## 3 Results
### Verification of the Study  
Due to the greater complexity of the geometry and the asymmetrical distribution of deviations, the verification of the shrinkage and linear dimension compensation methodology was carried out on the samples with a hole. To verify the proposed methodology for determining corrections related to linear shrinkage and light bleed, samples with a hole were printed with an exposure time of t = 3 s. To verify the shrinkage correction (s = 0.44%), four samples were printed with a scale of 1.0044 and without defining an offset (referred to as scaled samples). Figure 22 presents the values of the relative marker shift dr% on the samples before and after the applied corrections. The trend line for the samples after linear shrinkage compensation clearly shifted toward the value of 0. The average value of the dr% indicator for the samples after compensation was 0.003%.  
Figure 21: Dependence of the number of pins (blue) and holes (red) on exposure time t, along with the desirability function.  
Figure 20: Views of the samples (**top**) with holes printed with the shortest, optimal, and longest exposure time \(t\), along with extracted hole interiors used for counting (**bottom**).  
The last step was to check the linear dimension compensation procedure. To compensate for dimensional errors, it was proposed to first compensate for shrinkage. After measuring the dimensional errors on the _scaled_ samples, an appropriate offset was selected. Depending on the slicer used, the offset is either constant for the entire contour, or it is possible to define two different offsets for the outer and inner contours. However, slicers may also differ in the quality of recognizing outer and inner contours. In the study, the most universal option was adopted, i.e., a constant offset--regardless of the geometry type. In the case of analyses without anti-aliasing (anti-aliasing was not the subject of the study), the offset size translates to the number of pixels removed. Knowing the errors of the scaled samples, an offset value of 0.06 was adopted (removing two pixels into the material). Four samples were printed using both the scale factor and the offset correction. The results of scale and offset correction are presented in Table 5.  
The application of the scale increased the external and internal dimensions by 0.095 mm and 0.085 mm, respectively. Applying the offset resulted in a reduction of the external dimension by 0.088 mm and an increase in the internal dimension by 0.057 mm. As before, the different values of contour shifts may result from the interaction between shrinkage and light bleed. Compared with the initial state (without correction), the internal dimension of the sample decreased by about 0.14 mm (over 167%). The reason for the limited correction of the external dimension error was the use of an equal offset for both the outer and inner contours. Reliable quantitative benchmarks for mSLA accuracy are scarce. Nevertheless, in [28] the authors relied solely on a classical Jacobs working curve calibration and obtained dimensional errors in the range of 40-50 \(\upmu\)m. Their experiments were carried out on industrial-grade DLP machines, which intrinsically provide higher XY precision than the consumer class mSLA system used here. Therefore, the accuracy levels achieved in the present work can be regarded as highly promising.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{2}{c}{_dm, mm_} \\ \hline
**Dimension Type** & **Without Correction** & **CORRECTED SCALE** & **Corrected Scale and Offset** \\ \hline external & \(-\)0.060 & 0.035 & \(-\)0.053 \\ \hline internal & \(-\)0.159 & \(-\)0.074 & \(-\)0.017 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Average linear dimension error \(dm\) before and after correction using the scale and offset functions.  
Figure 22: Relative marker shift values (dr%) on the samples with hole before and after the applied corrections (lines represent trend lines).