## 5 Experimental Results and Discussion
### Manufacturing Design
#### 5.1.2 ANOVA: Experimental Results  
In this section, we discuss the results obtained after applying the developed discrete-event simulation model, which acts as a digital replica of the real manufacturing system. Basically, it is shown how the 3 objectives taken into consideration (i.e., Productivity, Utilization Level Machine, Flow Time) vary, as the 4 exchange factors (i.e., number of workers, reorder level, conveyor speed, and operator's efficiency) vary. Figures 11 and 12 show the main effects plot and the interaction plot for the productivity. The sign (*) means multiplication. We can see that the number of operators and the efficiency of the operators have a high incidence for productivity, while the speed of the conveyor has no influence because even the increase in speed does not increase the number of products manufactured, probably because the reduction in the time of inter-arrival of semi-finished products will increase the waiting time of these in the various buffers. As expected, productivity is significantly  
Figure 11: Main Effects Plot for Productivity. Figure 12: Interaction Plot for Productivity. higher when the number of operators is 15 and efficiency is 0.9. For the reorder level, the number of manufactured products is higher when this is equal to 60 wood panels. In Figure 13, we can find the effects related to the interactions through the Pareto Chart of the Standardized Effects. We can see that the conveyor speed does not interact with any other factor. There is a slight interaction between the reorder level and the efficiency, and between the reorder level and the number of operators, because when the efficiency is at 0.7 and when the number of operators is at 10, the choice of the reorder level is indifferent; vice versa, the situation changes when the efficiency and the number of operators are at the maximum level: in fact, there will be a greater productivity with a reorder level of 60 because it guarantees a more continuous production. Basically, we can see that all the effects related to the speed of the conveyors can be neglected while the number of operators is the factor that has the greatest impact on productivity. Figures 14 and 15 show the main effects plot and the interaction plot for the utilization level machine. Once again, conveyor speed has no impact on the level of machine utilization. The number of operators has an important influence, followed by the efficiency of the operators and the reorder level. It can be noted that there are interactions between the reorder level and the efficiency, the reorder level and the number of operators, since when they are set to the minimum values, the choice of the reorder level is indifferent, while if they are set to the maximum values, the situation changes. All these aspects find confirmation within the Pareto Chart of the Standardized Effects in Figure 16.  
Figure 14: Main Effects Plot for Utilization Level Machine. Figure 13: Pareto Chart of the Standardized Effects for Productivity. Figure 16: Pareto Chart of the Standardized Effects for Utilization Level Machine. We can see how even here, the number of operators is the main incident factor together with their efficiency. In this case, in addition to the speed of the conveyor, the choice of the reorder level is also irrelevant. As regards the interactions, we note a very slight interaction between efficiency and the number of operators as there is a greater reduction in shifting from 0.7 to 0.9 in efficiency when the number of operators is 10 rather than 15, probably because with a number of operators of 15, we already have a good reduction in flowtime that can be improved to a lesser extent by shifting from 0.7 to 0.9 for the efficiency of the operators.