Modeling and Emulation of 3d Dither Stability in Orthogonal Turn-Milling
International Journal of Hybrid Information Technology
Aiming at 4-axial orthogonal turn-milling by end mill, its theoretical 3d model for stable range of dither was put forward on the basis of its cutting principle by using analytical method. Based on modal trial, the stable range leaf figure of end mill's dither in 4-axial turn-milling with eccentricity was simulated and analyzed. The results show that besides geometrical shape of mill, material of workpiece and frequency response function of machine-tool's structure etc that can produce dither
... an produce dither in 4-axial turn-milling, the rotating speed of mill and cutting depth are also related to dither. In trial of 4-axial turn-milling by end mill, the results of cutting force spectrum analysis show that: cutting is stable and un-dither when frequency of cutter tooth cutting-in plays leading role in force spectrum. Dither is produced when modal frequency of system plays leading role in force spectrum, the measured value of cutting force and surface roughness are also higher than those in the condition of un-dither. Thus the theoretical model and results of emulation can predict stability of end mill's dither in 4-axial orthogonal turn-milling with eccentricity correctly and can provide theoretical guidance for surface quality and processing efficiency of workpiece. force and spectrum analysis of 3rd point in workpiece respectively. In Figure 9a , the cutting depth is 2mm and rotating speed of end mill is 2400rpm at the position of point 1 in the figure. There is severe dither exists which can be observed in trial and can be verified by force spectrum. Dither occurs at frequency of 1608Hz which is close to 1st modal of system. There is slight dither exists at the 2nd point where the cutting depth is 2mm and rotating speed of end mill is 2700rpm in Figure 9a . There is un-dither the 3rd point where the cutting depth is 2mm and rotating speed of end mill is 3600rpm in figure 9a . The force spectrum shows that forced vibration frequency of main shaft or forced vibration cutting frequency of cutter tooth is around 240Hz or its integral multiple. In order to avoid dither, the stability of machining can be predicted by different cutting depth and rotating speed of main shaft. However, there is still some slight dither in stable range leaf figure of dither, so the model of 3d stable range of dither needs to be optimized properly.