## 2 Materials and Methods
### Thermal Debinding and Sintering  
A previous study by the authors [70] reported that the shaped copper specimens did not survive the sintering regime since the heating rate of 5 K/min from room temperature up to 1050 \({}^{\circ}\)C did not allow for the decomposition of the backbone component before sintering occurred. Using fast heating rates led to the complete loss of shape since the binder melted before it decomposed. Therefore, in this study, thermal debinding was performed at 2 K/min between room temperature and 250 \({}^{\circ}\)C, and between 250 and 450 \({}^{\circ}\)C. The profile included two plateaus of 1 h at 250 and 450 \({}^{\circ}\)C (Figure 3) to allow for the gradual removal of any residual main binder component and the insoluble backbone component. Finally, a 1 h plateau at 1050 \({}^{\circ}\)C was used to sinter and densify the specimens. It was possible to obtain specimens without defects, such as bloating or blistering, using this longer thermal debinding cycle. The mass loss from green to sintered parts was in the range of 7.89 to 8.19 wt.% (average and standard deviation of 7.95 \(\pm\) 0.04 wt.%), with no dependence on the infill geometry or the presence of cover. Examples of sintered specimens are shown in Figure 7.  
Defects were observed on the specimens having a cover and low infill density (25 and 50%); since the bridges were not adequately supported during printing, debinding and sintering, the material slumped into the cavity due to gravity. These defects could be observed already after solvent debinding but were especially pronounced after thermal debinding and sintering. Figure 7a-c show that the cover defects were minimized as the infill increases since the infill could better support shorter bridges. The specimens with a 25% and 50% infill had material dips and roughness in the sections where no material was present underneath (Figure 7a,b). Specimens with a 75% infill had a smoother surface, but the larger bridging distance for the Hexagonal 75% YES specimens than for the Diagonal 75% YES or the Linear 0/90 75% YES specimens resulted in the rough surface discussed in the previous section. Figure 6: Comparison between bending specimens with the same infill grade and different infill pattern with and without cover. Another defect observed after the sintering of the specimens is the delamination between the infill structure and the perimeter, especially for the specimens with a lower infill degree (Figure 7a,d). Moreover, specimens with a hexagonal infill, and especially specimens with a 0/90 infill, had more pronounced delamination than specimens with a diagonal infill, in which the zones in contact between the perimeter and the infill were larger and prevented the delamination (as can be observed in Figure 7). The delamination between the perimeter and infill is a common defect in parts produced by MEX [27]. It can be solved by programming a defined overlap between the perimeter and the infill structure when slicing the parts [35]. No overlap adjustments were considered in this study to determine the bonding between the perimeter and the infill. During the sintering, specimens shrank considerably (Figure 7d) after the particles fused, and the porosity of the parts was reduced. The shrinkage of the various specimens was recorded in length (longest dimension), width (intermediate dimension), and height (shortest dimension). The shrinkage after sintering for the different types of specimens is shown in Figure 8. The highest shrinkage occurred in the length and width, while the height had the lowest shrinkage. The largest significant differences in shrinkage were observed for the specimens with 100% infill degree. For instance, the shrinkage in length was significantly lower than the shrinkage in width for Linear 90 100% YES and Linear 0/90 100% YES specimens (Figure 8d). While in series Linear 0 100% YES, the shrinkage in length was significantly higher than the shrinkage in width (Figure 8d).