Muda mura muri

Muda mura muri
See also
Lean manufacturing Lean supply chain management Quality assurance Toyota production system Just in time 7 wastes of lean Philip B. Crosby Jidoka Process strategies

Muda, mura and muri (3Ms of lean) are the pillars of fight with waste in production and services. They are important part of Toyota Production system and Lean manufacturing. They mean:

• Muda - actions that don't add value for the customer,
• Mura - unevenness or inconsistency in processes,
• Muri - overburden of employees, machines, processes

Muda, mura and muri are the example of hidden factory. The organization performs many actions that are not paid by the customer. They are loss for the company. Implementation of lean thinking leads to removal of hidden factory.

Muda

Muda is the waste created by actions that don't add value to the customer. There is a list of 7 wastes in production and another list for services.

Modern approach to business is not about product only, but about product extended by additional service and support. Therefore, modern enterprise should take into account both lists of wastes.

7 wastes of production

The wastes are described in detail in another article 7 wastes of lean.

1. Overproduction
2. Inventory
3. Defects
4. Motion
5. Over-processing
6. Waiting
7. Transportation

7 wastes of services

The wastes are described in detail in another article 7 wastes of services.

1. Delays
2. Duplication
3. Motion
4. Unclear communication
5. Inventory
6. Errors
7. Opportunity lost

Mura

Do you have to "make the numbers" at the end of reporting period? In order to improve results, salesmen decrease prices. Therefore, production has to be increased. But at the beginning of new period it almost stops. This increases overburden (muri) and risk of wastes (muda). As you can see, all three of them are connected. The enterprise has to maintain higher capacity than necessary in order to deal with unevenness. After weeks of increased work, sometimes on three shifts, including Saturdays and Sundays, come weeks of waiting for next order. Workers forget their skills and at the beginning of new period increased number of defects is detected.

Reducing mura using heijunka and just in time

The mura can be reduced using proper organization of production. One of the methods that help reduce mura is Heijunka (production levelling). Using prediction models it is possible to forecast the demand and find optimum level of production. This eliminates the Forrester effect, which is one of mura causes.

It is important to state, that reduction of mura can appear not fully compatible with TPS or Lean manufacturing, as implementation of Heijunka requires increased finished goods inventory. The optimization of whole enterprise can require sub-optimization of its parts. It shouldn't be a surprise.

Reduction of mura using just in time is not possible, as JIT leads to reduction of inventory at a cost of production unevenness. The top management has to decide which is more important.

Muri

The overburden is a cause of many quality problems, as well as safety threats. The muri is created by mura or low efficiency of management. The overburden is caused by:

• performing work that workers are not trained in,
• wrong layout of workplace,
• cluttered workplace,
• unclear communication,
• wrong communication routes,
• incorrect tools, equipment, inventory,
• mura
• wrong maintenance
• low quality equipment
• unreliable process.

References

• Imai M., (1997) Gemba - Kaizen, A Commonsense, Low-Cost Approach to Management, McGraw Hill Companies, Inc., New York 1997
• Imai M., (1986) Kaizen (Ky' zen) The Key to Japan's Competitive Success, McGraw Hill, Inc., New York 1986
• Womack J.P., (2006) Mura, muri, muda?, Lean Enterprise Institute (PDF)

Author: Slawomir Wawak