Papers by Author: Kenji Yamaguchi

Abstract: Water-soluble cutting fluids are routinely used as coolants and lubricants in the metalworking process. The properties of these water-soluble cutting fluids change during operation. In the management of the properties of water-soluble cutting fluids, it is crucial to maintain the concentration within an appropriate range. In typical manufacturing facilities, the concentration of water-soluble cutting fluids is measured using Brix. The commonly used Brix meters are of the sampling type. However, measuring the concentration of cutting fluids in numerous machine tools can be time-consuming. In addition, there has been a recent demand for automated measurement and management of concentration and data accumulation. In recent years, relatively inexpensive automatic Brix meters have become available in Japan. In this study, we tried to continuously measure the concentration of water-soluble cutting fluids using an automatic Brix meter. We installed an automatic Brix meter in a tank that continuously circulates 40L of water-soluble cutting fluid and measured it for several tens of days, confirming that it can measure stably. However, depending on the type of water-soluble cutting fluid, the measurement results may become unstable immediately after starting the measurement. Therefore, it was found that the choice of the water-soluble cutting fluid to be used is also important for the concentration measurement by the automatic Brix meter.

Abstract: The crafts such as lacquerware have made unique strides through decorating techniques using gold such as “Makie”, the technique to draw picture by scattering powdered gold, and “Chinkin”, the technique to rub gold into the design engraved by carving knives. In conventional techniques, practical knowledge and ability are essential to produce craft products. Therefore, screen printing which consists of simple processes has been developed. However, screen printing requires a masking plate made of silk or nylon to create patterns for transcribing ink into objects. This paper presents the formation of a decorative film by inkjet printing with gold nanoparticles for crafts such as lacquerware. The proposed method consists of on-demand process, which makes design changeable without masking. The aims are threefold: 1) to establish a sintering process of gold nanoparticles for acrylonitrile butadiene styrene (ABS) and phenol resin substrates used for synthetic resin products; 2) to characterize the sintered gold film; 3) to examine applicability to industry. The major results obtained are as follows: the appearance and the reflectance spectra of the gold nanoparticle film vary with heat conditions; the proper heat conditions which prevent thermal damage to substrates are the temperature of 373 K or below for the ABS resin substrate, and 423 K or below for the phenol resin substrate, respectively; the gold nanoparticle film possessed a good surface integrity without any voids when the sintering temperature is higher than 323 K for 1 h. Moreover, the film had such a high adhesion to substrates that no separation occurred after cross-cut test; the proposed method applied a lacquerware product made of ABS resin, yielding the decorative film

Abstract: Cutting fluid is commonly used during metal cutting process for cooling and lubrication. Fluid types are generally classified into mineral or fatty oils and water miscible oils. In Japan, the former is called water-insoluble coolants, and the latter is called water-soluble coolants. Water-insoluble coolants are specified as dangerous material by the Japanese law due to its flammability. Therefore, the water-insoluble coolants are not appropriate for unmanned operation of machine tools. Therefore, the usage rate of water-soluble coolants is increasing. Water soluble coolants are diluted with a water by several ten times. The waste management of the water-soluble coolant become important for environment-conscious green manufacturing. We have been developing a recycling system for water-soluble coolants. In the recycle system, water is extracted from the waste coolant and the water is then reutilized as a diluent of a new coolant. We have developed various types of chemical or bio-chemical water recovery methods for recycling systems. We found a commercially available amine-free water-soluble coolant is suitable for the recycling system. The processing time, processing cost, and the biochemical and chemical oxygen demand of the extracted water are improved by the amine-free water soluble coolant compared with a conventional amine-containing coolant. However, its corrosion inhibition performance was poor in general machining applications. Our cooperative company developed a prototype of a corrosion-inhibition-improved amine-free water-soluble cutting coolant. The prototype coolant showed a good stability and cooling and lubricating performances, and its recyclability was as good as that of conventional amine-free coolants. In this study, we focused on repeated recycling of the prototype coolant. We repeatedly applied the water recycling process to the recycled coolant. The recyclability of the prototype coolant was not affected by repeated recycling; however, process residues increased with the number of recycles, and a deterioration was noticed in the corrosion-inhibition performance of the coolant diluted with recycled water.

Abstract: The essential features and scale of sensor data was discussed to monitor the tool anomaly in the machining process from the pattern variation of large scale sensor data such as vibration and effective power. The cycle data, the time series sensor data collected with an acceleration or power sensor in one periodical machining of the given groove shape, had been measured periodically. In this study, the graphic pattern formed by overwriting the time series cycle data on a specific coordinate system was treated as the “big sensor data”. The big data from the effective power sensor can stably respond to the cutting power changes and showed a strong possibility as a detecting device for tool anomaly such as abrasive wear and chipping. While the big data from the acceleration sensor only responded to a big event like the chattering vibration. The number of cycle data needed to generate the big sensor data also affected on the detection sensitivity for tool anomaly. It had been required a family of time series sensor data enough to represent the cutting power change as a visual graphic pattern.

