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Milling machines are widely used for producing a range of products used across various industries such as mold and dies, consumer products, automotive, etc. One of the main components of a milling machine is the spindle drive. The spindle essentially provides the rotational movement of the cutting tool and the power required for material cutting. Commonly, a servo or gearbox electric motor is used for powering the spindle. An alternative method is to use a hydraulic-powered motor. In this study, a hydraulic-powered spindle is developed and installed on a milling machine. Analysis of the milling process with the hydraulic spindle as well as the determination of machining parameters is compared with the conventional mechanical spindle. Mechanical spindles have disadvantages such as unstable spindle speeds under different operating conditions, mechanical impedance in gears, and thermal stress problems, which can have negative effects on part surface quality and cutting forces. On the other hand, the hydraulic spindle has advantages, such as higher stability, higher performance accuracy, and thermal stress removal, which may be the main factors in this study. Milling experiments were performed using AISI 304 stainless steel to compare the performance of the hydraulic spindle with the mechanical spindle in terms of surface roughness and cutting forces. Three factors including spindle rotational speed, feed rate, and depth of cut were selected as input parameters. The results showed that surface roughness and cutting force in hydraulic spindle milling improved significantly compared to that from the mechanical spindle. [ABSTRACT FROM AUTHOR]

High accuracy in production parts and manufacturing quality are the requirements of production. Residual stress affects the surface quality and dimensional accuracy of manufactured parts. Production of parts with geometric tolerance, optimal residual stress, and suitable surface quality is always required by manufacturing industries. When machining parts, tensile residual stresses are created in them, which is one of the main reasons for the loss of geometric tolerances and distortion in the workpiece. This study investigated the effect of the ultrasonic-assisted vibration compared with conventional machining in various conditions of a 2024 aluminum workpiece on the surface quality, runout, straightness, and tensile residual stresses. In this article, the effects of geometric tolerance parameters, tensile residual stress, and surface roughness have been investigated simultaneously. A total of 18 experiments in different cutting speeds and feed rates in two machining states of conventional and ultrasonic vibration states were performed. The results showed that ultrasonic vibrations could be used to achieve 31% lower run out and 36% lower straightness in the parts. Also, the values of tensile residual stress in the ultrasonic vibration machining were 11% lower compared to conventional machining. Ultrasonic vibrations can also be used in most cases to achieve better surface quality, tolerance, and tensile residual stress according to machining parameters compared to conventional machining. The experimental results show that ultrasonic-assisted turning is a reliable method for machining, which can obtain lower tensile residual stress and improve the machined surface integrity and better tolerances. [ABSTRACT FROM AUTHOR]