Tomohiko Kawai

Manufacture of Multiple-focus Micro Fresnel Lenses by Means of Nonrotational Diamond Grooving

Abstract The study deals with the manufacture of multiple-focus micro Fresnel lenses by means of nonrotational diamond cutting tools mounted on a 5-axis control ultraprecision machining center with the positioning accuracy of 1 nm and the rotational one of 0.00001 degree. Multiple-focus micro Fresnel lens, consisting of several micro Fresnel lenses, is not rotationally symmetric, thus requiring the introduction of 5-axis control ultraprecision machining center. Two-focus and three-focus micro Fresnel lenses are designed and manufactured by controlling the movement of nonrotational diamond cutting edge along the designed microgrooves at the cutting speed of 40 mm/min. As a result, the nonrotational diamond cutting method allows multiple-focus micro Fresnel lenses to be manufactured accurately and neatly without any burr generation.

Creation of Ultra-precision Microstructures with High Aspect Ratios

In recent years, ultra-precision micromachining technology has been used in a variety of fields such as optical instruments, electronic devices, medical equipments, etc. At present, it is essential to meet the requirement of producing various shapes, one of which is a structure with a high aspect ratio. Such structures are applied, for example, to a shaft of micro robot, a long part of microactuator and micromachine, a microneedle for syringe, etc. However, due to its fragile nature, it is extremely difficult to fabricate the structure with a high aspect ratio since it is easily damaged during cutting. It is intended to produce micro towers with high aspect ratios by applying the ultra-precision milling technology using a single crystal diamond cutting tool. The method enables accurate creation of a variety of microstructures with high aspect ratios. In addition, the study also proposes a new machining method to create microneedle arrays, avoiding the contact of cutting edge with already machined parts again. As a result, it is concluded that the proposed method has the potential of producing a variety of microstructures with high aspect ratios.

Improvement of Machining Accuracy of 5-Axis Control Ultraprecision Machining by Means of Laminarization and Mirror Surface Finishing

Air bearings are often used in ultraprecision machine tools requiring high accuracy. With increasing the high accuracy for machine tools, it is required to pay attention to microvibration with nanometer order. The fluctuation in compressed air applied to air bearings causes the air turbulence, which results in the microvibration. The study presents the laminarization by the optimal design of piping and air bearing surfaces as well as mirror surface finishing, so that the laminarization can be realized to suppress the microvibration. From experimental results, it is found that the surface roughness of workpieces can be drastically improved by using a revised ultraprecision machining center.

Creation of Flat-End V-Shaped Microgrooves by Non-Rotational Cutting Tools

Abstract The study deals with the creation of V-shaped microgrooves with flat-end, which play an important role in case of generating intermittent grooves. Microgrooves by use of rotational cutting tool have a long radius in disengagement from the workpiece. Thus, two cutting methods by use of non-rotational cutting tool are devised so that V-shaped microgrooves with flat-end can be created. The first method makes use of straight chips generated under some cutting condition. Non-rotational cutting tool compresses the chips at the groove end and cuts the excessive parts of chips over the plane. The second method is to transcribe the surface of a tool indented vertically into a workpiece. As a result, it is experimentally found that the methods enable the creation of flat-end microgrooves.

Application of an Ultraprecision Milling Machine Based on Friction-Free Drive Concept to Micromachining

The study deals with the development of an aerostatic servo motor on the basis of the friction-free drive concept and the application to 5-axis control ultraprecision milling machine. The aerostatic servo motor equipped with a high resolution optical encoder of 64 million pulses per rotation, enables a linear motion of 1 nm positioning and a rotational one of 0.00001 degree respectively. The ultraprecision milling machine makes it possible to manufacture ultraprecision microparts, together with a devised high speed air spindle unit and pseudo ball end mills.

