Abstract
This paper presents an experimental study of the positive effects of vibration-assisted deep drilling of aluminum alloy Al-6061. The four most important evaluation criteria in drilling—machinability, workpiece temperature, torque, and material removal rate—were chosen to be investigated. Holes with a depth-to-diameter ratio of 13 were drilled by high speed steel (HSS) twist drill bits of 3 mm diameter, using both methods of conventional drilling (CD) and ultrasonic-assisted drilling (UAD). Three levels of axial force of 6 kgf, 9 kgf, and 12 kgf were kept constant for each pair of comparison experiments. It was found that workpiece temperature and torque not only changed from one drill to the other, but were also dependent on the hole depth being drilled. Comparisons were made in-pair between CD and UAD under the same axial force and at the same order of hole numbers. The result shows that the material removal rate with UAD was up to 3.5 times higher than that with CD and the average workpiece temperature and torque in UAD were reduced by 3.5 and 6 times, respectively. Moreover, tool life in UAD was observed to increase from 2.5 to 5 times, in terms of number of holes drilled, compared to that in CD.
Highlights
Aluminum and its alloys are considered one of the easiest machining materials
This paper implemented an approach to give an insight into the mechanisms providing benefits of ultrasonic-assisted drilling (UAD) over conventional drilling (CD)
Under a certain axial force acting on the workpiece, the tool was unable to cut after the first hole hole produced with CD, in contrast to five holes with UAD
Summary
Aluminum and its alloys are considered one of the easiest machining materials. These materials are difficult to drill with conventional drilling (CD) due to their ductility and softness causing persistent elongated contact with cutting edges and flutes. Several methods such as using a special tool geometry, coating tool, or even reducing the material removal rate (MRR), etc., have been employed to deal with such problems. A promising technique well known as vibration-assisted machining (VAM) has been reported to overcome problems of drilling difficult-to-cut materials, including aluminum and its alloys. The improved cutting machinability of aluminum in UAD and the causes behind this phenomenon have been rather limited in the literature
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