## 3 Lean Management and Industry 4.0 Integration: Conceptual Approach
### Correlation Model for the Industry 4.0 Solutions with the Lean Practices  
Through its intelligent, high-tech solutions and applying the three key elements that create technological value [89] within Industry 4.0 processes--connectivity, intelligence and flexible automation--Industry 4.0 has managed to develop cybernetic manufacturing systems consisting of physical and digital interconnected objects capable of optimizing processes in real time. By applying the new Industry 4.0 technologies to the Lean manufacturing systems guided by the principles of continuous improvement and increase in added value by reducing waste, there are also major transformations of business models that lead to better performance and competitiveness of companies. As a result, a new challenge is the correlation of the two practices applied, often isolated, in the current production and the elaboration of a graphic conceptual model for the integration of the key elements that create added value (Figure 4). The implementation of Industry 4.0 in production systems can be achieved in three directions of integration [64]: vertical integration, horizontal integration and \"end-to-end\" engineering integration. Reference [17] states that \"the principles of 14.0 are the horizontal and vertical integration of production systems driven by real time data interchange and flexible manufacturing to enable customized production\". According to the model developed in [64], at every stage of Industry 4.0 integration, we can apply the five basic Lean management principles [4]: identifying value in order to eliminate waste in the value chain; drawing the current value steam map (VSM) in order to identify critical points in the system; creating the value stream (future VSM); developing \"pull systems\" in order to ensure continuous manufacturing stream; continuous process improvement. \begin{table}
\begin{tabular}{c c} \hline \hline
**Industry 4.0 Technologies** & **Concepts** \\ \hline \multirow{4}{*}{**Artificial intelligence (AI)**} & Through AI techniques, such as machine learning, algorithms and computer-developed expert systems, human intelligence can be simulated and understood (through intelligent speech recognition programs, facial recognition and natural human languages). \\ \hline \multirow{4}{*}{**Augmented reality (AR)**} & State-of-the-art technology that enables real-time visualization of objects in the real environment by superimposing virtual information generated by a computer over the human image in an existing environment. \\ \hline \multirow{2}{*}{**Virtual reality (VR)**} & Advanced technology that allows the creation of a cyber environment through simulation so that the user can experience elements of the real world. \\ \hline \multirow{2}{*}{**Additive manufacturing (AM)**} & A technology that consists of manufacturing by successive deposition of layers of material, with the whole process being computer controlled including 3D printing and rapid prototyping techniques. \\ \hline \multirow{2}{*}{**Simulation**} & A technique by which real physical processes can be modeled on computers using specialized software in order to study their dynamic operation and optimization. \\ \hline \multirow{4}{*}{**Digital twin**} & A state-of-the-art technology in smart manufacturing that integrates physical and digital elements. By making a faithful digital copy of a real physical system, simulation can accurately reproduce the behavior of the system to increase performance and process control. \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._Figure 5 displays the developed graphical model of the integration of I4.0 into the application of Lean principles, specifying the main benefits resulting from their correlation. Following the analysis of the principles of Industry 4.0 technologies and Lean tools, a model to identify common goals (Figure 6) was developed to integrate them into a general framework and to analyze the impact on production by correlating the two modern production development tools.