Machining performance on AISI 304 steel in the milling machine with mechanical and hydraulic spindle

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.