Muda, Mura and Muri: the three M's of waste

The terms Muda, Mura and Muri are often used together within the Toyota Production System. Together, they describe the three types of waste that must be eliminated to make a process as efficient as possible.

Muda (無駄): Waste

Muda refers to any activity that consumes resources without adding value for the customer. These are steps that the customer does not want to pay for. Two types of Muda are distinguished:

• Type 1 Muda: Necessary waste that cannot be eliminated immediately with current technology or standards. For example, the extra work after an imperfect paint process to still make the final product acceptable.
• Type 2 Muda: Unnecessary waste that can be quickly and easily eliminated using Lean such as Kaizen. Examples include unnecessary movement of materials or waiting times.

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Mura (斑): Irregularity

Mura stands for irregularity, imbalance or fluctuations in the work process. This often results from erratic scheduling that is not aligned with actual customer demand. An example is a production line where employees have to alternately rush and wait because the workload is unevenly distributed. Eliminating Mura is a crucial step in creating a stable and predictable process.

Muri (無理): Overload

Muri is the overworking of employees or machines. This happens when they have to work harder than they are designed to over a long period of time. Consider an employee who has to perform tasks that are too heavy or a machine that has to run structurally above its capacity. Muri leads to stress, errors, downtime and, in the long run, breakdowns.

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The interconnectedness

Muda, Mura and Muri are closely linked. Addressing one waste often leads to the elimination of the other.

Example:

‍Supposeyou need to transport 6 tons of material with a truck that has a maximum capacity of 3 tons.

• Option 1 (Muri): You try to transport everything at once. This overloads the truck (Muri), which can lead to damage and breakdowns (Muda) and unpredictable arrival times (Mura).
• Option 2 (Mura and Muda): You make two trips: one with 4 tons and one with 2 tons. This causes Mura (irregular supply), which leads to waiting times and unused capacity (Muda). Moreover, the truck is still overloaded during the first trip (Muri).
• Option 3 (No Muda, Mura or Muri): You make two trips, each with the perfect load of 3 tons. This is the ideal solution that eliminates all three wastes, resulting in a smooth, predictable and efficient process.

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