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The Forgotten M’s

By Ron Updated on May 29th, 2017

Those familiar with lean manufacturing have likely heard the word muda many times. Muda is the Japanese word for waste and is the enemy of us all whether we know it or not.

Strangely enough muda is not the only enemy of a lean system. There are two more, less popular (at least in Western companies), M’s we must also be aware of – namely mura and muri.


Mura in its simplest form means “unevenness.” For example, mura results when your operators are told to work like crazy early in the morning only to stand around and do nothing late in the day. Heijunka may be the answer to this problem but let us save that for another blog.


Muri means to “overburden” equipment or operators. For example, if your entertainment center is only meant to hold 200 pounds and you place your new 425 pound super duper HD Ready TV on it we have muri. We also have other issues like a very real safety concern!

Leads to Muda

So the next time someone drops the word “muda” in their attempt to show you how much they know about lean you may be able to educate them on the other two M’s that are just as important as the infamous muda. Of course you should be humble and polite during this education process.

For the overachievers out there who can tell me which of the three M’s (muda, mura, muri) are visible in the donkey picture above?


  1. Jon Miller

    January 28, 2007 - 12:48 pm

    Good post.

    It’s worth mentioning the cause and effect relationship of these three. When there is mura (variability or unevenness) you do muri (overburden) causing muda (waste).

    A simple example is when you customer demand varies (mura), and you try to meet this customer demand too closely even though your system is not set up to do this (muri), and you either have idle capacity or excessive inventory (muda).

    It’s easy to come up with other examples.

    This is highly relevant to the theme of this blog, as it suggests that the source of waste (muda) is variability (mura) and our effort to forcibly close the gap (muri) between what is and what we want it to be.

    So maybe Six Sigma is the answer after all…

  2. Ron Pereira

    January 28, 2007 - 7:57 pm

    As always, excellent examples Jon. Thanks for checking in!


  3. DMR Panda

    February 3, 2008 - 6:04 am

    Great example and explanation.

    Donkey is the result of OVERBURDON – MURI.

  4. Ron Pereira

    February 3, 2008 - 4:41 pm

    Thanks for the comment DMR Panda!

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