CFD based Investigation on Internal Cooling of Twist Drills

To investigate the influence of cutting fluid flow rate and cooling channel exit position on tool wear when drilling with internally cooled cemented carbide twist drills, a model for CFD (computational fluid dynamics) simulations was used. The CFD model's quality regarding fluid flow was evaluated by a comparison between its results and high-speed cinematographic pictures of real flow conditions. The simulations’ results showed significant influences of cutting fluid flow rate and cooling channel exit position on heat flux between tool and coolant as well as for residual temperatures within the wedge. Coolant flow rates were varied between 1.2 and 4.8 liters per minute for drills with a diameter of 10 mm. The simulations were evaluated by analysis of heat flux through the major flank face and average temperature above the flank face. To explain these results average velocity and turbulence kinetic energy below the wedge were taken into account. When neglecting the cutting fluid flow rate the average temperature within the wedge was 1.28 times higher for the most unfavorable exit position in comparison to the best one. The influence of cutting fluid flow rate is almost identical for all exit positions. By averaging the results for all exit positions the lowest flow rate results in average temperatures within the wedge that are 1.19 times higher than the ones for the highest flow rate.