Papers by Author: Tsunemoto Kuriyagawa

Abstract: Amorphous NiP plate is used as a mold of precision optical parts owing to the superior machinability. In the amorphous NiP plate, some pores, whose diameter is about 100m, are generated occasionally. At present, the amorphous NiP plates with pore are rejected. However, because size of the mold becomes large in recent years, the possibility of pores becomes high. In addition, the cost of the amorphous NiP plate also becomes high. Therefore, reparation method of the pore in the amorphous NiP plate should be developed. In this paper, laser assist powder jet deposition is proposed as a reparation method of the amorphous NiP plate. And fundamental experiments are carried out.

Abstract: This study aims to develop an ultrasonically assisted grinding technology for precision internal grinding of a small hole measuring several millimeters in diameter, such as those formed in a fuel injector for an automotive engine. In a previous work, an experimental apparatus mainly composed of an ultrasonic vibration spindle was designed and constructed, and grinding experiments were carried out. The previous investigation found that applying ultrasonic vibration to the wheel decreased the normal and tangential grinding forces, respectively, and improved the surface roughness in surface grinding. The purpose of this paper is to examine the effect of ultrasonic vibration on grinding force and surface roughness in internal grinding when the grain sizes of small cBN grinding wheel are changed. The experimental results indicate that applying ultrasonic vibration to the wheel decreases the normal and tangential grinding forces by more than 83 % and 80 %, respectively, and improves the surface roughness by as much as 62 % while the wheel grain size is changed. In addition, over the range of grinding conditions employed in this paper, the grain size as small as 3 µm can be used in ultrasonically assisted internal grinding.

Abstract: . Micro ultrasonic machining (micro-USM) is an effective machining method for hard brittle materials. In the micro-USM process, the workpiece materials are machined through the accumulation of small brittle fractures generated by the impacts of abrasive grains. Therefore, it becomes difficult to obtain a smooth machined surface. In the proposed electrorheological fluid-assisted ultrasonic machining (ER fluid-assisted USM), the behavior of abrasive grains is controlled using the effect of dielectrophoretic force acting on the abrasive grains and the ER effect. The behavior of the abrasive grains can be controlled by changing the electric field distribution. In the present paper, the shape and position of the auxiliary electrode are arranged in order to control the abrasive grains to the side surface of the micro rectangular tool. By positioning the auxiliary electrode parallel to the micro rectangular tool, it becomes possible to concentrate abrasive grains to the side surface of the micro rectangular tool. Smoothing of the side surface of the workpiece by using the side surface of the micro rectangular tool is then investigated. As a result, the surface roughness of the side surface of the workpiece can be improved.

Abstract: Ultraprecision diamond-ground silicon wafers were irradiated by a high-frequency nanosecond pulsed Nd:YAG laser equipped on a four-axis numerically controlled stage. The resulting specimens were characterized using a white-light interferometer, a micro-Raman spectroscope and a transmission electron microscope. The results indicate that around the laser beam center where the laser energy density is sufficiently high, the grinding-induced amorphous silicon was completely transformed into the single-crystal structure. The optimum conditions for one- and two-dimensional overlapping irradiation were experimentally obtained for processing large-diameter silicon wafers. It was found that the energy density level required for completely removing the dislocations is higher than that for recrystallizing the amorphous silicon. After laser irradiation, the surface unevenness has been remarkably flattened.

Abstract: Ultrasonic machining (USM) is an effective machining method for hard brittle materials. In the USM process, the slurry is supplied to the gap between the ultrasonic vibrating tool and the workpiece. Materials are removed by the accumulation of small brittle fractures made by the impacts of abrasive grains. In a previous study, we proposed electrorheological fluid (ER fluid) assisted-USM, and the effect of ER fluid-assisted USM was confirmed practically by machining precise micro-holes and micro-grooves on hard brittle materials. In the present paper, in order to confirm the effect of ER fluid assistance for micro USM in more detail, the behavior of abrasive grains in the machining area is observed. The effect of dielectrophoretic force acts on the abrasive grains and the effect of using ER fluid assistance are investigated. As a result, the abrasive grains can closely approach the micro tool by the effect of dielectrophoretic force and be fixed around the micro tool by the effect of ER fluid assistance. Under these conditions, the workpiece is removed primarily by the accumulation of small brittle fractures, and the chipping can be reduced.

