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The influence of various process parameters on the building of maraging steel powder by the selective laser melting (SLM) processes is investigated. The microstructure in the built part was observed and the influence of the heat treatment was evaluated. As results, the depth of solidified layer was higher than that of deposited metal powder, and its value was influenced with the process parameters. The microstructure in the boundary between the built part and the substrate was quite different from the built part even if the suitable heat treatment was performed.

The quality of built parts by selective laser melting (SLM) relies on the comprehension of the phenomena that takes place during the melting and solidification of the metal powder. The scattering of spatter particle as liquid metal during SLM process affects the layer consolidation of powder bed in addition to the surface quality of built part. The present study is focused on the spatter particle behaviour of maraging steel during SLM to achieve a thorough understanding of the phenomena that occur during the melting and fusing of the metal powder. The spatter particles are tracked using high speed imaging, and the effects of the process parameters on the spatter particle behaviour are investigated. The spatter particles ejected from the melt pool are also physically and chemically evaluated. The results showed that the spatter particles were classified as being spherical or satellite types, according to their scattered volumes; some spatter particles were larger than the particles in the initial metal powder. Most spatter particles were ejected from the droplet formed around the melt pool and from the melted powder in front of the melt pool; the number of spatter particles ejected from the melt pool was relatively low. The surface roughness affected the generation locations and tracks of the spatter particles, and the substrate surface wettability was the principal factor affecting the spatter particle behaviour.

In this study, the tool performance of two types of binderless diamond tools – single-crystal diamond (SCD) and nano-polycrystalline diamond (NPD) – is investigated in the high-speed cutting of titanium alloy (Ti-6Al-4V) with a water-soluble coolant. The NPD tool allows for a larger cutting force than the SCD tool by dulling of the cutting edge, despite NPD being harder than SCD. This large cutting force and the very low thermal conductivity of NPD yield a high cutting temperature above 500°C, which promotes the adhesion of the workpiece to the tool face, thereby increasing tool wear. Based on the morphology of the tool edge without scratch marks and the elemental analysis by energy-dispersive X-ray spectroscopy (EDX) of both the flank face and the cutting chips, diffusion-dissolution wear is determined to be the dominant mechanism in the diamond tool. A thin TiC layer seems to be formed in the boundary between the diamond tool and the titanium alloy at high temperatures; this is removed by the cutting chips.

This research deals with the hard turning of cemented carbide with CBN and diamond tools, and focuses on the tool performance, mainly tool wear with respect to cutting force and cutting temperature. The internal turning tests without cutting fluid are executed with the vertical machining center. Seven types of tool materials: SC, CVD-SC, two PCDs, BL-NPD (Binderless nano-polycrystalline diamond) and CBN: are selected for cutting three grades of cemented carbides WC having the different Co binder content (12%, 20% and 25%). Attrition has been found to be the main tool wear mechanism for all tools with slight adhesion of the workpiece binder on the tool face. In cutting of softest carbide WC-m (25% Co), the polycrystalline CBN tool has the lowest tool wear than any other PCD tools. In turning of harder carbides WC-d (20% Co) and WC-t (12% Co), both polycrystalline CBN and PCD cannot be used continuously due to their low hardness, and BL-NPD, SC and CVD-SC tools are applicable. And the BL-NPD tool has the best cutting performance with less flank wear. As for WC-d, extremely stable cutting can be done with BL-NPD where the principal cutting force is kept almost constant at 40 N. Only BL-NPD tool can continue to turn the hardest WC-t. In spite of turning hard materials, the tool temperatures measured are relatively low below 450°C due to the high thermal conductivities of tool materials. However, cutting temperature is directly related to the tool wear and cutting force rather than thermal conductivity of tool in turning of WC-m and WC-t.

