Papers by Author: Toshiki Hirogaki

Abstract: The purpose of this study is to explore the use of laser additive manufacturing of bamboo powder to produce items with fewer variations than the traditional heat press method using a die. Although metal and resin powders are commonly used in powder additive manufacturing, bamboo powder presents unique challenges owing to its lack of material uniformity, low carbonization temperature, and dependence on pressure for adhesion. To address these issues, the appropriate laser power and irradiation time were determined by irradiating the laser at several power levels and examining its effects on the powder temperature and chemical changes during molding. The results indicated that rapid heating occurred at approximately 150 °C, and carbonization began at approximately 190 °C. As the energy loss for carbonization decreases with increasing laser power, this method is expected to be effective for producing bamboo products with fewer variations. In addition, restriction of continuous oxygen inflow by the glass plate lid makes it feasible to prevent heat generation and carbonization. Furthermore, pressurization by the glass plate makes it feasible to improve adhesion. Future research will focus on the suppression of carbonization by inert gas and heating at low temperatures for long periods of time, as well as the effects of different magnitudes of pressure on the process.

Abstract: The purpose of this study is to clarify the effect of the sparsity of the glass cloth that makes up the printed wiring board (PWB) on the shape of the laser-processed holes. In addition, pyrolyzed resin and hot glass fibers are ejected during processing. We investigated how this phenomenon changes depending on the position of laser irradiation on the glass cloth. PWBs consist of copper foil and insulation layers, which are composite materials composed of a glass cloth and epoxy resin. Because materials with different physical properties are processed simultaneously, the processing phenomena become extremely complex. In this study, we removed the copper foil by etching and performed laser drilling only in the insulation layer to investigate the effect of glass fibers on the shape of the machined holes. Simultaneously, the relationship between the shape of the machined hole and the ejecta generated during machining was investigated using a high-speed camera to capture images of the ejecta generated during machining. As a result, it was found that the diameter and roundness of the machined hole changed depending on the sparseness and density of the glass cloth. In addition, it was found that there are two mechanisms for the removal of glass cloth and that these mechanisms change the shape of the machined hole. Finally, it was found that these changes in the shape of the machined hole could be inferred from the ejecta.

Abstract: In recent years, as global environmental problems have become increasingly serious, the concept of sustainable development, such as the 3Rs, has gained importance. Against this backdrop, machinery and equipment are becoming smaller, lighter, more sophisticated, and multifunctional, with highly integrated products increasingly requiring the machining and assembly of minute mechanical parts. However, the relatively large amounts of servo standby power generated by small machine tools during operation highlight the need for machining methods that reduce power consumption. In this study, we developed a novel 5-axis controlled machine tool equipped with an idling-stop function in the feed-driving system to reduce the power consumption of machining processes. Since this function stops the servo lock of the feed axis, it was unclear whether the same machining accuracy could be maintained as with the original setup. Therefore, in the present study, we measured straight cutting and endpoint areas using a laser microscope and an acceleration sensor and examined the change in machining accuracy due to the idling-stop function. It was found that when the idling-stop was turned off, vibration occurred, resulting in excessive cutting.

Abstract: The recent development of computer-aided design/computer-aided manufacturing (CAD/CAM) systems has enabled unskilled workers to generate NC programs easily. However, determining the cutting conditions, which is crucial for machining, still relies on the knowledge and experience of the skilled workers. Therefore, this study aimed to discover tacit knowledge about cutting using data mining methods and construct a system to support unskilled workers. Given the recent progress in the practical use of barrel tools, this study attempts to predict the cutting conditions of barrel tools by utilizing catalog information on radius and ball end mills. First, the databases of all the tools were integrated. Next, new variables were introduced for highly accurate predictions. After verifying the validity of the new variables through cutting experiments, they were used to predict cutting conditions. It was found that the new variables could be used in the clustering process to achieve highly accurate predictions.

Abstract: This study focused on cutting trace control for machining three-dimensional contours, such as molds, with high accuracy and efficiency. In this study, experiments were conducted to generate a honeycomb structure with hexagonal cutting marks and a lattice structure with square cutting marks in the cutting process of a two-blade ball-nose end mill using a runout adjustable holder, with the aim of adapting the cutting-mark control to the production level. In this study, the relationship between runout, machined surface, and cutting force is shown, and the effects of runout, honeycomb structure, and lattice structure on surface adsorption are investigated and evaluated for applications in the production field.

Abstract: In recent years, electronic devices have become lighter, thinner, shorter, smaller, and more multifunctional, driving advancements in drilling technologies. To meet the demands of electronic applications, this study proposes a drilling machine tool with a counterbalanced vibration control mechanism. In this study, machining experiments were conducted using a machine tool equipped with a left-right ball screw counterbalance mechanism during the step operation. Observations were made with a high-speed camera and a thermal camera, followed by examinations of the drill and holes after machining. As a result, significant findings regarding the drill tip temperature and runout were obtained. It was also confirmed that drill wear and runout affect machining quality.

Abstract: In this study, we measured the rolling motion of a spherical six-axis inertial measurement unit (IMU) fabricated via FDM (Fused Deposition Modeling) using wireless communication. When a sphere rolls on a plane, the axis of rotation is undefined, and the amount of rotation is unlimited. Therefore, the conventional Euler angular representation for pose estimation produces singular points (gimbal locks), and a continuous pose representation is not possible. In this paper, we propose an algorithm that incorporates micro-quaternions to achieve continuous posture representation, even at singular points. Subsequently, we discuss its applications.

Abstract: This study proposes a method for passing through the singularity and its vicinity, the biggest challenge on off-line teaching for end-milling by industrial robots. When passing through the singularity and its vicinity, some joints rotate rapidly. However, by changing the wrist configuration: NONFLIP and FLIP, when passing through the singularity, the robot motion can be stabilized. This was verified with a six-degree-of-freedom manipulator. This robot was moved in a linear path such that the end-effector passed through the wrist singularity and its vicinity, and the encoder values were measured simultaneously. The results showed that the commanded rotational speed of the wrist joint exceeded the maximum rotational speed of the servomotor when passing through the wrist singularity and its vicinity, resulting in a trajectory tracking error. However, by changing the wrist configuration, the robot could pass through the singularity and its vicinity without decreasing the trajectory tracking accuracy.

Abstract: This study investigated the effects of tool runout on chatter vibration taking images of a machined surface to assess the vibration strength, number of vibrations, and phase difference depending on the spindle speed and axial depth of the cut. This study obtained significant results regarding the stability pocket represented by the spindle speed. We observed that the stability limit changed depending on tool runout.

Abstract: An improved melt-blowing method have developed to manufacture the organic nonwoven nanofibers through our previous study. As a parallel phase, this study explores the potential of polylactic acid (PLA) nanofibers as a plant growth substrate, emphasizing the unique properties and performance when mixed with pellets. Preliminary experiments comparing different fiber materials, cultivated crops, and fiber diameters demonstrate the favorable characteristics of PLA, such as wettability and growth promotion. Comparative experiment with rockwool, a commonly used medium, shows that PLA nanofibers exhibit superior growth performance. On the other hand, a solidified PLA medium is produced and tested. Hydroponic tests using solidified medium configurations with varying fiber diameters and soil conditioners further confirm the benefits of PLA as a medium for plant growth. The findings suggest that PLA nanofibers have the potential to revolutionize cultivation practices, providing sustainable and environmentally friendly alternatives to traditional substrates.