# Sustainable Manufacturing Decisions through the Optimization of Printing Parameters in 3D Printing
## 2 Materials and Methods  
### Experimental Design  
The five printing parameters affecting the dimensional accuracy, carbon dioxide emissions, and three printing costs are summarized by the literature review in Section 1, and they are the fan rate, printing speed, nozzle temperature, build plate temperature, and layer thickness. The printing parameter was considered due to the capability of the printing machine and the material properties of the filament. In addition, it is understood from experience that during the printing process using PLA material, the cooling fan must be turned on to avoid the situation of printing failure. Therefore, the fan rate is set to 50% and 100%. The range of the printing parameters is shown in Table 1. The 3D printer used in this study is the delta-type ATOM 2.5 EX [25], and the filament material is poly lactic acid (PLA) [26], which is environmentally friendly and easy to obtain. The printed object follows the ASTM-1708 standards [27], as shown in Figure 1. During the printing process, the object was placed at the center of the build plate without the need for any support materials. After printing, the outer width (OW), inner width (W), outer length (OL), and thickness (T) of every object were measured to determine the dimensional accuracy, as shown in Figure 2. The size was measured using [PERSON]'s dial calipers [28], and an average of three values was used for recording. The energy consumption of the printer during a printing cycle was recorded by a smart plug (TP-Link, HS100) [29]. The energy consumption data were updated every two seconds and then recorded in an Excel sheet. Therefore, the total energy consumption could be calculated from the time sequence. The printing cycle was divided into five stages, \begin{table}
\begin{tabular}{c c c} \hline \hline
**Factor** & **Printing Parameter** & **Range** \\ \hline A & Fan rate (\%) & 50–100 \\ \hline B & Print speed (mm/s) & 20–30 \\ \hline C & Nozzle temperature (\({}^{\circ}\)C) & 190–210 \\ \hline D & Build plate temperature (\({}^{\circ}\)C) & 15–60 \\ \hline E & Layer thickness (mm) & 0.1–0.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Printing parameters and ranges. Figure 1: ASTM-D1708 specimen. Figure 2: Standard measurement size. as shown in Figure 3. Stage 1 involves heating the nozzle temperature to the set value and completing the incoming line procedure. Stage 2 aims at heating the build plate to the set temperature and maintaining the set temperature of the nozzle, and Stage 3 aims at printing the object. In Stage 4, the decline procedure is performed after printing, and the main step is heating the nozzle. In Stage 5, the filament is extracted, and the nozzle module returns to its original position. Carbon dioxide equivalent (CO\({}_{2}\)e) is the standard unit for measuring CO\({}_{2}\) emissions. The concept is to use the same unit to express the degree of influence of different greenhouse gases (GHGs) on global warming. Thus, GHG sources with different CO\({}_{2}\) emissions could all be expressed using a single unit. The CO\({}_{2}\)e of electricity production for Taiwan in the year 2021 was 0.502 kg CO\({}_{2}\)e/degree. Therefore, the CO\({}_{2}\) emission during a printing cycle can be obtained using Equation (1). \[\text{Carbon dioxide emission (kg CO${}_{2}$e/degree)}=\text{A}\times 0.502 \tag{1}\]  
where A is energy consumption (unit: kilowatt-hour). The three printing costs are related to electricity, filament, and labor. The electricity cost estimation is also based on the energy consumption of each printing operation recorded by the smart plug. The charging rate for industrial electricity for Taiwan in 2021 was TWD 2.6 per kilowatt-hour, and the electricity cost of each print is given by Equation (2). \[\text{Electricity cost ($\$NT)}=\text{B}\times 2.6 \tag{2}\]  
where B is energy consumption (Unit: kWh). The filament cost could be calculated using the usage amount and filament price. The total filament usage was obtained from the Cura software [30], and the price was TWD 2 per gram.