Papers by Author: Keiji Yamada

Abstract: It is well known that the surface roughness in turning consists of the theoretical roughness, vibration in the depth of cut direction, and overcutting by adhered work material. Some of authors had already proposed the method to calculate surface roughness components. In this method, the approximate arc was used as a representative tool contour of the tool contour to dividing roughness curve into each feed marks. The arc was defined by the height of the intersection of the measured tool contours set at feed intervals horizontally. However, when the boundary wear occurred in the finished surface formation area, the arc defined by the height of the intersection sometimes didn’t agree with theoretical roughness obtained by the measured tool contours set at feed intervals horizontally. As a result, there was concern that the difference affected the prediction reliability of tool edge contour position during cutting. Therefore, both of theoretical roughness and approximate arc of the measured tool contour were defined by the peak point of the measured tool contours set at feed intervals horizontally. Additionally, the representative tool contour was also defined by the different arcs to adopt the asymmetry of tool wear. Using the newly representative tool contour, the reliable roughness components could be calculated regardless of the tool pattern.

Abstract: In this study, the transition of cutting force in the tangential and radial direction during one cut was investigated in milling of AISI-1045, AISI-304, and Ti-6Al-4V with a TiN coated carbide throw-away insert. In the case of 1045 and Ti-6Al-4V, there was not obvious difference in tangential forces between up-cut and down-cut. However, up-cut showed larger radial force than down-cut in any material. In down-cut, tangential force showed almost the same regardless of radial depth of cut. 304 and Ti-6Al-4V caused larger radial force with the increase of radial depth of cut at the same cut chip thickness.

Abstract: In this paper, preheating temperature was investigated for the laser assisted machining (LAM) of Inconel 718 under different conditions for the milling test. The experimental results show that the requirement of laser power for the particularly preheating temperature proportionally increased with the table speed. The resultant cutting force for sufficient shearing work material in LAM was lower than conventional machining (CM) approximately 11, 21 and 28% for the cutting speed of 30, 50 and 75 m/min, respectively. The tool wear in LAM could be improved at relatively high cutting speed of 75 m/min and the hardness of machined surface in LAM was slightly higher than CM.

Abstract: In this study, the difference of finished surface roughness and feed mark shape in lubricity of the cutting fluids were investigated in turning SUS440C. In the cutting speed of 20m/min, the oil having excellent oiliness caused the smallest finished surface roughness among the tested cutting fluids at the feed rate of 0.1mm/rev, while, the oil having high extreme pressure property was best at the feed rate of 0.2mm/rev. The feed marks were hardly recognized at any conditions. In the cutting speed more than 20m/min, the finished surface roughness in any lubricant conditions showed almost the same or slightly larger compared with that in dry conditions. The feed marks were recognized, and the transcription of cutting edges shape under wet conditions trended to be the same or worse than dry conditions.

Abstract: This study investigated the cutting characteristics of electrodeposited diamond core drill when used to drill a CFRP under wet condition. The effects of different tool shapes, grain sizes and feed rates were examined. A normal core drill, an eccentric with slits core drill (E.S.), and an eccentric with slits and chamfers core drill (E.S.C.) were used. The normal core drill had the shape of a hollow cylinder. The E.S. core drill had the inner cylinder shifted from the center of this tool and slits in the bottom of this tool. The E.S.C. core drill had chamfers on the periphery of this tool. The normal core drill caused severe workpiece core jamming even at 1st hole drilling, and its electro-deposited area was covered entirely by adhered chips. In the case of the E.S. core drill and E.S.C. core drill, the workpiece core did not jam and the thrust force was smaller than that of the normal core drill. The effect of chamfers was little. The E.S.C. core drill with #200 caused smaller surface roughness than that with #100. However, the thrust force was two times larger, and the delamination was observed at the exit point of the hole. In the lower feed rate per revolution the better surface roughness and the lower thrust force were obtained irrespective of the tool shape while the cutting speed showed little effect.

