In the review paper, two phenomena associated with high-speed and ultra-high-speed machining, which were difficult to understand comprehensively, are discussed. One is the improvement of tool life with increasing cutting speed in a certain range of cutting speeds. This is made clear based on changes in wear mechanism and chip formation with increasing cutting speed. The other phenomenon is the mechanism of ultra-high-speed machining when the cutting speed is higher than the plastic wave speed under the condition of uniaxial stress. Theory of wave propagation and finite element simulation of machining lead to a conclusion that increase in hydrostatic pressure around the cutting edge increases the speed of plastic wave.
The new analytical model to predict the evolution of microstructure is proposed. This model aims at predicting the formation on ultrafine microstructure of steel after hot forming with severe plastic deformation. The outline of the proposed model is described first, and then it is clarified by comparing the predicted ferrite grain size and ferrite volume fraction with the experimental measurement. Through the investigation, it becomes clear that the proposed model can give us an acceptable result for the microstructure of steel transformed from the deformed austenite.
Ultra-high-speed injection molding, in which the cavity filling time may generally be less than 30ms, is widely utilized especially for ultra-thin-wall molding products. The ultra-high-speed in-mold phenomena exemplified by this technology, are quite difficult to analyze with existing visualization and experimental technologies. Under such circumstances, new methods and technologies are expected to be developed for solving the above problems; e.g., visualization method with higher time/special resolution, and mold structures with higher pressure endurance, etc. This article introduces the overall advancement of visualization technologies applied inside the injection mold, and their potentialities through application results of new visualization and measuring technologies, which our research group has successfully developed in the past seven years, focusing on the experimental analysis of ultra-high-speed injection molding phenomena.
Fabrication of very porous scaffold for regeneration of organs with high metabolic rate is reported. Polycaprolactone (PCL) powder was mixed with fine grains of sodium chloride as filler and SLS (Selective Laser Sintering) processed to develop an object including fine flow channel network. The object was rinsed with water to desolve the salt, and a high porosity of 90% was successfully obtained. In addition, unsintered powder in the channels was effectively removed owing to disappearance of the filler. Through micro-CT observation, it was confirmed that channels of which diameter was smaller than 1mm were fabricated. Measurement for the amount of residual salt proved that the salt can increase salt concentration of culture media no more than 1% of that for physiological saline solution. It is indicated that excessive sintering, which lowers geometrical resolution of laser sintering process using water leachable inorganic filler, is mainly caused by high speed heat conduction through the filler. Result of culture test is also reported.
Research on the power-assist control of the electric wheelchair is one of the most interesting topics in the field of welfare engineering and there exist many ongoing projects. In this paper, the surface electromyography(EMG) of adductor pollicis muscle are measured to extract the rolling and grip force on the handrim of the wheelchair. Then, at the propelling phase, we assist the wheelchair by using the filtered EMG signal so that the wheelchair can move before the driver propels handrims. At the propelling phase, we assist wheelchair by using the estimated torque signal calculated by the disturbance observer. Experimental results validate that the proposed power-assist method realize early, stable and smooth acceleration.
To observe the moment when motor protein is inhibited by some specific molecules or reacted with substrate under microscope, we should construct the observation chamber in which the objective molecules could be introduced rapidly and completely. Here, using micro fabrication technology, we constructed the buffer exchange chamber in which simple plastic one-way valves integrated on the cover slip. Testing results shows that the valves have nearly ideal performance under both forward and reverse flow. Under this chamber we can directly measure inhibition rate of rotary motor F1-ATPase by NaN3.
In this paper, we describe a simple method to form steps of nano-scale depth on glass surface. Steps about 10 nm in depth can be formed by using a mask and applying O2 plasma. Atomic force microscopy (AFM) confirmed that the surface exposed to plasma was atomically flat over a large area. Furthermore, steps with vertical dimensions < 10 nm were successfully transferred to the poly(dimethylsiloxane) (PDMS) slab when we performed PDMS replica molding of these nano-steps. Finally, nano-steps with smaller horizontal features were also fabricated using particles (φ 1 μm) as mask. We believe this technique will be useful for simple nano-scale patterning of glass surfaces.
Through our studies, we developed processes to reproduce micro-features to large areas and to embed metal to the grooves. We designed and produced a mold for glass pressing. The mold was 12 x 12mm and had micro-grooves with a minimum width of 170nm and a minimum pitch of 340nm. The mold was made of bulk CVD-SiC and Fast Atom Beam (FAB) produced the micro-features. We determined the optimum press parameters for glass pressing with our mold, and we showed that the filling rate of pressing is approximately linear to the logarithm of time. We also developed processes to produce metal embedded subwavelength gratings by sputtering a metal film on a glass substrate with micro-features, spin-coating resin to flatten the surface, and dry etching it with FAB. We further evaluated the polarization device and found it had 0.9 degree of polarization to a light of wavelength 650nm. We confirmed the results by comparing the measured results with numerical analysis. For further enhancing the optical performance of the device, we need to optimize the grating cross-sectional shape and improve the precision of reproduction.
A diamond blade is widely used as a cutting tool for slicing materials such as stones, ceramics and glasses in a straight line. Generally, it has many slots and their functions have the effect of reducing cutting resistance and increasing the tool life. Against this background, the application of photocurable resins to the blade with slots has been examined on both single-layered blade and multi-layered blade. In this paper, a combined-structure blade was proposed and experiments were performed to investigate cutting characteristics during dicing. As the results of a series of cutting tests on silicon wafers utilizing the combined-structure blade, the remarkable improvement of cutting performance was verified.
For precise injection molding, it is quite effective to monitor molding phenomena inside a cavity per each shot; such as pressure profiles, melt temperature profiles, etc. We proposed a new sensor for measuring the flow front velocity vector, which has three optical fibers inserted into the pin edge. Experiment results indicate that the new sensor can successfully be used as a practical tool for measuring the flow front speed velocity vector. In addition, it was also confirmed that even a single optical sensor can precisely detect the melt front velocity focusing on the change of output profile.