Enhancement of Machinability Study in Longitudinal Ultrasonic Vibration-assisted Milling Inconel 718 Using High-frequency-vibration Spindle

Longitudinal ultrasonic vibration-assisted machining (LUVAM) is a machining technique that offers several benefits such as low cutting force, good surface quality, and prolonged tool life. A new set of LUVAM spindle with high-frequency vibrations was designed to enhance the efficiency of LUVAM and the critical cutting speed of "tool-workpiece separation." The spindle's stepped axial vibration transducer is designed analytically, and its amplitude is amplified. The spindle's performance was assessed by measuring resonant frequencies and amplitudes of tungsten carbide and high speed steel tool at varying lengths. Experimental results showed that the transducer's maximum resonance frequency was around 33.52 kHz, and its maximum amplitude was approximately 24.03 μm. The maximum spindle speed exceeded 20,000 rpm, and the runout error was low during high-speed operations. Additionally, Inconel 718 was machined with the new spindle, and the experimental cutting force, machining temperature, surface morphology, chip, and surface integrity were analyzed under different machining parameters. The test results showed that LUVAM could successfully reduce cutting force and temperature while improving surface integrity when separation conditions are met. Compared to conventional machining, LUVAM reduced cutting force and average cutting temperature by up to 23.3% and 19.8%, respectively. The new spindle design provides a new approach for high-quality, efficient, and eco-friendly machining of difficult-to-cut materials.