This paper discusses the utilization of the minimum quantity lubrication (MQL) method in end milling using a coated carbide tool for stainless steel and titanium alloy workpieces. The effects of MQL were mainly evaluated by tool flank temperature, cutting force, tool wear behavior, and surface roughness. In MQL cutting of stainless steel and titanium alloy at cutting speed v = 25 m/min, the tool flank temperature decreased by approximately 50 and 100 °C, respectively, in comparison with dry cutting. The effect of MQL on tool flank temperature was especially pronounced at low-cutting speeds. Conversely, the tool flank temperature in MQL cutting of titanium alloy was higher than that of dry cutting at v = 100 m/min or more. In high-speed cutting of titanium alloy, it was observed that several chips had adhered to the cutting edge of the rake face, which reached a high temperature due to the heat generated by cutting. In the cutting of titanium alloy, the tool flank temperature at both a higher feed rate and depth of cut was lower than that in high-speed cutting under conditions where the cutting efficiency was the same. Peeling of the coating film covering the tool in dry and air-blow cutting of stainless steel and titanium alloy was more pronounced than that in MQL cutting. The surface roughness was greatly improved by supplying an oil mist in low-speed cutting of stainless steel.

Selective Laser Sintering/Selective Laser Melting (SLS/SLM) is one of Additive Manufacturing (AM) processes that utilize layer by layer powder deposition technique and successive laser beam irradiation based on Computer Aided Design (CAD) data. During laser irradiation on metal powders, melt pool was formed, which then solidified to consolidated structure. Therefore, melt pool is an important behavior that affects the final quality of track formation. The study investigates the melt pool behavior through visualization of the consolidation process during the single track formation on the first layer. In order to understand the transformation process of metal powder to consolidated structure and mechanism involved, high speed camera was used to monitor the process. Yb:fiber laser beam was irradiated on metal powder at maximum power of 150W. The laser processing parameters such as laser power, scan speed and layer thickness were varied in order to investigate their influence on the consolidation process. The result shows the size of melt pool increased with laser power and decreasing with increment in scan speed. Furthermore, with the increase of layer thickness, melt pool formation was unstable with chaotic movement. Significant amount of molten powder splattering was recorded from the melt pool. At high layer thickness also, the molten powder formed spherical shaped and the solidified molten powder failed to wet with the substrate.

This paper deals with the measurement of surface temperature on metal powder during the laser consolidation process with two-color pyrometer. Additionally, the aspect of selective laser sintering (SLS) and selective laser melting (SLM) of metal powder is visualized with high speed video camera. As a result, the surface temperature during the laser irradiation was ranged 1520-1810 °C and the consolidation phenomena was classified according to the melting point of metal powder. The metal powder at the heating process cohered intermittently to the melt pool although the laser beam was continuously irradiated to the powder surface. © 2013 CIRP.

This study deals with the cutting performance of ceramic tools in turning of mild steel and BN free-machining steel based on it. The tool lives of ceramic tools in turning standard steel were less than 15 min at the cutting speed 250 m/min. On the other hand, the tool lives in turning of BN free-machining steel were obvious longer than that of standard steel. The tool life of TiC added alumina ceramic tool reached almost 10 hours in the case that the tool life criteria was set at VB=0.3mm. This tool life was twice as long as that of coated carbide tool.

This study describes a finishing performance of cooling channel with a face protuberance inside a molding die with free abrasive grains. A fluid flow in the cooling channel is calculatedly simulated, and the effect of internal face protuberance which is spirally arranged on the finishing performance is experimentally investigated. The molding die used in the experiment is fabricated with layered manufacturing equipment. The internal face of cooling channel is finished by the fluid flow with free abrasive grains which are passed through the cooling channel. The results showed that the fluid flow with the face protuberance is flowing spirally according to the face protuberance on the internal face, and the velocity distribution inside the molding die was quite small. The internal face roughness in the cooling channel was improved significantly up to the early finishing time by the removal of unstable powder, such as the stain, the partially molten powder and the adhered powder. The application of the face protuberance on the internal face was quite effective for the improvement of the alloyed face in the cooling channel.

