## 2 Theoretical Foundation
### Lean Tools
#### 2.2.2. Value Stream Mapping (VSM)  
VSM allows one to describe the flow of the entire production process, including the flow of materials, the flow of information, and the flow of products from suppliers to customers [19]. For this reason, it allows one to visualize, identify and quantify activities as Value Added (VA), Non-Value Added (NVA), and Necessary Non-Value Added (NNVA) activities. VA refers to the actual part of the process that translates into effective output and actual production for which the customer pays and integrates activities of information  
\begin{table}
\begin{tabular}{c c c c} \hline
**Overproduction** & **Waiting** & **Transportation** & **Movements** \\ \hline This waste refers to the idle time of workers or equipment & This waste refers to the temporal and monetary waste that is manifested by the transportation of materials & This waste refers to any unnecessary physical movement that diverts \\ demanded by the market, i.e., the manufacture of products well in advance or quantities bigger than the ones sold on the market. & This waste refers to the temporal and monetary waste that is manifested by the transportation of materials from one location to another, involving the movement of work tools, machine parts, and increased probability of product damage, i.e., non-value added activities & This waste refers to any unnecessary physical movement that diverts \\  & & & workers from actual work such as searching for, reaching for, or stacking parts and tools, and long and unnecessary walking distances, among others. \\  & & & among others. \\ \hline
**Overstocking** & **Defects** & **Overprocessing** & **Underutilization of Human Potential** \\ \hline This waste exists when an organization has unnecessarily high levels of inventory (of raw materials, finished goods, or work-in-progress stock), causing long lead times, obsolescence, damaged goods, transportation costs, and delays, as well as the fact that extra stock camouflages problems in production. & This waste refers to taking unnecessary steps to process parts/products due to the poor design of tools and products. Doing more than what the customer requires & This waste refers to the lack of recognition and utilization of workers’ talent, skills, and knowledge. Recognizing the value of each employee will increase the performance of the organization. \\ \hline \end{tabular}  
To reduce and/or eliminate the presented wastes, the Lean philosophy makes use of several Lean tools. Some of these tools will be presented in the next subsection.  
\end{table}
Table 2: The Seven Wastes (based on data available in [2; 15; 16]).  
transformation, engineering transformation, and accounting, among others. NVA activities refer to pure waste and NNVA activities refer to those that are necessary even if they do not add value from the customer's perspective (for example, inspections, control systems to check that procedures are being followed, and documentation, among other activities) [15].  
When value streams are analyzed, it is possible to identify activities that do not create value (NA and NNVA, that is, waste); identify that these activities consume most of the time and resources; and find, through their elimination, that is is possible to bring radical improvements in time and cost and ensure a continuous flow of value-creating processes [20]. For this purpose, the premise behind this tool is the elaboration of a VSM of the Current State of the operations, analyzing the real value of the product, followed by redesign (using analysis to reduce waste, shorten delivery times, and improve material flow) and, finally, the development of a VSM of the Future State of operations [3].