**2.1 Lean thinking**

During the 1970s and 1980s, Western companies gradually became aware of what Toyota was doing, especially car manufacturers, because of the impressive results they were achieving. Terms such as *Just In Time* and *Kanban* became very popular as referring the Toyota practices during the 1980s but the word "Lean" as referring the general Toyota approach to production was introduced in 1988 [3] and later popularized by the famous book "The Machine that Changed the World" [4]. The word "lean" attached to words such as "production", and "manufacturing", started to be part of the vocabulary of industrial engineers and managers around the world. Lean as a way of thinking, called "Lean Thinking", was then proposed by [5] and supported by the following five principles:

