Thrust Force %0一 88见 Torque (a)n=1 (b)n=1000 5101520253035 Figure 17: Hole exit in drilled GFRP(Ve Work thickness: 10 mm: drill; fish tail carbide drill dial Number of holes drilled n 10 mm; feed: 0. 1 mm; cutting speed: 163 m/min (301 Figure 15: Variation of maximum thrust force torque and In [30], the problem of burr generation in drilling of GFRP flank wear with number of drilled holes [26] composites with different cutting tools is studied. The fish x Uncoated tool, o dlc tool tin coated tool tail drill is found to be very effective in suppressing the generation of burr. Several grades of carbide materials In [27 the tool life of uncoated and diamond-coated were tested as fish tail drills. Among the tested carbides carbide tools in drilling of GFRP composites was studied K01 and K10 showed the highest cutting performance and (Figure 16). The comparison of the tool life of the different drill wear depended only on the fibre type and volume types of tools illustrates the protective effect of the lese drills, tool wear causes diamond layer. In addition to the protection against generation of burr after a certain length of drilling. Figure abrasive wear, the diamond layer also protects against 17 shows an example of burr after drilling 1000 holes on a thermal wear. a shift of the tool life line towards highe values is obtained for higher cutting speeds. Nevertheless mainly caused by the outer corner wear of the drill the tool life curve of the diamond-coated carbide bends at To get a longer tool life, it is necessary to use higher wear high cutting speeds. This indicates the thermal failure of resistant tool materials and diamond is the most suitable the substrate material. An increase in cutting speed is a trial diamond endmill with sintered diamond blades connected with an increase in cutting temperature On the Compared with carbide drills, the wear of diamond development and, on the other, by the decrease in tool life endmills was very small and after drilling 1000 holes the for uncoated carbide tools due to the insufficient heat burr was scarcely generated. In addition, the torque and esistance of the substrate [28] thrust for diamond endmills was less than a half of that for [29] an overview of the potential uses of PCD in FRP carbide drills. The roughness of the hole wall drilled with composite drilling was shown and PCD tools were carbide drills and diamond endmills was compared. Holes compared to carbide tools in terms of both economics and drilled with fish tail carbide drills have a high roughness uality. It was found that drilling processes performed on with Rmax 30 um after drilling 1000 holes. Holes drilled with diamond endmills have a low roughness with rmax <5 implemented. PCD is an economical alternative to carbide um even ater drilling 1000 holes despite the higher cost because tool life is longer and As regards the geometry of fish tail drills, clearance angle higher processing speeds can be used point angle and helix angle were examined. As the elastic deformation of composites is rel machining, the contact area between the flank of the drill and the finished surface may become quite large when the 100 cle To find out the suitable clearance angle, drilling tests were conducted with fish tai carbide drills and variable clearance, point and helix angles. The most suitable angles for drilling gFrP were clearance angle 15, point angle 75, helix angle 35 DCC Figure 18 shows the photos of the exit side of holes aft drilling 1000 holes on 10 mm thick GFRP with each drill The effect of machining parameters on the cut quality and the mechanical behaviour of GFRP composites was verified in [31] during drilling tests. A correlation between width of the damage zone and drilling speed and feed ratio was found: the higher the ratio, the better the cut quality Carbide Dynamic modelling and adaptive predictive control of thrust force in the drilling of CFRP composite laminates and control of CFRP composite laminates were presented n[33] the thrust force defined by the discrete Hocheng Dharan equations was compared with the experimental Cutting speed vc(m/min) thrust force at the pre-exit drilling phase. A theoretical study and a series of experiments were conducted to Figure 16: Tool life of carbide and diamond-coated carbide develop a dynamic model of the process which was used tools vs cutting speed in drilling of GFRP(V+=55%) to design a supervisory adaptive predictive controller that Drill diameter: 10 mm: work thickness: 18 mm. estimates model parameters and applies predictive control feed: 0.08 mm[271 for force regulation(a) n = 1 (b) n=1000 Figure 17: Hole exit in drilled GFRP (Vf = 60%). Work thickness: 10 mm; drill: fish tail carbide; drill diam.: 10 mm; feed: 0.1 