## 2 Materials and Methods
### Calibration of the Laser Profilometer  
The proper mounting and calibration of the profilometry system forms the basis for metrological properties and reproducible measurements. The calibration was done by defining and implementing a constant horizontal zero plane using reference measurements inside the installation space. To capture the complete installation space, the sensor had to be inclined by 6\(\mathrm{\SIUnitSymbolDegree}\) in relation to the normal vector of the powder bed surface. The inclination of the sensor had to be corrected manually via the Keyence's evaluation software since automatic inclination correction is only provided up to an angle of 45\(\mathrm{\SIUnitSymbolDegree}\). This was done by manually defining the zero-level in relation to the sensor inclination. In order to ensure process conditions during the calibration, a powder coating of Nx layers was applied inside the process chamber to achieve an identical level of production. The surface of the powder bed surface was defined as the zero level for all subsequent measurements. Sintered components were excluded from the calibration by manually masking exposed areas to avoid zero level shift due to the melting depth. The measured value correction is based on a two-point principle by multiplying the resulting height values by a coefficient. Two measuring points are considered as a reference, and associated height values are given before and after the correction. The evaluation software calculates the correction for the entire range of measuring by interpolation. At the beginning of each iteration, the melting  
\begin{table}
\begin{tabular}{c c} \hline \hline Reference distance & 380 mm \\ Measuring range in z-direction & +96 to \(-\)220 mm \\ Measuring range in x-direction & 320 mm at far side \\ Laser wavelength & 405 nm \\ Spot size & 275 mm \(\times\) 249 \(\upmu\)m \\ Linearity & \(\pm\)0.035\% \\ Profile data interval & 50 \(\upmu\)m \\ \hline \hline \end{tabular}
\end{table}
Table 1: Parameters of Keyence IJ-X8400 laser profilometer.  
Figure 8: Mounting of the laser triangulation system at the EOS Formiga P 110. The triangulation system was mounted on the linear unit to enable linear translation alongside the laser protection glass and to capture the complete powder bed surface inside the installation space.  
depth was defined as the reference and calibration point, which according to EOS GmbH is on average 50% of the layer thickness, in order to obtain reproducible measurements and to ensure error-free calibration of the laser profilometer. As can be seen in Figure 9, an average value of 54 \(\upmu\)m was detected at the melting depth during calibration after laser exposure, which confirms correct calibration. Figure 9a shows the complete topology of the surface in powder bed fusion of polymers for the first time.  
In addition to the correct positioning and calibration of the profilometry system, the compensation of performance errors is crucial. When capturing 3D images from individual 2D profiles, even minimal vibrations of the linear unit lead to distorted measurement results due to the high resolution of the sensor. To compensate for deviations and guarantee the quality of the output results, a noise filter was applied to remove irregularities from topological data and provide an additional correction function for profile orientation. The noise filter detects peak values and replaces them with values of neighboring measurement points when there is a sudden increase of more than 100 \(\upmu\)m compared to the neighboring point. The correction function for profile orientation levels deviates of the 2D profile in the x-, y- and z-directions.