Research On Laser Drilling Using Moving Focal Point With Machining Time And Vibration Assisted Laser Cutting Of Metal Sheet

The aerospace and automotive industry are the most industries demanding laser drilling and cutting of materials, the laser machining has many advantages over the conventional mechanical machining, or the electrical discharge machining such as the high machining speed, low cost and good surface finishing. However laser machining is accompanied with defects that reduce the drilling and cutting quality such as Heat Affected Zone, Taper formation and Striations. This study presents two novel techniques applied with laser machining, which are moving the focal point during laser drilling and vibrating the work-piece during laser cutting. This work aims to improve the laser processing of metal sheet. In addition this study build the simulation model of laser drilling and laser cutting to predict the laser machining efficiency.Theoretical model describes the temperature field distribution through the material during laser machining based on Heat Transfer Equations. FEM(Finite Element Method) is used to simulate the interaction between laser and material. The moving heat source in Z direction is modeled with ANSYS APDL, and meanwhile the advanced “element death” technique is applied to simulate the material removal process due to laser drilling and cutting.The axial movement of focal point by moving the laser head aims to improve the geometrical quality of hole, especially decrease the taper’s angle. The hole’s morphology is evaluated after simulating the material removal process. The FEM model established has the advantage to predict taper form that accompanies the conventional laser drilling and gives the best parameters to eliminate the taper by using moving heat source. The FEM results show that the moving focal point during laser drilling improves the geometrical accuracy of the hole, especially remove the taper. The experiment results indicate the close relationship with simulation. The simulation predicts the material melting due to laser heating. The simulation and experiment results together show that the cylindricity of hole is improved while using this method.The simulation and experiment study of using vibration assisted laser cutting is investigated to improve the cutting edge quality. From one hand, the simulation result of laser cutting process indicates that the vibration reduces effectively the work-piece’s temperature. From another hand, experiment result shows that the striations are reduced from the cutting edge, as a result, improve the cutting quality. Fiber laser at 2000 W power is used to cut the steel grad C45 sheet with thickness of 1mm, 4mm and 6mm. The experiment result validates the simulation result.This work provide novel techniques to improve surface quality during laser drilling and laser cutting. They will contribute to promote the laser machining technology.