# Surface Durability of 3D-Printed Polymer Gears
## 2 Materials and Methods
### Sample Preparation  
There were four 3D-printed gears considered, manufactured from PA (polyamide), PLA (polylactic acid), ABS (acrylonitrile butadiene styrene) and PP (photopolymer). All four gears (z\({}_{w}\)) had the same modulus, m = 1 mm, number of teeth, z = 56, and gear thickness, b = 12 mm. FDM (fused deposition modeling) and SLA (stereolithography) were used as the printing technologies. In the case of FDM technology (Figure 1), the Anycubic Mega S printer produced by HONGKONG ANYCUBIC TECHNOLOGY CO., LTD., Hong Kong, China was used. The Anycubic Mega-S printer is capable of achieving layer heights as low as 0.05 mm (50 microns), allowing for relatively high precision prints. Through FDM, three gears were made from different materials: PA (polyamide), PLA, and ABS. Regarding the structure, the printing parameters were identical in the case of the three samples, namely a degree of filling of 100% and size of the printing layer of 0.2 mm. A filling degree of 100% was adopted to avoid errors introduced by possible changes in the basic structure of the evaluated models.  
The structural resistance of the tested models was not the object of this research; the aspects related to the wear of the teeth were strictly of interest.  
The printing and bed temperatures (Table 1) were set according to the specific recommendations for each material [26; 27; 28] and by printing samples with different printing temperatures.  
In the investigation of PA gears, the research underscores the significance of the moisture levels in relation to the tensile strength, surpassing the influence of the printing temperature [29]. Taking into account the extruder's maximum operating temperature of 260\({}^{\circ}\) Celsius, the printing temperature for the PA toothed wheel was set to 250\({}^{\circ}\) Celsius.  
Most studies recommend 215 \({}^{\circ}\)C as the best printing temperature for PLA. This is because the best tensile performance of PLA is achieved at this temperature [30]. After conducting several 3D printing experiments on the Anycubic Mega-S, a temperature of 210 \({}^{\circ}\)C was determined as optimal for printing the PLA gear to mitigate issues of excessive stringing/oozing.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Material** & **PA** & **ABS** & **PLA** & **PP** \\ \hline
3D printing technology & FDM & FDM & FDM & SLA \\ Printing temperature & 250 \({}^{\circ}\)C & 240 \({}^{\circ}\)C & 210 \({}^{\circ}\)C & NA \\ Bed temperature & 110 \({}^{\circ}\)C & 105 \({}^{\circ}\)C & 50 \({}^{\circ}\)C & NA \\ Radiation (nm) & NA & NA & NA & 405 \\ \hline \hline \end{tabular}
\end{table}
Table 1: 3D printing parameters.  
Figure 1: FDM 3D printer: (**a**) 3D slicer; (**b**) Anycubic Mega-S 3D printer.  
For ABS filaments, the recommended printing temperature typically ranges between 220\({}^{\circ}\) and 250 \({}^{\circ}\)C [30; 31], with variations based on specific printer models, filament quality, and desired print characteristics. A commonly recommended starting point is around 230 \({}^{\circ}\)C to 240 \({}^{\circ}\)C. The experimental tests conducted determined the optimal printing temperature to be 240 \({}^{\circ}\)C.  
In the case of the toothed wheel executed by SLA, an Anycubic Photon printer with ANYCUBIC resin photosensitive to radiation with a wavelength of 405 nm was used. Both the printer and the resin are products of HONGKONG ANYCUBIC TECHNOLOGY Co., Ltd., Hong Kong, China.