## 3 Results
### Prerequisites
#### 3.1.2 Compression Testing  
In order to ascertain the impact of strut thickness on lattice stiffness in the selected TPU material, compression tests were conducted on predefined test specimens. Cylindrical parts interspersed with Voronoi-based lattice structures with a unit cell size of 7 mm, a height of 10 mm, and a diameter of 30 mm were fabricated from the TPU 1301 material. The selected height pertains to the height of the saddle pad to be manufactured. Furthermore, a continuous bottom surface with openings on the underside of the samples, with a thickness of 1 mm, has been incorporated to facilitate the closest possible approximation to the structure of the planned saddle pad. The thickness of the struts varied between the samples, with measurements selected in 0.1 mm increments between 0.8 mm and 1.7 mm, resulting in a total of 10 test specimens. The geometry of the samples was generated with the softwareCarbon(r) Design Engine Pro and is precisely identical between the specimens with the sole variable being the thickness of the struts. A selection of test specimens can be observed in Figure 2a. A PA12 specimen holder was employed as a solid component to guarantee that the specimens were positioned securely (Figure 2b). This ensured that the specimens could be positioned correctly and efficiently after each measurement. Samples with a strut thickness of 0.8 to 1.3 mm exhibited a readily compressible nature when subjected to manual compression between two fingers. Manual compression was no longer a viable option for all samples with a strut thickness of 1.5 mm or greater. In purely visual terms, it was evident that as the strut thickness increases, areas that should have been devoid of material were partially filled with solidified material. This indicated that the stiffness of these components would be further augmented through the manufacturing process alone. The observed accumulation of material is presumably attributable to two factors, namely the increased use of heat during SLS, which results in the production of thicker struts, and a maximized lattice density during the respective manufacturing process. The compression tests were conducted using a Testmatic System Z5-X1200 (Nurnberg, Germany) tensile compression testing machine. The testing machine was configured with the parameters visible in Table 2. While ISO 604:2002(E) [37] was employed for orientation purposes, it is important to note that this standard is not intended for use with test specimens comprising lattice structures. However, an overview of the classification of thermoplastic compression specimens is provided. The compression test also yielded information about the behavior of the material. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Test speed [mm/min] & 10 \\ Max. force [N] & 4500 \\ Compression [mm] & 4 \\ Test method & Compression test \\ Y-axis & Force [N] \\ X-axis & Travel [mm] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Compression test settings. Figure 2: Test specimens and compression testing setup; (**a**) test specimens from TPU 1301, (**b**) compression test setup with AM sample holder and prepared test specimen (left), starting position (right). Each sample was subjected to three consecutive tests, with a compression of 4 mm in each instance. The initial two measurements served the purpose of a precycle, facilitating the elastic deformation of the sample. It has been demonstrated that these measurements exhibited a markedly higher stiffness than the third measurement. In practical applications, elastomers are subjected to vibrations and loads that reflect real-world conditions. In the event that components have not been subjected to a load for an extended period of time, their response behavior is markedly stiffer than that of components that have been continuously loaded. The subsequent analysis was conducted using solely the values obtained from the third measurement.