The 8 Wastes of Lean (Muda): How to Spot and Eliminate Them
On the shop floor, everything looks busy: people working, machines running, forklifts driving. How much of it moves the customer forward? Waste, muda in Japanese, is anything that costs time, material or money but creates no value for the customer. This lesson covers the 8 wastes of lean: Taiichi Ohno's seven classic wastes plus the eighth, unused talent, each with numbers from a worked value stream.
Muda, mura, muri
The Toyota Production System distinguishes three forms of loss. Muda is waste: activities that add no value for the customer. Mura is unevenness, such as fluctuating customer orders or changing batch sizes. Muri is overburden of people and equipment. Mura and muri create muda: uneven scheduling builds up buffers, and overloaded equipment produces breakdowns and defects.
Not every non-value-added activity can be cut right away. Lean distinguishes value-added activities, necessary non-value-added activities (such as legally required inspections) and pure waste. The third group is eliminated, the second kept as small as possible.
Ohno's seven wastes
Taiichi Ohno described the seven wastes in "Toyota Production System". The examples come from the steering bracket line in the video:
- Overproduction: producing more or earlier than the next process needs. Welding 2 works off a weekly schedule; behind it sit 1,600 welded parts, almost two working days.
- Inventory: material that sits. There are 13,380 parts in the value stream; one driver is stamping batches of 1,000 pcs, because a changeover takes an hour.
- Waiting: parts or people wait. The part waits 11.3 days for 2.6 minutes of processing; with 80% uptime, Welding 2 is down one minute in five.
- Transportation: moving material without changing it. Coils arrive by truck twice a week, and every trip between warehouse, station and supermarket costs time and floor space.
- Motion: walking, searching and bending at the workstation. It is barely visible on the value stream map and only shows up at the workstation, for example in a spaghetti diagram.
- Overprocessing: more effort than the customer requires, such as duplicate inspections or tighter tolerances than needed.
- Defects: scrap and rework. Assembly has 2% scrap; every scrapped part has gone through all previous stations. This raises the effective cycle time from 62 to 63.3 seconds.
The eighth waste: non-utilized talent
An eighth waste was added later, among others by Jeffrey Liker ("The Toyota Way"): the unused knowledge, skills and ideas of employees. The people working on the line know the breakdowns, detours and daily annoyances best. If you do not ask them, you give away the cheapest improvements.
Why overproduction is the worst waste
Ohno called overproduction the worst waste because it causes the others: whatever is produced too early has to be stored, moved, counted and searched for. It also hides problems. As long as there are enough parts, nobody notices a breakdown. That is why eliminating waste usually starts with production control: fewer schedules for individual stations, more pull.
Finding waste in the value stream
You can see four wastes directly on the value stream map: inventory as triangles with days of supply, waiting in the timeline, overproduction at schedules sent to individual stations with large inventory behind them, and defects in the scrap rate and effective cycle time. Transportation shows up in truck and milk run symbols with their frequency. Motion, overprocessing and non-utilized talent, on the other hand, can only be found at the workstation.
Waste walk: a guide for tomorrow
A waste walk is a structured tour of the floor with one goal: count waste instead of complaining about it.
- 30 minutes, one product family, a notepad, ideally in pairs.
- For each of the eight wastes, at least one example with a number: how many parts, how many feet, how many minutes. Without a number it is an opinion; with a number it is a starting point.
- Track one person's walking path for an hour (spaghetti diagram).
- At every inspection step, ask: does the customer really require this?
- Ask the people on the line what bothers them most.
- Capture the result as a value stream: inventories as triangles, ideas as kaizen bursts with owner and due date.
Practice in the editor
Open the template "Steering bracket (current state)" and find a spot with a number for each of the eight wastes. Add two ideas as kaizen bursts.
Open the template in the editor Start blankFrequently asked questions
What are the 8 wastes of lean?
Transportation, inventory, motion, waiting, overproduction, overprocessing, defects and non-utilized talent (skills), often remembered as TIMWOODS. The first seven come from Taiichi Ohno and the Toyota Production System; the eighth was added later.
What is the 8th waste?
The unused knowledge, skills and ideas of employees. It was added later, among others by Jeffrey Liker in "The Toyota Way".
What does muda mean?
Muda is the Japanese word for waste: anything that uses resources but creates no value for the customer. Mura (unevenness) and muri (overburden) are related causes.
Which waste is the worst?
Overproduction, because it leads to inventory, transportation, searching and storage space, and it hides problems.
Is every inspection waste?
No. Required inspections are necessary non-value-added activities. They are not eliminated but kept as lean as possible. Duplicate inspections or inspections the customer does not require, on the other hand, are overprocessing.