| As one of the most important medical devices in surgical operation,the medical micro drill plays a vital role in the quality of surgery.However,there are problems in the existing preparation technologies of medical micro drills,such as complex preparation process,difficult-to-machine and high production cost.Laser additive manufacturing technology is characterized by good material utilization,short process,free forming and rapid manufacturing,which can make up the shortage of the existing preparation technologies of medical micro drills effectively.Thus,the selective laser melting forming process,the grinding process and the drilling performance of the medical micro drill were investigated in this paper.The temperature field of micro devices forming by selective laser melting was simulated,so as to analyze the effect of the laser power and the scanning speed on the temperature field.It was found that the maximum temperature of the powder layer,the maximum half-width and depth of the molten pool were decreased with an increase in the laser scanning speed,while increased with an increase in the laser power.A set of suitable process parameters was obtained.The selective laser melting forming process and the precision grinding process of the medical micro drill were investigated.A medical micro drill blank was manufactured by selective laser melting.A new grinding process,including flank grinding,chisel edge grinding and diameter grinding,was proposed for grinding the medical micro drill blank.After grinding,a medical micro drill with a diameter of 03mm was successfully manufactured.Upon inspection,the medical micro drill met the technical requirements.The cortical bone drilling process by using the medical micro drill was simulated,so as to analyze the effect of the spindle speed and the feed rate on the drilling temperature and the thrust drilling force.It was found that the maximum drilling temperature was increased with an increase in the spindle speed,while decreased with an increase in the feed rate.On the contrary,the average thrust drilling force was decreased with an increase in the spindle speed,while increased with an increase inthe feed rate.A set of suitable drilling parameters was obtained.The drilling performance of the medical micro drill was experimentally investigated by drilling cortical bone,so as to analyze the drilling process.It was found that there was no phenomenon that the chip removal was affected by the spiral flute without grinding.When the spindle speed was 600r/min and the feed rate was 40mm/min,the maximum drilling temperature was 43 and the average thrustdrilling force was 41N.The difference between the experiment results and the simulation results was reasonable,which indicated that the finite element simulation results were reliable.The hole quality and the drill wear were investigated.It was found that there were no apparent defects at the entrance and the wall of the drilled holes except a few burrs at the exit of the holes,which indicated that the hole quality was satisfactory.The main failure modes of the medical micro drill were flank wear and chipping.The farther away from the chisel edge,the more serious the wear was.The wear mechanism of the drill flank was abrasive wear. |
