Simulation And Experimental Study On Microdrilling Of Difficult-to-machine Material

The micro drill used for drilling is small in size,poor in strength and stiffness.It is easy to produce serious wear and damage when machining difficult to machine materials such as stainless steel,and reduce the tool life and the quality of the hole.Based on the traditional cutting principle and scale effect theory,the 3D model of 0.8mm diameter drill bits were established.The drilling process of 316 L stainless steel was simulated.The results show that the cross section of the non-grinded drill point is parallelogram,the grinding drill point is zigzag,the drilling force at the cross edge of the non-grinded drill bit accounts for 59.3% of the total drilling force,while the drilling force at the chisel grinded edge of drill bit accounts for 5% of the total drilling force,and the axial force and temperature of the cross edge grinding drill bit are respectively 45% and 10% lower than those of the non-grinded drill bit under the same cutting parameters.The results of orthogonal experiments with helix angle,top angle and core diameter ratio as the levels show that the optimal tool parameters are helix angle 35°,top angle 120° and core diameter ratio 0.3.The results of micro drilling experiments show that the main cutting edge and the chisel edge are the most worn positions of the drill tip,and the wear type is mainly abrasive wear.The wear degree of the main cutting edge gradually decreases from the outer edge of the cutting edge to the cross edge direction.The most worn position of the cross edge is near the inflection point of the outer edge of the cross edge.After 20 holes are drilled at feed speed of 20 mm/min to 80 mm/min,the roundness at the entrance is 1.057 to 1.07,while that at the exit is about 1.03.When 316 L stainless steel is drilled at feed rate of 20 mm/min,uniform burr is produced at the exit of hole,and crown burrs is produced at feed rate of 80 mm/min.The optimized bit geometry improves the cutting performance of the micro bit and provides data reference and technical support for the actual production.Figure 50;Table 14;Reference 55...