7 Wastes

Study notes

• The seven wastes are overproduction, waiting, conveyance, processing, inventory, motion, and correction.
• Overproduction is producing ahead of what is actually needed by the next process or customer; the document calls it the worst form of waste because it contributes to the other six.
• Waiting is operators standing idle as machines cycle, equipment fails, or needed parts fail to arrive.
• Conveyance is moving parts and products unnecessarily, such as from a processing step to a warehouse and then to a subsequent processing step when the second step could be adjacent to the first.
• Processing is performing unnecessary or incorrect processing, typically from poor tool or product design.
• Inventory is having more than the minimum stocks necessary for a precisely controlled pull system.
• Motion is operators making movements that are straining or unnecessary, such as looking for parts, tools, or documents.
• Correction is inspection, rework, and scrap.
• Two categories of work are value-creating work, which is directly necessary for making products, and incidental work, which must be performed but does not create value from the customer's standpoint.
• Waste is motions that create no value and can be eliminated, such as walking to get parts or tools that could be positioned within reach.
• Type one muda creates no value but is unavoidable with current technologies and production assets; an example is inspecting welds to ensure they are safe.
• Type two muda creates no value and can be eliminated immediately; an example is disconnected steps in process villages that can be reconfigured into a cell.