Papers by Author: Shin-Ichiro Hira

Abstract: Replication of micro structures on a polymer substrate employing two-stage hot embossing is described in this paper. Linear channels with rectangular cross section were fabricated on a master mold of a brass plate by means of a computer numerical control (CNC) machining center using a micro end mill. In the first embossing process, the master mold with concavity features was embossed on a polycarbonate (PC) plate in order to make a “polymer replication mold”. Polytetrafluoroethylene (PTFE) was chosen as a material of polymer substrate used in the second embossing process. The replicated structure on PTFE substrate was observed and each dimension of its cross-sectional shape was also measured in order to assess the replication accuracy. According to the results, it was found that the depth of a replicated channel was near 90 % of that on the master mold. But roundness at each corner could be also found due to the insufficiency of plastic flow. Furthermore the deformation of the structures on a replication mold of PC before and after 2nd hot embossing process was also examined. As a result, it was found that the deformation ratio at temperatures below 145 oC was roughly smaller than 10 %.

Abstract: The distribution of magnetic field in the container is important for the polishing ability of a permanent magnet-type magnetic barrel finishing machine. Therefore, in this study, the magnetic field distribution was measured with different magnets arrangement. It is found that the polarity and strength of magnets on a magnet block greatly affect the distribution of magnetic field. Polishing experiments were done to investigate the polishing ability. The relationship between the magnetic field distribution and the polishing ability was discussed. As a result, it was concluded that strong magnetic field led to superior polishing ability.

Abstract: At present, a commercially available magnetic barrel machine equipped with permanent magnets has some faults arising from constructional reason. That is, grinding or finishing ability is different from place to place in the machining region, resulting in the limitation on the region we can use in the container of workpieces. Therefore, in this research, authors made the new magnetic barrel machine equipped with three dimensional (3D) magnet arrangement to overcome these faults. The grinding ability of the new 3D magnetic barrel machine converted was experimentally examined, and compared with that of the traditional magnetic barrel machine. As a result, it was shown that we can use much broader region in the new 3D machine. It was also shown that the grinding ability became higher. The distribution of barrel media in action was recorded by means of a high speed video camera. It was clarified that the media rose up higher and were distributed more uniformly in the container by the effect of the magnet block newly set up. It was supposed that this must be the reason for the above-mentioned improvement of grinding ability.

Abstract: This report describes fabrication of polytetrafluoroethylene (PTFE) to make up a micro-fluidic device for the application to a Micro-Total Analysis System ( -TAS). This material is chosen as a material of the device because of many excellent properties such as high chemical resistance and high heat resistance in comparison with the other polymers. Mechanical micro-cutting process is employed for the fabrications of the required elemental micro-structures such as a micro-channel and a micro-reservoir for the device. In general, burrs are easily generated in the cutting of soft materials such as PTFE. It is thought to be the most important to find how to prevent the burr generation and how to clean the generated burrs to assure the device quality. Therefore, in order to obtain the fundamental information about the burr generation in the micro-cutting of PTFE, through hole drilling, groove milling and face milling are performed. As a result, the elemental micro-structures without burrs are fabricated on PTFE plate. Furthermore the plate is sealed by sealing film assisted with pressure. By testing leakage with fluid sample, it is confirmed that the pressure-aided sealing is useful.