Papers by Author: Heisaburo Nakagawa

Abstract: This paper proposes a novel process strategy for micro-cutting edge fabrication. Micro-cutting edges need a hardening process for the ridgeline parts that requires abrasive resistance, as well as edge sharpness and shape accuracy, based on their applications. Micro-cutting edge shapes also vary greatly in ridgeline profile and section. The proposed method is shape fabrication after laser hardening, which easily addresses these issues. In the present paper, effects of the proposed method are discussed and the results of a demonstration test are introduced.

Abstract: Fundamental characteristics in the micro drilling of carbon fiber reinforced plastic (CFRP) plates are investigated in the present paper. When micro drilling with a high-speed spindle, cutting forces during drilling, such as thrust force and torque, were measured by high resolution dynamometers and drill temperature was monitored by thermography. Comparing the experimental results of CFRP with that of drilling glass fiber-reinforced plastics (GFRP) revealed some unique tendencies. The cutting forces and drill temperature increased drastically. Moreover, drill wear rapidly accelerated. The tool life of CFRP plate drilling is much shorter than that of other plates.

Abstract: In our previous study, it has been shown that improvement of the adhesive strength and substrate hardness of ceramic coated steels without compromising the film hardness can be achieved by applying laser quenching. In the present research, in order to demonstrate further development of this method, the fracture strength of laser-irradiated ceramic thin films (CrAlN, TiAlN and CrN) was investigated by sphere indentation testing. To prevent heat-induced changes in the substrate hardness, a cemented carbide WC-Co rather than steel was used as substrate material. While the fracture strength of each film decreased significantly through furnace heat treatment, it remained almost unchanged in case of the laser irradiated films. Laser quenching has been shown to effectively reduce the fracture strength loss of the ceramic thin films in coated steels.

Abstract: This paper proposes a novel manufacturing process of a fine mesh filter screen with a pulsed laser. The fine mesh filter screen, made of stainless steel, has many small diameter holes with high aspect ratio and fine pitch. In the conventional process, an electron beam drills in a vacuum. However, this is very costly because of the expensive equipment required and batch process. Therefore, a laser drilling process for small diameter hole drilling in air with higher flexibility was proposed. The post-processes after the laser drilling completed the fine mesh filter screen.

Abstract: This paper describes the laser hardening of micro-cutting edges using an on-machine heat treatment system with a YAG laser. Various laser conditions were evaluated to perform laser quenching on a machine tool without melting at the edges. We also investigated the influence of the motion accuracy of the machining center on the quenching characteristic of micro-cutting edges after laser irradiation. We clarified that we could quench both the straight and curved corner parts by arranging proper laser irradiation conditions considering the motion accuracy of the machining center.

Abstract: In this study we attempted to suppress chatter vibration in end-milling of austenitic stainless steels with an end-mill having different helix angles. We showed there were two types of chatter vibration in end-milling with a conventional end-mill with regular helix angle. The two types of chatter vibration depend on the cutting speed. We detected these two types of chatter vibration by the developed monitoring method using laser Doppler vibrometers. We classified the two types of chatter vibration according to chatter generating tendency, frequency and vibration mode. We showed that chatter vibration generated at lower cutting speeds was regenerative chatter vibration. On the other hand, chatter vibration generated at higher cutting speeds was another type. We showed that a end-mill with different helix angles could prevent generative chatter vibration at lower cutting speeds and was also effective in suppressing chatter vibration at higher cutting speeds.