a Japanese term indicating efforts that do not add value (waste). Some categories of muda are defects, over production or excess inventory, idle time and poor layout. OR Japanese for waste; any activity that consumes resources but creates no value for the customer.
Muda is a traditional Japanese term for an activity that is wasteful and doesn't add value or is unproductive. It is also a key concept in the Toyota Production System (TPS) and is one of the three types of waste (muda, mura, mur) that it identifies. Waste reduction is an effective way to increase profitability.A process adds value by producing goods or providing a service that a customer will pay for. A process consumes resources and waste occurs when more resources are consumed than are necessary to produce the goods or provide the service that the customer actually wants. The attitudes and tools of the TPS heighten awareness and give whole new perspectives on identifying waste and therefore the unexploited opportunities associated with reducing waste.
Muda has been given much greater attention as waste than the other two which means that whilst many Lean practitioners have learned to see muda they fail to see in the same prominence the wastes of mura (unevenness) and muri (overburden). Thus whilst they are focused on getting their process under control they do not give enough time to process improvement by redesign.
The seven wastes
One of the key steps in Lean and TPS is the identification of which steps add value and which do not. By classifying all the process activities into these two categories it is then possible to start actions for improving the former and eliminating the latter. Some of these definitions may seem rather 'idealist' but this tough definition is seen as important to the effectiveness of this key step. Once value-adding work has been separated from waste then waste can be subdivided into 'needs to be done but non-value adding' waste and pure waste. The clear identification of 'non-value adding work', as distinct from waste or work, is critical to identifying the assumptions and beliefs behind the current work process and to challenging them in due course.
The expression "Learning to see" comes from an ever developing ability to see waste where it was not perceived before. Many have sought to develop this ability by 'trips to Japan' to visit Toyota to see the difference between their operation and one that has been under continuous improvement for thirty years under the TPS. Shigeo Shingo, a co-developer of TPS, observed that it's only the last turn of a bolt that tightens it - the rest is just movement. This level of refined 'seeing' of waste has enabled him to cut car body die changeover time to less than 3% of its duration in the 1950s as of 2010. Note that this period has allowed all the supporting services to adapt to this new capability and for the changeover time to undergo multiple improvements. These multiple improvements were in new technologies, refining value required by 'downstream' processes and by internal process redesigns.
The following "seven wastes" identify resources which are commonly wasted. They were identified by Toyota's Chief Engineer, Taiichi Ohno as part of the Toyota Production System.
Each time a product is moved it stands the risk of being damaged, lost, delayed, etc. as well as being a cost for no added value. Transportation does not make any transformation to the product that the consumer is supposed to pay for.
Inventory, be it in the form of raw materials, work-in-progress (WIP), or finished goods, represents a capital outlay that has not yet produced an income either by the producer or for the consumer. Any of these three items not being actively processed to add value is waste.
As compared to Transportation, Motion refers to the producer, worker or equipment. This has significance to damage, wear and safety. It also includes the fixed assets and expenses incurred in the production.
Waiting or (WIP) Work in Process
Whenever goods are not in transport or being processed, they are waiting. In traditional processes, a large part of an individual product's life is spent waiting to be worked on.
Over-processing occurs any time more work is done on a piece than what is required by the customer. This also includes using tools that are more precise, complex, or expensive than absolutely required.
Overproduction occurs when more product is produced than is required at that time by your customers. One common practice that leads to this muda is the production of large batches, as oftentimes consumer needs change over the long times large batches require. Overproduction is considered the worst muda because it hides and/or generates all the others. Overproduction leads to excess inventory, which then requires the expenditure of resources on storage space and preservation, activities that do not benefit the customer.
Whenever defects occur, extra costs are incurred reworking the part, rescheduling production, etc.
An easy way to remember the 7 wastes is TIMWOOD.