Hard machinability of titanium alloys severely limits its development in the field of aviation. It has been proved that micro-texture has a good effect on friction-reducing in turning under the conditions of Minimum Quantity Lubrication (MQL). In this paper, cutting tool with micro-texture on its rake face is fabricated and then experiments are carried out under the conditions of dry continuous turning titanium alloys. A dynamometer is set under the workpiece to measure three components of the cutting forces and the data is processed by Business software MATLAB. Average coefficient μ is calculated according to the mechanical model. Experimental results show that under the dry conditions, micro-texture plays a role in the specific cutting parameters while losing its role in most cases. Also the reasons which lead to the failure of improving the friction properties are analyzed.
In this paper, a torus is designed as an adding mass to modify the dynamic characteristics of the tool-holder system in free boundary condition and in fixing boundary condition. The torus is fixed on the holder of a given face milling cutter, which may change the mass distribution and the stiffness distribution of the system, to adjust the frequency and damping ratio of the tool tip. Although the dynamic characteristics of the tool tip are significantly influenced by holder-spindle interface, the influence of the tool-holder can’t be neglected. In this attempt, by adding mass on the tool holder, the first order frequency decreased by 37% in free boundary condition and 6.7% in fixing boundary condition. The first damping radio increased by 48% in free boundary condition and 4.5% in fixing boundary condition. Chatter suppression is verified in the cutting process by adding mass on the holder.
Vibration is a common phenomenon in cutting process, which is harmful for machining quality and machine tools. This paper focused on the occurrence and characteristics of vibration of the cutting tool and workpiece by changing cutting speed in milling of stainless steels 304. Vibration acceleration signals of both the cutting tool and the workpiece were sampled and analyzed in time domain and frequency domain. Vibration noise and vibration mark were used to judge the occurrence of violent vibration. In the experiments, both self-excited vibration and violent forced vibration were found at different value of cutting speed. Violent forced vibration was easy to be induced owing to interrupted continuous impulsion cutting.The Maximum amplitude of vibration acceleration signals varied with the cutting speed changing. With the cutting speed increased, the probability of violent vibration increased. Bigger amplitude of vibration will not always lead to vibration mark on surface of workpiece, obvious vibration mark only occurred when n=600 r/min and 700 r/min. In order to reduce the impact of violent vibration on machining quality, more attention should also be paid to the static and dynamics characteristics of the cutting tools and workpiece in milling of stainless steels.
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