The cutting performance of indexable insert drill that has non-axisymmetrical geometry for drilling of difficult-to-cut materials is investigated. A twisted drill is also used to compare the cutting performance. The cutting characteristics are evaluated by tool flank temperature at peripheral corner edge θα, thrust force Ft, chip geometry and surface roughness Ra. The temperature of cutting tool is measured using a two-color pyrometer with an optical fiber. As work materials, the carbon steel, stainless steel, titanium alloy and nickel-base alloy are used. The θα and Ft of indexable insert drill are lower than that of solid drill in cutting of titanium alloy and nickel-base alloy. In the case of titanium alloy, the Ft of indexable insert drill is only 40% in the case of solid drill. On the other hand, this tendency reversed for stainless steel, and θα and Ft of indexable insert drill become higher than that of solid drill. The chip geometry by indexable insert drill is divided into parts in fragments so that there is chip breaker on the rake face of insert while the chip geometry by solid drill is continuous and long. The difference of surface roughness by the indexable insert drill and solid drill is negligible in the cutting of difficult-to-cut materials.

The cutting characteristics of newly proposed PVD coated tools by UBMS (Unbalanced Magnetron Sputtering) method are investigated. Dry side milling tests of austenitic stainless steel (AISI 304) and Ti–6Al–4V alloy (ASTM B348) are carried out with five kinds of coated tools: two UBMS coated tools and three commonly used AIP (Arc Ion Plating) coated ones. The UBMS coated films, especially UBMS-TiCN have smoother surface without droplets and lower friction coefficient than those of any other AIP coated tools studied. The lubricating ability of the UBMS-TiCN film reduces the cutting force, cutting temperature and adhesion of chips, so that long tool life and good finished surface are obtained.

In this study, the influences caused by the wear of grinding wheel are investigated experimentally. The infrared radiation pyrometer with an optical fiber is developed and applied for the temperature measurement in the surface grinding process of carbon steels. Experimental data such as the temperature, the number and the size of effective cutting grains and the grinding forces are obtained over the wheel life, and they are used for the calculation of the thermal energy fraction to the workpiece, the grinding wheel and the chips. Thermal damage begins to be caused on the ground surface, as the attrition wear of grains decreases the number of effective cutting grains and degrades the efficiency of grinding wheel. The measuring of radiation pulses from the cutting grains makes it possible to detect the degradation of grinding wheel at an early stage of wheel life and prevent the severe damages on work surface.

This paper deals with a finishing method for the internal face of a cooling channel located in an injection mold that makes use of free abrasive grains. The injection mold is fabricated by layered manufacturing equipment using a ferrous based metal powder. When the internal pressure is loaded to the hydraulic cylinder, the solution containing the free abrasive grains is passed through the cooling channel. The internal face is then finished by the free abrasive grains. The effects of various conditions on finishing characteristics are investigated experimentally. The results showed that the internal face roughness of the cooling channel improved significantly during the first 1000s of finishing. The significant improvement achieved during the initial stages of finishing is due to the removal of the aforementioned unstable powders. Free abrasive grains are employed to remove the unstable powder on the internal face rather than to polish the alloyed face. The high-speed flow of the free abrasive grains results in an increase in their kinetic energy, thereby increasing the force with which they collide with the internal face and resulting in an improvement of the surface roughness. The internal face finishing was effective for the improvement of the thermophysical properties in the cooling channel.

In this study, cutting performance of CBN tools and PVD-coated carbide tools in end-milling of hardened steel was investigated. In high-speed dry hardmilling, two types of CBN tools were applied: the CBN-rich type and an ordinary one. In the case of relatively low-speed milling, on the other hand, a few coated carbide tools were selected where four kinds of coating films, TiN, TiCN, TiAlN and multi-layered TiAlN/AlCrN, were deposited on the K10 and P30 grade carbide. The cutting performance was mainly evaluated by tool wear, cutting temperature, cutting force and surface roughness. In dry cutting of hardened carbon steel with the ordinary CBN tool, the cutting tool temperature rose rapidly with increase in cutting speed; and tool temperature reached approximately 850 °C at the cutting speed of 600 m/min. In the case of the CBN-rich tool, the cutting temperature decreased by 50 °C or more because of its high thermal conductivity. It is remarkable that tool wear or damage on a cutting tool was not observed even when the cutting length was 156 m in both CBN tools. In the case of coated carbide tools, the temperatures of TiN-, TiCN- and TiAlN-coated carbide tools rose as cutting proceeded because of the progress of tool wear, but that of TiAlN/AlCrN-coated carbide tool hardly rose due to little tool wear. When the base material was K10 grade carbide, tool temperature was lower than that of P30 with any coating. The tool flank wear depends considerably on hardness and oxidizing temperature of the coating film.

