2.2.2. Machining Tests Machining Strategy

The machining tests were performed in a HAAS VF2 CNC milling center, capable of reaching 10,000 rpm and having a maximum power of 20 kW. A strategy was devised to machine the material: as its geometry was round, the tools would machine the material in a spiral motion, going from the outside of the raw material to its center. The machining tests were performed using a water-miscible cutting fluid projected externally (5% oil in water); furthermore, a set of parameters were chosen by considering the optimal values for machining operations that were suggested by the tools' substrate provider. The machining parameter values were determined and applied to all the tools to enable the comparison of their wear behavior and cutting performance. These parameters can be observed in Table 4. To ensure the repeatability of the tests, each milling test was performed three times for each set of cutting conditions to produce a greater number of results regarding wear mechanisms and the surface roughness of the machined surface, thus improving the consistency of the obtained data. Regarding the machining parameters, a constant radial depth of cut and vertical depth of cut were used, these being 3 mm and 0.08 mm, respectively. Furthermore, a constant cutting speed of 60 m/min was used. To evaluate the influence of feed on the machined surface roughness and on the tools' wear, this parameter was varied by 25% by creating test conditions that employed 75% and 125% of the recommended feed value, which was 479 mm/min. To determine the best cutting length to carry out this comparative experimental work, the cutting force analysis was used. For this purpose, one of each fabricated tool was used for the machining of the material, using the strategy and parameters described above. For this preliminary test, a cutting length of 25 m was used in the procedure described in detail (mentioning the equipment) in the following subsection.


