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This study investigated the effects of simultaneously machining pilot holes and threads, as well as the accuracy of thread machining after pilot hole drilling. In addition, the thread machining of S50C and SKD61, which are work materials with different hardness, was also examined. Furthermore, a smart machining method for thread milling using helical interpolation was developed by monitoring cutting data using a wireless holder. The results show that the proposed monitoring method is effective for improving the accuracy of thread machining using helical interpolation motion of the threading tool. Moreover, this study discussed the differences in results due to the presence or absence of pilot holes. Finally, the influence of the hardness of the work material on the results was analyzed. [ABSTRACT FROM AUTHOR]

A five-axis machining center (5MC) is capable of synchronous control, which makes it a feasible tool for quickly and accurately machining complicated three-dimensional surfaces, such as propellers and hypoid gears. Recently, the necessity of improving both the machined shape accuracy and the machined surface roughness of free-form surfaces is growing. Therefore, in our previous study, we aimed to maintain the feed speed vector at the end-milling point by controlling two linear axes and a rotary axis of the 5MC to improve the quality of the machined surface. Additionally, we developed a method for maintaining the feed speed vector at the end-milling point by controlling the three axes of the 5MC to reduce the shape error of the machined workpieces (referred to as the shape error herein), considering the approach path of the tool determined via calculation. However, a high machining force at the start of the workpiece cutting was observed and the factor contributing to this phenomenon was not determined, although this phenomenon leads to a shape error to a certain degree according to the machining condition. In this study, the main objective is to suggest a method to reduce the machining force at the start of the workpiece cutting and shape error. Hence, we develop a theoretical method to estimate the machining force by using an instantaneous cutting force model, which considers the synchronized motion of two linear axes and a rotary axis of the 5MC. Subsequently, we determine the most suitable approach path of the tool considering the prediction of the machining force. The results of this study indicate that the machining force can be estimated by applying an instantaneous cutting force using the feed per tooth and machining angle, and that both a high machining force at the start of the workpiece cutting and shape error reduction can be realized by using the proposed approach path of the tool. [ABSTRACT FROM AUTHOR]

In this study, an existing superfinishing method used for polishing glass surfaces was refined using a five-joint closed-link compact robot with fixed abrasive grains. In previous studies, a voice coil motor was used to control the constant-pressure pressing force while maintaining the polishing force for a relatively short period. However, maintaining the polishing force for long periods is imperative for achieving a high-quality polished surface. Thus, in this study, a strain gauge load cell was adopted in addition to a conventional piezoelectric force sensor to maintain the polishing force for a long period. First, the amounts of DC drift of the piezoelectric force sensor and strain gauge type load cell were compared to confirm the necessity of signal processing as well as the compatibility of long-term force measurement and high-frequency vibration measurement by application. Further, a method was proposed in which the change in the pressing force was recorded from the connected sensor; when the pressing force fluctuated, chatter vibrations were determined to occur, and the pressing force was temporarily set to 0 N. This method could obtain a better polished surface than the proportional-integral-differential (PID) control, which simply controls the pressing force at a constant value. Finally, chatter vibrations could be determined by detecting high-frequency sounds using a sound level meter. Notably, a finely polished surface could be obtained. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced plastic (CFRP) is a lightweight material with exceptional mechanical properties such as high specific strength, high specific modulus, and retained fatigue strength. It exhibits outstanding characteristics derived from its carbon content such as electrical conductivity, low thermal expansion, chemical stability, and high thermal conductivity. These unique features make CFRP a highly versatile material. It can be extensively used across various industries, offering advantages over steel, aluminum, and glass fiber reinforced plastic. Moreover, its anisotropic nature allows for innovative design possibilities, providing different mechanical properties for different fiber orientations. The increasing demand for CFRPs, particularly in the aerospace and automotive industries, is attributed to their high reliability and design flexibility. Consequently, the requirement for efficient and high-quality CFRP processing techniques has led to numerous studies focusing on trimming and hole drilling of CFRP parts. Previous research has also highlighted the significant impact of processing temperature on the quality of CFRP and other fiber reinforced plastics, such as aramid fiber reinforced plastic. However, many existing reports are limited to specific processes such as trimming or hole drilling, without addressing broader concerns such as tool wear, burrs, fiber damage owing to heat, or the lack of multi-purpose cutting tools suitable for CFRP when considering tool costs. In addition, the aerospace industry demands precise hole drilling for thousands of holes, facilitating assembly with rivets or screws; this requires high-precision hole drilling processes. To address CFRP hole drilling challenges, this study proposes and develops a cBN electroplated ball end mill to enable an efficient and high-quality hole drilling in CFRPs. As machining demands evolve with diverse workpiece materials, technological innovations are continuously being sought in hole drilling processes, exploring alternatives beyond conventional drilling such as employing end mills and enhancing tool functionality. In this study, we employed a ball end mill and helical interpolation motion to tackle CFRP hole drilling. The delamination occurring at the exit side of the drilled holes was investigated using strain gauges. Additionally, finite element analysis was employed to compare and analyze experimental results, leading to guidelines for an efficient and high-quality hole-drilling approach that balances productivity and workpiece integrity. We achieved high-efficiency hole drilling while maintaining the quality by adjusting the cutting parameters under conditions that prevent delamination. The proposed cBN electroplated ball end mill offers promising potential for advancing CFRP processing methods, addressing the growing demand for this exceptional material in various applications. [ABSTRACT FROM AUTHOR]