7 Wastes of TPS
Transportation (Conveyance)
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 willing to pay for.
Inventory
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.
Over-processing (Processing)
Over-processing occurs any time more work is done on a piece than is required by the customer. This also includes using components that are more precise, complex, higher quality or expensive than absolutely required.
Overproduction
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 often consumer needs change over the long times large batches require. Overproduction is considered the worst type of waste 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.
Motion
Unnecessary human movement (walking, reaching, bending, etc.) that wastes time and energy. In contrast to transportation, motion refers to the damage that the production process inflicts on the entity that creates the product, either over time or during discrete events. (walking, reaching, bending, etc.)
Defects (Rework)
Whenever defects occur, extra costs are incurred reworking the part, rescheduling production, etc. This results in labor costs, more time in the "Work-in-progress". Defects in practice can sometimes double the cost of one single product. This should not be passed on to the consumer and should be taken as a loss.
Waiting
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.
