The eight wastes (DOWNTIME)
| Waste | What it looks like |
|---|---|
| Defects | Scrap, rework, returns, incorrect information |
| Overproduction | Making more, sooner or faster than the next process needs |
| Waiting | People or machines idle for parts, approvals, information or the previous step |
| Non-utilised talent | Skills, ideas and knowledge of people not used |
| Transport | Moving materials or products further than necessary |
| Inventory | Raw material, work in progress or finished goods beyond what is needed |
| Motion | Unnecessary movement by people: walking, reaching, searching |
| Extra processing | Doing more work or higher quality than the customer values |
Where the list comes from
Taiichi Ohno described seven wastes (muda) in the Toyota Production System. The eighth, non-utilised talent, was added by Western lean practitioners to make explicit that an organisation which ignores its people's ideas is wasting its most valuable resource.
How the wastes relate to each other
Overproduction is often called the worst waste because it creates the others: it builds inventory, hides defects, forces extra transport and motion, and makes people wait for the right part among the wrong ones.
Finding the wastes
- Walk the process (a gemba walk) and watch for waiting, searching and moving.
- Map the value stream and time each step; non-value-adding time is usually most of the lead time.
- Ask the people doing the work. They know where the waiting and rework are; whether anyone asks is the non-utilised-talent test.
- Review tier boards. Repeated misses on delivery or quality measures point at specific wastes.
Waste, overburden and unevenness
Lean also names two companions of waste: muri (overburden of people or equipment) and mura (unevenness in demand or workload). Removing waste without addressing overburden and unevenness tends to be temporary.
What to do with a waste once it is found
Name it, measure it, find its cause and remove the cause. A waste that is only noted becomes part of the scenery; one that goes through structured problem solving and a changed standard stays gone.