## 2 Materials and Methods
### Design of Calibration Models  
In the study, two pairs of calibration models were developed. The first pair of models aimed to determine shrinkage and offset. The second pair was used to identify the optimal exposure time \(t\), taking into account the strength and detail of the 3D print. Two calibrator models were used to determine shrinkage and offset. The first consists of a square plate with 25 mm \(\times\) 25 mm dimensions (referred as the solid sample) (Figure 3a), while the second also contains a square-shaped hole with a side length of 7 mm in the center (referred as the sample with hole) (Figure 3b). On both calibrators, markers were placed in square holes measuring 1 \(\times\) 1 mm and 0.5 mm deep. The corners of the hole were inclined by adding a 0.5 mm chamfer. A marker was also added as a cross with arms 0.2 mm wide and 0.4 mm deep, with the center at the midpoint of the square hole. In this way, the marker's center can be determined precisely during optical measurement. Figure 3: Models with markers to determine shrinkage and offset: (**a**) the solid sample and (**b**) the sample with hole. The next set of calibration models were designed to test the effect of exposure time \(t\) on the strength and detail of the 3D print. The calibration models were modeled using NX-Siemens software. Based on Anycubic's calibration model, the calibrators consist of a 24 mm \(\times\) 24 mm square plate. The calibrator for determining model strength consists of 5 rows of pins whose diameter decreases with a resolution corresponding to the width of a pixel, i.e., 28.5 \(\upmu\)m (Figure 4a). The biggest pin is located in the middle row. Its dimensions are 1.5 mm \(\times\) 1.5 mm \(\times\) 7 mm. The pin is constructed so that 4 mm from the base is narrowed to 0.6 mm. The range of diameters used was determined experimentally. Using pins that are too thin makes them unable to stay on the platform, regardless of the exposure time. Conversely, pins that are too thick do not contribute any relevant information. The pin described above is a base pin duplicated using a symmetrical array. Thus, the right and left rows are symmetrical relative to the middle row. In contrast, the diameter of the subsequent pins in the rows decreases by the pixel's width to a width of 0.1995 mm. The calibrator with thin sheath pins is used on three sides, which is easily detached from the base to make it easier to grip the sample during post-processing and reduce the risk of damage to the pins during rinsing. It is assumed that, if the pin, despite this sheathing, cannot survive the rinsing process, it is not counted as part of the set of pins correctly manufactured when evaluating the sample. As fine pins are repeated twice, assessing whether damage results from chance is possible. The calibrator for determining model detail consists of a matrix of holes, where, in one direction, the characteristic dimension is reduced from 0.8 mm to a size of 0.342 mm (Figure 4b) with a step of twice the pixel width. In the other direction, one dimension is reduced by an additional pixel width, causing a transition from a square to a rectangular shape. Consequently, the smallest hole is 0.342 mm \(\times\) 0.114 mm, which is placed in the opposite corner to the largest hole. The thickness of the calibrator base is 2 mm. A hole is considered to be reflected correctly if light shines through it. In exporting 3D-CAD models to a 3D-STL model for NX-Siemens software, the accuracy of the generated model is influenced by parameters related to angular and chordal tolerance. To achieve a balance between the accuracy of the 3D-STL model generation and the capabilities of the mSLA Anycubic M3 Premium 3D printer used in NX Siemens software, it is best to undertake the following:  
* Select the binary format for STL file storage (the American Standard Code for Information Interchange (ASCII) format generates a larger file size);
* Set the chordal tolerance to a value of 0.0025 mm;
* Set the angular tolerance to a value of \(1^{\circ}\).