In Toyota's production system, it defines three Enemies of Lean:
1) Muda (waste),
2) Muri (overburden), and
3) Mura (unevenness).
The three enemies of Lean can be found in both production and office processes. In fact, they can be found more in office processes than in production processes. One reason for this is that production processes are visible. Everybody who walks through a factory can see the inventory waiting to be worked on. In the office environment however, processes are often hidden inside our computers, in mailboxes and IT-systems.
MUDA is known as “waste” and is the direct obstacle of flow. As written in previous issues, there are 8 distinctive types of Muda which all lead to waiting times, and therefore longer lead times in a process.
However, simply taking out the Muda does not work. Usually, there is a reason why the Muda is there, and this reason often has to do with the other two enemies: Muri and Mura. This means the three enemies of Lean are interrelated and should therefore be considered simultaneously.
There are numerous tools available to identify and remove waste from your process, which include: Poke Yoke, Kanban, Takt Time, SMED and One-Piece flow. The most common tool that helps to improve productivity by removing all 8 wastes, however, is 5s also presented in previous issues.
MURI is known as “overburden”, and can result from Mura, and from removing too much Muda (waste) from the process. When operators or machines are utilized for more than 100% to finish their task, they are overburdened. This means breakdowns when it comes to machines and absenteeism when it comes to employees.
To optimize the use of machines and make sure they function properly, preventative maintenance can be implemented. To prevent overworked employees, safety should be the focus of all process designs and all standard work initiatives.
MURA known as “unevenness”, can be found in fluctuation in customer demand, process times per product or variation of cycle times for different operators. In production environments with low-volume, high product variation, flexibility is more important than in high-volume, low-product variation environments. When Mura is not reduced, one increases the possibility for Muri and therefore Muda. Mura can be reduced by creating openness in the supply chain, change product design and create standard work for all operators.
Liker, J, 2004, “The Toyota Way, 14 management principles from the world greatest manufacturer”, New York: Mc-Graw Hill, USA
Panneman, T, 2017, “Lean Transformations: when and how to climb the four steps of Lean maturity”, Maarssen, NL