Papers by Author: Koichi Okuda

Abstract: Experiments were conducted with the main objective of improving the precision of drilling small-diameter, deep holes in austenite stainless steel (JIS SUS304). In the experiments, the step feed amount, rotation speed, and feed rate were varied and the thrust force and cutting temperature were measured to investigate the effect of cutting conditions on hole properties in drilling small-diameter deep holes. The results show that a combination of step feed amount and feed rate can reduce thrust force and drilling time, and that making the step feed small can suppress the cutting temperature.

Abstract: This paper deals with the characteristics of tool wear in small end milling of nickel-titanium alloy which is used as a medical material. Cutting experiments were carried out by varying the axial relief angle of an end mill of a diameter of 0.5 mm from 0 to 15 degrees with a step of 5 degrees, and tool wear and surface roughness was evaluated. The result revealed that tool wear of a small end mill with an axial relief angle of 0 degree was smaller by 60% than that of 15 degrees, suggesting that tool wear is reduced more with a smaller axial relief angle.

Abstract: The chip formation mechanism during precision cutting of metallic glass (Zr₅₅Cu₃₀Ni₅Al₁₀ at%) was investigated around the glass transition temperature (673 K). Orthogonal cutting of metallic glass are conducted on a fly-cutting machine at various cutting speeds. The new surface of the chips was slightly shiny while the free surface exhibited lamellar slip structure. The cutting temperature was a proportional to the cutting ratio and chip shear angle. The surface integrity worsened with an increased flow of cutting chip due to an increase in the cutting speed. An increase in the cutting temperature caused the chips formation to change from flow type chips to discontinuous chips. When the cutting speed exceeded 300 m/min, the shear angle increased while the shear pitch of the chips decreased. It appears that when the cutting temperature exceeded the glass transition temperature, the strength of the metallic glass decreased and the ductility mode changed due to viscous flow.

Abstract: In this study, it is discussed how the cutting conditions for drilling deep holes in austenite stainless steel affect the machining accuracy of the hole straightness and the cutting temperature rise. As a result, it is possible to reduce the thrust force and make the machining time short by the combination of the step-feed amount and the feed rate. By changing the drill in incremental step from short drill length to long drill length, the straightness was improved. It was also found that the temperature rise of the drill was around 10 K regardless of the cutting speed when the small step-feed amount of 10 μm was given.

Abstract: In this study, the screw cutting experiments of stainless steel 15-5PH was carried out by employing the tapping center in order to investigate the tool damage of threading tap tool. Mainly, the effect of the machining conditions and the ground chamfer shape of tap tool on the thrust force and the tool wear were discussed. As a result, it was found that the thrust force was strongly influenced by the ground amount of tap tool chamfer. Especially, large change of thrust force occurred when the tap tool engaged to the pilot hole and returned out of hole.

Abstract: The high-pressure coolant supply cutting has attracted attention from a viewpoint of chip evacuation and tool life. In this study, the influence of high-pressure coolant supply on chip shape, cutting force and tool wear were investigated. The tests were carried out during external turning of stainless steel with cemented carbide cutting inserts. The results suggest that the length and radius of the chips got shorter with high-pressure coolant supply, especially supply pressure more than 5MPa. The cutting force was increase slightly with high-pressure coolant supply. However the thrust force was decrease. The uniform flank wear and crater wear were reduced and tool life was improved by high-pressure coolant supply.

Abstract: This paper describes an influence of the cutting atmosphere and the carbon content on the surface roughness and tool wear in CO₂-blow cutting of carbon steel with a diamond tool. The cutting tests were carried out by changing the cutting atmosphere and carbon contains in order to investigate the effect on the improvement of surface finish and the reduction of tool wear. The results indicated that the roughness on finished surface was improved by cutting in CO₂ gas blow atmosphere and the tool wear increased with a decrease in the carbon content.

Abstract: This paper describes influence of the cutting conditions on the hole shape accuracy in deep-hole machining of stainless steel with small-diameter drill. The drilling tests were carried out by changing the step feed, the rotational speed and the feed rate in order to investigate the relationship between the straightness of the hole and the cutting conditions. As a result, it was found that the thrust force decreased with a decrease in the step feed amount and accordingly the straightness was improved. By changing the drill in incremental step from short drill length to long drill length, the straightness was improved.

Abstract: Data-mining methods using hierarchical and non-hierarchical clustering are proposed, which could help manufacturing engineers determine guidelines for deciding end-milling conditions. We have constructed a novel system that uses clustering techniques and tool catalog data to support the determination of end-milling conditions for different types of recent difficult-to-cut materials. In the present report, we especially focus on the cutting speed to estimate the performance of this system. A comparison with the conditions recommended by famous tool makers in Japan, reveals that our proposed system can be used to determine the cutting speeds for various difficult-to-cut materials. That is, milling experiments using a square end mill under two sets of end-milling conditions (conditions derived from the end-milling condition decision support system and conditions suggested by expert engineers) for difficult-to-cut materials (austenite stainless steel; JIS SUS310) showed that the catalog mining method is effective for deriving guidelines for deciding end-milling conditions at the beginning of the manufacturing stage.

Abstract: Recently, the demand for long life to industrial products has risen. The high strength alloy coating on necessary part can decrease a manufacturing cost for life prolongation. This study proposes a laser surface alloying method to form an Fe-Al alloy coating on a carbon steel. By laser heating to an Al foil stuck on the steel, the mutual diffusion proceeds and the Fe-Al alloy grows. The material property of the generated alloy is greatly different according to a heat treatment temperature. For example, Fe₃Al grows at 950 °C or more, and it has high toughness. A furnace heating effects the properties of inside of base material negatively. A high-frequency heating is not suitable for a local surface reforming. The laser processing is suitable for a local surface reforming. A defocused CO₂ laser was irradiated to the Al foil stuck on the steel block by the shot lining in various processing conditions. The metal structures of the laser irradiated area was observed, to search for the suitable processing conditions for alloy coating. It was clarified that a local Fe-Al alloy coat was able to be formed without change of the properties of base material by high speed laser scanning.