Key Engineering Materials Vols. 407-408

Abstract: This paper investigates the effects of using nitrogen gas on Mist cutting. In this study we tried to improve the cooling effect of mist on cutting by using N2 gas to assist cooling. As a result, tool breakage was prevented when using carbide tools and a large reduction in tool wear was confirmed when using cermet tools. Our conclusion is that N2 gas assisted mist cutting reduces oxidation wear, which means that the cutting characteristics are better than in conventional mist cutting.

Abstract: Cutting heat dissipation in high speed milling of medium carbon steel was experimentally investigated based on calorimetric method under the cooling conditions of hard cutting, applying compressed air or water. Special containers holding water medium were designed to collect cutting heat in chips, workpiece and tool respectively, and the heat distribution ratio in these components was calculated in terms of the temperature varieties of each component. The results were compared with the cutting power which came from the cutting forces measured.

Abstract: MQL technique has been recognized as the most representative method of environmentally friendly near-dry machining. In machining of aluminum and its alloys, since they have highly adhesive characteristics, effective lubrication is often necessary and MQL machining sometimes finds difficulty. This paper therefore investigates the lubricating action of MQL media with various compositions in machining of aluminum. Detailed examination regarding the contents of carrier gases has demonstrated oxygen leads to the low cutting performance and its concentration in carrier gases has to be kept below the level between 1% and 10% to attain successful MQL machining of aluminum. Further, increasing the amount of MQL lubricant supply by boosting the air pressure is the efficient and convenient way to make MQL drilling of aluminum satisfactory.

Abstract: A micromilling experimental study on AISI 4340 steel is conducted to understand the micromilling principle deeply. The experimental results, especially on the surface roughness and cutting force, are discussed in detail. It has been found the minimum chip thickness influences the surface roughness and cutting force greatly. Meanwhile, the material elastic recover induces the increase of the axial micromilling force. The average cutting force and its spectrum analysis validate the minimum chip thickness approximation of AISI 4340 is about 0.35μm.

Abstract: A new surface finishing method by large-area electron beam irradiation (EB-polishing) for stainless steels for orthopedic surgical tool was proposed in our previous paper, and it was shown that high-efficient surface finishing was possible by the EB-polishing. In this report, the surface structure of EB-polished stainless steel is analyzed by TEM and EDX. Also, surface modification effects such as resistance to corrosion and blood repellency are evaluated. Then, the applicability of the EB-polishing as a new surface modification method of stainless steel for orthopedic surgical tool is discussed.

Abstract: Thickness uniformity of an AT-cut quartz crystal wafer is essential requirement for higher productivity of quartz resonator in the sense of reducing the frequency adjusting process after dicing the wafer. However, commercially available quartz crystal wafers typically have a thickness distribution of ±0.1%, which is induced in conventional mechanical fabrication processes, such as cutting with a wire saw, lapping and polishing. Furthermore, owing to the poor parallelism and the existence of subsurface damage, many spurious peaks, which deteriorate resonance characteristics, are observed in a resonant curve. To resolve these issues, we proposed a new damage-free finishing method to correct the thickness distribution of an AT-cut quartz crystal wafer by the numerically controlled scanning of a localized atmospheric pressure plasma. By applying a new finishing process, the thickness uniformity of a commercially available AT-cut quartz crystal wafer was improved to less than 50 nm level by applying one correcting process without any subsurface damage. Furthermore, applying of the pulse-modulated-plasma drastically decreased the correcting time of the thickness distribution without breaking of the quartz crystal wafer by the thermal stress.

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: This paper describes the cutting characteristics and the shape error of groove when PMMA and PTFE are finished by the end mill with small diameter. Direct cutting experiments of micro channel by a miniature end mill were carried out in order to consider the possibilities of the fabrication of micro devices by machining. As the results, it was found that the surface roughness of 1 μm Rz or less was obtained and the width of channel became less than the tool diameter and the deflection of the end mill caused by the cutting force affected the shape error of the groove.

Abstract: The ultraviolet irradiation-assisted ultra precision polishing was performed on single crystal diamond substrates. This polishing method has been newly developed in our laboratory. The change of polishing performances was investigated by the presence of the UV irradiation. The polished surfaces were evaluated by the observation with WYKO. The experimental results are as follows; Surface roughness of diamond substrates polished under UV irradiation has become clearly smoother than that without UV irradiation. The surface roughness by this polishing method was reached to be 0.19 nm Ra on (100) surface of single crystal diamond. The equivalent surface was obtained on (110) surface by the UV-polishing.

Abstract: Patterning of numerous microlenses on a surface improves the optical performance of components such as liquid crystal displays. A cutting method using a diamond tool is examined to fabricate a molding die that employs arbitrary array patterns to mold millions of microlenses. The present paper investigates machining of microlenses on the order of 2 kHz, using a piezo-actuated micro cutting unit and a synchronous control system of the cutting unit with an NC controller. Experiments using this system revealed that it is possible to machine a large number of microlenses on a molding die with high precision.