Papers by Author: Hiromi Isobe

Abstract: This paper reports the stress distribution inside the workpiece under ultrasonic vibration cutting (UVC) condition. Many researchers have reported the improvements of tool wear, burr generation and surface integrity by reduction of time-averaged cutting force under UVC condition. However general dynamometers have an insufficient frequency band to observe the ultrasonically varying processing phenomena induced by UVC. In this paper, stress distribution inside the workpiece was observed by combining the pulse laser as light source synchronized with ultrasonically vibrating cutting tool and the photoelastic method. The one shot of pulse laser with pulse width of 15nsec visualizes an instantaneous stress distribution. Sweeping the phase of emission against to ultrasonic oscillation, 360 frames for 35.7μs, one period of ultrasonic oscillation, are captured. Because UVC induced an intermittent cutting condition, the stress distribution changed periodically and disappeared when the tool leaved from the workpiece. The ideal chip-generating period is calculated by relative motion between tool and work. We found that the actual chip-generating period was extremely longer than ideal period.

Abstract: Ultrasonic cutting is a technique that can improve machinability such as fine surface, reduce tool worn out and etc. To improve processing speed of ultrasonic cutting is difficult due to the effects of tool oscillation are invalidated when cutting speed exceeds maximum tool oscillating velocity. In this study, high speed principal direction ultrasonic turning experiments for soft magnetic stainless steel were carried out to investigate effects of cutting speed and products quality. Surface roughness, chip worn out and built up edge were investigated in this study. In case of ultrasonic turning, tool worn out and built up edge generation were reduced compare with ordinary turning. High speed ultrasonic cutting can improve cutting performances in phase of turned surface quality, cutting force and processing speed.

Abstract: Ultrasonic cutting is a technique that can improve machinability such as fine surface, reduce tool worn out and etc. To improve processing speed of ultrasonic cutting is difficult due to the effects of tool oscillation are invalidated when cutting speed exceeds maximum tool oscillating velocity. In previous report, high speed principal direction ultrasonic turning without thrust direction vibration experiments for stainless steel were carried out to improve processing speed and products quality. In ultrasonic turning, tool worn out and built up edge generation were reduced compare with ordinary turning. Fine surface without thrust direction periodically cut marks were obtained in ultrasonic turning experiments. In this study, the effects of chip breaker shape and insert material were investigated. Surface roughness, chip worn out and built up edge generation were investigated in this study.

Abstract: Recently, technologies for medical inspection have been increasing rapidly. In biomedical industry, a demand of Micro Total Analysis System (μ-TAS) has been growing which used in automatically inspection for chemical analysis. The μ-TAS have micro passageway which is constructed by many fine micro holes. Final polishing by skilled workers are carried out after drilling to obtain smooth surface of holes. Because new manufacturing technique is required instead of skilled workers, it increases productivity and cost performance of the μ-TAS. Drilling technique with low temperature environment around cutting edge is required to prevent heat crack or adhesion on holes surface, because acrylic resin heats sensitive material. In this study, ultrasonically assisted micro drilling technique is proposed to increase productivity of μ-TAS and quality of micro holes. Ultrasonically assisted machining has effective technique to improve machinability, e.g. reduce cutting force, increase chip removability and machined surface quality. This paper describes the cutting characteristics of ultrasonically assisted micro-drilling for acrylic resin to employ the μ-TAS manufacturing to solve above problems.

Abstract: Cutting edges protrusion properties for cutting tools have significant effect of grinding surface finish and its characterization is crucial in understanding tool-work interaction. Existing definition of reference datum in surface topography analysis is not suitable for abrasive tool cutting edges protrusion characterization in relation to tool-work interaction. This paper proposed Surface Reversal Method for the reference datum determination in the characterization of cutting edge protrusion on flat end face of cylindrical cutting tool meant for vertical grinding. Fabricated cylindrical artefact is used to test the theory, accompanied with a specially made fixture. Performance of the proposed method is evaluated based on the repeatability of step height measurement on the topography component and inclination of the reference datum which extracted from primary surface measured by laser confocal scanning microscope. The proposed method provides better datum definition than conventional method for height measurement of the abrasive tool topography in relation to the tool-work interaction.

