## 4 Production System Case Study
### Design of the Simulation Models Depending on the Improvement Status  
It included the description and formulation, logical relationships, and differences within the models. There were many simulation models used to define status along the improvement process. For this study, the simulation models (SMs) were defined as:  
1. SMs before lean (status 0);
2. SMs with lean manufacturing (status 1);
3. SMs with six sigma (status 2);
4. SMs with TOC (status 3);5. SMs with QRM (status 4);
6. SMs with AM (status 5). Exemplary extracts of the interrelationships and logic between indicators can be seen in Figure 4:  
The simulation models were presented as small incremental cases studies along the transformation process. This meant that the SS effects were added to the LM effects, and, consequently, the LSS effects were added to the TOC implications. The following Table 2 presents the logic of the simulation models. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Simulation Models**} & \multicolumn{3}{c}{**Logic Formulation**} \\ \cline{3-5}  & & **Situation, Methods, and Techniques** & **Description of Impacts** & **Impact on KPIs** \\ \hline \multirow{8}{*}{1} & \multirow{8}{*}{Non-Lean} & & 1.1. Lead times unknown & \multirow{8}{*}{Low availability, performance, quality, and OEE rates} \\  & & 1.1. Processes non-transparent & 1.1.-1.2. Suboptimal decision making & \multirow{8}{*}{Low-capacity utilization} \\  & & 1.2. Separated kingdoms & 1.3. Gap between supply and demand & \multirow{8}{*}{Low labor productivity} \\  & & 1.3. Push strategy & 1.3. Unbalanced capacities along the & \multirow{8}{*}{High stocks} \\  & & 1.4. Reactive quality & production process & \\  & & management (inspection) & 1.4. Unsolved quality & \multirow{8}{*}{Long production lead times} \\  & & 1.5. Reactive maintenance & \multirow{8}{*}{Low service level} \\  & & management & 1.5. Production stops, unknown & \multirow{8}{*}{High operational costs} \\  & & (breakdown-driven) & & machine condition \\  & & & 1.1-1.5. Lack of continuous & \multirow{8}{*}{Low ROI} \\  & & & improvement & \\  & & & 1. & \\  & & 1. & 2. & \\  & & 2. & 2.1. Process and lead times known, & \multirow{8}{*}{High investments} \\  & & 2.1. VSM & & value is identified \\
2 & LM & 2.2. S5 & 2. Waste and condition are visible & \multirow{8}{*}{Lower operational costs} \\  & & 2.3. Pull strategy & 2.3. Production system is driven by & \multirow{8}{*}{Higher labor productivity} \\  & & 2.4. TPM & customer orders & \\  & & 2.5. Poka-Yoke & 2.4. Improve asset condition & \multirow{8}{*}{Higher labor productivity} \\  & & 2.6. Kanban & 2.5. Avoid production failures & \multirow{8}{*}{Higher labor productivity} \\  & & & 2.6. WIP scheduling and control & \\  & & & 3.1. Process stability and capability & \multirow{8}{*}{Higher quality} \\
3 & (Lean) Six Sigma & 3.1. SPC & 3.2. Increase in customer satisfaction. & \multirow{8}{*}{Higher performance} \\  & & 3.2. TQM & 3.3. Predictability of production & \multirow{8}{*}{Lower operational costs} \\  & & 3.3. PDCA-DMAIC & processes & \multirow{8}{*}{Higher profits} \\  & & 3.1–3.3. Continuous improvement & & \\  & & 4.1. Identification of bottlenecks & \multirow{8}{*}{Higher service level} \\
4 & TOC & 4.1. Five-step TOC & 4.1. Capacity levelling along the & \multirow{8}{*}{Higher system performance} \\  & & improvement process & production process & \\  & & 4.1. Supply-demand matching & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation models’ relationships: logic formulation. Figure 4: Available production capacity determination: logic and interrelationships among factors (own elaboration). Based on the logic described, the simulation models were developed. Main inputs for the model were the market demand for the products considered, the capacities for supplier, production processes, and distribution as well as the specific settings for the improvement strategy scenario. Output values were the key indicators that were used to evaluate the results.