# Switch-Off Policies in Job Shop Controlled by Workload Control Concept
## 6 Numerical Results  
The simulations for the benchmark case are repeated for different values of the workload norm to obtain a better performance. The workload norm that leads to better performance is equal to 12 for all simulations conducted. Table 4 reports the values of the thresholds, alfa, and beta that lead to performance similar to policy 1, which is the policy proposed in the literature. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Power** & **Case 1** & **Case 2** & **Case 3** & **Case 4** & **Case 5** & **Case 6** & **Case 7** & **Case 8** & **Case 9** \\ \hline Work (Kw) & 5 & 5 & 5 & 5 & 5 & 5 & 5 & 5 \\ \hline Idle (Kw) & 3 & 4 & 5 & 3 & 4 & 5 & 3 & 4 & 5 \\ \hline Stop (kw) & 0.1 & 0.1 & 0.1 & 0.1 & 0.1 & 0.1 & 0.1 & 0.1 \\ \hline Warm-up (Kw) & 5 & 5 & 5 & 4 & 4 & 4 & 3 & 3 & 3 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Power sensitivity analysis. Figure 2 shows the reduction in energy consumption compared to the case of always on for the five switch-off policies considering the nine cases of power consumption and three warm-up times. Policy 1 always leads to better energy reduction for all cases tested. The increment in the warm-up times reduces the energy reduction consumption for all policies tested. This is due to the higher energy consumed during the warm-up period. Cases 1, 4, and 7 lead to lower energy reduction; these cases are characterized by lower energy consumption in the idle state of the machines. The cases with higher energy consumption in the idle state (3, 6, and 9) improve energy reduction. Then, it is important to evaluate the characteristics of the machines to estimate the energy reduction in the switch-off policies. Except for case 2, policy 4 leads to better energy reduction than the other policies that include workload computation. Table 5 reports the ANOVA (\(\alpha\) = 0.05) analysis conducted considering the idle, warm-up power, and warm-up time as the source of variance. The sources of variance are relevant for all policies tested except policy 5. The ANOVA analysis highlights how policy 5 is more robust in terms of the warm-up characteristics. Figure 3 shows the impact of the main effects of energy reduction for the five policies studied. Policies 2, 3, 4, and 5 reduce the variability of the energy reduction compared to policy 1 based only on the queues. Figure 4 shows the number of on/off activities that can affect the tear of the machines. Policy 2, 3, and 4 limit this value between 12,000 and 12,500. Policy 1 (based on the queues) increases the number of on/off activities, and this policy is more affected by the warm-up time. Figure 5 shows the number of parts in delay compared to the model always being on. As per the previous measure, policies 2, 3, and 4 have better performance, while policy 1 is the worst, except when the warm-up time is lower. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Parameter** & **Value** & **Value** \\ \hline
**Policy 2** & **Threshold\({}_{\mathbf{1}}\)** & \(1\) & & \\ \hline
**Policy 3** & **Threshold\({}_{\mathbf{2}}\)** & 0.05 & & \\ \hline
**Policy 3** & **alfa** & 0.6 & **beta** & 0.4 \\ \hline
**Policy 4** & **Threshold\({}_{\mathbf{3}}\)** & 0.05 & **Threshold\({}_{\mathbf{4}}\)** & 1 \\ \hline
**Policy 5** & **Threshold\({}_{\mathbf{5}}\)** & 0.09 & **Threshold\({}_{\mathbf{6}}\)** & 1.1 \\ \hline  & **alfa** & 0.6 & **beta** & 0.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Parameters for the switch-off policies. Figure 2: _Cont._  
Figure 2: Energy consumption reduction. The same consideration of the part delayed can be confirmed by the total time delay, as shown in Figure 6.  
Figure 7 shows the time delay for the unit of the part delayed. The improvement in this performance means that the increment in total time delay is not proportional to the increment in parts delayed. Then, the parts delayed increase with switch-off policies' increase with lower delay time accumulated. This can be important if the penalty is related to the time delay of the parts. Figure 3: Main effects.