Abstract: This study investigated phenomena of ultrasonic cutting in case of high speed conditions. Ultrasonically assisted cutting techniques were developed by Kumabe in 1950’s. He found “critical cutting speed” that limits cutting speed to obtain ultrasonically assisted effects and is calculated by frequency and amplitude of oscillation. In general, ultrasonically assisted cutting is not suitable for high speed cutting conditions because the effects of ultrasonically applying are canceled due to tool contacts with workpiece during cutting operation. Present ultrasonically assisted cutting cannot increase cutting speed because cutting speed is limited by above reason. And ultrasonically assisted cutting cannot improve productivity due to long processing time. We conducted high speed ultrasonic cutting, maximum cutting speed of this research was 160m/min which is higher than general critical cutting speed. Workpiece material is JIS SUS304 stainless steed and cemented carbide tool inserts were employed in this research. In ordinary cutting, generate terrible built up edge on to tool rake face. In case of low amplitude ultrasonic cutting, tool rake face hasn’t built up edge and periodically marks by ultrasonic oscillation were remained on the surface. Cutting phenomena of ultrasonic cutting is different compared with ordinary cutting conditions.

Abstract: The grinding performance is strongly affected by grain condition. Especially loading directly raises the grinding force, reduces tool life and deteriorates accuracy of machining. In this study, ultrasonic exciter which applies vibration energy on grinding fluid was developed. The resonant frequency of 28kHz. The exciter is set between the fluid supplying nozzle and grinding wheel. The discharging grinding fluid from the nozzle is supplied to grinding wheel between the teeth of comb-shape horn. The performance is verified on surface grinding machine with vitrified WA grinding wheel. It was experimentally demonstrated that the excited grinding fluid prevented the loading and improved the surface roughness even for grinding of aluminum. And also improvement of surface roughness was recognized on alloy tool steel.

Abstract: A drill processing for the difficult to cut material such as ceramics, hardened steel, glass and heat-resistant steel is widely requested in the industrial world. Furthermore the drilling process becomes more and more difficult in the case of that the requested hole diameter is less than one millimeter. In order to achieve requirements for drilling process, ultrasonically assisted machining is applicable. Ultrasonic vibration assisted machining techniques are suitable to machine difficult-to-cut materials precisely. The ultrasonic vibration assisted sub-millimeter drilling process reduces the cutting forces and prevents severe wear of tools. However, it is difficult to observe directly the effect of vibration action because the process of ultrasonic drilling is dynamic instantaneous and micro cutting process. In this report, high speed camera with appropriately arranged polarized device realized the visualization of process of ultrasonic drilling based on the photoelastic analysis. For the conventional drilling, the stress distribution diagram showed the intensive stress occurred under the chisel and side wall. On the other hand, the ultrasonic drilling produced lower and stable cutting force and decreased the tool temperature.

Abstract: This study investigated phenomena of ultrasonic cutting in the case of high-speed conditions. Ultrasonically assisted cutting techniques were developed by Kumabe in the 1950s. He found a critical cutting speed that limits cutting speed to obtain ultrasonically assisted effects and is calculated by frequency and amplitude of oscillation. In general, ultrasonically assisted cutting is not suitable for high-speed cutting conditions because the effects of ultrasonic application are cancelled due to tool contacts with the workpiece during the cutting operation. Present ultrasonically assisted cutting cannot allow increased cutting speed because cutting speed is limited by a critical cutting speed that is less than that compared with general cutting speed. And ultrasonically assisted cutting cannot improve productivity due to long processing time. We conducted high-speed ultrasonic cutting, and the maximum cutting speed in this research was 300 m/min which is higher than general critical cutting speed. The workpiece material was A5056 and cemented carbide tool inserts were employed in this research. Without ultrasonic oscillation, machined surface retained some built up edge and surface roughness is 28 μmRz. In the case of ultrasonic cutting, surface hasnt built up edge and periodically marks due to ultrasonic oscillation remained on the surface. The roughness of conventionally cut surface is better than in ultrasonic cutting. The cutting phenomena of ultrasonic cutting are different compared with those under conventional cutting conditions.

Abstract: Drill processing of difficult-to-cut materials such as ceramics, hardened steel, glass and heat-resistant steel is widely required in the industrial world. Furthermore the drilling process becomes more and more difficult in the case of hole diameters less than one millimetre. In order to achieve the requirements for the drilling process, ultrasonically assisted machining is applicable. Ultrasonic vibration assisted machining techniques are suitable for machining difficult-to-cut materials precisely. However, the cutting process of ultrasonic drilling has not been clarified. It is difficult to observe directly the effect of vibration. The aim of this study is to observe the dynamic, instantaneous and micro cutting process. In this report, a high-speed camera with a polarized device, which is appropriately arranged, realized the visualization of the process of ultrasonic drilling based on photoelastic analysis. For conventional drilling, the stress distribution diagram showed that the intensive stress occurred in limited areas under the chisel because the chisel edge of the drill produces large plastic deformation. On the other hand, the ultrasonic drilling produced spread stress distribution and a stress boundary far away from the chisel. The photoelastic analysis showed the explicit difference of drilling processes.