Papers by Author: Keiji Ogawa

Abstract: In recent years, the recycling of resources has become important because of the aggravation of global environmental concerns. In light of this, it is necessary to minimize the resource needs of current production systems. This concept is called sustainable development. When this concept is applied to machine tools, the assumption is that small parts should be processed using small machines. Additionally, the diversification of consumer needs and the ephemeralization of product life cycles are progressing in industry. As a result, the overall production system has changed from high-mix low-volume production manufacturing, to variant types in variable quantity. In this background, the cell production system is receiving attention as a production system that can achieve variant types in variable quantity. The cell production system also requires miniaturization and process consolidation of machine tools, which has given rise to the need to consolidate heat treatments, especially as part of the process consolidation of machine tools. Laser beams have proved to be effective heat sources when integrated into heat-treatment processes, such as quenching and tempering on machine tool tables. On the other hand, In the case of the thin plate, it is well known that the deformation of a plate occurs due to laser irradiation, as named a laser forming. The laser forming is also effective to generate the complex shape without a press die set. Thus, we propose that the hybrid process of laser heat treatment and forming of thin plate with a small power semiconductor laser, and demonstrate that the proposed method makes it feasible to generate the hardened sheet metal products with a compact machine tools. Moreover, considering the power consumption in laser quenching and forming process, we investigate an appropriate laser irradiation condition from a view of reducing the environmental burden.

Abstract: Recently, there has been an increasing demand for miniaturization and multi-functionalization of electronic equipments due to the developments in information technology (IT). Thus, the miniaturization of printed wiring boards (PWBs) and fabrication of highly dense electrical circuit layers are needed to realize the miniaturization and densification of the semiconductor package PWBs. Micro-drilling technology has been attracing attention to machine the electronic micro-through holes with an ultra-high-speed spindle, more than 160 krpm. However, problems have emerged; the drill tool bends and suffers breakage in the drilling process and the heat damage around the drilled hole after a drilling process occurs due to the increase in the drilling aspect ratio between hole depth and diameter. In general, a step feed drilling method is considered an effective way to solve these problems. However, short stroke alternating motion in the spindle axis is needed to do the step drilling process and its motion causes various kinds of vibration. We constructed a machine tool with a novel counter balance mechanism in the spindle driving Z-axis and investigated a model to estimate a proper balance mass for the step drilling process. We compared the frequency response results from a proposed model with the experimental ones, and discussed a control on vibration due to the counter balance mechanism. The results demonstrate that a proposed vibration proof method was found to reduce the vibration in high-speed step-micro-drilling motion and to improve the drilled hole quality and the efficiency of micro-drilling process in the PWB manufacturing fields.

Abstract: Nowadays, resource saving technologies have become important because of increasing global environmental problems. Moreover, demand is increasing for the manufacturing and machining of small mechanical parts because of the downsizing of electronic mobile devices. Thus, one requirement has emerged that these small parts have to be fabricated by smaller machine tools to reduce the environmental burden. Here, when we look at the heat treatment process, it is found that most small parts are generally treated with a large size furnace as well. Therefore, we focus on compact machine tools to develop the clean and energy-saving technology in the manufacturing fields. In the present report, we consider an in-situ laser heat treatment technology integrated on the table used for compact machine tools. In particular, we perform the entire laser hardening of a small thin plate with a small power semiconductor laser, which is an attempt to harden a whole steel sheet. However, thin plates deform during the laser hardening process, which is called “laser forming.” Thus, we discuss an effective irradiation path to prevent the deformation of plates while quenching the entire plate. Moreover, considering the power consumption in the laser quenching process, we investigate an appropriate laser irradiation condition.

Abstract: Recently, the development of electronic devices, such as smartphones, has meant that printed circuit boards (PCBs) have become complex multi-layer ones to provide both multiple functions and be compact. Blind via holes (BVHs) connecting the layers of the multi-layer board are processed by using a CO₂ laser. The many benefits of direct processing by CO₂ laser include a lower disconnect of the hole position as a result of the base drilling process in the inner layer circuit pattern. Also, efficiently dissipating heat from components improves the quality of the product as digital home appliances are increasingly compact, lightweight, and thinner. Using PCBs raises the radiation performance by the addition of alumina filler at the insulated layer. However, adding alumina filler means that laser processing is difficult, processing efficiency is reduced, and debris on the surface around the drilled hole increases. We consider what causes the changes in the processing hole by changes in the alumina filler content on the basis of data on drilling phenomena gathered with a high-speed camera. We found that the insulating layer material didn’t effect the diameter of the drill hole per laser spot diameter. The cross-section processing is done in a cone initially, and the truncated cone is then processed. And, we found that the hole depth and processing overhang was reduced, and the amount of scattering increased with the amount of alumina content filler.

