An experimental study on rotary ultrasonic drilling small-diameter holes of high volume fraction silicon carbide-reinforced aluminum matrix composites (SiCp/Al)

High volume fraction silicon carbide-reinforced aluminum matrix composites (SiCp/Al) have many excellent properties while they are one of typical hard-to-machine materials. Due to the existence of hard SiC reinforcements, it is very difficult to machine holes of this material, especially small-diameter holes. Rotary ultrasonic drilling (RUD) is a suitable machining method to process hard brittle materials. In order to improve the machining quality of small-diameter holes, RUD is used to machine this kind of advanced material. In this research, small-diameter single holes and cross holes are processed by RUD and the results are compared with these processed by conventional drilling (CD). The basic principle of RUD is analyzed. It finds that RUD is a discontinuous process. The drill separates with the workpiece periodically. This motion is good for chip breaking, chip removal and circulating of cutting fluid. Experimental results show that the cutting force decreases with the increasing of the spindle speed and increases with the raising feed speed both in RUD and CD. The cutting force can be significantly reduced in RUD and the range of maximum reduction is up to 75%; the machining precision is similar in RUD and CD when drilling single holes. However, when drilling cross holes, the machining precision cannot be guaranteed in CD while RUD can ensure the size consistence. It can reduce the edge chipping in inlet and outlet of holes and improve the machining quality of small-diameter cross holes.