金沢大学理工研究域機械工学系, This paper deals with the reduction of residual stress induced during the selective laser melting with a mixture of ferrous based metal powder. To evaluate the residual stresses induced during layered manufacturing processes, a strain gauge is attached on the bottom face of the base plate. The residual stress within the consolidated structure is calculated from the amount of strain change measured by the strain gauge when the consolidated structure is cut with an end mill. The influences of base plate thickness and consolidated structure height on the residual stresses are investigated. In addition, the effect of pre-heating and post heating by a laser beam irradiation are evaluated. The results showed that the deformation of the base plate increased with the increase of the consolidated layer and the decrease of base plate thickness, and the deformation was flattened when the consolidated structure was completely removed with the end mill. The deformation was related to the induced residual stresses. The residual stress distribution within the consolidated structure in the z direction was extremely large at the top layer of the structure and the boundary between the base plate and consolidated structure. The residual stress at the first layer of the structure decreased when the base plate was heated before consolidating the deposited powder. The residual stresses decreased when each of the consolidated layers was repeatedly heated by the laser beam irradiation. © (2010) Trans Tech Publications.

Cutting process of difficult-to-cut material such as stainless steel, generates immensely excessive heat, which is one of the major causes related to shortening tool life and lower quality of surface finish. It is proven that application of cutting fluid during the cutting process of difficult-to-cut material is able to improve the cutting performance, but excessive application of cutting fluid leads to another problem such as increasing processing cost and environmental hazardous pollution of workplace. In the study, Extreme Cold Mist system is designed and tested along with various Minimum Quantity Lubrication (MQL) systems on turning process of stainless steel AISI 316. In the study, it is obtained that, Extreme Cold Mist system is able to reduce cutting force up to 60N and improve the surface roughness of the machined surface significantly.

金沢大学理工研究域機械工学系, This study deals with the laser beam assisted milling to improve the machinability of a consolidated structure formed by layered manufacturing processes. The laser beam used is a continuous CO2 laser with a maximum output power of 100 W. The metal powder for layered manufacturing is a ferrous-based mixture. To investigate the influence of laser conditions on the machinability, specific cutting force, tool wear and tool temperature of the flank face are measured. The results showed that the specific cutting force of the consolidated structure was decreased by the effect of energy input on the structure surface. The progress of wear on the flank face assisted by the laser beam was 20% slower due to the softening of the consolidated structure and the melting of the powder which remained on the structure surface. The dimensional accuracy and surface finishing of the consolidated structure were influenced by the rise of the tool temperature on the flank face. © KSME & Springer 2010.

Burring is a vital factor in metal cutting processes, since it may cause production-line problems that add unwanted time and cost required for deburring. We found that laser hardening of workpieces before face milling efficiently prevents burr formation. Our purpose here is to study optimum laser hardening conditions and cutter paths. Where no burring occurs, minimal chipping such as in chamfering is seen at the martensite layer on the workpiece exit face. The martensite layer thickens with laser power density, increasing chamfer height. The larger the exit angle, the more difficult it is to form a chamfer-like edge. Even for relatively small exit angles, the lower the feed rate, the more difficult it becomes to form a chamfer-like edge.

