Key Engineering Materials Vol. 516

Abstract: The estimation of accurate cutting time before cutting is important for improving productivity. Estimation of cutting time calculated by length of tool path / command feedrate can easily be obtained in commercial CAM systems because NC programs contain machining information, such as tool positions, feedrate, etc. However, the actual cutting time is longer than cutting time calculated by length of tool path / command feedrate due to acceleration and deceleration which occurs along the tool path. In this study, an estimation system of accurate cutting time based on the control system of the machine tool is proposed. Experiments were conducted to cut complex shapes using the NC machine tool to compare the actual cutting time, estimated cutting time of commercial CAM systems and those of the proposed system. The estimation error of the proposed system was only 2 %, while the estimation error of a commercial CAM system was 51 %.

Abstract: For the finishing of some difficult-to-machine materials, a novel polishing technique named plasma assisted polishing (PAP) was proposed. Ceria abrasive polishing with different electric power plasma irradiation was conducted on RS-SiC surface. Low RF power plasma (8 W) was used, many protrusions were generated which made the surface roughnesses bad (60.93 nm p-v, 5.51 nm rms). In contrast, the height and amount of protrusions decreased when RF power was increased to 12 W, which made the surface roughness better (31.83 nm p-v, 2.63 nm rms). Also, scratches completely disappeared after PAP. To explain the above results, the relationship of oxidation rate by plasma irradiation and material removal rate by abrasive polishing was taken into consideration. The different compositions in RS-SiC have different oxidation rates and levels of hardness. When the oxidation rate is higher than material removal rate, the heterogeneous polishing of RS-SiC is turned to homogeneous polishing of SiO₂, and then a flat surface with an oxide layer can be obtained. To prove the above assumption, we firstly oxidized the surface with plasma irradiation for 1 h, and then PAP with a much lower load was conducted on the oxidized surface for 0.5 h. A scratch-free surface with 12.61 nm p-v and 1.45 nm rms was obtained which coincides with the mechanism we propose.

Abstract: A flat surface was machined by shaping to investigate the influence of the cutting speed on surface finish. When the cutting speed was 10-30 m/min, the surface roughness deteriorated because fine valleys with a depth of 40-200 nm were caused. Because the pitch of the valleys was almost equal at different cutting speeds, it was concluded that the valleys were not caused by the natural vibration of the machine tool. The velocity of the tool tip was measured by a laser Doppler vibrometer to compare the tool motion and the work piece profile. The periodical velocity change of the tool corresponded to the pitch of valleys. When a work piece with higher phosphorus content was machined, the valleys were not caused at a cutting speed of less than 30 m/min. It is estimated that the smoothness of chip removal has an influence on the emergence of valleys.

Abstract: The present paper describes spatially selective adhesion of rat phenochromocytoma (PC12) cells on micro-structured fine particles. The particles are packed hexagonally in two-dimensional arrangements by self-assembly. Incubation allows most cells to be successfully adhered to the region of self-assembled particles, while few cells are found on the rest of the glass substrate. The line-and-space structure of particles aligns the cells in straight lines. The desired location of cells can be obtained for both appropriate line width and space of particles, because they dominate a spatial selectivity of cell adhesion.

Abstract: In this paper, we describe the design, development and experimental results of a 3-DOF precise inchworm mechanism with six contact points. During the last ten years, we have developed an omnidirectional and holonomic inchworm mechanism to provide flexible, compact, and precise microscopic processing. In a previous mechanism, four piezoelectric actuators connected a pair of U-shaped electromagnets arranged to cross each other so that the mechanism can move precisely in any direction. However, positioning repeatability was made difficult by an inclination of the U-shaped electromagnets. Therefore, we designed a new omnidirectional inchworm mechanism composed of a pair of Y-shaped electromagnets and six piezoelectric actuators to prevent the inclination of the electromagnets. In addition, we explain the drive principle of the newly developed mechanism. Finally, we show the experimental results of the positioning repeatability of translational motions in four directions with a payload.

Abstract: This paper deals with prediction of improvement in surface roughness in helical scan grinding by simulation of virtual ground surface with a 3D-CAD model. It has been found that, by choosing the value of parameters of several grit conditions such as grit arrangement, protrusion height, inclination angle and so on, randomly for a real wheel, the maximum unevenness of the virtual ground surface and tendency of its change with feed angle nearly coincide with the surface roughness in the experiment of helical scan grinding. It is found that this simulation method is effective for the prediction of a surface ground by helical scan grinding.

Abstract: Electrically conductive polycrystalline composite diamond (EC-PCD), which consists of electrically conductive diamond particles manufactured by doping boron atoms, has recently been developed for the purpose of providing material with both excellent tool properties and good machinability. This paper deals with an investigation into the machinability of EC-PCD by EDM with a copper electrode. As a result, it was found that the material removal rate of EC-PCD made up of diamond particles of 10 and 25 µm in diameter respectively was far higher than that of the conventional PCD. Furthermore, it was confirmed in the single pulse EDM experiment with a needle electrode that the EC diamond region in the EC-PCD was removed together with the cobalt region whereas only the cobalt region of C-PCD was removed when the electrode was set at plus polarity.

Abstract: This paper proposes a feed drive simulator which consists of a parameter identification module and a simulation module. The simulation module is based on a mathematical model which consists of mass, inertias, stiffness, damping, frictions, servo gains, electrical delay and control frequency. The parameter identification module consists of 3 functions: friction parameter identification function, frequency response identification function and electric delay identification function. The identification algorithms for unknown parameters are newly proposed. In order to confirm the effectiveness of the simulator it was applied to actual feed drive systems. According to the results of the confirmation, it is confirmed that the developed simulator can identify the parameters systematically, and various motions can be simulated by the simulator.

Abstract: High sensitive biosensing is required in many research fields and our lives. In this paper, we describe the fabrication of microstructured silicon (Si) surface to increase surface area and the evaluation by a highly sensitive immunoassay on that surface. Microstructured Si surface was fabricated by etching a Si wafer with a mask of self-assembled microparticles. The surface area of the microstructured surface was 1.5 times larger than that of flat surface. And the surface area was variable by changing particle diameter and etching time. An immunoassay was performed on this surface. It was confirmed that sensitivity was increased approximately 3.9 times with increase in surface area.

Abstract: This research proposes a method of production scheduling using autonomous distributed systems. A concrete message protocol is proposed to realize the production scheduling which includes not only Machine but also Human and AGV scheduling. Moreover this method realizes real time scheduling and parallel scheduling. Therefore, a new structure of production scheduling is proposed, which can realize a change of the type of production scheduler to correspond with a type of production system.