Nanoscale cutting using self-excited microcantilever

The application of self-excitation is proposed to improve the efficiency of the nanoscale cutting procedure based on use of a microcantilever in atomic force microscopy. The microcantilever shape is redesigned so that it can be used to produce vibration amplitudes with sufficient magnitudes to enable the excitation force applied by an actuator to be transferred efficiently to the tip of the microcantilever for the cutting process. A diamond abrasive that is set on the tip is also fabricated using a focused ion beam technique to improve the cutting effect. The natural frequency of the microcantilever is modulated based on the pressing load. Under conventional external excitation conditions, to maintain the microcantilever in its resonant state, it is necessary to vary the excitation frequency in accordance with the modulation. In this study, rather than using external excitation, the self-excitation cutting method is proposed to overcome this difficulty. The self-excited oscillation is produced by appropriate setting of the phase difference between the deflection signal of the microcantilever and the feedback signal for the actuator. In addition, it is demonstrated experimentally that the change in the phase difference enables us to control the amplitude of the self-excitation. As a result, control of the cutting depth is achieved via changes in the phase difference.

Nanoscale Cutting Using Self-Excited Microcantilever

The application of self-excitation is proposed to improve the efficiency of the nanoscale cutting procedure based on use of a microcantilever in atomic force microscopy. The microcantilever shape is redesigned so that it can be used to produce vibration amplitudes with sufficient magnitudes to enable the excitation force applied by an actuator to be transferred efficiently to the tip of the microcantilever for the cutting process. A diamond abrasive that is set on the tip is also fabricated using a focused ion beam technique to improve the cutting effect. The natural frequency of the microcantilever is modulated based on the pressing load. Under conventional external excitation conditions, to maintain the microcantilever in its resonant state, it is necessary to vary the excitation frequency in accordance with the modulation. In this study, rather than using external excitation, the self-excitation cutting method is proposed to overcome this difficulty. The self-excited oscillation is produced by appropriate setting of the phase difference between the deflection signal of the microcantilever and the feedback signal for the actuator. In addition, it is demonstrated experimentally that the change in the phase difference enables us to control the amplitude of the self-excitation. As a result, control of the groove cutting depth is achieved via changes in the phase difference.

Investigation of effect of uncut chip thickness to edge radius ratio on nanoscale cutting behavior of single crystal copper: MD simulation approach

Extremely small cutting depths in nanoscale cutting makes it very difficult to measure the thermodynamic properties and understand the underlying mechanism and behavior of workpiece material. Highly precise single-crystal Cu is popularly employed in optical and electronics industries. This study, therefore, implements the molecular dynamics technique to analyze the cutting behavior and surface and subsurface phenomenon in the nanoscale cutting of copper workpieces with a diamond tool. Molecular dynamics simulation is carried out for different ratios of uncut chip thickness ( a) to cutting edge radius ( r) to investigate material removal mechanism, cutting forces, surface and subsurface defects, material removal rate (MRR), and stresses involved during the nanoscale cutting process. Calculation of forces and amount of plowing indicate that a/ r = 0.5 is the critical ratio for which the average values of both increase to maximum. Material deformation mechanism changes from shear slip to shear zone deformation and then to plowing and elastic rubbing as the cutting depth/uncut chip thickness is reduced. The deformation during nano-cutting in terms of dislocation density changes with respect to cutting time. During the cutting process, it is observed that various subsurface defects like point defects, dislocations and dislocation loops, stacking faults, and stair-rod dislocation take place.

Investigation of tool geometry in nanoscale cutting single-crystal copper by molecular dynamics simulation

Molecular dynamics has been employed in this paper to investigate the nanoscale cutting process of single-crystal copper with a diamond tool. The behavior of the workpiece during material removal by diamond cutting has been studied. The effects of tool geometry including rake angle, clearance angle, and edge radius are thoroughly investigated in terms of chips, dislocation movement, temperature distribution, cutting temperature, cutting force, and friction coefficient. The investigation showed that an appropriate positive rake angle ([Formula: see text]), a suitable clearance angle ([Formula: see text]), or a smaller edge radius tip resulted in a smaller cutting force and a better subsurface finish. It was found that a tool with a rake angle of [Formula: see text] generated more chips, had a higher cutting efficiency, and produced a lower temperature in the workpiece, but a smaller rake angle tip was more conducive to protecting the groove compared to a large rake angle tip. Compared with a tool with a small clearance angle, the tool with a larger clearance angle generated more chips and caused a lower temperature rise in the copper workpiece, and prolonged its lifetime. In addition, a larger clearance angle tip was more conducive to protecting the groove. A smaller edge radius tip reduces the cutting heat during the nanoscale cutting process, while the volume of chips decreases. These results indicated that it is possible to control and adjust the tool parameters according to the tool rake angle, clearance angle, and edge radius during the machining of single-crystal copper, and a set of tool parameters were obtained: [Formula: see text] rake angle, [Formula: see text] clearance angle, and 0 nm edge radius which could reduce surface damage and the required cutting force.