Abstract: In this study, tool edge temperature was measured by a two-color pyrometer with an optional fiber. During one revolution of spindle, the tool edge passes over the fine hole at workpiece after cutting workpiece. An optical fiber inserted into the fine hole transmits infrared ray radiated from tool edge to two detectors with different spectral sensitivities. One peak signal from each detector can be obtained by each spindle revolution. The tool edge temperature can be calculated by taking the ratio of outputs from these two detectors. The relation between cutting heat calculated from cutting force and tool edge temperature was discussed. The tool edge temperature at the same cutting heat could be compared. The wet cutting condition caused lower tool edge temperature than the others at the same cutting heat. MQL and dry showed almost same tool edge temperature. The dispersion of tool edge temperature in wet cutting is wider than that in dry cutting and MQL cutting.

Abstract: This study reports an experimental investigation about the wear behavior of TiN and TiCN coated carbide tools during the face milling of pearlitic and ferritic ductile cast iron. Pearlitic ductile cast iron caused the highest cutting forces and flank wear in both TiN and TiCN coated tools. Due to its protective effect, the TiCN coated carbide tool outperformed the TiN coated carbide tool regarding flank wear. The main issue when face milling ferritic ductile cast iron with TiN coated tools was notching wear. The principal reason for notch wear was pointed as adhesive wear caused for the high tendency of ferrite to adhere on the tool. The results demonstrated that the TiCN coating did not showed notching wear when face milling ferritic ductile cast iron, therefore a good choice of coating material can prevent notching wear.

Abstract: The surface of worn dies are often machined to remove the worn layer and then to re-form its shape. But, in machining operations for hardened materials, the high cutting force sometimes yields bending deflection of low stiffness tools, and results the decrease in productivity and accuracy.In this study, surface treatment by pulsed laser is applied for the high hardness materials to improve the machinability in the machining operation. Die steels are used as work material machined with ball endmills of carbide in the experiments where the cutting force and the actual depth of cut are measured to obtain the specific cutting energy and to evaluate the machinability. In endmilling operations of the nitrided die steels, the actual depth of cut is decreased by the bending deflection of endmill. However, the surface treatment with laser moderates the decreasing of the actual depth of cut. It is confirmed that the surface of workpiece pre-treated with laser has larger roughness than un-treated ones, and the specific cutting energy is decreased by laser surface pre-treatment.

Abstract: In this paper, a new truing method is proposed instead of the conventional mechanical truing that has low truing rate for metal bonded diamond grinding wheels. In the proposed method, the metal-bond diamond grinding wheel is rubbed by a steel truer rotating at high speed. Generated frictional heat increases the oxidization and the diffusion of carbon into the steel truer, then diamond grains are thermally attrited on the wheel surface, so that the machinability of wheel is improved. Subsequently, high truing rate is achieved by mechanical truing with abrasive stones. These experiments are conducted using bronze bonded diamond abrasive stones and stainless steel truers, and the relation between truing resistance, truing temperature, and truing rate are investigated. The truing temperature is measured using the thermo couple embedded in the truer. The thermo couple consists of the steel wire embedded and the bronze which is the bonding material of the abrasive stone. The surface profiles of abrasive stones are measured by scanning stylus before and after truing, then the removal volume of abrasive stones is derived from these profiles. Truing rate is also obtained from the removal volume and the truing time. Experimental results for diamond abrasive stones are as follows: The waviness of bronze bond is decreased by proposed truing method. Truing rate is increased as truing resistance and truing temperature increase.

Abstract: Behavior of the material adhered to the cutting edge of a cermet insert was evaluated based on the profile of the machined surface in continuous turning of an austenite stainless steel SUS304. Height of the adhesion material decreased rapidly with increase of the cutting speed from 10m/min to 20m/min. The behavior of the adhered material was more stable than we expected. The adhered layer near the cutting edge was very stable, while the growth or breakage of the adhered material happened on the surface of the stable layer.