Advanced Materials Research Vols. 76-78

Abstract: Surface roughness is an important item to evaluate the surface quality. Many researches focused on the optimization of cutting parameters in the specified cooling/lubrication conditions. But the effect of different cooling/lubrication conditions was still less considered. Aimed at this problem, the effect of cutting parameters on the average surface roughness (Ra) in the different cooling/lubrication conditions, including MQL, wet, dry cutting, was analyzed in this study. Orthogonal arrays were applied in the design of the experiments and Ti6Al4V end-milling experiments were performed on the DAEWOO machining center. The white light interferometer was used to obtain the 3D profile of machined surface and calculate the Ra values. The regression analysis and statistical analysis of variance were employed in the process of the experimental data. The relationships between Ra and cutting parameters in the different cooling/lubrication conditions were obtained and the optimum values of the cutting parameters in the range of the experiments were selected.

Abstract: Owing to the fast development in photonic, telecommunication, and opto-electronic industries, the demand for various micro-lens arrays is rapidly growing. The slow tool servo technique was applied on an ultra-precision diamond turning machine in the present research in conjunction with the tool path generating algorithm for aspheric micro-lens array fabrication. An aspheric lens array of 100% filling factor was successfully produced and the form accuracy and surface roughness were better than 0.15μm and 3nm for all the obtained lenses.

Abstract: The confine of ductile-mode cutting and brittle-mode cutting seems to be a crucial step for designing a brittle material removal process. However, the existing transition from ductile-mode to brittle-mode for BK7 material makes the confine of different mode very difficult. Through a series of micro/nano-machining tests, measurements of cutting forces and morphological appearance of cutting groove as well as the cross section at the certain depth of cut, the confirmation of ductile-mode cutting, transition-mode cutting and brittle-mode cutting has been clearly described in the paper. This lays a foundation for the fundamental understanding of cutting physics concerning of material characteristics and cutting tools, and thereafter for the development of optimal process technology.

Abstract: Glass is a kind of difficult-to-machine material due to its hard and brittle properties. Although many special hole machining methods for brittle and hard materials have been developed, the traditional drilling is still widely applied because it is simple and reliable. However, the drilling tool for hard and brittle material is an obstacle, especially for small hole drilling. In this paper, two types of diamond abrasive core-tools which are made by electroplating and sintering process are used to machine small holes in glass plates, their structures are introduced and their machining performances are compared. The experimental result indicates that these diamond abrasive tools are satisfied for small hole machining in glass, and the performance of electroplating tool is better than that of sintering one.

Abstract: Carbon nanotube (CNT) probe used in atomic force microscopy (AFM) was fabricated by using electron beam induced Pt deposition method. The bonding force for CNT probe was found to be larger than 500nN. The nanotube probe’s length was shortened by focused ion beam milling process. It is confirmed that the CNT probe shows higher aspect ratio than the Si probe. The nanotube probes with fullerene-like cap end present higher imaging resolution than those with open end.

Abstract: We propose to use nano structures directly to fully utilize the nice mechanical and thermal properties for nano machining. In this project, CNTs were directly used as cutting grains. For the CNT grains, we use epoxy as one of the bonding materials of our choice. A series of CNT grinding wheels were fabricated to demonstrate the effectiveness of the proposed new type of abrasive tool. Preliminary experimental tests were conducted for the proposed method of abrasive tool making. The CNT wheels are made of 1% MWCNTs or Multi Wall CNTs. Preliminary test results show that CNT wheels without functionalization or chemical treatment give the best average results. In the developed abrasive tool, CNT nano cutting edges are clearly seen in the TEM image. Carbon nanotubes can be used as cutting grains for nano machining. Further experiments are necessary.

Abstract: In micro endmilling, because of small uncut chip thickness comparable to the tool edge radius and low rigidity of tool, the cutting process must frequently transit between rubbing/ploughing and cutting, and it may deteriorate the machining stability, surface finish and tool wear. In this report, such unique cutting phenomena are investigated by modeling a mechanism, computer simulations and experiments. As a result, a possibility of the unique cutting phenomena proposed has been certified.

Abstract: In this study, an approach by the feed rate control was applied for the improvement of form accuracy in the micro end milling process. In this approach called adaptive control constraint, the feed rate is controlled so that the cutting load is constantly kept and the deflection of tool does not occur. However, this method is not always effective in the micro cutting process that the influence of size effect cannot ignore. Therefore, the relationship between the cutting conditions and the form error in the micro end milling is experimentally investigated. The experiments on the machining of metal mold steel with the micro end mill are carried out and the formulation as function of the cutting conditions and the form error is identified by means of regression analysis. The performance of the feed rate control was validated based on experimental results. As the result, it was confirmed that the form accuracy was improved.

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.

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 %.