High-speed and high-precision machine tools developed recently have contributed to shorten machining time in parts machining. However, it consumes long time to determine operation parameters such as machining area, machining method, cutting tool and cutting conditions, and they deeply depend on operators' knowledge and experience. Thus, the preparation time before parts machining remains as a critical issue to be solved to achieve high-mix low-volume production. Therefore, in order to improve the efficiency of process planning, this study proposes an operation planning system to derive operation parameters based on case-based reasoning using recognized machining features. By using information of machining features, it becomes possible to widely deal with operation parameters such as not only cutting tool and cutting conditions, but also tool approaching and retracting patterns that are required to be input in CAM system. Additionally, since machining cases are added to a case database sequentially, the rules for case retrieval are automatically adjusted to utilize the past machining cases effectively in this system. From the result of a case study, it is confirmed that the developed system has a possibility to derive proper operation parameters in parts machining.
For accurate fabrication of a vascular structure by 3D gel printing, it is necessary to increase in the solidification rate of gel so that the gel can maintain its shape as it is printed. In this study, we developed a novel 3D gel printing system with a new cross-linking agent which enables solidification of alginic acid-based sol immediately after its mounting onto a targeted point. We proposed a new CaCl2-based cross-linking agent by mixing with agar which has high coagulation. Also, we installed two syringes filled with the cross-linking agent as they sandwich a syringe filled with alginic acid-based sol. Both the cross-linking agent and alginic acid-based sol are quantitatively discharged from the top of the device, enabling to add the cross-linking agent to both sides of the object at the same time. After the molding experiments of 200 layers and 300 layers of the vascular structures with changing concentration of agar in the cross-linking agent, the shape accuracy was evaluated from the following viewpoints; (i) inner radius, (ii) outer radius, (iii) thickness, (iv) aspect ratio. By cross-linking the inner and outer walls at the same time, gradual expansion of wall thickness from upper to lower layers was prevented. Because of shrinkage in the circumference direction caused by the cross-linking reaction, the outer wall contracted to the ideal shape, but the inner wall was narrowed to less than half of the ideal shape. Among 0, 2.0, 3.0 mg/mL concentration, the more agar was added into the cross-linking agent, the narrowing of the inner wall tended to be prevented, and the wall thickness did not become excessive. The accuracy of the shape in the case of 3.0 mg/mL agar concentration was the best, while that in the case of 4.0 mg/mL was worse in terms of inner radius, aspect ratio and wall thickness. This can be explained that increase in the viscosity of the cross-linking agent by increase in agar concentration induces large frictional resistance with the wall surface, and flow of the cross-linking agent dragged the gel to the center of the vascular structure. In summary, the effectiveness of addition of agar to a cross-linking agent was demonstrated by the fact of the achievement of high shape accuracy of a vascular structure, but excessive increase in the viscosity of the cross-linking agent due to high concentration of agar needs to be suppressed.
The authors have reported the laser-induced metal sphere migration in the glass. The metal sphere migrated toward the light source along the optical axis. In this paper, we describe the metal sphere separation by two laser beam illumination from the opposite direction. A stainless-steel sphere in borosilicate glass was heated by two continuous-wave green laser illumination. The laser beam diameter influenced the separation result. One metal sphere was separated to two spheres, when the beam diameter was 60 and 80 µm. When the beam diameter was 100 µm, the one metal sphere was not separated and maintained the shape and migrated toward one direction. When the beam diameter was 20 and 40 µm, laser illumination separate two small sphere from the metal sphere and one metal sphere was left. Hence the one metal sphere separated to three metal spheres. In-situ observation with a high-speed camera and numeral temperature calculation clarified the separation process. Finally, the size control of the metal sphere was demonstrated by changing the beam diameter.
To realize a small-sized floating-type wave energy converter, a vibrational power generator that utilizes the gyroscopic effect and a geared acceleration is presented. First, equations of motions of the spin accelerating mechanism are derived. Next, it is shown by the numerical analyses that the spinning velocity of the gyro-flywheel is accelerated by the rotating vibration, a steady-state small vibration with the frequency twice the input frequency exists in the flywheel spin, and the generated power is 10 W at the conditions that the flywheel diameter is 600 mm, the weight is 20 kg, the input frequency is 0.2 Hz and the amplitude is ±10 deg. Finally, an experimental apparatus of the spin accelerating mechanism with a flywheel of φ300 mm is developed to show that the experimental and calculated spin and precession velocities agree well.