Abstract: This paper investigates the deformation in monocrystalline silicon subjected to single-point cutting with the cutting speed up to 46.78 m/s, the depth of cut of 2 μm, and the feed rate of 5 and 30 μm/rev. Raman spectroscopy and transmission electron microscopy were used to characterize the subsurface damages. It was found that the increase of either the feed rate or cutting speed increases the thickness of amorphous layer and penetration depth of dislocations. At the feed rate of 30 μm/rev and cutting speed of 12.48 m/s, a new dislocation system was initiated. An unknown peak was detected by Raman spectroscopy, which may indicate an unknown Si phase.

Abstract: Ultraprecision diamond-cut silicon wafers were irradiated by a nanosecond pulsed Nd:YAG laser, and the resulting specimens were characterized using transmission electron microscopy and micro-Raman spectroscopy. The results indicate that at specific laser energy density levels, machining-induced amorphous layers and dislocated layers were both reconstructed to a complete single-crystal structure identical to the bulk region. Similar effects were confirmed for diamond-ground silicon wafers. Effects of overlapping irradiation were investigated and perfect crystallographic uniformity was achieved in the boundary region. The recovery process involved rapid melting of the near-surface amorphous layer, followed by epitaxial regrowth from the damage-free crystalline bulk.

Abstract: Thick films are needed in micro-electro-mechanical systems (MEMS) as insulation, piezoelectric and ferroelectric materials. To form the thick film, powder jet deposition (PJD) method has been proposed. In the PJD process, microparticles are sprayed out from nozzle under the conditions of room temperature and atmospheric pressure, and make a film on the substrate. We have developed a new jet mechanism of double-nozzle type, and reported its results previously [1]. In this study, we optimized the shape of the nozzle through investigating the influence of different dimensions and shape of the nozzle on the particles blasting velocity. As a result, it is found that nozzle diameter has a large affect on particles velocity.

Abstract: This study aims to develop an ultrasonically assisted grinding technology for precision internal grinding of a small hole measuring several millimeters in diameter, such as those formed in a fuel injector for an automotive engine. In a previous work, an experimental apparatus mainly composed of an ultrasonic vibration spindle was designed and constructed, and grinding experiments were carried out. The purpose of this paper is to examine the effect of ultrasonic vibration on grinding force and surface roughness when the grain size and concentration of small cBN grinding wheel are changed. The experimental results indicate that applying ultrasonic vibration to the wheel decreases the normal and tangential grinding forces by more than 50% and 78%, respectively, and improves the surface roughness by as much as 10% when the wheel grain size and concentration are changed. In addition, over the range of grinding conditions employed in this paper, the grain size as small as 5μm can be used in ultrasonically assisted grinding.

Abstract: Ultrasonic machining (USM) is an effective method for machining of hard brittle materials. In this process, the slurry is supplied to the gap between the workpiece and the ultrasonic vibrating tool, and the materials are removed by the impacts of the abrasive grains that are pressurized by an ultrasonic vibrating tool. The purpose of this research is to achieve precise and efficient microfabrication on hard brittle materials by USM. However, in the case of microfabrication, chipping which is generally observed around the edges of machined micro holes and grooves, deteriorates the machining accuracy. In addition, there is another problem in that the machining efficiency decreases with the progress of the machining. Electrorheological fluid-assisted USM has been proposed as a countermeasure to these problems. In the present study, the problems and countermeasures associated with the machining of high-aspect ratio micro holes in hard brittle materials by electrorheological fluid-assisted USM are investigated. By positioning an auxiliary electrode under the workpiece, it becomes possible to keep the electric field high even when the machining depth becomes large. As a result, high-precision and high-aspect ratio micro holes can be machined on hard brittle materials.