Abstract: This paper proposes a novel process strategy for micro-cutting edge fabrication. Micro-cutting edges need a hardening process for the ridgeline parts that requires abrasive resistance, as well as edge sharpness and shape accuracy, based on their applications. Micro-cutting edge shapes also vary greatly in ridgeline profile and section. The proposed method is shape fabrication after laser hardening, which easily addresses these issues. In the present paper, effects of the proposed method are discussed and the results of a demonstration test are introduced.

Abstract: Bamboo grows faster than other renewable natural materials. Bamboo fiber, in particular, has attracted attention as an environmentally superior material. Therefore, we propose a sustainable manufacturing system using bamboo. A method is also proposed for extracting bamboo fibers end-milled using a machining center with in-situ measurement. Bamboo fibers with highly precise shapes are efficiently acquired. Previously, we proposed the fabrication of a binder-free composite by a hot press forming method that only uses bamboo fibers extracted by a machining center. We experimentally demonstrated various hot press forming conditions and achieved proper ones to optimize the forming process. However, we have not yet constructed a method to obtain the best fiber extracting and molding conditions considering both its efficiency and performance. Therefore, in this report, we investigate the influence of the length of used bamboo fiber on the characteristics of the molded products, as its length deeply affects the extracting efficiency and focuses on a degradable plastic as a standard of molded product strength.

Abstract: Recently, with regard to global warming energy shortage, the saving energy has become a global issue. The demand for variety, variable production, high speed, high accuracy, and complex processing in the manufacturing fields has been emerged. Furthermore, automatic extinction of computer numerical control (CNC) screens and automatically hold of oil pressure pump in idling has been raise to do on research. On the contrary, there are few reports dealing with reducing power consumption based on existing machining tools system. The method presented in this report can be applied to various size and weight of machining tools. The experimental result of standby power and minimum power with emergency stop circuit of various machining tools is discussed in this research work. To expand the stage of the proposed method, a brand new system is developed. As a result, power consumption of a machining tool with the phase of idling can be effectively reduced through emergency stop circuit. By activating emergency stop circuit, power consumption can be equalized with the condition of main power-ON only. The standby electric power increases along with increasing weight of machining tools. Through the proposed original system, it is possible to set switching of servo ON and OFF to each section. Consequently, the methodology would be applied into many fields of precision processing.

Abstract: Data-mining methods using hierarchical and non-hierarchical clustering are proposed that will help engineers determine appropriate drilling conditions. We have constructed a system that uses clustering techniques and tool catalog data to support the determination of drilling conditions for printed wiring boards (PWBs). Variable cluster analysis and the K-means method were used together to identify tool shape parameters that have a linear relationship with the drilling conditions listed in the catalogs. The response surface method and significant tool shape parameters obtained by clustering were used to derive drilling condition decision equations, which were used to determine the indicative drilling conditions for PWBs. Comparison of the conditions recommended by toolmakers demonstrated that our proposed system can be used to determine the drilling condition for PWBs. We carried out the drilling experiments in accordance with the catalog conditions and mining conditions, and estimated the board temperature around a drilled hole, the drilling forces, and the roughness of the drilled hole wall.

Abstract: Data-mining methods using hierarchical and non-hierarchical clustering are proposed that will help engineers determine appropriate end-milling conditions. We have constructed a system that uses clustering techniques and tool catalog data to support the determination of end-milling conditions for different types of difficult-to-cut materials such as austenitic stainless steel, Ni-base superalloy, and titanium alloy. Variable cluster analysis and the K-means method were used together to identify tool shape parameters that have a linear relationship with the end-milling conditions listed in the catalogs. The response surface method and significant tool shape parameters obtained by clustering were used to derive end-milling condition decision equations, which were used to determine the indicative end-milling conditions for each material. Comparison with the conditions recommended by toolmakers demonstrated that our proposed system can be used to determine the cutting speeds for various difficult-to-cut materials.

Abstract: Demand is increasing for the manufacturing and machining of small mechanical parts. We focus on using a multi-functional desktop-sized machine tool to meet such demands because power consumption is decreased when they are machined. However, few reports have focused on heat treatment among manufacturing processes, we investigate the laser heat treatment of small parts as a highly efficient and eco-friendly method and propose in-situ heat treatment on a desktop-sized machine tool using a low-power diode laser beam. We quenched a small thin steel plate with a 30 W diode laser source. Our proposed method makes it feasible to quench a small thin steel plate and effectively reduces the power consumption of in-situ heat treatment by a desktop-sized machine tool.