Turning with a spinning insert called actively driven rotary tool (ADRT), where the cutting tool revolves by a powered and programmable spindle, is investigated from the thermal aspects. Dry and MQL external turning tests of austenitic stainless steel (AISI 304) and heat-resistant Ni-based alloy (Inconel 718) are carried out. The tool temperature at the flank face is measured using a newly assembled fiber-coupled two-color pyrometer. In dry turning of AISI 304 steel, the tool temperature decreases from approximately 730 °C to 640 °C as the tool rotation speed increases from 10 m/min to 200 m/min.

This paper investigates tool wear mechanisms of a ball end mill in cutting laser sintered material. Cutting edge temperature is measured by using a three-color pyrometer with an optical fiber. Bulk carbon steel JIS S55C is selected as the standard steel. Experimental results show that tool life in cutting sintered material is shorter than that in cutting JIS S55C. Observations by SEM show that adhesion of the work material and micro chipping are the main wear mechanisms in cutting sintered material. The corresponding cutting edge temperature shows a continuous increase as wear evolves with cutting time.

This study describes the consolidation characteristics of chromium molybdenum steel (SCM) based powder used for rapid tooling. The laser beam used was a Yb:fiber laser with a spot diameter of 45 μm and a maximum power of 40 W. In order to investigate the influence of irradiation conditions on the maximum temperature at the focal area, a two-color pyrometer developed by the authors was used. In addition, the cross section of the consolidated structure was analyzed with an electron probe microanalysis, and the cutting force was measured with a dynamometer. The result showed that the maximum temperature at the focal area was related to the consolidation characteristics of the metal powder. The main parameters which affected the consolidation characteristics were laser power and scan speed of the laser beam. The deposited powder and the plate surface were melted with generated heat and alloyed in the process of the solidification. The specific cutting force was greatly influenced by the consolidation conditions. The highest value of a specific cutting force was obtained when the melting of the powder and the solidification of the molten powder were performed repeatedly and the structure was consolidated linearly.

This paper describes an experimental investigation on the cutting mechanism of laser sintered material using small ball end mill focusing on the temperature of the cutting edge. Sintered material was produced by irradiating a laser beam on a layer of loose fine SCM–Ni–Cu powder. Bulk carbon steel AISI 1055 was selected as reference steel. The influence of cutting conditions, tools diameter and unsintered metallic powder on the cutting edge temperature were examined. Comparison of the cutting edge temperature between the peripheral and surface milling were investigated. Investigations of the tool life and wear mechanisms in cutting the sintered material and AISI 1055 were also carried out. Results indicated that the cutting edge temperature for sintered material was higher than for bulk AISI 1055. Cutting at the outer surface of sintered material produced higher temperature than at the inner surface. The temperature of the cutting edge was greatly influenced by the cutting speed followed by depth of cut and feed per tooth. Cutting temperature for different tool's diameter was almost similar under the same rotational speeds and cutting conditions. Cutting tool temperature in peripheral milling was higher than in surface milling. Adhesion of the work material and chipping were the main wear mechanisms of the ball end mill in cutting sintered material.

This study deals with the influence of tool characteristics on the cutting edge temperature in turning case hardened steel. The cutting test is undertaken with the inserts which have different thermal conductivity and coating layer. The tool edge temperature is measured with a two-color pyrometer. The tool edge temperature increases with the increase in cutting speed. The higher thermal conductivity cutting insert causes lower tool edge temperature. The coating hardly affects the tool edge temperature. The white layer thickness increases with increasing cutting speed reaching a maximum at certain cutting speed and decreases with cutting speed.

Burr is formed at workpiece edge in most metal cutting process. These burrs make troubles on production lines in terms of added cost and time for deburring process. The purpose of this study is to investigate the influence of workpiece hardening on the burr formation in face milling of carbon steel AISI 1045. Before machining, laser hardening by CO2 laser is irradiated on the side face along the line where burr is expected to be formed. The laser irradiated area of carbon steel has high hardness and brittle characteristic in comparison with mother phase. In case of machining laser hardened workpiece, the burr height was smaller compared with standard steel. By controlling laser irradiation conditions, burr is not observed so that the chipping (negative burr) like chamfering is caused. From these results, it was clarified that laser hardening is effective to prevent burr formation and this technique can be applied to high efficiency processing.

