When people begin their lean journeys, they are usually taught about the 8 Wastes or Muda. The 8 Wastes are taught as the foundation of Lean. But the 8 Wastes (Muda) are actually just one part of the puzzle. There are two more categories that often go untaught and forgotten. These two are Mura which means Variation or Unevenness, and Muri, which means Overburdened or Over-worked. Muda, Mura and Muri are interrelated and one cannot be removed or influenced without affecting the others. It is paramount for Lean learners to know about all 3 and know how they affect each other.
Muda in Japanese means “Useless” or “Waste”. Other synonyms would be “Futility” and “Uselessness”. All these terms are essentially opposites of, or contradict “value-addition”.
So, Muda can be defined as any activity that is a waste and consumes resources, but does not add value to the customer. There are two types of Muda – Level I and Level II.
- Level I Muda are the non-value added activities or Incidental Wastes in the processes that are necessary to guarantee a safe product – Ex: Safety Testing & Inspection, Regulatory Compliance activities etc.
- Level II Muda are the purely non-value added activities or Pure Wastes, which do not add any value and can be eliminated without any effect on the customer. The 8 Wastes or Muda’s are
- Not-Utilizing Talent
- Motion and
- Excess Processing
- These are the most widely known types of Muda and is what most people beginning their lean education learn and focus on eliminating first. An easy way to remember is to remember the acronym D.O.W.N.T.I.M.E (see letters in bold above)
Muri in Japanese can mean Over-burden, Unreasonableness and feeling like things are beyond your control. Overburden (Muri) typically results from Mura (Variation) and in some instances, be caused by eliminating too much Waste(Mura) from the process.
What are some common ways in which Muri shows itself?
- Scheduling more tasks than there is capacity to do. This can apply to people or machines.
- Scheduling all tasks assuming 100% utilization. Not accounting for machines breaking-down, or people falling sick etc.
- Assigning work beyond a person’s capability, skill-set or experience.
- Not having standardized work instructions
- People working over-time for long periods of time
Muri can result in people getting burnt-out, machines breaking down and cause a lot of the other Wastes like Waiting (when said machines break down or if people get burnt out and fall sick, leave the company etc), Excess Inventory, Defects (Making mistakes when rushing through jobs, working late etc).
MURA (Variation or Unevenness)
Mura can mean Variation, Unevenness or Irregularity. Most people don’t even think about Mura and focus all their attention on Muda instead. But, if you really think about how Muda gets created, it’s through Mura. Variation creates Overburden which in turn causes Waste. Mura is the root-cause of Muda.
What are examples of Mura or Variation?
- The unpredictability of Customer Demand. For ex: Ordering Qty. 200 today and Qty. 600 tomorrow, Qty. 50 day-after and so on.
- Constantly changing priorities on active projects. For ex: There is a daily chaotic fire-fight, that everybody needs to jump on while abandoning their other tasks.
- Randomness with which work tasks are assigned to engineers
- Teams with people of varying levels of skill-set and experience
- Number of projects constantly changing
- Constantly changing number of staff available as resources for projects
And if you carefully think about the examples above, you can see how these would lead to people getting over-burdened and then making mistakes that lead to the different wastes.
So, all though I started with explaining Muda, went on to Muri and ended with Mura, in reality, it is best to start learning with Mura, go onto Muri and wrap it up with Muda. This way, even if you are focusing on eliminating Muda first, you know it is going to recur frequently unless you eliminate the root-cause, Mura. By keeping attention on Mura, you focus on the root-cause which will drive down the severity of the Muda, which are the symptoms, and keep them from recurring.
What Ever Happened to Mura by Ken Eakin – https://www.lean.org/LeanPost/Posting.cfm?LeanPostId=957  Mura, Muri, Muda by Jim Womack – https://www.lean.org/womack/DisplayObject.cfm?o=743 What is Muda, Mura and Muri by Doanh Do –https://theleanway.net/muda-mura-muri