Experimental evaluation for internal trapezoidal thread with axial ultrasonic vibration cutting of Ti–6Al–4V

Renewal of the manufacturing process for thread is important in a variety of products and industry applications. Especially for machining the internal trapezoidal thread, the cutting edge is in a semi-closed state, three cutting edges and two cutting tips are in contact with the workpiece, resulting the heat is not easy to spread out. At the same time, the narrow space of the internal thread leads to the poor rigidity of the tool, the instability of the machining state, which seriously affects the surface machining quality of the parts. Here, a new precision processing device of axial ultrasonic-assisted turning (AUAT) is designed, which can achieve the industrial application of machining internal thread parts. The device can work stably at a working frequency of about 28.8 kHz. Secondly, considering that the bottom and flank of the thread need to be machined at the same time, the contact mode of the tool is different between them. The main cutting edge of the tool contacts the workpiece intermittently on the flank tooth, forming the texture surface which is conducive to the transmission of the thread pair. On the bottom teeth, the main cutting edge is always in contact with the workpiece and carries out the axial sawing movement. The high-frequency axial vibration damping effect is obvious, which suppresses the unstable machining state such as chatter and improves the machining surface quality of the bottom teeth. Finally, Ti–6Al–4V trapezoid thread is selected in the verification, in which the separation effect of ultrasonic vibration cutting is verified, the cutting force is tested, and the machined surface topography of the workpiece is analyzed. Experimental results show that the quality of thread was significantly improved in AUAT.