Carbon fiber reinforced plastics (CFRP) have been used for various applications such as aerospace, automobiles, and sporting goods due to their superior properties, and the demand for through-hole drilling of CFRP is increasing. A novel hybrid helical milling technique applying ultrasonic vibration and cryogenic tool cooling method is proposed in this paper, as an effective machining method for CFRP. To investigate the effects of ultrasonic-vibration-assisted machining and cryogenic tool cooling method, cutting performance evaluations based on thrust force, machining accuracy, and tool wear were conducted in this study. The results of the cutting tests clearly indicated that the proposed cutting method provides reductions in thrust force, and suppresses delamination at the machined surface.

Carbon fiber-reinforced thermoplastics (CFRTP) are just beginning to be utilized for various applications such as aerospace, automobiles, and sporting goods in place of CFRPs, and the demand for through-hole drilling of CFRTPs is increasing. In this study, the machinability in drilling of CFRTPs under various conditions was experimentally analyzed in terms of the material properties, and a feasibility study of ultrafast feed drilling was conducted. The results showed that delamination at the outlet surface can be significantly suppressed during high rotational drilling when the feed rate is set to more than 3000 mm/min. By providing appropriate drilling conditions to prevent polymers in CFRTPs from softening, ultra-fast drilling of CFRTPs was successfully achieved under dry conditions.

In recent years, many composite materials have been used in industry. Among such materials, the demand for carbon fiber-reinforced plastic (CFRP) is increasing. Although CRFP is used in various fields such as the aerospace industry, automotive industry, and sports equipment because of its light weight and high strength, it has poor production efficiency. Thus, carbon fiber-reinforced thermoplastic (CFRTP), with characteristics similar to CFRP but higher in production efficiency, has attracted attention in areas such as the automotive industry. Because CFRTP is used as a structural element, it is usually drilled to allow connection to other parts. However, it is a difficult-to-cut material requiring the development of a high-accuracy, high-efficiency processing method. This study proposes high-feed-speed processing as a method that achieves high-quality drilling at low cost. The cutting temperature was estimated to verify the effect of the high-feed-speed processing method, and processing conditions that prevented delamination and burring were identified.