## 3 Internal Stress in the Component Parts Manufactured via the DMLS Technology
### Optimization of Structural Topology  
The Netfabb Premium program by the Autodesk company was used for the optimization of the shaped intermediate piece, which shall be consequently examined in terms of mechanical processes occurring in the manufacturing process via the DMLS technology. The alternative solution was proposed via the program. This alternative solution was further analysed in the ANSYS environment in regard to the occurring internal stress and material predispositions from the basic model. The proposed and examined alternative was a structure based on the elements in the shape of a star. A section of the shaping intermediate piece with the internal structure in the shape of the star is demonstrated in Figure 8. The thickness of the wall of external areas and stepping from the mounting holes and cooling supply is 5 mm for the proposed alternative. A perforated hole was placed in the bottom part for removal of excessive dust after completion of the manufacturing  
\begin{table}
\begin{tabular}{c c} \hline
**Direction of Stress Action** & **Value of Stress (Pa)** \\ \hline Direction of action xx & \(8.32\times 10^{9}\) \\ Direction of action xy & \(2.52\times 10^{9}\) \\ Direction of action yy & \(8.38\times 10^{9}\) \\ Direction of action yz & \(5.27\times 10^{9}\) \\ Direction of action zx & \(4.46\times 10^{9}\) \\ Direction of action zz & \(3.18\times 10^{10}\) \\ \hline \end{tabular}
\end{table}
Table 1: Maximum stress in individual directions.  
Figure 7: Overall residual stress acting during manufacturing of shaped intermediate piece via the DMLS technology.  
process. Subsequently, the analysis of mechanical processes during manufacturing via the DMLS technology with the machine and material parameters identical to those of the original monolithic-shaped intermediate piece was performed.  
Figure 9 shows that maximum overall stress is reduced to a level of 1.12 \(\times\) 10\({}^{10}\) Pa and does not act in critical points where the manufactured shaped intermediate piece was detached from the base plate of the machine. The value of stress occurring in the detachment spots is at the level of 4.3 \(\times\) 10\({}^{9}\) Pa. The entire distribution of stress within the frame of the model is more balanced when compared to the original model.  
Not only the reduction of overall stress but also the reduction of stress in the individual directions can be observed, as well as the reduction of overall and some partial shifts when compared to the original model. The values of partial stress are given in Table 2. These maximum stresses are concentrated in the extreme positions of the part and are indicated in Figure 8. These are critical places where the part was torn from the base plate.  
The comparison of the monitored parameters of the proposed alternative consisting of the elements in the shape of a star with the original full model is shown in the graph on Figure 10. The data show that the proposed solution with the internal structure built from the elements in the shape of a star reduces occurring residual stress. The reduction of the stress exceeds 50% when compared to the full volume. The significant indication is also the stress occurring in the \(z\)-axis where the highest reduction can be observed; thus, the assumption that this stress represents an important factor influencing the formation of cracks and occurrence of detachment of the manufactured component part from the base plate of the machine can be made.  
Figure 8: Section through the shaped intermediate piece with internal structure in the shape of the star.  
Figure 9: Maximum action of stress in the case of the alternative with the topology elements in the shape of the star.