## 4 Conclusions  
1. This article successfully developed a nanosecond fiber laser cutting and finishing process for PCD inserts. As discussed in this paper, the variations in the processing path and operating parameters affect the surface morphology and surface quality of the laser-cut and finished PCD workpiece. Based on the investigation of the processing parameter, the most stable kerf depth and best material removal rate can be obtained with the scan rate of 5 mm/s and 5 cutting passes per path.  
2. This study revealed that the number of cutting passes per path significantly influence on the kerf depth magnitude than the scan rate. In this study, we used a nanosecond fiber laser with average power of 30 W. The investigation of the kerf depth revealed that the magnitude of laser pulse energy affects it more than the peak power. In the cutting process, the deepest kerf of 155.2 \(\upmu\)m was obtained at the pulse width of 200 ns and pulse repetition rate of 30 kHz.  
Figure 19: Coherence correlation interferometry measurement for the laser processed PCD workpiece with tilted stage angle of 5.2\({}^{\circ}\) (Ra = 0.202 \(\upmu\)m).  
Figure 18: Optical microscope image (**a**) and SEM morphology (**b**) of the PCD workpiece processed using Method 3 with the stage tilted by 5.2\({}^{\circ}\).  
3. The processing technique adopted in this study successfully cut through the PCD workpiece by applying a reactive fusion cutting mechanism combined with horizontal shifting followed by vertical lifting to cut the material layer by layer. It is concluded that during the laser processing, the cut part on the right-hand side was subjected to repeated action of the laser on the sidewall of the cut edge, resulting in improved laser finishing with good surface morphology and surface quality. Furthermore, it is clearly shown that laser cutting provides better surface roughness of Ra = 0.378 \(\upmu\)m than that obtained by WEDM (Ra = 0.684 \(\upmu\)m).  
4. The laser finishing study presented the optimal laser processing paths followed in Method 3 (horizontal shifting followed by vertical lifting to process the next layer, with 20 passes per path). The feasibility of using a nanosecond fiber laser as a tool for surface finishing was verified. Excellent surface quality (Ra = 0.202 \(\upmu\)m) was achieved after laser finishing.  
5. Finally, the laser processing was conducted with the PCD workpiece placed on a single-axis curved stage with a tilt of 5.2\({}^{\circ}\) for the laser cutting and finishing. The test results revealed that the issue caused by the tilted cut edge was solved by using this arrangement.  
It is evident that the nanosecond fiber laser can not only perform the cutting and finishing process for the production of PCD inserts but it can also be used in applications such as those involving an oriented PCD workpiece with various rake angles and clearance angles.  
6. Future research may study the optimal number of paths to cut through the PCD workpiece. Furthermore, it is worth developing a laser machining process suitable for producing a very sharp cutting edge or a tool nose with a tiny radius, which can be used in high-precision cutting tools manufactured from PCD blanks.  
Conceptualization, F.-Y.C., C.-F.H. and W.-H.L.; methodology, F.-Y.C.; software, C.-F.H. and W.-H.L.; validation, F.-Y.C., C.-F.H. and W.-H.L.; formal analysis, F.-Y.C., C.-F.H. and W.-H.L.; investigation, C.-F.H. and W.-H.L.; resources, F.-Y.C.; data curation, C.-F.H. and W.-H.L.; writing--original draft preparation, C.-F.H.; writing--review and editing, F.-Y.C.; visualization, C.-F.H.; supervision, F.-Y.C.; project administration, F.-Y.C.; funding acquisition, F.-Y.C. All authors have read and agreed to the submitted draft of the manuscript. This research received no external funding. This research was supported by the Ministry of Science and Technology, Taiwan, Republic of China under grants MOST 106-2221-E-011-071-MY2 and MOST 108-2221-E-011-128. The authors declare no conflict of interest.