Influence of stiffness on thrust force and exit burr in drilling titanium plates

For drilling process of thin titanium plates, the influence of workpiece's stiffness on thrust force and exit burr is investigated experimentally and theoretically. The interaction of workpiece's bending and thrust force has been studied. Additional feed rate caused by bending of workpiece could be obtained through differential of deflection. Then, a model is developed to predict thrust force for plates with low stiffness. Equations for burr thickness calculation and burr growth deciding are also established to analyze the influence of stiffness on burr type and size. Drilling experiments are conducted with varying stiffness and feed rate. Experimental results show that with the decrease of workpiece stiffness thrust force rises slowly, descends quickly, the maximum value decreases slightly; while, burr type changes from crown to uniform, and burr becomes lower and thicker. Predicted curve of thrust force has the same trend with the experimental curves. Predicted errors of maximum values are within 8%. Analytical results of burr type and size agree with the experimental results. Stiffness affects drilling process through changing the actual feed rate, thus stiffness should be considered to control burr in drilling titanium plates with low stiffness.