In turning by engine lathe, it is empirically known that chatter vibration may be suppressed when the cutting tool is mounted upside down on the tool post (hereinafter, this method called ‘upside-down tool mounting method’). This study discusses the suppression mechanism of chatter vibration of this tool mounting in terms of the tool vibration trajectory such as vibration direction and amplitude. Because the translational motion in the height direction of the tool is dominant in upside-down tool mounting, the vibration in the tool axis direction is reduced compared to that of usual tool mounting. The effect suppresses chatter vibration in upside-down tool mounting method. Then, tool shank structures for the normal cutting operations were designed to demonstrate the similar tool vibration trajectory to the cutting opetation with the upside-down tool mounting. A parallel leaf spring structure promotes the translational component in the tool height direction to reduce the chatter vibration. The chatter vibration largely depends on the tool vibration trajectory as well as modal paramters of tool clamping.
Although metal additive manufacturing (AM) gathers attention from various industries, the process stability in metal AM still remains in an important issue for ensuring the production quality. In particular, powder-based directed energy deposition (DED) is difficult to stabilize because large amount of metal is contentiously molten with a high-power heat source. Furthermore, the material powder flow needs to be precisely converged on the meltpool; otherwise the considerable amount of materials would be wasted. Against these challenges, this study aims to analyze the turbulent flow in the fabrication space for converging the powder trajectories on the meltpool stably and accurately. By constructing a gas-solid multiphase-flow simulation for the coaxial nozzle for DED, the influence of carrier and shield gases on the powder flow is numerically calculated. According to the estimated particle distribution, the particle concentration on the top surface of deposit decrea ses in the higher-layer deposition. Moreover, the particle-flow convergence is enhanced with higher carrier gas-flow rate. These analyses highly agree with the experimental results on powder distribution measured with a laser light sheet system. As a conclusion, it is clarified that the carrier gas supply should be higher at higher layer deposition to keep the powder convergence stable in DED.
In wire electrical discharge machining (EDM), wire brakeage often occurs and the shape accuracy tends to deteriorate when cutting corner shapes. However, the influence of jet flushing conditions on the debris exclusion and wire deflection in the corner shape cutting has not yet been investigated so far, while the influences of discharge conditions and spark distribution wire were studied. In this study, the flow fields and debris movements in the machined kerf during the corner shape cutting in 1st-cut wire EDM were simulated by CFD analysis. Also, the wire deflection was discussed by a structural analysis of wire with stress distribution due to hydrodynamics force obtained by the CFD analysis. The results showed that the flow and pressure fields around the wire by jet flushing and the debris movements in the kerf significantly changed just after changing the cutting direction at the corner. Additionally, the corner shape error with wire deflection was experimentally measured and compared to the analytical result of wire deflection with hydrodynamics force. It was found that the influence of hydrodynamics force on wire deflection was as large as discharge explosive force under general 1st- cut conditions, which suggests that the influence of jet flushing on the corner shape accuracy is large under jet flushing conditions with relatively high flow rate.
Solving environmental problems and energy problems is global urgent task. Weight saving of transportation equipment and robot is one of the effective solutions. The direct joining of metal and resin using a blasted surface is effective for weight saving. The problem is that the parameters of JIS/ISO standard have insufficient correlation with the shear strength of the direct joining of metal and resin using a blasted surface. In this paper, new surface roughness parameters that considered various geometrical characteristics of surface texture are proposed. And, proposed parameters are confirmed that have higher correlation with the shear strength than the parameters of JIS/ISO standard.
This paper considers the trade-off between flow disturbance attenuation and transmissibility reduction for pneumatic isolation tables. In the active control of the pneumatic isolation table, compressed air is supplied to air springs. However, the pressure of the compressed air fluctuates. This pressure fluctuation, which is called flow disturbance, causes the vibration of the isolation tables. Since the pressure fluctuation is periodic, repetitive control is utilized so as to compensate for the flow disturbance. The feedthrough term in a repetitive controller is usually designed as a static compensator. Although the flow disturbance is further attenuated by increasing the gain of the static compensator, the transmissibility becomes large in the frequency region of mechanical resonance of the isolation tables. Therefore, this paper focuses on the setting of the feedthrough term. In the proposed approach, a dynamic compensator is adopted as the feedthrough term instead of the static compensator. Two break-point frequencies of the dynamic compensator are tuned on the basis of the bandwidth of the pressure fluctuation and the mechanical resonance. It is shown that, by using the proposed setting method, the flow disturbance can be attenuated and the peak of the transmissibility can be reduced.
In this research, the automatic pipe routing system aimed at reducing the man-hours of piping design work is developed. In this system, the piping route is obtained by the Dijkstra method reflecting design knowledge obtained from hearing to the designers as evaluation values for getting a path that match the designer's intentions. By the verification of this system, one piping was created in 33 seconds by the function to automatically create the generated route on CAD. Furthermore, it was confirmed that the automatically generated piping route does not interfere with other parts and satisfies the designer's knowledge.