## 3 Results and Discussions
### Structural Characteristics  
#### 3.1.1 Dimensional Accuracy  
In order to determine the dimensional accuracy of the uniform lattice structures and FGLSs produced by MJ, all lattice structures were imaged with a Dino-Lite AM3113T Digital Microscope. The obtained values from the measurements are given in Table 3. The  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Property** & **Standard** & **Unit** & **Value** \\ \hline Tensile strength & ASTM D-638-03 & MPa & 50–65 \\ Elongation at break & D-638-05\% 15–25 & \% & 15–25 \\ Elastic modulus & D-638-04 & MPa & 2000-3000 \\ Flexural strength & D-790-03 & MPa & 80–110 \\ Distortion temperature & D-648-06 & \%C & 45–50 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Mechanical properties of the RGD 720 [53].  
Figure 4: Compression tests of lattice structures fabricated by MJ.  
As a result of the measurements, it was found that all strut diameters were larger than the CAD strut diameters. This was due to the lack of resolution of the support material used in MJ. For FGLSs graded from 0.4 mm to 1 mm strut diameter, it was observed that the difference between the CAD model and the printed specimens increased as the strut diameter decreased. In FGLSs, the maximum deviation at the minimum strut diameter, designed as 0.4 mm, was determined to be 18.5%, while the maximum deviation at the 1 mm strut diameter was determined to be 10.4%. The most important reason for the higher deviations for small strut diameters compared to large strut diameters is that the support material used during printing with MJ is more difficult to clean at small diameters. This suggests that thin structures are at greater risk of deflection due to incomplete dissolution of the support material.  
It was observed that the dimensional deviation in uniform lattice structures was less than that in gradient structures. The largest deviation in the strut diameters of the uniform lattice structures was seen in the rotation lattice structure, with a deviation of 8.2%, while the lowest deviation was seen in the chiral structure, with a deviation of 5.4%. The lowest deviations between the strut diameters in FGLSs (between 3.4% and 9%) were obtained in chiral lattice structures. Thus, it was shown that the chiral lattice structure provides higher geometric accuracy. It was observed that the highest deviation among all strut diameter values was observed in the rotation lattice structure, with deviation values between 8.2% and 18.5%. In light of these evaluations, it can be said that the main factor that complicates the solution of the support material in rotating structures is CAD design.  
In printing processes, the risk of defects is higher for thin structures and more careful finishing is required. The results show that the cleaning of support materials is still an important issue in the MJ method for high printing accuracy. Another consequence of this is that printed lattice structures are heavier than CAD designs (Table 3). Chiral structures are the heaviest lattice structures among both uniform and gradient structures.  
According to the results obtained from microscopic images, the lattice structure that most meets the design expectations in terms of dimensional accuracy, geometry and strut connections are chiral structures. On the other hand, it was observed that the connections in the re-entrant structures are weaker than in the other structures. The reason for this is that the strut end connections cannot be formed strongly due to the star geometry in the re-entrant structure. As shown in Figure 5, in re-entrant lattice structures, the end connection of the star honeycombs could not be established; they were held only by body connections. Connection problems in cavity lattice structures also pose a problem in establishing specific geometric features during fabrication.