## 3 Results and Discussion
### Results of the Optimisation of the CPM Mechanism Links
#### 3.3.3 Results of Optimising Links 1 and 2 of the CPM Main Positioner  
As with the methods described above for optimising links 3 and 4 of the CPM motion apparatus, drive links 1 and 2 were also optimised. The tool used was also the Creo Parametric software. Optimisation studies using Generative Design methods focused on the selection of a single structural material, 316 Stainless steel. Loading moments on the structure were determined in ANSYS Workbench in previous studies. The mass of link 1 before optimisation was 0.61516 kg. Strength tests in the Creo Parametric programme showed that the von Mises stress for link 1 was 0.0934 MPa, and the displacement magnitude was 2.8600 \(\times\) 10\({}^{-7}\) mm. The number of finite elements used in the numerical study was 23,012. A single finite element had a size of 0.001498 m. Table 10 summarises the results of the Generative Design optimisation of link 1.  
The most favourable optimisation result was achieved for the limit volume of 75%. The mass of the optimised link 1 was 0.452 kg, resulting in a mass reduction of 0.16316 kg. It is worth noting that the values of the displacement parameter and the von Mises stress are practically the same in the assumed boundary volume ranges from 75% to 85%. Thus,  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline
**Parameter** & **Limit Volume 20\%** & **Limit Volume 30\%** & **Limit Volume 40\%** & **Limit Volume 50\%** \\ \hline Starting mass, [kg] & & & 1.5611 & \\ Valid value, [\%] & 14.2 & 25.1 & 36.3 & 49.3 \\ \hline \multicolumn{5}{c}{Parameters of link 4 after Generative Design optimisation} \\ \hline Displacement, [mm] & 4.7928 & 6.1504 & 3.7318 & 2.1634 \\ Von Mises Stress, [MPa] & 249.96 & 201.12 & 202.90 & 203.02 \\ Final mass, [kg] & 0.2210 & 0.3910 & 0.5670 & 0.7696 \\ \hline \hline \end{tabular}
\end{table}
Table 9: Results of Generative Design optimisation of link 4—material MG-AL ALLOY.  
the only parameter determining the optimum solution was the mass of the object after optimisation. Below the 75% volume, the Creo Parametric software was unable to generate the optimum structure because there was not enough material to create the correct link structure.  
For the Generative Design optimisation of link 2, the mass of the object before optimisation was 0.63436 kg. Strength tests in Creo Parametric software showed that the von Mises stress for link 2 was 87.9776 MPa, and the displacement magnitude was 2.8833 \(\times\) 10\({}^{-3}\) mm. The number of finite elements used in the numerical study was 10,650. A single finite element had a size of 0.002 m. Table 11 summarises the results of the Generative Design optimisation of link 2.  
In the case of the link 2 optimisation study, the Creo Parametric only allowed the optimisation to be performed with a maximum volume limit of 90%. In this case, the mass of the link was reduced from 0.63436 kg to 0.538 kg (17.9% reduction). The values of the displacement parameter and the von Mises stress, due to their low value, do not affect the accuracy of the positioner movement in the practical implementation of CPM. Below the limit value, 90% of Creo Parametric was unable to generate a valid structure.