This study deals with the influence of laser hardening for a carbon steel AISI 1045 on machinability in turning. Turning test was conducted for the purpose to clarify the influence of laser hardening for steel surface on the chip controllability and surface roughness. In turning laser hardened steel, continuous chip is broken in the laser hardened zone during cutting due to higher brittleness. The broken chips have spiral form and their length is approximately equal to those generated by less than 10 revolution cutting. The surface roughness shows slightly lower compared with non-laser hardened steel.

In order to manufacture the part of a small lot at lower cost and shorter lead-time, various techniques, such as a rapid tooling, reverse engineering and high speed milling, are proposed. Recently, milling-combined laser metal sintering system, which is the device of sintering the metal powder and milling the sintered metal with end mill at the one process, has been developed to produce the injection molding dies. In this report, the sintering characteristics of the metal powder used for rapid tooling with Yb fiber laser are described. Relationship between the scanning speed of laser beam and the width of sintered material on the different surface plate are investigated. Moreover, the cross section of sintered material is analyzed with EPMA and cutting force is measured by the dynamometer in the various conditions.As a result, it was shown that the suitable irradiation energy for laser sintering should be selected to obtain the good shaped structure, which is occurred the melting, the cohesion and the solidification of the metal powder repeatedly. The shape of sintered material is formed like a spherical in the conditions of too much energy supply, and not formed partially in the conditions of a little energy supply. The melted metal powder with the generated heat by laser irradiation alloyed with the plate surface on the process of the solidification. The specific cutting force of sintered material on the surface with sandblast is quite larger than that on the standard surface by the difference of the wetting of melted metal powder.

金沢大学理工研究域 機械工学系, In this research, Milling combined Laser Sintering System (MLSS) is used to make a sintered material. MLSS is a rapid tooling system using a fine metallic powder integrated with machining process whereby it can do laser sintering of fine metallic powder and also high-speed milling. This paper deals with the investigation of sintered material machinability by measuring its specific cutting energy and tool flank temperature. Carbon steel (JIS S55C) is selected as a standard steel. The effects of cutting conditions, laser consolidation energy density, powder consolidation mechanisms and unsintered powder on its machinability are measured. It is demonstrated that tool flank temperatures for all sintered materials are higher than JIS S55C. Low energy density for consolidation of metal powder increases the machinability of sintered materials. Cutting at the partially molten powder decreases the machinability of sintered material. Cutting with the existence of unsintered metallic powder surrounding the sintered material diminishes its machinability.

In drilling, the temperature of the cutting edges of a drill is measured using a two-color pyrometer with an optical fiber. A cemented carbide drill with a diameter of 10 mm is used as a cutting tool, and carbon steel, cast iron and aluminum die-cast alloy are used as work materials. The temperature distribution along the cutting edge of a drill is measured and the influence of spindle speed and feed rate on the tool temperature is investigated. The maximum tool temperature is observed during the drilling of carbon steel. The effect of oil mist supplied from oil holes in the drill on the tool temperature is examined and the result is compared to that in turning and end milling. The temperature reduction in oil mist turning is approximately 5%, while in oil mist end milling it is 10–15% and that in oil mist drilling is 20–25% compared to the temperature in dry cutting.

This study deals with the trial for improvement of chip controllability in turning with selective laser heat treatment for workpiece. Selective heat treatment for carbon steel JIS S45C was carried out with Nd:YAG laser which could be transmitted through an optical fiber and shows higher absorption rate against carbon steels than CO2 laser. In turning of these selective laser heat threatened carbon steel, the chip form changed regular curl from irregular curl and chip breakability was improved compared with non-laser treated carbon steel. Surface roughness was obviously smaller comparing with non-laser treated carbon steel. Especially in the case that the depth of cut was larger, the surface roughness was smaller. As for cutting force, the principal force was slightly smaller, but the thrust force and feed force were almost the same. The cutting temperature was slightly lower. The tool wear was almost same as that in the case of non-laser treated carbon steel.

