7 wastes of lean

7 wastes of lean
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The 7 wastes of lean (jap. muda) are the hidden costs of poor quality and management. Identification and removal of the waste is one of the most important principles of Toyota Production System and Lean manufacturing. The 7 wastes were first described by Taiichi Ohno, Toyota's Chief Engineer. The wasted referred originally to production. The description of wastes in services was created later.

The waste is everything that doesn't create a value for the customer. The customer wants good product. The company should manufacture if right first time without any additional costs. The customer doesn't want to pay for additional transport, storage or quality inspection.

Types of waste

There are two types of waste:

  1. Activities that don't add value for the customer, but are necessary.
  2. Activities that don't add value for the customer and are not necessary.

The first type of waste doesn't create value for the customer, however can be required by legislation or safety issues. The second type consists of 7 types of wastes.

7 wastes

The wastes below refer to production. See also: 7 wastes of services.

1. Overproduction

In order to assure good product for the customer, organization can manufacture more products. E.g. the quality level is 95%, which means that 5 out of 100 products are defected. In order to sell 100 good products, the organization has to manufacture more than 105 products (100 / 95% = 105,26). This additional production is waste of resources.

2. Inventory

The organization wants to be prepared for large customer orders. Therefore it keeps some finished products ready for shipping, some work-in-progress near the workplaces and some raw materials. All of these freeze the capital, that could be used otherwise. Any more inventory than required in order to keep the flow of the process is a waste. The organization should apply e.g. Just in time to reduce it.

3. Defects

Each defect has to be evaluated. If the organization manufacture defected products, it need quality inspection. Products that cannot be repaired are waste. But also products that can be repaired are waste, because of additional time of workers and use of machines.

4. Motion

Any motion in the workplace which extends time of production or stops it is a waste. E.g.:

  • searching for tools (see: 5S method),
  • searching for raw materials,
  • accidents during work.

5. Over-Processing

If the product has features that are not used by customers, creating them is waste. This should not limit creativity in design process, however the company should take into account needs of customers and evaluate which new features may create additional sales. Adding features that are not used increases costs of design, production, increases risk of defects. See also: designed quality.

6. Waiting

If the amount of raw materials and work-in-progress is too small, workers have to stop their work and wait. This waste is therefore related to 2. Inventory. However, there are also other situations when work is stopped, e.g.:

  • machines out of order (see: Total productive maintenance),
  • wrong harmonization of work - workplace have lower productivity than one next in process.

7. Transportation

Each move of raw materials, work-in-progress or finished products creates costs. Moreover, it is an occasion to damage the product. The production floor should be designed in such a way that reduces transportation to the minimum. The first workplace should be close to raw materials. Distance between the workplaces should be as low as the place for processed elements (output from one workplace and input to another). The last workplace should be close to the place where products are sent to customers.


Author: Slawomir Wawak