Satoshi Sakamoto

Effect of cutting force control on cutting characteristics of CFRP in diamond saw cutting

We examined the relation between the cutting force and the cutting characteristics of CFRP in diamond saw cutting. When a larger cutting force was applied, the cutting had been propagated with a mixed mechanism of the cutting by cutting edges and the cleaving of carbon fiber by shear force. While a good cutting surface was formed in the case of cutting with less than 23 N of cutting force. In this condition, the cutting had been propagated only by the cutting with cutting edges.

A Dynamic Observation Concept to Keep Water-Soluble Coolant in Normal Condition for Long Time

We propose a dynamic observation concept to pretend aged degradation of water-soluble coolant. The first-hand observation of coolants by a CCD microscope is extremely useful for monitoring the drastic appearance change. The appearance changes of coolant also could be monitored by combining the reflectance changes from the Red, Green and Blue LED lights. The physical process of absorbing light is occurred only at the specific wavelength in the water-soluble coolants. The absorbance at the specific wavelength would become a reliable indicator to predict the controlled condition of water-soluble coolant. Setting up these sensing systems to the machine tools make it possible to observe the coolant dynamically and on real time.

Machining of Difficult-to-Cut Materials with a Lubricant Coated Tool

Tools coated with TiBON films of varying boron concentrations were made, and the influence of boron concentration on tool wear was investigated. The TiBON coating film acts as a lubricant at high temperature. Tools coated with such films were applied to the machining of difficult-to-cut materials (Ti-6Al-4V and Inconel 718), where　the cutting temperature increases rapidly and heavy adhesion occurs. In the experiment, turning and interrupted cutting were performed. In cutting of Ti-6Al-4V, the tool coated with a film of high boron concentration showed long tool life. In turning of Inconel 718, the tool coated with a film of a boron concentration of 15% showed the longest tool life-about four times longer than that of a tool coated with TiAlN.

Study on Precision Polishing Using Gelatin Stone

A gelatin stone having a new polishing mechanism that can polish a free-form surface is proposed in this study. The gelatin based stone can easily control the hardness and the melting point by changing the density, the cooling condition and the kinds of additives. The main conclusions obtained in this study are as follows. The proposed gelatin stone can polish the surface of various materials. The high density of gelatin is suited for a gelatin stone. Surface roughness improves as the polishing time gets longer. Polishing by gelatin stone needs a high-speed relative motion.

Property and Recyclability Change of Corrosion-Inhibition-Improved Amine-Free Water-Soluble Cutting Fluid with Repeated Recycling

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.

Fundamental Characteristics of Grooving Aiming at Reduction of Kerf Loss Using an Ultrafine Wire Tool

Thinning of silicon wafers and reduction of kerf loss can minimize the manufacturing costs of semiconductor products. Currently, the volume of kerf loss is about the same as the volume of the wafer itself. Therefore, we study slicing techniques for silicon wafers that result in reduced kerf loss by using an ultrafine wire tool and fine abrasive grains. As a first step, grooving characteristics using an ultrafine tungsten wire tool and fine abrasive grains are investigated in this paper. A borosilicate glass is used as the work material. The main conclusions are as follows: Precision machining using ultrafine wire tool is possible and the kerf loss decreases because the groove width decreases. However, a larger diameter of the wire tool results in a deeper groove. A faster relative speed produces a shorter wire tool lifetime, but a deeper groove. To supply enough abrasive grains to the machined portion, it is necessary to use abrasive grains having a suitable particle size for the specific diameter of the ultrafine wire tool.

Feature Extraction from Sensor Data Streams for Optimizing Grinding Condition

A visualization method for time-series sensing data was designed to optimize grinding condition. The fluctuation pattern of time-series data streams can be visualized as a white and black pattern by utilizing the spindle power change rate average. The designed visualization method was applied to a condition monitoring in lapping operation. The relation between the fallout abrasive grain content and lapping behaviour was experimentally examined. In the lapping with grinding fluid containing no fallout abrasive, the spindle power decreased in a monotone manner with lapping time, while in the lapping with fallout abrasive, the spindle power decreased with lapping time up to 20s of lapping and then tended to converge on a constant value. The spindle power change rate average displayed as a white and black pattern reproduced the changes of spindle power very well. The appearance probability of white or black pattern has a strong relation with the fallout abrasive content and the designed data processing scheme could make possible to predict the grinding fluid condition from the easy-handling grinding test.

A Utilization Method of Big Sensor Data to Detect Tool Anomaly in Machining Process

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.

Evaluation of the Thermal Shock Fatigue Resistance of Cutting Tools Using a CO2 Pulse Laser Beam

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.

Influence of the Brittle Behavior of Work Materials on Microgrooving

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.