## 3 Results
### Replication  
The results of the cold embossing experiments (see Table 4) show that for Experiment 1, no replication was observed; this result indicates that E\({}_{t}\) is a critical factor for replication. Specifically, the speed process factor in this experiment did not allow the polymer to flow into the lens cavities effectively.  
Experiment 2 is presented in Figure 8, where the images for the first three replications (Test 1-3) and the last three replications are shown (test 46-48). The images show that replication of the lenses is present on the polymer surface (some contamination is observed). Further replication analysis using Alicona Infinite Focus variation was used to compare the master tool against the 48 th cold emboss test performed in Experiment 2. The image shown in Figure 9 provides further evidence that the process can replicate complex geometrical surfaces.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **Mean** & **StDev** & **SE Mean** \\ \hline VS & 31.23 & 8.44 & 0.69 \\ \hline Non-VS & 2.085 & 0.036 & 0.008 \\ \hline T-Value & DF & \(p\)-Value & \\ \hline
42.13 & 148 & 0.000 & \\ \hline \hline \end{tabular}
\end{table}
Table 5: Two-Sample T-Test gloss results.  
Figure 7: Boxplot of GU results for VS and non-VS parts.  
The control parameters for Experiment 3 allowed for replication, but fidelity declined after the 7 th replicate (Figure 10). By the 15 th test, only a faint replication of the lens was achieved. Further imaging (Figure 11) showed that test 1 was successful and that a faint replication exists after the 48 th test.  
To complete the characterisation, the polymer test part was coated with a thin metal layer of platinum using sputter coating using an Agar (Cressington) HR Sputter coater (Agar Scientific, Rotheram, UK) to enhance its surface conductivity for scanning electron microscopy (SEM) analysis. A film thickness monitor terminated the coating when approximately 10 nm of platinum was applied. This was verified by a calibration check post-process. The sputtering process ensured uniform coverage, minimising charging effects during imaging. Subsequent SEM inspection of Experiment 1 using a Zeiss Evo LS25 SEM (Jena, Germany) enabled high-resolution visualisation of the component's surface morphology, revealing fine structural details of the Fresnel lens and topographical ring features (Figure 12). The image shows that the process is capable of micro-scale replication; in particular, the lens ring thickness of 9 \(\upmu\)m is replicated. This level of replication is normally associated with \(\upmu\)-injection moulding and time-consuming HE.  
Figure 8: Experiment 2 test results.  
Figure 9: Experiment 2 replication images for the master tool and 48 th test.  
Figure 10: Experiment 3 test results.  
This result highlights the influence of \(\mathrm{E_{t}}\) on the process, as the softening of the test piece diminishes over time, affecting the polymer's ability to mould to the lens features. The cycle time plays a crucial role; a duration of 454 ms for an emboss is insufficient for adequate polymer flow to replicate the master, while an increased time of 9364 results in the polymer hardening, thereby hindering replication. This finding is significant as it demonstrates that cold embossing can be utilised to incorporate complex features into 3D-printed parts. Moreover, optimising the cycle time can enhance productivity. This research provides a pathway for improving the precision of embossed features while maintaining the structural integrity of 3D-printed components.