Papers by Author: Hiroo Shizuka

Abstract: This research proposes the application of laser forming to repair dents made in stainless steel sheets. Stainless steel sheets are widely used for the exterior coverings of trains or automobiles. When dents are made in an exterior sheet, it is necessary to detach the panel and strike the sheet from the inside with a hammer. This research indicates that dents were repaired by irradiating them from the outside with a laser beam. It is effective to repair dents without detaching the exterior sheet from the body of the vehicle. In the proposed method, a laser was scanned along the shape of the dent under the condition that the sheet bent by the temperature gradient mechanism or upsetting mechanism. In our experiments, circular dents were made in a 1-mm-thick SUS304 sheet. The laser was scanned along several circular scan lines on the circular dent with a diameter of approximately 20 mm. The depth of approximately 1.5 mm of the dent decreased by 85% using this technique.

Abstract: This paper deals with finish cutting of thermally affected layer on cemented carbide by a diamond tool in order to machine efficiently the carbide mold with high accuracy and good surface without a polishing. The microstructure of thermally affected layer left by EDM process was observed and analyzed by EPMA. Its hardness and thickness were measured. Subsequently, the cutting experiments were carried out by using a PCD tool and an ultra-precision cutting machine. The effects of the thermally affected layer on the surface roughness, the cutting force and the tool wear were investigated. As a result, it was confirmed that the cutting force decreased with an increase in the depth of cut. Furthermore, it was found that the tool wear and the surface roughness obtained by cutting the thermally affected layer were greater than those of the original workpiece.

Abstract: This paper describes an influence of the cutting condition on the tool performance and the hole shape accuracy in a deep-hole machining of stainless steel with small-diameter drill. The drilling tests were carried out by changing the feed, tool diameter and drill length in order to investigate the appropriate cutting conditions for drilling the holes with deep depth. The results indicate that the increase of the thrust force leads to the buckling of the drill and the work hardening of the workpiece causes the tool failure.

Abstract: In this research, deformation behavior of titanium sheet in laser forming was simulated. In preliminary experiments, we had carried out single-straight-line bending and investigated the relationship between the bended angle and the laser processing conditions. It was clarified that the bended angle formed by laser forming to the free edge became larger than the angle formed by laser forming to the center, even if laser scanned in same processing conditions. To investigate the influence of the free edge, heat-transfer analysis and structural analysis were carried out by using a finite element analysis software ANSYS 11.0. It was confirmed that the bended at the free edge became large because the plastic strain of the lower surface has decreased greatly more than the strain of the upper surface decreases.

Abstract: This paper describes the effect of the tool tilting angle on the tool wear and the surface roughness in micro ball end milling. The cutting tests of hardened stainless steel were carried out by using of the micro ball end mill with radius of 100mm under the conditions of tilting angle from 0° to 45°. The spindle speed was fixed in a constant of 120,000 min^-1. The feed per tooth, axial depth of cut and radial depth of cut were also fixed. The flank wear, the surface roughness and the cutting force were investigated. As a result, the maximum width of flank wear of the micro ball end mill tended to decrease with an increase in the tilting angle of spindle. The surface roughness became almost constant not depending on the tilting angle of the spindle.

Abstract: The effects of cutting conditions on the surface roughness in a micro-end-milling process of a mold material are described in this paper. Micro-end-milling operations were performed under different cutting conditions such as feed rate and depth of cut, in order to investigate the factors that had the greatest influence on the finished surface during micro-end-milling. It was revealed that the surface roughness begins to deteriorate when the radial depth of the cut exceeds the tool radius. In addition, it was found that this phenomenon is peculiar to micro-end-milling processes.

Abstract: This study deals with the cutting characteristics of titanium materials when milled by a small-diameter end mill, or a micro end mill. It is well known that titanium is difficult to cut by conventional means. However, its cutting characteristics have not yet been made sufficiently clear in cases where a micro end mill less than 1 mm in diameter is used. This study chiefly involves the experimental investigation of tool wear and surface roughness of micro-end milling of Ti-6Al-4V. The findings were that tool wear did not increase much when the cutting speed was increased from 50 m/min to 200 m/min. Furthermore, the cutting force required to cut decreased at high speeds and during wet cutting. In wet cutting, the surface had a roughness (Rz) of only 0.3 μm at 200 m/min in contrast to 0.6 μm at 50 m/min.

Abstract: This paper deals with laser forming procedure to bend pure titanium sheets along arbitrary curved shape. In preliminary experiments, single straight-line bending was carried out and the relationship between bending angle and laser irradiation conditions was investigated. It was clarified that the bending angle was able to control with scanning velocity and the number of scanning passes. With use of obtained experimental formula for the bending angle, we tried to bend the Ti sheet along given parabola shape with a multi straight-line bending. The experimental result was corresponding to the target shape well. This paper proposed a laser forming procedure for curved shapes which include both convex curve and concave curves. It was confirmed that it was able to curve a titanium sheet along arbitrary curved surface with proposed method.

Abstract: This paper describes the cutting characteristics of lithium niobate, which is used for surface acoustic wave type micropumps, regarding the formation of micro grooves by direct cutting. Since lithium niobate is a brittle material with a strong crystal orientation dependency, significant differences were observed in the characteristics of the finished surface according to different directions of cutting. The ductile mode cutting of lithium niobate was found to be feasible with cutting depths of approx. 5 μm or less. Also, results of the study show the feasibility of the formation of minute grooves through the cutting of lithium niobate, using milling with an end mill.