7 forms of waste

Taiichi Ohno created a categorization of the seven main forms of waste commonly found in mass production: 

  1. Overproduction: producing more than what the next customer or process actually needs. This is the worst form of waste because it fuels the other six. 
  2. Waiting: operators who have nothing to do when machines are running, equipment is malfunctioning, needed parts are not coming in and so on.
  3. Transfer: unnecessary movement of parts and products, such as through a warehouse from one machining step to the next machining step when the second step could also take place immediately after the first step.
  4. Machining: performing unnecessary or incorrect machining steps, often due to poor design of machinery or products.
  5. Stock: having more than the minimum stocks necessary for a precisely controlled pull system.
  6. Movement: operators making movements that are burdensome or unnecessary, such as searching for parts, tools, documents and so on.
  7. Correction: inspection, repairs and outages.

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