In this study, a laser beam is used as a non-contact thermal dressing tool for a bronze bonded diamond wheel. The pulsed-Nd:YAG laser beam is irradiated on the wheel surface and the bond material partially removed by laser irradiation only. In order to efficiently remove the bond material, it is necessary to direct an air jet on the spot irradiated by the laser so as to blow away the molten binder before it solidifies again. Less damage of diamond particles such as micro-cracks or graphitization occurs. In grinding with a laser-dressed wheel, the grinding forces are almost the same as those for a conventionally dressed wheel. Consequently, effective laser dressing can be expected with the associated dressing conditions.

In this paper, the influence of oil mist on the tool temperature in cutting is investigated experimentally. The turning of a carbon steel with oil mist applied is performed, and the temperature of the alumina tool at the tool-chip interface is measured using a two-color pyrometer. The tool temperature in dry cutting at a cutting speed of 300 m/min is ∼1060°C, but it is ∼1000°C when oil mist is supplied. In intermittent turning, the oil mist has more effect on the tool temperature because it is supplied more efficiently to the tool-chip interface. In end milling with the oil mist applied, the tool temperature at the flank face is ∼580°C at a cutting speed of 400 m/min, though in dry cutting it is ∼660°C.

金沢大学理工研究域機械工学系, In this study, a new technique of in-process evaluation of a grinding wheel surface is proposed. Some specific wheel surfaces are prepared as references by the appropriate truing and/or dressing procedure, and grinding sounds generated by these wheels are discriminated by analyzing the dynamic frequency spectrum by a neural network technique. In the case of a conventional vitrified-bonded alumina wheel, the grinding sound can be identified in the optimum network configuration. Therefore, this system can instantaneously recognize differences in the wheel surface with a good degree of accuracy insofar as the wheel conditions are relatively widely changed. In addition, the network can perceive wheel wear because the grain tips are flattened as grinding proceeds and the grinding sound becomes similar to that of a wheel generated with lower dressing feed. The resinoid-bonded cubic boron nitride (CBN) wheel is also discriminable when a grinding sound in a higher frequency range is analyzed.

The water-solution type coolant is used instead of ordinary. oil type coolant and the effect of the coolant on the finishing is investigated experimentally. As work materials, titanium, titanium alloies and Ni-based alloy are used. Electrolytic in-process dressing is employed to promote the ability of metal removal because the water-solution type coolant is inferior to that of oil type one in the permeability. The specific cutting energy k s of these materials are compared with k s of a bearing steel in order to evaluate the machinability of the work materials. The results obtained are as follows. The superfinishing opera-tion using a water-solution type coolant is the effective method to finish the surface of these difficult-to-cut materials when the electrolytic in-process dressing is applied together. The suitable conditions in electrolytic dressing for each work material are obtained, and the titanium which has the highest adhesive property needs the strongest electrolysis among the work materials used in this study. The electrolytic-in-process dressing makes it possible to maintain the cutting ability of the finer grain size stone for a long time, and to obtain the mirror surface of Incoloy 800 with #8000 SD diamond stone.

This report deals with both microscopic and macroscopic behaviors of the CBN wheel surface during the cylindrical traverse grinding, which are closely related to the grinding performance. The microscopic behaviors are investigated by observing the cutting edges, and by measuring the cutting edge spacing and the depth of chip pocket with a newly developed equipment, the computer handling system of wheel surface. In the circumferencial wheel surface of starting side, the bond is removed rapidly and the wear, the fracture and falling-off of cutting edges occur within the initial stage of grinding, so that the depth of chip pocket and the cutting edge spacing increase rapidly to the certain value, respectively, corresponding to the grinding conditions, that is, the larger depth of chip pocket than that obtained with the usual method is required in this area. These phenomena are observed in the advanced stage of grinding as the position of wheel surface is apart from the starting side, and the large amount of stock removal is necessary at the opposite side of the wheel. The wheel shape during grinding changes in company with the behavior of cutting edges.