Papers by Author: Keisuke Hara

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 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. In this study, the effects of tool oscillating direction and tool chip shape for cutting properties of soft magnetic stainless steel were investigated. Cutting properties such as turned surface roughness, cutting force and ejected chip were compared.

Abstract: Acrylic resin is employed in optical products such as lenses and light guiding panels because it is highly transparent. Optical components made using acrylic resin require hand polishing by skilled workers to give a mirror finish to the surface of components in order to obtain the required optical properties. However, polishing takes a lot of time and two problems that exist are that skilled workers are aging and that young skilled workers are few in number. In this research, a method of ultrasonic milling of acrylic resin which would give a mirror-surface finish to acrylic resin products without the need for hand polishing by skilled workers was proposed.

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: This paper reports the stress distribution inside the workpiece under ultrasonic vibration cutting (UVC) condition. Many researchers have reported the improvement 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 processing phenomena caused by UVC. In this paper, stress distribution inside the workpiece during UVC was observed by combining the flash light emission synchronized with ultrasonically vibrating cutting tool and the photoelastic method. Instantaneous stress distribution during UVC condition was observed. Because UVC induced an intermittent cutting condition, the stress distribution changed periodically and disappeared when the tool leaved from the workpiece. It was found that instantaneous maximum cutting force during UVC condition was smaller than quasi-static cutting force during conventional cutting when the cutting speed was less than 500 mm/min.

Abstract: In this study, drilling for nickel alloy was carried out with ultrasonic vibrating carbide drill. Micro drilling is not an easy machining process due to remarkable tool wear, lower stiffness of the tool, difficulty of chip and heat removal from cutting point. Ultrasonic vibration assisted machining has effects of decrease of cutting force, generation of fragmented small chip, extension of tool life and improvement of surface integrity. In this study, ultrasonic vibration drilling for nickel super alloy was investigated to improve the tool life and productivity. The drilling for heat-resisting nickel super alloy was performed with the drill of 0.3mm in diameter. As a result, ultrasonic vibration drilling performed 302 holes with thickness of 2.0mm by applying minimum quantity lubrication to blow off the chips on the flutes. Ultrasonic vibration improved deviation of position of drilled hole because the hammering motion of the chisel edge results in good bite of tool on work surface. The productivity is directly depends on feed rate. The increasing feed rate from 6mm/min to 60mm/min dramatically reduced the tool life one thirtieth under conventional drilling condition. On the other hand, the ultrasonic vibration drilling reduced the tool life only one half.

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: 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.