Lean Manufacturing Theory

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2.4.4 History
For the first time the term Lean appeared in the article “Triumph of the lean production system” by Krafcik in 1988. However, Lean became known through the book “The machine that changed the world” by Womack et al. in 1990 [31]. While the first mention of Lean falls on the last decades of the XX century, the origins of Lean belong to an earlier period.
In 1574 King Henry III of France built galley ships in a short time using a continuous flow system [30]. In the middle of the XVIII century Benjamin Franklin (1706-1790) in his studies mentioned about waste elimination and inventory control [30]. At the end of the XVIII century Eli Whitney (1765-1825) created interchangeable parts, which were invented while he was working on manufacturing
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Value specification
Value is the first step, which needs to be identified in Lean thinking. Value of a product can be defined as an extent of significance and need for the customer at specific time and for what he is willing to pay. Customer is one who gets the goods or services produced or provided by the company or organization [30]. The customer defines what the value is. Questions such as “What does customer want?”, “When does he want it and at what price?”, “Which properties and features should present?” help to specify the value for the customer [33].
2. Value stream identification
Value stream is the term used to describe how activities and processes are combined together in order to produce a good or service [30]. All activities within a process can be value-adding or non-value adding. Value-adding activity should meet all three points below [30]:
• The customer is willing to pay for it.
• The activity contributes to the transformation of a product or service into an end result.
• The activity should be done right the first
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Waiting is another type of waste. Workers can wait for materials, equipment, other workers, instructions, previous processes to be finished.
3. Transportation
Any movement of products, parts or materials from one place to another that do not add value to the process is transportation waste [37]. Such conveyance can lead to material damage or people injuries.
4. Overprocessing
This waste is a result of unnecessary steps taken to process the product or parts and which has no value for the customer [33, 37]. Overprocessing occurs when more work is done than it is needed or as a result of using complex equipment or technology instead of simple [32].

5. Inventory
It is critical to reduce unnecessary inventory as it takes up a lot of space and increases lead time, which prevents problem identification [38]. In addition, excess material storage may cause obsolescence, goods damages and additional costs.
6. Motion
Motion waste is any unnecessary movement by a person which does not add value to the process [30]. Unnecessary movement is walking, bending, twisting and reaching [30]. Motion waste can lead to poor productivity and quality problems [37,

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