Key Engineering Materials Vols. 375-376

Abstract: Piezoelectric-driven stick-slip actuators have been drawing extensive attention for applications in the fields of scanning microscopy, micro robotics, and microsystems due to their well-defined step size and theoretically-unlimited displacement. In such an actuator, the dynamics of the end-effector displacement is of importance for its control and optimal design, yet challenging to be modeled due to the complexity involved. By taking into account the dynamics of piezoelectric element and the presliding friction acting on the end-effector, a model representative of the end-effector displacement is presented in this paper. The effectiveness of the developed model is illustrated by the experiments on the piezoelectric-driven stick-slip actuator prototyped in the authors’ lab.

Abstract: This paper investigates the effect of spindle clamping force on the static and dynamic characteristics of the spindle-tooling system through measuring the frequency response function of the tool end point in variable spindle clamping force. The research shows that the limited static stiffness increases accordingly and normal static stiffness changes little as the spindle champing force increases. The high spindle clamping force leads to reduce the modal damping of the spindle-tooling system while the natural frequency varies slight. The analyses of process stability indicates that the low spindle clamping force can improves the process stability because of the higher damping in some clamping force range.

Abstract: In order to improve the attenuation ability of grinding wheel spindle and manufacturing quality of workpiece, an ultrahigh speed grinding spindle system with a SFD was designed based on the theory of squeeze film damping, and a series of experiments were done. The study results show that the application of SFD technology can effectively restrain vibration which is caused by the imbalance quality when the grinding wheel spindle turning at ultrahigh speed. And the speed of the grinding spindle is higher and the effect of attenuation of SFD to grinding spindle is better. Research works provides a new technology for the design of the ultrahigh speed grinding spindle system.

Abstract: According to the characteristics of high speed face milling process, the models of dynamic cutting forces and frequency spectrum were established. By means of frequency spectrum analysis for dynamic cutting forces of high speed face milling cutter, the law of influence of cutter’s structure and parameters on dynamic cutting performance of cutter was acquired, high speed face milling cutter for machining aluminum alloy was developed, and evaluation for dynamic cutting performance of cutter was processed based on experiment. The results indicate that more teeth of cutter and greater cutting contact angle can make the energy more dispersible, higher cutting speed and greater rake of cutter can depress dynamic cutting forces, and improve effectively dynamic cutting performance of cutter. High speed face milling cutter with five teeth takes on better dynamic high speed cutting performance for machining aluminum alloy, as cutting contact angle exceeds ninety degrees but it is less than one hundred eighty degrees, and cutting speed exceeds 2260m/min.

Abstract: The existent studies on the milling of the thin-web components are reviewed first, then the cutter selection strategies are discussed theoretically based on the mechanistic model of the milling cutter, and several experiments are carried out to verify the theoretical analysis. At last, the conclusions are given on the cutter selection strategy in the milling of the thin-web components.

Abstract: The machining accuracy and the surface roughness of workpieces machined by the PKM named BJ-04-02(A) are evaluated by machining experiments in this paper. The machining accuracy includes that of size, shape and position. Size includes the diameter and length. Shape accuracy includes straightness, roundness and cylindricity. Position accuracy includes perpendicularity, parallelism, inclination and concentricity. The experiment results show that the surface roughness and the straightness basically meet the demand of JB/T8771.7-1998, but other accuracy indexes are not consistent well with the mechanical standard. However, the machining accuracy becomes bad when machining tool is far away from the center of the workspace.

Abstract: Generator is one of the key factors in Micro WEDM, which can affect machining quality, precision and efficiency largely. The factors influencing discharge energy are discussed and analyzed, the pulse addition method increasing energy density under maintaining the single pulse energy is advanced. To reduce the influence of voltage to single pulse energy, the gap voltage is also controlled. The generator is designed and the validating experiment shows this generator can increase machining efficiency and quality to a certain extent.

Abstract: The tool geometry such as rake angles and cutting edge inclination angles play significant roles in determining machining performance. The task of selecting cutting tool inserts and cutting conditions is traditionally carried out on the basis of the experience of process planners with the help of data from machining handbooks and tool catalogues. This situation urges the need for development of some intelligent tooling system to reduce these inefficiencies for optimum economic and technological machining performance. A model of turning tool mechanism having the function of controllability in changing the tool inclination angle and tool approach angle is described. The mechanism is realized through the use of three specific slopes which work simultaneously to compensate the tool tip deviation due to the change of inclination angles so that the tool tip always stays at working point in space. Based on the ‘classical’ oblique cutting operation, analytically simulated prediction of the tangential cutting forces were presented with MATLAB software.

Abstract: According to lateral powder system due to gravity, the controllable rapid powder switch is first tried based on the principle that air pressure can change the direction of power. Then, three kinds of modified schemes are provided based on the experiment to remedy the lack of first try. Finally, one scheme is selected and realized, which can solve the problem of synchronization of laser and powder, and advance powder utilization factor.

Abstract: Strain films in the thin film resistance strain gauge are prepared by magnetron sputtering method. Some results concerning the electromechanical and structural properties of nichrome (Ni80Cr20 wt.%) thin films are presented. As compared to the well-known Ni-Cu (constantan) alloy film, which are widely used for manufacturing pressure and force sensors, nichrome (Ni80Cr20 wt.%) thin films exhibit gauge factor values of the same order of magnitude, but they are much more corrosion resistant and adherent to the substrate. The influences of composition and post-deposition annealing on the electrical resistance, temperature coefficient of resistance (TCR) and gauge factor of nichrome (Ni80Cr20 wt.%) thin films are discussed.