Drilling of micro-holes on titanium alloy using pulsed Nd:YAG laser: Parametric appraisal and prediction of performance characteristics

Abstract

Laser drilling is a preferable method in drilling micro and slender holes because of its non-physical contact between the tool and the workpiece leading to elimination of the problems like chatter and vibration. In this article, an experimental investigation of the laser drilling process is carried out on thin sheet (0.5 mm) of titanium alloy (Ti6Al4V) using pulsed Nd:YAG laser. The study investigates the effect of laser parameters such as laser energy, pulse repetition rate, pulse width and gas pressure on hole quality characteristics, namely, circularity at entry and exit, taper and spatter area. Taguchi’s L27 orthogonal array is adopted for conducting the experiments to establish significance of control parameters on the performance measures with less number of experimental run. Analysis of variance shows that laser energy and pulse width significantly influence on circularity, taper and spatter area. Optimal parameter setting for all the performance measures is suggested. Statistically valid empirical models relating hole quality characteristics with laser parameters have been developed based on least square regression analysis. Backpropagation artificial neural network is used predict the output responses considering laser process parameters as inputs. A mean square error within 5% for both the training and testing data suggests the adequacy and robustness of the proposed artificial neural network model. Variation of performance measures with respect to process parameters is predicted through the well-trained artificial neural network model. The pattern of variation exhibits good agreement with the main effect plots obtained through Taguchi method. Artificial neural network model produces mean relative error of 0.001, 0.001, 0.0437 and 0.0234 for circularity at entry, circularity at exit, taper and spatter area, respectively, when compared with experimental values. Since small values of mean relative error are obtained, the proposed artificial neural network model can be satisfactorily used for prediction of quality characteristics of laser micro-drilled holes.

Experimental Investigation of Productivity, Specific Energy Consumption, and Hole Quality in Single-Pulse, Percussion, and Trepanning Drilling of IN 718 Superalloy

“…When a laser beam with high pulse energy interacts with the top side of the workpiece, it melts and vaporizes the material instantly and increases the mean (entrance) hole diameter [12]; however, the intensity of the laser beam decreases as it passes through the thickness, which results in a small exit hole diameter, less material removal, and produces a high hole taper. This variation is consistent with the findings of Chatterjee et al [37] and Yilbas [12].…”

An integrated analysis of productivity, hole quality and cost estimation of single-pulse laser drilling process

“…The intensity of the laser beam decreases due to diffraction as it penetrates, which increases the hole taper. Similar findings have been observed by Sarfraz et al 15 and Chatterjee et al 42 Influence of gas pressure and gas flow rate on hole taper. The effects of gas pressure and gas flow rate on hole taper are revealed in Figure 8.…”

“…Moreover, an increase in pressure does not permit the molten metal to set down inside the hole cavity. Thus, hole taper reduces when higher gas pressure is used which is in accordance with the findings of Chatterjee et al 42 A similar trend has been observed with the increase in gas flow rate because higher compressed air flow rate increases the localised temperature due to its combustible supportability and results in efficient removal of the material from the hole exits which results in lower hole taper, as stated by Nawaz et al 20 Influence of pulse energy and pulse duration on drilling cost. Figure 9 illustrates the response of pulse energy and pulse duration on drilling costs.…”

Study of the effect of surface laser texture on tribological properties of cemented carbide materials

“…However, titanium alloys have high chemical activity, low thermal conductivity and low elastic modulus, which cause a high cutting temperature and likely reaction with the carbide tool materials in the cutting/ milling process. 1 The above characteristics of titanium alloys have significant effects on the tool life, tool consumption and wear resistance of the tool surface. 2,3 At present, many scholars have shown great interest in improving the friction characteristics between the tool and the workpiece (titanium alloys) by changing the surface morphology of the tool.…”