWOODS; 5MQS; The Three Mu’s, and the Yamada Method, among others.
Their ultimate goal is to eliminate waste, which is defined as activities that do not add value to the end product or service.
This post will cover another way of doing it, called the Three Mu’s: Muda, Muri, and Mura.
The Three Mu’s
Muda, Muri, and Mura are Japanese terms for three fundamental types of waste related to capacity and flow.
The main advantage of this method over the previous ones is that the Three Mu’s are closely related and linked, one flowing into another.
The goal of thinking about waste in this way is to reach the most balanced flow of work and materials.
But what are the Three Mu’s?
Translated into English, Muda means Waste, and can be thought of in two ways:
- In a general sense, meaning any activity that does not add value to the end product or service.
- In terms of excess capacity.
The focus is usually put on capacity in the three Mu’s. Muda thus refers to the waste of a system with a capacity greater than the load placed on it.
It may seem counter-intuitive that a system with excess capacity is wasteful. Some may see it as a benefit.
After all, if you are able to work more than required, your job is supposed to be easy. However, in the business world, this unused capacity is a waste of resources, space, and employees.
Muri means Overload, and is the waste that results when the load exceeds the capacity.
Like Muda, this waste can sometimes seem necessary. It may seem essential to push employees and machines to meet a pressing demand. However, we should keep in mind that this excess stress can lead to waste, such as more errors, defects, and malfunctions.
It can also cause the next Mu: Mura.
This Japanese term is translated as Unevenness or Irregularity, and represents the waste of unequal load and capacity. It means that the capacity is sometimes greater than the load (Muda), and other times less than the load (Muri).
An example of Mura is when workers hurry after a time of waiting for the workload.
We can avoid Mura by implementing Just-In-Time and other pull-based strategies that limit overproduction and excess inventory. The key concept in these systems is to deliver and produce the right part, in the right quantity, and at the right time.