## 5 Conclusions  
This study used a systematic approach to develop tailored, original chip breakers in polycrystalline diamond inserts, to assist the removal of chips generated under specific cutting conditions. FE analysis was utilized to create a 3D geometric design for a suitable chip breaker. Then, the 3D geometry was produced by the ablation of sequential layers of ablated material in the PCD insert using laser parameters optimized via initial experimental trials. Finally, real turning tests were conducted to compare the behavior of inserts with and without a chip breaker, with regard to chip formation and chips evacuation and, thus, to assess the reliability and efficiency of the chip breaker. The outcomes, in reference to the surface finishing and curly chip formation proved a clear and distinct improvement with the addition of the chip breaker.  
Specific conclusions are as follows:  
* It was confirmed that the important geometric parameters defining the shape of the chip breaker are as follows: Rake angle, \(\alpha\); land width, \(a\); tool-chip contact length, L; and radius of curvature, R.
* Higher rake angles led to lower cutting forces, but that as stress in the tool edge increased, the tool became weaker.
* It was found that a rake angle of 17\({}^{\circ}\) produced chips associated with a relatively low cutting force, while keeping sufficient tool strength to endure machining stresses without premature failure.
* Optimum curling was found to take place with a land width being equal to half the feed rate.
* For small chip breaker radius of curvature, (e.g., 1.0 mm) the chips were prone to getting clogged, leading to a dramatic increase of cutting efforts. A 1.4 mm radius of curvature for the chip breaker gave the best solution.  
Figure 14: Inserts used in the machining trials (**a**) large built-up-edge (BUE) and noticeable scratches in the insert without chip breaker and (**b**) small BUE and minor scratches in the insert with chip breaker.  
Figure 13: Machined surfaces produced by inserts: (**a**) Without chip breaker, where uncontrolled chips scratched the newly machined surface; (**b**) with chip breaker, where chips were properly removed from the cutting zone and good quality finishing is preserved.  
* The results showed that a nano-second pulsed laser can be properly used to manufacture chip breakers.
* The insert that included the chip breaker was demonstrated to provide a curled chip formation, and reduced surface roughness significantly as well. This confirmed that the new tool-insert with a chip breaker is an effective solution, that the FE modelling is useful for the design stage, and that a nano-second laser is suitable for laser ablation.  
Conceptualization, I.C., J.A.S. and A.E.; data curation, I.C. and J.A.S.; formal analysis, I.C., J.A.S. and A.E.; funding acquisition, I.C. and J.A.S.; investigation, A.E., I.C. and J.A.S.; methodology, I.C., J.A.S. and A.E.; project administration, I.C. and J.A.S.; resources, I.C. and J.A.S.; software, I.C., J.A.S. and A.E.; supervision, A.E.; validation, A.E., I.C. and J.A.S.; visualization, A.E. and I.C., J.A.S.; writing--original draft, I.C., J.A.S. and A.E.; writing--review and editing, A.E.  
This work was supported by the Department of Economic Development and Competitiveness of the Basque Government under HAZITEK program and by the budget of the European Regional Development Fund (ERDF) (grant number ZL-2017/00092).  
The authors thank the support of [PERSON]. Also, the authors gratefully acknowledge [PERSON] from Tekniker for his technical assistance.  
The authors declare that there are no conflicts of interest.