## 2 Materials and Methods
### Laser Sensor for Detecting Defects on Printed Products  
The utilization of laser sensors has the potential to minimize errors and variations in the final products produced by the 3D printing process. The integration of such devices into equipment and machine control systems is facilitated by the provision of both analog and digital output signals [44]. The sensors are capable of measuring the dimensional properties of the objects that are being printed with great precision [45]. The Keyence LJ-X8020, (Keyence Internation NV/SA, Mechelen, Belgium) a high-precision 2D and 3D laser displacement sensor from the LJ-X8000 series, is widely employed in industrial settings, particularly in the inspection of defects in FDM 3D-printed products. Renowned for its high level of precision and material compatibility, the LJ-X8020 employs a blue semiconductor laser with a wavelength of 405 nm. This feature allows for the production of a precise and finely focused beam of light, which is ideal for conducting meticulous and precise inspections of surfaces. In particular, the resolution of the LJ-X8020 is contingent upon the selected measurement mode and configuration. It should be noted that the Z-axis resolution (height) is contingent upon the selected measurement range. The Z-axis resolution of the LJ-X8020 can be as low as 0.1 \(\upmu\)m (microns), contingent on the selected range and settings. The resolution along the X-axis (width) is contingent upon the width of the measurement range. The LJ-X8020 can achieve a resolution along the X-axis of up to 4.5 \(\upmu\)m [46]. All parameters you can see in Table 6. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Temperature** & **Layer Height** & **Print Speed** & **Estimated Print Time** \\ \hline
190 \({}^{\circ}\)C & & & \\ \hline
210 \({}^{\circ}\)C & & & \\ \hline
230 \({}^{\circ}\)C & & & \\ \hline
250 \({}^{\circ}\)C & & & \\ \hline
270 \({}^{\circ}\)C & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Setting critical parameters (change—temperature). \begin{table}
\begin{tabular}{l c c} \hline \hline
**Print Speed** & **Estimated Print Time** & **Temperature** & **Layer Height** \\ \hline
50 mm/s & 13 m 20 s & & \\ \hline
100 mm/s & 8 m 9 s & & \\ \hline
150 mm/s & 7 m 4 s & & \\ \hline
200 mm/s & 6 m 55 s & & \\ \hline
350 mm/s & 6 m 12 s & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Setting critical parameters (change—print speed). One of the LJ-X8020's key features is its integration capability, allowing for its seamless incorporation into existing manufacturing and quality control systems via analog and digital output signals. This versatility makes it suitable for real-time monitoring and control in 3D printing. The continuous scanning and measurement of the printed layers enable the sensor to dynamically adjust the printing parameters, minimizing defects and enhancing the overall print quality [47]. The LJ-X8020's advanced software enables precise data analysis and defect identification, facilitating the detection of issues like layer misalignments, warping, and surface roughness for a comprehensive quality assessment. This functionality is crucial in high-precision manufacturing environments, where maintaining the product quality is essential. In addition, the LJ-X8020 is capable of high-resolution measurement, which permits the detection of even the smallest defects, such as surface irregularity, dimensional inaccuracy, and structural inconsistency, in 3D-printed objects. The sensor's capacity to capture 3200 points per profile ensures a comprehensive analysis of the printed surface, which is essential for the preservation of the quality and integrity of 3D-printed parts [48].