## 5 Experimental Results and Discussion
### The M&S Framework for Manufacturing Resilience Assessment: Preliminary Study  
The Digital Model of the real manufacturing system was also used to carry out assessments in terms of resilience, and to simulate possible response strategies. Indeed, the recent COVID-19 pandemic has highlighted all the fragility of supply chains and production systems in the face of unexpected and disruptive events. The M&S approach was first used to assess the impact of the following two main events:  
1. The supplier of the wood, which is the main raw material of the finished product, delays deliveries due to unavailability of the transporters, affected by COVID-19. 2. Unavailability of some operators within the production system, due to a COVID-19 outbreak. Overall, 15 scenarios were taken into account, since for supplier delays, we considered the cases of 2, 5, 7 days, while for the unavailability of operators within the manufacturing system, respectively, 7, 10, 14 days. A summary is available in Table 2. S0 refers to the standard scenario, where there are no disruptive events. Figure 18: Interaction Plot for Flow Time. First, it is important to specify that the reliability of the results obtained is confirmed by the indicator in the last column of the table, given that in the vast majority of cases, there is no intersection between the 95% confidence intervals. It is extremely important to evaluate how the productivity value changes according to the various events, starting from S0. A 2-day delay in supplier deliveries (i.e., S3) has a very limited impact on the production system, so much so that on average, productivity has a decrease of 0.2%. As expected, the worst productivity value can be found in the ninth scenario, where the effects of disruptive events are maximum, with an average reduction of 31.8%. Overall, it can also be noted that pairs of scenarios have similar effects on the production system and are S1-S15, S2-S13, S6-S14. Furthermore, it can be stated that, for the same number of days, the non-deliveries of the supplier seem to have a greater impact than the unavailability of a part of the workforce; indeed, S4 guarantees an average productivity higher than S1 of 18.9%. From the results in Table 3, it is evident that unexpected and disruptive events can have important effects on the production system, which demonstrates limited resilience. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Scenario**} & **Supplier’s Delay** & **Manufacturing Operators’ Unavailability** \\  & **(Day)** & **(Day)** \\ \hline S0 & - & - \\ S1 & 7 & - \\ S2 & 5 & - \\ S3 & 2 & - \\ S4 & - & 7 \\ S5 & - & 10 \\ S6 & - & 14 \\ S7 & 7 & 7 \\ S8 & 7 & 10 \\ S9 & 7 & 14 \\ S10 & 5 & 7 \\ S11 & 5 & 10 \\ S12 & 5 & 14 \\ S13 & 2 & 7 \\ S14 & 2 & 10 \\ S15 & 2 & 14 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Scenarios for assessment of impacts related to COVID-19. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Scenario**} & **Mean** & **Min** & **Max** & **stdDev** & **95\% Confidence** \\  & **(Unit)** & **(Unit)** & **(Unit)** & **(Unit)** & **Interval (Unit)** \\ \hline S0 & 697.3 & 693.0 & 701.0 & 2.710 & (695.4; 699.2) \\ S1 & 568.0 & 562.0 & 572.0 & 3.651 & (565.4; 570.6) \\ S2 & 639.0 & 633.0 & 645.0 & 3.916 & (636.2; 641.8) \\ S3 & 695.9 & 689.0 & 701.0 & 3.446 & (693.4; 698.4) \\ S4 & 675.0 & 669.0 & 681.0 & 4.082 & (672.1; 677.9) \\ S5 & 652.0 & 646.0 & 657.0 & 3.712 & (649.3; 654.7) \\ S6 & 612.7 & 605.0 & 616.0 & 3.561 & (610.1; 615.2) \\ S7 & 510.7 & 507.0 & 515.0 & 2.830 & (508.7; 512.7) \\ S8 & 489.2 & 485.0 & 493.0 & 2.860 & (487.2; 491.2) \\ S9 & 475.4 & 471.0 & 479.0 & 2.221 & (473.8; 477.0) \\ S10 & 580.4 & 576.0 & 586.0 & 3.534 & (577.9; 582.9) \\ S11 & 556.8 & 551.0 & 560.0 & 2.974 & (554.7; 558.9) \\ S12 & 504.7 & 500.0 & 509.0 & 2.983 & (502.6; 506.8) \\ S13 & 637.8 & 633.0 & 642.0 & 3.048 & (635.6; 640.0) \\ S14 & 608.9 & 605.0 & 613.0 & 2.961 & (606.8; 611.0) \\ S15 & 571.2 & 567.0 & 574.0 & 2.530 & (569.4; 573.0) \\ \hline \hline \end{tabular}
\end{table}