Abstract: It is well-known that a series of cracks sometimes gets initiated perpendicular to the cutting edges on the rake faces of brittle cutting tools made of materials such as cemented carbide, ceramics, and cermet under high-speed intermittent cutting. The tools used in intermittent cutting processes are exposed to elevated temperatures during cutting and then cool quickly during the noncutting time. Previous studies have suggested that such repeated thermal shocks generate thermal stress in the tool and that the thermal cracks are then propagated by thermal fatigue. Recently, high-speed machining techniques have attracted the attention of researchers. To apply new cutting tool materials to this machining process, it is important to evaluate their thermal shock fatigue resistances. During high-speed intermittent cutting, the frequency of thermal shocks becomes high and the action area of the thermal shocks is limited to the rake face of the tool. Therefore, conventional thermal shock resistance evaluation methods are unsuitable for this case. Consequently, the authors have developed a new experimental evaluation method using a CO₂ laser beam. In this study, we irradiated cemented carbide and TiN cermet cutting tools with the CO₂ pulse laser beam and gauged the effectiveness of the proposed thermal shock fatigue resistance evaluation method. The results show a correlation between the thermal shock due to the CO₂ pulse laser beam and those due to the intermittent cutting experiments.

Abstract: A wire tool having electrodeposited diamond grains is frequently used for machining hard and brittle materials such as silicon ingots, magnetic materials, ceramics, and sapphires. This study aims to examine the wear characteristics of the tool during the microgrooving of ceramics. We conducted microgrooving experiments for alumina ceramics. The results indicate that the grooving time and the machining distance influence the groove depth. However, as the damage in a wire tool progresses, the groove depth does not depend on the machining distance. A fast relative velocity leads to serious damage in the wire tool even when the machining time is short. In the case of wet grooving, the damage to the wire tool was smaller than that in the case of dry grooving.

Abstract: An electroplated diamond wire tool is frequently used for the machining of hard and brittle materials such as silicon ingots, magnetic materials, ceramics, and sapphires. This study aims to examine the influence of brittle behavior of work materials on machinability (including tool wear); therefore, we conduct dynamic ultramicro hardness measurements and microgrooving experiments for three types of ceramics. The results indicate that the groove depth of a work material tends to increase with the processing time. Moreover, material properties of a work material, such as hardness and toughness, have a significant impact on the fluctuations in its groove depth. However, kerf width of a work material does not depend on the processing conditions and material properties. In addition, a faster relative velocity improves processing efficiency but also increases tool wear.

Abstract: An innovative cutting method, constant load feeding method, is proposed as a high precision secondary working tool in CFRP cutting. The constant load feeding can restrain the occurrence of cutting defects such as burr and scuffing in a diamond saw cutting. The combining of constant load feeding with point contact eliminated most of the cutting defects even in the CFRP cutting with a low rigidity cutting tool like the diamond saw blade. In addition, there was no apparent cutting damage on the cutting surface obtained from the drilling with constant load feeding. These facts indicate that the self-generated feed rate in the constant load feeding would be the optimal feed rate to realize a defect-free drilling of CFRP composites.

Abstract: Thinning of the silicon wafers and decrease in kerf loss can minimize the production costs of semiconductor products. Currently, the quantity of kerf loss is about the same as the volume of the wafer itself. If we drastically reduce kerf loss, we can easily lower production costs. Therefore, we studied techniques for slicing silicon wafers with reduced kerf loss using a wire tool. As a first step, we performed micro-grooving with a fine wire tool. In this paper, we discuss the micro-grooving performance of a fine wire tool made of tungsten. A borosilicate glass is used as the work material. The main conclusions are as follows: When a fine wire tool and small-diameter abrasives are used, the kerf loss decreases. However, the strength of fine wire tools is very low. The relative velocity and abrasive diameters have a significant influence on the micro-grooving characteristics. Fine wire tools are easily fractured at fast relative velocities and with large-diameter abrasives. However, the grooving rate increases. Groove depth and grooving efficiency do not depend on the relative velocity and are dependent on the abrasive diameter.

Abstract: The concern for environmental problems has been increasing rapidly in recent years. Water-soluble coolants are widely used in machining processes. To reduce management costs and the environmental load of water-soluble coolants, the authors studied a recycling system for water-soluble coolants. With this recycling system, water is extracted from a waste coolant by chemical or biochemical treatment; the recovered water is re-utilized as a diluent for a new coolant. Coolant recyclability depends on the coolant type. Most water-soluble coolants contain alkanolamines for corrosion inhibition and maintenance of putrefaction prevention. However, alkanolamines are difficult to eliminate from water-soluble coolants by chemical and physical waste treatment processes. Some amine-free, water-soluble coolants have been developed and are commercially available. The reduction of environmental load in the treatment of waste coolants is anticipated for amine-free coolants. We applied the recycling process to a commercially available amine-free, water-soluble coolant. The amine-free coolant showed good recyclability and lubricating performance. However, the corrosion inhibition performance of the coolant was inadequate for use in general machining. Recently, our cooperative company developed a prototype amine-free, water-soluble coolant with improved corrosion inhibition. In this study, we experimentally examined the recyclability and performance stability of this newly developed coolant. The experimental results showed that the new amine-free coolant has good corrosion inhibition equivalent to conventional amine-containing coolants. In addition, the recyclability, stability, and cooling and lubricating performance of the coolant are equal to conventional amine-free coolants. The amine-free, water-soluble coolant with improved corrosion inhibition has the advantage that it can be used in the recycling system for water-soluble coolants.