Manual welding continues to be an indispensable skill in custom fabrication and high-mix low-volume production. Hence, skilled welders are needed throughout the metal working industry. On the other hand, many people have little inducement to enter the field because of high physical risk and the demanding training required. Virtual reality technology may provide an effective solution, and several VR systems have been proposed for welding training. Such VR simulations offer the possibility of safe and highly efficient training. This paper deals with a high efficiency training method for manual arc welding, which employs a simulation of a simplified, idealized welding situation. In the proposed method, trainees are presented with an idealized, easy-to-weld situation in the beginning stage of training, and the welding challenges gradually become more difficult and realistic in the following stages. Experimental results show the proposed training method can reduce the fatigue reported by trainees.
Dense point-clouds of engineering facilities can be captured using terrestrial laser scanners. It is important for many engineering applications to generate 3D models of components in facilities from captured point-clouds. In our previous work, we proposed a method for reconstructing pipe structures from a single incomplete point-cloud. In this paper, we extend this method for reconstructing consistent models using multiple point-clouds captured at different positions. In our method, pipe models are generated from each point-cloud and overwrapping pipes are merged into unified pipes. Then we estimate other connecting parts on the basis of pipe models. Since point-clouds of facilities include a lot of occluded portions, multiple candidates of connecting parts are often generated. For solving this problem, we introduce visibility checks from multiple positions and select a consistent set of part models. We also discuss how to evaluate reliability of generated models.
The machining of lens array mold for optics is attracting attention for fabricating camera lens modules. The profiles of axisymmetric aspheric lenses ranging from 1 to 5 mm in diameter are regularly arranged on lens array molds, allowing multiple optical lenses to be molded simultaneously. An ultra-precision machine tool for machining the lens array mold that has high-speed motion and high-accuracy positioning is needed. To solve this problem, we developed an ultra-precision 5-axis machine tool. In this paper, this machine tool was evaluated by high speed machining of the lens array mold. A surface roughness of within 2 nm and a form accuracy of within 0.1μm have been achieved using the shaper machining. The performance of the machine tool and the evaluation results for the machined mold are reported herein.
It is difficult to fabricate a nonwarped substrate, because a thin wafer cannot be fixed during the polishing process without deformation occuring. To resolve this matter, a SiC freezing pin chuck has been developed. This paper describes the peeling strength of freezing liquid due to the thermal stress generated by polishing and the deformation of a large warpage quartz wafer fixed by the freezing pin chuck. Stress distributions in the frozen liquid caused by the thermal stress were calculated with the finite element method (FEM). When the quartz glass wafer is fixed with the freezing liquid cooled at 5℃ and the surface of the wafer is heated at 30℃, the maximum tensile and shear stresses become 1700 and 1100 kPa, respectively. These are smaller than the experimental results, 1800 and 1200kPa. Accordingly, it is inferred that the wafer is not peeled from the chuck. For the 300-mm-diameter, 1.2-mm-thick quartz glass wafer with the warpage of about 200 μm, the deformation amount between initial and before solidifying with the freezing pin chuck is decreased one tenth less than that with the plane freezing chuck, and that between before and after solidifying becomes one half less than that with the other. As a result, it was clarified that three times polishing with the freezing pin chuck enable to decrease the warpage of about 200μm to less than ±1μm.
The nanoparticle is key materials in the area of nanotechnology, and there is a strong demand to measure the particle size accurately and easily. We proposed a novel nanoparticle sizing method based on fluorescence polarization analysis, and constructed the rotational diffusion coefficient measurement system using fluorescent DNA probe (fl-DNA). Nano particle sizing is achieved by measuring the rotational diffusion coefficient of fl-DNA, which is labeled to nanoparticle. In this report, we investigate the relation between the rotational diffusion coefficient of fl-DNA and the size of the nanoparticles standard. The rotational diffusion coefficients of gold nanoparticles of diameters from 6 nm to 20 nm were measured using the proposed method.