Laser-assisted full-size PDC bit: Drilling performance and parameter optimization

Laser-assisted drilling combined with full-size polycrystalline diamond compact (PDC) bit is considered a feasible solution to enhance the drilling performance of engineering machinery. In this method, determining the optimal collaborative control parameters that support rapid drilling is crucial for improving the combined performance. This study used average drilling speed, average torque, and total specific energy for quantitative analysis to characterize the efficiency and economy of combined rock breaking. Given the advantage of the response surface methodology in providing high-precision predictions with limited experimental data, regression models of the average drilling speed, average torque, and total specific energy were established. The results showed that as the laser power and irradiation time increased, the average drilling speed first increased rapidly and then leveled off, while the average torque decreased sharply before decelerating. The total specific energy initially decreased and then increased, with the combined drilling outperforming conventional mechanical drilling within specific parameter ranges. As the weight on bit increased, both the average torque and total specific energy first decreased and then increased. With rising rotating speed, the average torque exhibited a trend of initial increase, then decrease, and final increase, whereas the total specific energy increased slowly at first and then sharply. Both parameters exhibited optimal values at which the average torque and total specific energy remained at minimal levels. For granite combined drilling, the optimal performance was achieved at a laser power of 3000 W, irradiation time of 31 s, the weight on bit of 2.4 kN, and the rotating speed of 97 r/min.