## 4 Experimental Tuning Validation Tests  
Practical machining tests were conducted to compare the performance of the tool-insert with its original geometry (no chip breaker) and with the one including the chip breaker. The test consisted in the longitudinal turning of an aluminum 6082 workpiece with the following cutting conditions: \(\mathrm{Ap}=1.0\) mm, f = 0.10 mm and a \(\mathrm{Vc}=100\) m/min, see Figure 11.  
A profilometer Mitutoy SJ-201P, Kawasaki, Kanagawa, Japan, was used to assess the finishing and also photos of the chips generated were taken.  
Figure 12 shows the generated chips with and without a chip breaker. In particular, Figure 12a,c presents the chips that are the result of not using the chip breaker. Clearly, the chips generated were not curled and wrapped themselves around the workpiece. However, as can be seen in Figure 12b,d, with an insert including the chip breaker, the result was the generation of curly chips. Although these chips did not spontaneously break, they were curled and did evacuate from the newly machined surface and rake face of the insert in a controlled manner similar to that predicted by the simulation.  
Figure 11: Turning trials: Set up for an aluminum workpiece.  
Figure 10: Measurement of the ablated chip breaker in the PCD insert.  
This did help maintain a high-quality machined surface and did not increase the stresses on the cutting insert. These tests clearly confirmed that the insert with the chip breaker did generate curled chips, removing them from the cutting zone; and they also confirmed the fitness of the design of the chip breaker.  
The roughness of the machined surfaces produced by both inserts were measured over two areas, close to the beginning and close to the end of the cutting path. For each area, five spot measurements were taken along a line parallel to the center line of the workpiece and the mean value was determined. The roughness, Ra, for the turning test using no chip breaker was 0.74 \(\upmu\)m close to the beginning and 1.61 \(\upmu\)m close to the end of the cutting path. The increase in Ra from 0.74 \(\upmu\)m to 1.61 \(\upmu\)m is attributed the presence of the uncurled chips, see Figure 12a,c. Close to the beginning, the chips can be seen to have moved away, at least partially, from the newly machined workpiece but as more chips are generated, their path is uncontrolled and they tend to clog the cutting zone and wrap around the workpiece, scratching the newly machined surface and lowering surface quality, see Figures 12a and 13a. However, when conducting the turning test with a tool including a chip breaker, the Ra was 0.51 \(\upmu\)m close to the beginning and 0.56 \(\upmu\)m close to the end of the cutting path. Here the curling of the chips generated contributed to preserve high-quality finishing by ensuring the chips were evacuated from the working zone in a controlled manner; see Figure 13b.  
This difference in generated roughness close to the beginning of the cutting path between the turning test using no chip breaker (Ra = 0.74 \(\upmu\)m) and the test carried out using insert with chip breaker (Ra = 0.51 \(\upmu\)m) can be attributed to the fact that the rake angle is bigger for the insert with chip breaker. Thus, the insert is sharper and the cut is smoother, reducing the built-up-edge (BUE).  
Figure 14a,b show how the BUE was much pronounced in the tool without chip breaker when compared with the insert with chip breaker. Besides, the scratches can be seen in the insert as well. While the insert without chip breaker showed noticeable scratches, the one with chip breaker showed only minor scratches.  
Figure 12: Generated chips (**a**) turning test using insert without a chip breaker with generated chips wrapped around the workpiece, (**b**) turning test with insert including chip breaker, where chips are evacuated, (**c**) straight chips as a result of turning test with original insert geometry, no chip breaker, and (**d**) curly chips as a result of turning test with insert including chip breaker.