Prediction Modelling of Recast Layer and Circularity for Laser Drilling of Polyethylene Terephthalate (PETG) Thermoplastic

Laser drilling is a promising industrial machining application. However, the recast layer and improper circularity are the two important drawbacks for the practical manufacturing industry. The aim of this study is to develop prediction models of the recast layer and circularity by using Taguchi method. For the design of experiment (DOE) aspects, an L9 orthogonal array design has been chosen and conducted nine experiments with three runs for each experiment. Experimental results indicated minimum recast layer at laser power 700 watts, gas pressure at 1.5 bars and cutting speed at 4000 mm/s. Whereas average circularity has been found at laser power 700 watts, gas pressure at 1.0 bar and cutting speed at 3500 mm/s. In addition, the percentage of contribution for recast layer of laser power is 27.66%, gas pressure is 23.68% and cutting speed is 48.66%. Whereas for circularity, laser power contribution is 23.89%, gas pressure is 26.00%, and cutting speed is 50.11%. Moreover, the 2nd order prediction models have been found excellent agreement with the experimental data. This research will extend knowledge to predict the desired circularity and minimum recast layer of the Polyethylene terephthalate (PETG) thermoplastic which is very important in the field of medical and packaging industry.