Muda, muri and mura, also known as the three Ms of lean, represent three types of waste in TPS. They are deviations from an optimal allocation of resources that decrease the efficiency and profitability of the process.
Muda means wastefulness or uselessness in Japanese. It refers to a process that uses or consumes resources that are necessary to create value for the consumer or customer. Muda is intended to maximize the elements of the process that add value and minimize those that do not add value.
There are two types of muda that do not add value in a process. Necessary elements such as testing cannot be eliminated as they are, by nature, required for the process. Unnecessary elements can be eliminated from the process to enhance its efficiency and profitability. There are seven original categories of unnecessary muda: transport, inventory, motion, waiting, over-processing, overproduction and defects. Resources, talent and by-products are often added to the list.
Muri means unreasonableness, overburden and beyond one’s power. It results from placing unreasonable demands on a processes’ people and equipment — making them work longer, faster, harder or more intensely than is appropriate. Signs of muri include absenteeism and broken or poorly functioning equipment.
Muri drives muda by unnecessarily burdening or stressing the people and equipment engaged in the process. To reduce or eliminate muri, ensure that the demands made on both people and equipment are reasonable and address mura with standardized processes and even schedules. Adequately and preventively maintain equipment and ensure the safety of all employees.
Mura translates to unevenness and lack of uniformity. It results in, or drives, muda as a lack of constancy in scheduling and the pace of work stresses both processes and people and generates waste. To reduce or eliminate mura, adopt standardized work processes and take measures to ensure a more even and consistent pace and schedule — for example, enhancing communication along the supply chain.
Taken together, muda, muri and mura help businesses to eliminate waste, enhance efficiency and effectiveness and increase profitability.
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