MICROCHANNEL ARRAY CREATION BY MEANS OF ULTRAPRECISION MACHINING

ABSTRACT The study deals with ultraprecision machining of microchannel array chips made of several metals to evaluate the compatibility between blood and metallic materials which are buried in human bodies as parts of artificial internal organs, etc. The blood-compatibility of the metallic materials is very important since their influences for human bodies are not completely clear. Therefore, it is essential to estimate their bio- and blood-compatibilities. To evaluate them efficiently, it is planned to employ the blood fluidity measurement by a microchannel array chip with a micro-rheology device. However, the chips are made of silicon and the shape of their microchannels is limited since they are generally fabricated by photolithographic technologies. To solve the problem, it is required to fabricate the chips with various-shaped microchannels made of several metals. In the study, consequently, ultraprecision cutting is applied to the fabrication of the microchannel array. From the experimental results, it is found that ultraprecision cutting has potential of fabricating arbitrary-shaped microchannel array made of various kinds of metals with high accuracy.

Manufacture of fly-eye mirror in an extreme-ultraviolet lithography illumination system by means of ultraprecision diamond cutting

This study deals with the manufacture of so-called Fly-eye mirror in EUV lithography by means of an ultraprecision 5-axis control milling technology. It is extremely difficult to manufacture a highly accurate Fly-eye mirror by conventional methods such as photolithography, mechanical cutting by a lathe, etc. since it is composed of 500 circular arc mirror elements of 15 mm in length and 1 mm in width having a spherical surface of 295 mm in radius, and there are minute steps among them. In order to manufacture Fly-eye mirror with accuracy and efficiency, the study proposes a new machining method to manufacture spherical surface with any radius by employing a rotational single-crystal diamond tool with cutting edge angle of 90 degree. Oxygen-free copper was machined by this method. The machined workpiece shows smooth spherical surface and sharp steps among them without any burrs. It is found that the proposed method has the potential of producing the Fly-eye mirror.

Micro Structuring of High Aspect Ratio and Array by Means of Mechanical Machining

We introduce the ultra-precision micro structuring of high aspect ratio and array by means of mechanical machining with ultra-precision machine tool and single-crystal diamond tool.

Manufacture of Aspherical Fresnel Lens with Ideal Cross-sectional Profile with Oxygen-free Copper and Acrylic Resin

Fresnel lens is typically manufactured by means of photolithography and mechanical cutting by lathe. The study deals with a new machining method of lens grooves by use of a side-edge of diamond tool to enhance the cutting efficiency and to acquire the ideal cross-sectional profile of lens groove which consists of a perpendicular plane, a sharp bottom and a curved slope. The machining experiment was conducted to cut lens grooves with a pitch of 300 μm on an oxygen-free copper and an acrylic resin plate. The result showed an ideal lens groove with the surface roughness of 8 nm(P-V). The accurate focus of 100 mm was also confirmed by the optical assessment with a manufactured acrylic fresnel lens.

Direct Bonding of Small Parts by Means of V-Shaped Microgrooves. Accurate Positioning by Means of Two Directional Microgrooves.

The study proposes a new method to accurately bond two small parts without any adhesives by makinguse of ultraprecision V-shaped microgrooves created on the surfaces of each part. These V-shaped microgrooves, whose depth and dihedral angle are 20μm and 13 degree respectively, allow small parts to be tightly bonded together with high positioning accuracy dueto a wedge effect and an adhesion phenomenon between two mating surfaces. In the study, ultraprecision V-shaped microgrooves having two different directions are created by using an ultraprecision machining center with 1 nm positioning resolution and a single crystal diamond milling cutter. From experimental results, small parts of 4 mm x 4 mm x 4 mm that have V-shaped micro-grooves in two directions could be tightly bonded with 0.380 mm positioning accuracy. In addition, the new method has a possibility to bond different materials with each other. Two small parts with V-shaped microgrooves that are made of oxygen-free copper and aluminum are subjected to bonding test. The test shows the accurate and strong bonded result. As a result, the proposed bonding method is found to be effective to connect small parts accurately.