# The Difficulty of Measuring the Roughness of Glossy Surfaces Using the Triangulation Principle
## 2 Materials and Methods
### Measuring the Surface in a Contact-Free Way  
Figure 5 shows the setup of the laser profilometer, which consists of basic and additional parts. The basic components included a sturdy aluminum support structure  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Laser power & 3.200 W \\ Cutting speed & 2.1 m \(\times\) min\({}^{-1}\) \\ Maximum cutting depth & 12 mm \\ Slice-gap width & 0.2 mm \\ Focal length & 4.5 mm \\ The diameter of the focused beam on the nozzle & 2.3 mm \\ The type and pressure of auxiliary gas used & Nitrogen (17 Bar) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Technical parameters of the TruLaser 3040 cutting machine.  
Figure 4: Experimental samples were used. (**a**) Stainless steel; (**b**) Aluminum alloy.  
Figure 3: TruLaser 3040 material-cutting device from TRUMPF.  
comprising components for the vertical positioning of the measuring tube, a worktop mounted on stepper motors for movement along the \(X\) and \(Y\) axes, a laser beam source, a lens, and a camera equipped with a CMOS (complementary metal-oxide semiconductor) sensor and backlight. In our experiment, the light source was a laser blue diode StingRay with a wavelength of 445 nm. Additional parts of the laser profilometer setup included a computer with laser profilometry View control and evaluation software, as well as an image splitter.  
When measured by the contact-free laser profilometry system, the experimental samples on the worktop were first placed in an anti-vibration mass (Figure 6). The first reason was that the machined surface of the sample was imperfectly fitted to the laser profilometry worktop and the sample on the worktop shifted during the movement of the stepper motors in the course of measurement. The second reason was to eliminate the influence of ambient vibrations, which can affect the quality of the measured data.  
The gain mode (image signal amplification in the camera) was set to 1. The shutter time (time of measurement) for the laser profilometer was set to 19.520 ms after previous  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Axis Y Scan Distance** & **Axis X Scan Line** \\ \hline Scan lines count 45 & 4000 \(\upmu\)m \\ Scan lines step 110 \(\upmu\)m & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Input Parameters for Sample Measurement with the Laser Profilometer Setting.  
Figure 5: The assembly of the laser profilometer. (1) tube with laser and camera; (2) frame; (3) PC with operating and evaluation software; (4) worktop with step motors movable in \(X\) and \(Y\) axes.  
Figure 6: Measurement of the sample with the laser profilometer.  
test measurements. This shutter time was found to produce the clearest image with the least amount of noise. By optimizing the shutter time, the laser profilometer was able to capture a clear and accurate representation of the surface of the sample. This allowed for precise measurements of roughness and other surface features to be obtained. This setup was consistent with the observations made by [PERSON] et al. [27], [PERSON] [5], and [PERSON] et al. [26].  
The experimental laser profilometry enables the measurement and evaluation of surface roughness parameters of samples by ISO 4287 standard (Rq, Rv, Rz, Ra, Rp). The measured roughness data can be exported in a CSV format, which is suitable for the further processing of experiments in the form of raw data. The surface roughness parameters evaluated using laser profilometry were Ra (arithmetic mean deviation of the surface profile), and Rz (the tallest protrusion in the profile's unevenness).  
By following the recommended parameters, the laser profilometer was able to accurately measure the roughness of the sample surfaces. The parameters included in Table 2 may include the measurement range, the sampling frequency, and the scanning speed, among others, which can vary depending on the specific requirements of the measurement.