Research On Chatter Identification And FEM Simulation In Milling Process

Due to the unique purposes, the special-shaped workpieces have been widely used in modern manufacturing industry. Nowadays, milling is still a main processing method of semi-finishing to manufacture them. However, the chatter and improper milling parameters will greatly affect the milling efficiency in actual process. Therefore, one kind of steel casting processed by a certain company was took as research object and studies were carried out on it which contains chatter identification and FEM simulation of milling process. All of above jobs provide some suggestions for actual machining process.Firstly, the dynamic characteristic of milling system was identified and its model was established and analyzed using ABAQUS software, which are based on modal analysis theory. The results showed that the fitting curve of frequency response function is credible because its correlation coefficient and error with the actual curve are 0.9909 and 0.92%, which are compliance with testing standards. In view of the fitting curve of frequency response function, the natural frequencies of the first six modes are 452.21Hz,612.12Hz,1085.1Hz,1885.8Hz, 2473.7Hz and 2820.OHz respectively. And in order to eliminate the possibility of resonance, spindle speed should be avoided close to 9044.2 r/min which can derives from the first natural frequency 452.21 Hz. Moreover, the relative errors of natural frequencies and maximum/minimum of transient response between real value and simulative value are 13.48% and 13.96% respectively, which verify the dependability of the finite element model.Secondly, the orthogonal milling tests were conducted on this steel casting before summarizing the influence of milling parameters on milling forces and surface roughness. The results indicated that milling forces slightly decrease with the rise of spindle speed. Compare with milling force Fz, milling force Fx and Fy have greater slope when feed raises. With the increase of axial depth of cut, milling force Fx and Fy are increasing but milling force Fz is first decreasing then increasing. Milling force Fy is positively correlated with radial depth of cut, however, milling force Fx and Fz have both positive and negative correlation parts with it. Different from milling forces'change rule, the surface roughness has more simple variation tendency. It goes down along with the increasing of spindle speed, and augment in pace with enlargement of feed and axial depth of cut. At the same time, the relationship between surface roughness and radial depth of cut is positive correlation in addition to the exit cutting stage.Thirdly, time domain, frequency domain and wavelet analysis methods were applied to extract the features of milling forces for identifying the chatter. The findings demonstrated that tool breakage brings about the abnormal fluctuation of milling force in the time domain analysis. Depend on frequency domain discussion, the chatter occurs at a frequency of 1090.9 Hz and causes an increase of the high-frequency energy which aggravates tool wear. Owing to the chatter frequency, it is inappropriate to select the value of 2430 r/min of spindle speed. In the same way, increasing axial depth of cut does not necessarily lead to aggravate the chatter that is inconsistent with the traditional theory. According to the wavelet analysis, the detail signal d3 can be employed to monitor stability state.In the end, the FEM simulation of milling process was studied by means of DEFORM-3D software. The results revealed that the shape of the simulation chip and actual chip is similar; the simulation values of milling forces are close to the test values and the relative errors between them are less than 20%. They prove that the finite element model is realistic.