On the segmentation-driven vibration in milling titanium alloy

Abstract

Numerous hard, brittle metals have been shown to form segmented chips during machining operations, which has been shown to be linked to high vibration levels in turning and milling processes. This article concerns quantitative comprehension of segmentation-driven vibration in end-milling process. First, dynamic model of milling process with impact of segmented chip is presented, and a periodic cutting force model related with segmented chip is proposed. Second, for experimental observation, a series of tests are carried out concerning modal test of cutting system; chip morphology, tool vibration during cutting, surface location error, and high-frequency sampling measurements of cutting force signal are realized. The method used for calculating the frequency of segmentation chip by oblique cutting is deduced. It is found that at low feed rate, the periodic cutting force is affected by the natural frequency of cutting system, segmentation chip, and tool vibration. Finally, amplitude-frequency response for quasi-single degree of freedom is employed to elaborate the relationship between segmentation frequency and natural modes of system. The results show that when the ratio (frequency of segmented chip to natural frequency of system) is a noninteger value or above 3, no significant vibrations of cutting system are observed in milling titanium alloy Ti6Al4V.

Machinability improvement of titanium alloys in ultra-precision machining with micro-structured surface

“…9,10 Especially, the instability of the segmented chip formation process in the machining of titanium is responsible for fluctuations of cutting forces. [11][12][13] The tool wear mechanisms in machining of various titanium alloys include abrasion, adhesion, diffusion, coating delamination, chipping, and fracture, which change with tool materials and machining process. 14 Therefore, different methods are developed to improve titanium alloys' machinability and decrease tool wear: the control of cutting conditions, 15 the applications of new tool materials and cutting fluids, 16,17 new design of tool geometry, 18 etc.…”

Investigating the impact of tool inertia on machinability of a β-titanium alloy using tool deflection and acoustic emission

“…26 A recent study has put forward quantification of the effects of segmentation-driven vibration on the end milling’s performance measures. 27 The experimental investigation based on the milling of Ti-6Al-4V has found that the frequency of chip segmentation possesses significant effects on tool vibration, cutting forces, and work surface texture.…”