# Surface Durability of 3D-Printed Polymer Gears
## 3 Test Results and Discussion
### Gear Evaluation on ZWP 06 FRENCO Machine  
The ZWP 06 is a double-flank gear roll inspection machine specially designed for high-precision gears. FGIpro 2018 Software by FRENCO was used to record the data. The software determined the following parameters (Figure 4):  
* The total radial composite deviation Fi\" is the difference between the largest and the smallest center distance Cd\" during one rotation of the inspected gear (DIN3963 [32]);
* The tooth-to-tooth radial composite deviation fi\" is the largest difference between the center distance Cd\", which occurs at an angle of rotation corresponding to the duration of engagement of one tooth (DIN3963 [32]);
* The runout deviation by the composite test Fr\" is the value of radial runout of the gear between the maximum and the minimum radial distance from the gear axis as observed by removing the short-term or undulation pitch deviations and analyzing the long-term sinusoidal waveform;
* The short-wave component fk\". \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Material** & **PA** & **ABS** & **PLA** & **PP** \\ \hline
3D printing technology & FDM & FDM & FDM & SLA \\ Operating cycles & 5600 & 5600 & 5600 & 143 \\ Torque (Nm) & 0.75 & 0.75 & 0.75 & 0.75 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Test parameters. Figure 3: Photopolymer gear. During double-flank gear rolling inspection, two gears are rolled together free from backlash, which is suitable for plastic gears (Figure 5). This determines gear roll variations, tooth-to-tooth composite deviations, composite runout deviations, and the short-wave part and displays them clearly. Immediately after the measurement, it can be seen whether the gear is acceptable or not. From the colors, the visual comparison of the actual values and the reference value is made easier. For each deviation, different colors are used, and the operator can easily observe the wrong deviations. The gears were evaluated on the ZWP 06 FRENCO before the load tests (BT) and after the load tests (AT). The master gear (\(z_{m}\)) had, of course, a modulus of m\({}_{\text{m}}\) = 1 mm, number of teeth z\({}_{\text{m}}\) = 48, gear thickness of b\({}_{\text{m}}\) = 15 mm, and gearing angle of \(\alpha\) = 20\({}^{\circ}\) (Table 3). \begin{table}
\begin{tabular}{c c c} \hline
**Element** & \(\mathbf{z_{m}}\) & \(\mathbf{z_{w}}\) \\ \hline m, modulus (mm) & 1 & 1 \\ z, teeth number (-) & 48 & 56 \\ d, pitch diameter (mm) & 48 & 56 \\ x, displacement coefficient (-) & 0 & 0 \\ d\({}_{w}\), rolling diameter (mm) & 48 & 56 \\ h\({}_{a}\), height of addendum (mm) & 1 & 1 \\ h\({}_{\text{r}}\), height of foot (mm) & 1.25 & 1.25 \\ d\({}_{a}\), diameter of addendum (mm) & 50 & 58 \\ d\({}_{\text{r}}\), foot diameter (mm) & 45.5 & 53.5 \\ d\({}_{\text{b}}\), base diameter (mm) & 45.105 & 52.623 \\ \(\alpha_{\text{p}}\), gearing angle (\({}^{\circ}\)) & 25.56386 & 24.86658 \\ h\({}_{\text{0a}}\), height of addendum coefficient (-) & 1 & 1 \\ h\({}_{\text{0f}}\), height of foot coefficient (-) & 1.25 & 1.25 \\ \hline \end{tabular}
\end{table} 
Table 3: Geometric parameters of master gear and workpiece gears. Figure 5: FRENCO ZWP 06 double-flank gear roll inspection test. In analyzing the results, changes were generated by wear in the case of all spur gear samples (Table 4). Considering that the objective of the evaluation was not the inclusion of gears in a precision class but to establish the degree of wear, the results were processed in order to monitor the evolution of the reference parameters of the wheel after testing. Table 5 shows the extracted and averaged results obtained after the evaluation of the gears on the ZWP 06 FRENCO system. The gear made of PA and subjected to the wear test showed an evolution of the total radial composite deviation (Fi\") with a non-linear character. Both the positive deviation and the negative deviation compared to the reference increased in absolute value. Based on the values compared to the reference wheel, there was an increase in the total radial deviation by approximately 55%.