## 4 Technology Comparison  
The simulation is used to obtain a full technology comparison between the CM and AM process chains. The dynamic simulation helped to define lead times, identify bottlenecks, and understand resource utilization. Different scenarios were defined and simulated to achieve this, allowing opportunities for improvements. The methodology used in the simulation presented is inspired by [27]. As a first step for this analysis, the process flow for the fabrication of the selected tool had to be mapped. The simplified process flow schematic of CM and AM process chains is presented in Figures 2 and 3, respectively. Figure 1: Mold insert for plastic injection molding (adapted with permission from from [26]). Figure 3: Simplified scheme of the additive manufacturing process chain. Figure 2: Simplified scheme of the conventional manufacturing process chain. In the CM flow, the first step consists of drilling in the metal block the holes for cooling channels (CCs) and ejector pins and plugging one of the ends, followed by rough milling (RM) and grinding with three-axis CNC. Finish-milling (FM), semi-finishing (SF), and finishing (F) operations are conducted with five-axis CNC, in order to achieve the specified shape and dimensional tolerances. To achieve the required texture and shape for the plastic product, the next step consists of electrical discharge machining (EDM) or manual polishing. Laser engraving is performed to mark the surface of the cavity for traceability. The last two steps are ultrasonic cleaning (UC) of the insert, to remove all residual lubricants, oil, and chips, before proceeding to quality control (QC) via 3D scanning. The AM process chain starts with the MAM process and relative post-processes (i.e., powder cleaning, cutting from build plate, and support removal) and heat treatment. The next steps are then very similar to the CM workflow. However, at the start of each step, some additional time may be required to select the suitable cutting tools, as the printed part is near-net-shape and has different surface characteristics as compared with the CM-generated components. To build up the model and run the simulation, it was necessary to collect, among others, data regarding the setup time [28], processing time [29], availability (the ratio between the time the machine is running successfully and the total time in which it could be running) [30], MMTR (mean time to repair, i.e., the time necessary to repair a machine) [31], number of workers, and any special observations. The data were, as mentioned, collected through (i) conversations with experienced users, (ii) historical data, and (iii) literature research. An average was calculated when differences were noticed. The data were collected for each step of the manufacturing flow for both the CM and AM process chains. The processing and setup time data collected to run the simulations are presented in Table 1. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Process Step** & **Conventional Manufacturing** & \multicolumn{2}{c}{**Additive Manufacturing**} \\ \hline  & **Processing (min)** & **Setup (min)** & **Processing (min)** & **Setup (min)** \\ \hline AM process & N/A & N/A & 3240 & 120 \\ \hline AM post-processes & N/A & N/A & 130 & N/A \\ \hline Heat treatment & N/A & N/A & 2880 & N/A \\ \hline Drilling CC/ejectors & 180 & 60 & N/A & N/A \\ \hline Plugging & 60 & N/A & N/A & N/A \\ \hline Rough mill back & 180 & 30 & N/A & N/A \\ \hline Rough mill front & 180 & 90 & N/A & N/A \\ \hline Grinding & 30 & 30 & 180 & 180 \\ \hline Finish mill back & 105 & 75 & 180 & 120 \\ \hline Semi finish front & 540 & 60 & 540 & 60 \\ \hline Finish front & 540 & 60 & 540 & 60 \\ \hline EDM & 480 & 60 & 480 & 60 \\ \hline Laser engraving & 60 & 15 & 60 & 15 \\ \hline UC & 40 & N/A & 40 & N/A \\ \hline QC & 22 & 5 & 22 & 5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Time data for CM and AM manufacturing flow (N/A: not applicable).