2.2.4. Machined Surface Roughness Analysis

The analysis of the machined surface roughness provides valuable information regarding machining tool performance, which can be related to tool wear and optimal machining conditions to obtain the best possible surface quality. For this analysis, a Mahr Perthometer M1 profilometer (Mahr, Gottingen, Germany) was used. This equipment was used to determine the surface roughness parameters according to the ISO 21920-1:2021 standard [41]. Each test was performed with a cut-off value of 0.8 mm and a measurement length of 5.6 mm, which was seven times the cut-off value. The first and the last measurement segments of 0.8 mm were not considered due to errors resulting from the probe acceleration and deceleration at the time of measurement. The machined material's surface roughness was evaluated in the tangential and radial directions (in relation to the machining direction). This was performed to evaluate the machining stability, as a considerable difference between these values would indicate an unstable machining process. Furthermore, surface roughness assessment was performed in various areas of the workpiece's surface, namely in the center and periphery, again to evaluate the stability of the cutting process.

Due to the workpiece's dimensions and equipment availability, it was not possible to perform surface roughness area analyses (using profilometers). As such, only the mentioned equipment was used for surface roughness assessment.
