Advanced Materials Research Vol. 1136

Abstract: Fluid dynamic bearings, which have an advantage in high-accuracy revolutions, are employed for spindle motors of hard disk drive, cooling fans for central processing unit, spindles of machine tool, etc. Micro herring-bone grooves are manufactured on cylindrical surface of the shafts in the bearing units, and they generate dynamic pressure during spins. Although the depth of the herring-bone grooves is generally constant, the shafts of which groove depth decreases from the ends of the groove array to its center improve the performance of bearing. The micro grooves are mainly manufactured by chemical etching, electrochemical machining, cutting and form rolling. However, the chemical etching and the electrochemical machining are difficult to control 3D machining profiles with high accuracy. The cutting and the form rolling have problems in tool lives and manufacturing costs. On the other hand, blasting is expected as one of micro fabrication methods. Therefore, we focused on blasting, and have investigated its material removal capabilities by fundamental tests. The purpose of this study is to control machining profiles in cylindrical blasting. The machining profiles of cylindrical workpieces in blasting were simulated based on the material removal capabilities obtained by the fundamental blasting tests. Then, the simulated profiles agreed well with the experimental ones by blasting under the same experimental condition.

Abstract: Abrasive flow machining is a suitable technique for surface polishing due to its rheological characteristics, however, it's difficult to achieve uniform roughness for polished surfaces as the material removal mechanism is still ambiguous. In this paper the viscoelastic properties of abrasive flow media are incorporated to explore the phenomena of inconsistent material removal in the AFM polishing process, where the material removal near the edges is obviously higher than that in the middle along the flow direction. The rheological parameters of the viscoelastic constitutive model adopted are varied to study the polishing effectiveness under different process conditions. The results of numerical analysis reveal that there exist distinct differences of viscoelastic stress fields between the edges and the middle regions, which leads to the material removal near the edges is higher than that in the middle. It could be concluded that the viscoelastic properties of abrasive media play the dominant role for the inconsistent material removal in abrasive flow machining process.

Abstract: Machined surface quality is the deciding factor when evaluating the machinability of CFRP. This present work concerns the influence of fiber orientation on the machined surface quality of the machined surface in terms of surface morphology and surface roughness during milling of unidirectional T800/X850 CFRP laminates. Four group milling tests are conducted under the fiber orientation angle of 0°, 45°, 90° and 135°, respectively. For the fiber orientation angle of 0°, the machined defects are mainly fiber pull-out and fiber brittle fracture owing to interfacial debonding between the fibers and matrix resin. For the fiber orientation angle of 45°, the machined defects are mainly resin cavities and the surface morphology is rough and presents wavy fractures. For the fiber orientation angle of 90°, smooth or neat surface is observed except for the surface as the cutting tool cutting in the workpiece on which severe cracks are observed. For the fiber orientation angle of 135°, the surface is smooth with less fibers pull-out. Evaluation profile and surface roughness of the machined surfaces were measured as well. Dramatically fluctuate of the evaluation profile is observed for the fiber orientation angle of 45° with a high surface roughness Ra. Verification tests were also conducted on the multidirectional CFRP (cross-ply) laminates. It is indicated that the presence of the fiber orientation angle of 45° is the main factor leading to the decline of the machined surface quality.

Abstract: This study is carried out to investigate the influence of pulsed magnetic treatment on wear of carbide micro-end-mill. To analyze the friction behavior of micro-end-mill with workpiece, the special micro-end-mill with a chisel is fabricated and used in micro-milling experiments. A paramagnetic material aluminum alloy is employed as workpiece material. The experimental results indicated 17% and 27 % reductions in maximum minor flank wear width and chisel edge wear area of micro-end-mill after pulsed magnetic treatment, respectively. However, the surface roughness and morphology of machined aluminum alloy have no obvious changes with or without pulsed magnetic treatment. Consequently, the reduction of tool wear during milling aluminum alloy can be mainly attributed to the improvement of mechanical properties of carbide tool materials after pulsed magnetic treatment.

Abstract: Machining the aircraft skin, using CNC milling to replace the traditional chemical milling, is a trend owning to the great pollution of the chemical milling to the environment. Based on the instantaneous rigidity force hypothesis, a milling force model for mirror milling of aircraft skin was proposed, which was validated by the milling force measurement during mirror milling experiments. A FEM model was established to calculate the deformation of the aluminum plate in mirror milling. The effects of the supporting position on the deformation was analyzed.

Abstract: This study aims to develop a cutting method, which enables to generate a localized hydrostatic pressure field in the vicinity of cutting zone in order to improve the machined surface integrity without causing unnecessary plastic deformation. In the previous work, a molecular dynamics simulation was performed using a newly developed cutting tool equipped with a planer jig with a rectangular hole for the cutting chip elimination, and it was confirmed that the developed cutting tool has advantages in giving a relatively high-hydrostatic stress field in the vicinity of the cutting zone and in suppressing the burr formation. In this report, further molecular dynamics simulation was performed in order to clarify the influence of jig shape on the cutting phenomena and machined surface integrity. As a result, it is found that a cutting tool of which front and side except for the rectangular hole are covered by the planer jig is the most advantageous for supplying high hydrostatic pressure and suppressing burr formation.

Abstract: In this study, it is discussed how the cutting conditions for drilling deep holes in austenite stainless steel affect the machining accuracy of the hole straightness and the cutting temperature rise. As a result, it is possible to reduce the thrust force and make the machining time short by the combination of the step-feed amount and the feed rate. By changing the drill in incremental step from short drill length to long drill length, the straightness was improved. It was also found that the temperature rise of the drill was around 10 K regardless of the cutting speed when the small step-feed amount of 10 μm was given.

Abstract: Recently, high-combustion-efficiency jet engines have become essential 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, it is difficult to cut because of its low thermal conductivity. Consequently, wet cutting is typically used to reduce the heat generated in cutting Inconel 718. In this study, we conducted experiments to examine the relationships between the cutting characteristics and tool fracture in wet cutting.

Abstract: Micro-channel chips, which are used in micro total analysis systems, are attracting attention in the medical field. The photolithography technology used in semiconductor manufacturing is generally used to manufacture micro-channel chip 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. Therefore, this study examines how to form a fine groove by cutting with micro-endmills. This report experimentally examined the cutting performance of the tool run-out. In addition, effects of the tool run-out on the micro-grove milling, such as decrease in the cutting force changing,and the tool wear, were clarified.

Abstract: In this study, we investigated ultra-precision cutting technology of aluminum alloys for polygon mirrors made of Al-Mg Alloys. It is necessary to improve the geometric surface roughness achieved in the mirror cutting of Al-Mg alloys and remove tear-out marks and scratch marks that occur during the cutting process. Therefore, we investigated the cutting edge shape using 2 types of straight diamond tools and 2 types of round tools to decrease the surface defects in the ultra-precision cutting of Al-Mg alloys. As a result, a double-facet tool can achieved a good machined surface roughness and reduce the cutting force and the scratch marks compared with other tools.