Modeling and optimization of the flute profile of micro-drill

The profile of drill flute has a great influence on the drilling performance of micro-drill. It is promising to obtain a desired flute profile with a standard wheel by adjusting the wheel position parameters during the grinding process. To investigate the flute profile characteristics under different wheel position parameters and its effect on the drilling performance, this paper presents a method for modeling and optimization of the micro-drill flute considering the wheel installation angle and the offset distance from the wheel origin to the drill blank origin. Based on this model, the flute profile of micro-drill is numerically simulated by MATLAB software firstly, and then, the 3D model of micro-drill with different flute profiles is established by UG software. Finally, the micro-drilling process on 304 austenitic stainless steel is simulated by DEFORM software, and the chip morphology and the drilling force are analyzed and discussed. The results show that the wheel installation angle has an obvious effect on the flute profile and its radial rake angle and flute width, and the wheel offset distance only influences the flute width evidently. The micro-drill with flute ground by smaller wheel installation angle owns straighter cutting lip shape and larger chip evacuation capacity, and its thrust force and torque are smaller than those of other micro-drills. Moreover, spiral chip is generated due to the intense side curl and up curl of the chip, resulting in the easiness of the chip removal. However, for the micro-drills with flute ground by larger wheel installation angle, the chip morphology is string and the drilling force is larger. At last, the mathematical model of the drill flute and its numerical simulation result are validated by experimentally fabricating the micro-drill flute. Then, the optimized micro-drill is manufactured by a six-axis computer numerical control (CNC) grinding machine, and its flute profile is fabricated using a standard conical grinding wheel with a smaller wheel installation angle.

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