Eight Reasons for Buffer Inventory

Why have any Work-In-Process Inventory? Why have any intermediate subcomponents in your system?

1. It is a shock absorber for uncertainty.
   
2. It shows you where flow ends…thus you must do pull.
   
3. It shows you where you sense variability in your process.
   
4. It insulates you from vendors who don’t deliver on time.
   
5. It provides a tool for managing your entire process by observing buffer quanitities.
   
6. It gives you a quantitative way to see changes in customer demand.
   
7. It forces you to “declare” your process steps to others, making the process more transparent and visible.
   
8. It allows you to measure your progress to the degree you can decrease buffer inventory sizes as a proportion of your total inventory.
   

WIP, in itself is not a waste. Too much of it is a waste. And paying attention to it is central.

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