mm; cutting speed: 163 mhin [30]. Figure 15: Variation of maximum thrust force, torque and flank wear with number of drilled holes [26]. x Uncoated tool, DLC tool, + TIN coated tool. In [27], the tool life of uncoated and diamond-coated carbide tools in drilling of GFRP composites was studied (Figure 16). The comparison of the tool life of the different types of tools illustrates the protective effect of the diamond layer. In addition to the protection against abrasive wear, the diamond layer also protects against thermal wear. A shift of the tool life line towards higher values is obtained for higher cutting speeds. Nevertheless, the tool life curve of the diamond-coated carbide bends at high cutting speeds. This indicates the thermal failure of the substrate material. An increase in cutting speed is connected with an increase in cutting temperature. On the one hand, this can be explained by a crater wear development and, on the other, by the decrease in tool life for uncoated carbide tools due to the insufficient heat resistance of the substrate [28]. In [29] an overview of the potential uses of PCD in FRP composite drilling was shown and PCD tools were compared to carbide tools in terms of both economics and quality. It was found that drilling processes performed on FRP composites are strongly dependent on the tools implemented. PCD is an economical alternative to carbide despite the higher cost because tool life is longer and higher processing speeds can be used. Cutting speed vc (rnhin) Figure 16: Tool life of carbide and diamond-coated carbide tools vs. cutting speed in drilling of GFRP (Vf = 55%). Drill diameter: 10 mm; workthickness: 18 mm; feed: 0.08 mm [27]. In [30], the problem of burr generation in drilling of GFRP composites with different cutting tools is studied. The fish tail drill is found to be very effective in suppressing the generation of burr. Several grades of carbide materials were tested as fish tail drills. Among the tested carbides, KO1 and K10 showed the highest cutting performance and drill wear depended only on the fibre type and volume fraction. Even with these drills, tool wear causes the generation of burr after a certain length of drilling. Figure 17 shows an example of burr after drilling 1000 holes on a 10 mm thick GFRP laminate with Vf = 60 %. The burr is mainly caused by the outer corner wear of the drill. To get a longer tool life, it is necessary to use higher wear resistant tool materials and diamond is the most suitable. A trial diamond endmill with sintered diamond blades brazed on a carbide substrate was used for drilling GFRP. Compared with carbide drills, the wear of diamond endmills was very small and after drilling 1000 holes the burr was scarcely generated. In addition, the torque and thrust for diamond endmills was less than a half of that for carbide drills. The roughness of the hole wall drilled with carbide drills and diamond endmills was compared. Holes drilled with fish tail carbide drills have a high roughness with R, = 30 pm after drilling 1000 holes. Holes drilled with diamond endmills have a low roughness with R, < 5 pm even after drilling 1000 holes. As regards the geometry of fish tail drills, clearance angle, point angle and helix angle were examined. As the elastic deformation of composites is relatively large during machining, the contact area between the flank of the drill and the finished surface may become quite large when the clearance angle is small. To find out the suitable clearance angle, drilling tests were conducted with fish tail carbide drills and variable clearance, point and helix angles. The most suitable angles for drilling GFRP were: clearance angle 15", point angle 75", helix angle 35". Figure 18 shows the photos of the exit side of holes after drilling 1000 holes on 10 mm thick GFRP with each drill. The effect of machining parameters on the cut quality and the mechanical behaviour of GFRP composites was verified in [31] during drilling tests. A correlation between width of the damage zone and drilling speed and feed ratio was found: the higher the ratio, the better the cut quality. Dynamic modelling and adaptive predictive control of thrust force in the drilling of CFRP composite laminates were developed in [32]. The characterisation, modelling and control of CFRP composite laminates were presented in [33]; the thrust force defined by the discrete Hocheng￾Dharan equations was compared with the experimental thrust force at the pre-exit drilling phase. A theoretical study and a series of experiments were conducted to develop a dynamic model of the process which was used to design a supervisory adaptive predictive controller that estimates model parameters and applies predictive control for force regulation