Morphological Analysis Of Multi-axial Ball End Milled Surfaces And Research On Friction Coefficient

Compared with conventional three-axis machining, multi-axis ball end milling can greatly improve the processing efficiency and surface quality because it can avoid cutter-interference and many times of clamping. So multi-axial ball end milling was widely used in aviation, aerospace, automotive, mould & die and other manufacturing fields. Surface morphology is one important part of the integrity of the machined surfaces which have an influence on the friction and wear behavior, fatigue strength, stiffness, sealing and so on. So, many researchers focused on the surface morphology especially its characterization and analysis methods. In this paper, the fractal theory, the power spectral density and wavelet method were used to analyze the die steel HI3 surfaces milled by multi-axis ball end cutter, and the changing rules of the friction coefficients were also studied.The influence of processing parameters on the surface fractal dimension was studied. The result showed that the fractal dimension is small in the case of large single angle,0°angle and 315°rotation angle. When n is 12000rpm the fractal dimension is the largest. Fractal dimension has no distinct changing trend along with the change of the axial cutting depth. With the increase of radial cutting depth and feed per tooth, the fractal dimension firstly increases then decreases.The power spectral density function can be used to analyze the surface profile in frequency domain. In the situation of large single angle, the dominant frequency is concentrated in the low frequency. When the single angle was small, the dominant frequency was influenced by radial cutting depth and feed per tooth. Relatively high frequency ripple is the main factors of the high spindle speeds. The dominant frequency component has no distinct changing trend along with the change of the axial cutting depth. The frequency components which was caused by radial cutting depth or feed per tooth had a good corresponding relationship with the power spectral density.In this paper, frequency components of the ball end milled surfaces were separated and reconstructed with the wavelet method. We studied the influence of processing parameters on the roughness of various frequency bands. Single angle variations have large impact on the middle and low frequencies. The larger angle had more low-frequency vibration. With the increase of spindle speed, high frequency surface roughness had a tendency to increase. But the axial cutting depth had little influence on high frequency surface roughness. The radial cutting depth and feed per tooth had most significant effect on surface roughness of the median frequency components. And we also study the relationship between the fractal dimension and roughness.The tribological behavior of the surface directly affected the service life of mould & die. In this paper, we studied the friction coefficient of surfaces under different processing parameters and the result showed that cutter postures have an influence on the friction coefficient in the feed and the cross feed direction. In the case of large single angle,0°ngle,315°rotation angle and high speed machining, the friction coefficient is small. With the increase of the axial cutting depth, the friction coefficients in the two directions increase firstly then decrease. In case of larger radial cutting depth and feed per tooth, larger friction coefficients exist. The change of the friction coefficient was affected by two-dimensional surface roughness.