The 3 Ms of Lean Manufacturing
In 2003 James Womack, a contributing author to “The Book That Changed the World,” which is the book that helped make the lean method of production famous. Beyond the traditional lean manufacturing forms of waste, the TPS also established other causes of inefficiency other than the 8 types of waste (Muda) described above.
Muri (Overburden) is created through the overburden of an unreasonable amount of work. This can be either of a worker (mental or physical) or a machine. By creating a standardized process of production, similar to Henry Ford's assembly line, TPS is able to: increase efficiency, create an easy to follow workflow, reduce costs and increase employee morale because there will be little confusion as to what each person's role is within the production system. This theory can be applied to Lean Manufacturing because Lean Manufacturing seeks to standardize the way in which goods are fabricated ensuring that any waste related to Muri is no longer an issue at a manufacturing site.
In addition to Muda and Muri, the third issue that the TPS identified and that is applicable to Lean Manufacturing is Mura which means: unevenness, irregularity and lack of uniformity. This relates to inventory and parts within a manufacturing project.
If the parts for a project are ordered ahead of time and received ahead of time it is possible that the projects needs will change, therefore wasting resources to purchase unnecessary parts. By keeping Mura in mind and enabling a Just-In-Time system (JIT), which is when one piece of a project must be in its final stages before the next piece of the project is produced, the amount of waste produced will be limited.
The JIT system creates a pull system, requiring each step to give a green light to the next step so that there will never be an excess of inventory. Lean Manufacturing relies on the JIT system and pull method so that once one part of the manufacturing phase is nearly completed the next part can begin. This also reduces the wait time (TAKT time) on a manufacturing site leading to maximum efficiency and an on-time completion of the project.