INFLUENCE OF HELICAL CUTTING-EDGE ANGLE ON END-MILLING STABILITY

Increasing productivity, machining accuracy and efficient use of resources are important priorities for companies that manufacture competitive products. One of the main problems that hinders these processes is the vibration that occurs during cutting. Various methods are used to suppress vibration, one of which is the use of tools with a variable helical cutting-edge angle. However, when choosing the cutting-edge angle, it is important to consider the types of vibrations that occur during cutting, as they directly affect the efficiency of the milling process. In addition, the use of tools with different cutting-edge geometries, such as wavy, gives positive results in roughing, but becomes ineffective in finishing. The purpose of this paper is to study the effect of the helical cutting-edge angle on the stability of the end-milling at different cutting speeds. Both theoretical aspects and experimental data are considered, which make it possible to evaluate the effectiveness of using tools with different angles of inclination to ensure the stability of the machining process and increase productivity while minimizing vibrations in the most unfavorable third speed zone of oscillations for cutting. To conduct the experiments, a special stand was used to adjust the stiffness of the workpiece, record the vibrations that occur during cutting, and the time of contact between the workpiece and the tool. The milling was performed in the third high-speed oscillation zone using a tool whose design provides for the possibility of adjusting the angle of inclination of the helical cutting edge. Studies confirm that changing the angle of inclination can significantly affect the stability of the milling process, reducing the intensity of oscillations and improving machining accuracy. However, this effect depends on the initial cutting conditions, such as the cutting speed. With its increase, the amplitude of the accompanying free oscillations increases, regardless of the value of the angle of inclination. Ensuring the stability of the end-milling in the third speed zone by changing the angle of inclination is possible only at the speeds that determine the beginning of this zone. However, within the entire speed range covered by the third speed zone, it is impossible to ensure a stable milling process only due to the angle of inclination. The study emphasizes the importance of an integrated approach to selecting cutting parameters to achieve process stability.