Papers by Author: Hideaki Tanaka

Abstract: Recently, increasingly high efficiency and high performance have become to be required of information equipment. As a result, optical scanning parts that reduce optical aberrations, scatter, and diffraction are required in laser printers. It is therefore necessary to improve the geometric surface roughness achieved in mirror cutting of Al alloys and eliminate tear-out marks and scratch marks that can be created during the cutting process. In this study, we investigated the effect of tool wear on the occurrence of surface discontinuities in ultra-precision cutting of Al alloys. In our previous studies, a crystal orientation of {110} plane was adopted in cutting an Al-Si alloy (AHS material, 11wt% Si) and Al-Mg alloy (A5186 material, 4.5wt% Mg) using a straight diamond tool. The cutting edge recession that occurs when cutting AHS material has been reported to be approximately 5 times greater than that which occurs when cutting A5186 material. Therefore, we cut the AHS material for accelerated wear and investigated the cutting edge recession, the surface roughness and the cutting force. We found that the cutting edge recession decreases as the tool wear angle γ increase. For example, at a tool wear angle γ = 40°, the cutting edge recession is approximately 7 times greater than that which occurs at a tool wear angle γ = 12°. As the tool wear angle increases, the cutting distance increase, which produces a mirror like surface. In addition, we were able to obtain a good machined surface using a positive tool setting angle because side cutting edge produces residual stock of removal 0.1 μm when the cutting edge recession is 0.3 μm or more and when it is cut by following end cutting edge.

Abstract: Micro-channel chips used in micro total analysis systems are attracting attention in medicine. In generally the photolithography technology used in semiconductor manufacturing is used to manufacture micro-channel chip Si-dies. However, this technology requires many processes, such as mask fabrication and the application of photoresist to a substrate as well as expensive clean room facilities. A micro-channel chip has a micro-groove 30–100 μm wide. This study examined how to form a fine groove by cutting with a micro-endmill, with the aim of shortening the window time and reducing the cost. This steel die requires high accuracy, for example, a burr area ratio of not more than 5% of the groove bottom area, a surface roughness of the side and bottom faces of less than 1μmRz, and a change in the sectional area of less than 1%. So, this study examines micro-endmill’s cutting conditions, for example cutting speed, feed per tooth, and axial depth of cut. In MQL (minimum quantity of lubricant) cutting, the early fracture occurs when cutting was began. The cause has bad removing of the chips in MQL cutting, it is considered that the chips of hardened work have been re-cut as the result. Therefore, this study applied ultrasonic cavitation to milling, in order to solve this subject. This report experimentally examined the cutting performance of ultrasonic cavitation-assisted milling. We obtained the following results. In cutting distance of 20 m, the burr of MQL cutting is generated more than 5%, on the other hand, the burr of ultrasonic cavitation-assisted milling is less than that. In ultrasonic cavitation-assisted milling, a tool wear and fracture can be decreased by improvement of removing chips and lubrication.

Abstract: Recently, high-combustion-efficiency jet engines have become required in the aircraft industry. High burning temperatures are necessary to maximize the combustion efficiency of jet engines. Inconel 718, which has excellent mechanical and chemical properties, has been selected for use in many jet engine parts. However, Inconel 718 is a difficult material to cut because of its low thermal conductivity. Consequently, wet cutting is typically used to reduce the heat generated in cutting Inconel 718. Wet cutting, which uses a large amount of cutting fluid, is costly and requires considerable energy for maintenance and disposal of the cutting fluid, making this cutting method environmentally unfriendly. To reduce the associated cost and environmental load, the near-dry cutting method, which uses a very small amount of cutting fluid, may be preferable for cylindrical cutting of Inconel 718. However, this method has some drawbacks, such as the cutting stock removal rate and the wear on cemented carbide tools. For example, the cutting stock removal rate is lower than with wet cutting because cutting edge fracture occurs easily in near-dry cutting. In this study, we conducted experiments to examine the relationships between the tool materials, cutting speed and tool fracture in near-dry cutting and wet cutting, and we compared the results obtained using the two cutting methods. We found that an S05-type cemented carbide coating can reduce tool wear. We also found that in the early stages of cutting, between cutting speeds of V = 50 and 90 m/min, the tool wear can be comparatively reduced.

Abstract: Magnetic recording technologies are continuing to advance toward higher areal densities, driven by the availability of tunneling magnetoresistive (TMR) heads. However, high areal density heads require smaller physical dimensions, and this can render TMR heads more vulnerable to mechanical stresses generated during the lapping process. Although is important to verify the durability of TMR heads against lapping, it is very difficult to perform a crystallographic analysis of the affected layer because of the small dimensions involved. In this study, we attempted to establish an advanced TMR head verification method based on a magnetic performance analysis involving micro-Kerr hysteresis loops and the magnetic noise spectrum. We found that the magnetic performance changed when nanoscale scratches were removed from the lapped surface using ion beam etching. This indicates that the lapping process produces an affected layer which deteriorates the magnetic characteristics of the TMR head. A correlation was also found between the change in magnetic performance and the morphology of lapped surface.

Abstract: Patterning vast numbers of micro lenses on a surface increases technical importance to improve characteristics of optical parts such as liquid crystal displays. A cutting method using a diamond tool is examined to make a molding die by which array patterns of many micro lenses are molded. Realizing the cutting procedure, the developed machining system employs a cutting unit actuated by PZT and a synchronous control system of the cutting unit with a NC controller. The present paper investigates machining of micro lenses on the order of 2 kHz, using a piezo-actuated micro cutting unit. Experiments using this unit revealed that it is possible to machine a large number of micro lenses on a molding roll die for plastic film with high precision.

Abstract: In the lapping of magnetic heads and other electronic components composed of multiple materials, differences in the processing characteristics of the composite materials produce residual steps on the surface at composite interfaces. Residual step heights have been reduced to as small as a few nanometers. We investigated using fine abrasives in fixed abrasive lapping to further reduce the residual step height. This requires highly secure, high-density embedding of abrasives on the lapping plate. To this end, we evaluated the surface morphology of the lapping plate after diamond abrasive charging and investigated the embedding mechanism of diamond abrasive charging. The results obtained will assist in determining the direction of future research and development. A prototype charging ring that uses a vibrating system was developed to increase the density of abrasives embedded on the lapping plate. This diamond charging using a vibrating system was able to increase the embedded abrasive density and improve the flatness of the charging plate.

Abstract: In the lapping of magnetic heads and other electronic components composed of multiple materials, differences in the processing characteristics of the composite materials result in “residual steps” forming on the surface at composite interfaces. Residual step heights have been reduced to as little as a few nanometers. We investigated using fine abrasives in fixed abrasive lapping for this purpose, which requires highly secure, high-density embedding of the abrasives on the lapping plate. To this end, we modeled the abrasive embedding process and investigated the relationship between the mechanical properties of the lapping plate and the retention of the abrasive, to determine the direction of further research and development. The results of this investigation revealed a correlation between the work hardening in the plate and the resulting abrasive density and cutting edge height. The investigation also showed that it is possible to suppress the reduction in lapping rate that occurs during use by increasing the work hardening coefficient of the plate.

Abstract: We investigated the durability of giant magnetoresistive (GMR) heads to nanoscale scratches created during the lapping process. Analysis using high-field transfer curves after deliberate scratching with an atomic force microscope (AFM) identified changes in the magnetization of the head and a reduction in pinning strength, which is a magnetic performance indicator. Additionally, finite element method (FEM) analysis suggested that the overall effects on the GMR head following nanoscale scratching increased with scratch depth.