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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]

In recent years, collaborative robots able to work together with humans have become widespread in production sites and factory automation fields. In this context, the goal is to provide a production site where cooperative robots can share various types of tools with humans. However, we have not yet reached the point where collaborative robots and humans can share tools for advanced skills. Therefore, it is very important to investigate how a collaborative robot can control advanced tools requiring human skills and the processes for realizing such control. Musical instruments are some of the most difficult tools to handle. It is important to focus on musical instruments because they allow us to evaluate the robot's manipulation not only by evaluating its movements, but also by evaluating the resultant sound. In this study, we consider a flexible and large deformable musical saw as an unknown and advanced tool difficult for humans to manipulate. In a previous report, a support method for imitating a human was adopted and provided manipulation control based on striking sound feedback using a cooperative humanoid robot. In the present paper, the support method is improved at the tip of the musical saw to realize an advanced wrist motion. In addition, we discuss skillful manipulations based on striking sound feedback control while considering the positions and postures between the collaborative humanoid robot and musical saw. [ABSTRACT FROM AUTHOR]

Using computational fluid dynamics (CFD) technology, a stable manufacturing method for polymeric nanofiber non-woven fabrics based on an improved melt-blowing method and flash spinning is realized to achieve mass productivity. Subsequently, a method to predict filter efficiency using two production methods based on the effects of thickness, filling rate, and fiber diameter on filtration performance is developed to establish a filter design via CFD technology. CFD models featuring uniform fiber diameters are proposed. Next, the pressure loss and flow resistivity are calculated using CFD flow analysis software, as in a filter experiment. The proposed fiber diameter distribution model yields results similar to the experimental value, and the relationship among filling rate, fiber diameter, and flow resistivity is verified. The non-woven filter fabricated in this study demonstrates superior filtration properties, based on the results. Additionally, a method to satisfy both low pressure loss (low flow resistivity) and high filtration efficiency is discussed. Although the pressure loss increases, the filter yields a value below the standard for high-performance face masks, since the fiber diameter is on the nano-order. [ABSTRACT FROM AUTHOR]

In recent years, product sizes have decreased and products have become more multifunctional; process integration has been increasingly important for this purpose. Typically, laser hardening leaves an oxidised scale on the machined surface. This study aims to remove this oxide scale. Herein, we propose a laser hardening–forming process that combines laser hardening and laser forming. To successfully remove the oxide scale, we conducted a polishing process using nanofibers, which was compatible with numerical control (NC) and applicable to magnetic materials. This paper demonstrates the potential of integrating heat treatment, forming, and finishing by deploying an NC machine to construct origami engineering for thin plates. [ABSTRACT FROM AUTHOR]

Considered the characteristics of threading using a thread mill, which is an end-mill tool for threading using the helical interpolation motion of a machining centre for clarity.The tool tangential component force (principal cutting force) and radial component force acting on the thread mill during helical interpolation were measured using a piezoelectric dynamometer capable of measuring the four components of X-, Y-, and Z-directions and torque. In this report, a method to separate the thrusts using Equations (1)–(4) is proposed. Furthermore, the cutting force observed during thread cutting, conducted using the proposed method and a wireless holder, is analysed. Further, the phenomena that occur in rough cutting edges during thread cutting are validated. In addition, the analysis results of thread cutting are presented considering the relationship between the hardness of the work material and the cutting resistance. Finally, the measurement error between the wireless holder and the piezoelectric dynamometer and the consistency of each measuring machine are verified. [ABSTRACT FROM AUTHOR]

A five-axis machining center is known for its synchronous control capability, allowing complicated three-dimensional surfaces, such as propellers and hypoid gears, to be quickly created. Prior research has shown that it is necessary to improve not only the machined shape accuracy but also the machined surface roughness of free-form surfaces. Therefore, in this research, we aimed to maintain the feed speed vector at the endmilling point by controlling two linear axes and a rotary axis with a five-axis machining center to improve the machined surface quality. In previous research, we suggested reducing the shape error of machined workpieces (referred to as shape error in this research) by considering the differences in the servo characteristics of the three axes in the machining method. The shape error was significantly decreased by applying the proposed method, which uses a parameter (referred to as precedent control coefficient in this research) determined by calculation, rather than trial and error. Moreover, to maintain the feed speed vector at the endmilling point when machining complex shapes, a rapid velocity change in each axis is required, causing inaccuracy owing to torque saturation. The results of the experiments and simulations of previous research indicated that torque saturation can be evaluated via simulation. In this research, to reduce the shape error while avoiding torque saturation when movement has high angular velocity, we developed a theoretical method to obtain the most suitable precedent control coefficient of each axis by using a block diagram that considers torque saturation. Therefore, both shape error reduction and torque saturation avoidance can be realized by using the proposed method. [ABSTRACT FROM AUTHOR]

Planetary gear trains (PGTs) are widely used in many machines and are one of the most important mechanisms in hybrid and electric vehicles. Previous research, based on empirical knowledge gained from the automobile industry, indicates that high carrier-support stiffness and low ring-gear support stiffness are required to reduce ring-gear errors. Therefore, here, we evaluate the vibration characteristics of a PGT as a function of the support stiffness, which is varied by inserting urethane rubber into the driving shaft. We conducted experiments using a 2K-HV-type tester, which contains a coaxially rotating and revolving planet gear shaft based on a universal joint. This mechanism allows the observation of the inner workings of the mechanism with the use of a transparent acrylic carrier. We were able to detect the so-called "bounce" phenomenon consisting of a swaying motion when the rotation of the ring gear is reversed, and this result was confirmed by our internal observations of the mechanism. It is evident that the index of vibration increases due to the bounce phenomenon because the reversal of the ring gear causes a larger vibration than that of the carrier because the ring gear can vibrate without restraint, unlike the planet gear that is sandwiched between the sun and ring gears. Furthermore, the influence of the radial support stiffness of the driving shaft, load torque to the output shaft, and acceleration time of the reversing gear on the "bounce" phenomenon were evaluated. We found that a larger load torque corresponds to a greater difference depending on the acceleration conditions of the sun gear. During reversal, at the moment when the rotation speed is zero and rotation recommences, the ring gear exerts the maximum force, and the larger is the load torque, the greater is the effect of the difference in acceleration. [ABSTRACT FROM AUTHOR]

Because most industrial robots are taught using the direct teaching and playback method, they are unsuitable for variable production systems. Alternatively, the offline teaching method has limited applications because of the low accuracy of the position and posture of the end-effector. Therefore, many studies have been conducted to calibrate the position and posture. Positioning errors of robots can be divided into kinematic and non-kinematic errors. In some studies, kinematic errors are calibrated by kinematic models, and non-kinematic errors are calibrated by neural networks. However, the factor of the positioning errors has not been identified because the neural network is a black box. In another machine learning method, a random forest is constructed from decision trees, and its structure can be visualized. Therefore, we used a random forest method to construct a calibration model for the positioning errors and to identify the positioning error factors. The proposed calibration method is based on a simulation of many candidate points centered on the target point. A large industrial robot was used, and the 3D coordinates of the end-effector were obtained using a laser tracker. The model predicted the positioning error from end-effector coordinates, joint angles, and joint torques using the random forest method. As a result, the positioning error was predicted with a high accuracy. The random forest analysis showed that joint 2 was the primary factor of the X- and Z-axis errors. This suggests that the air cylinder used as an auxiliary to the servo motor of joint 2, which is unique to large industrial robots, is the error factor. With the proposed calibration, the positioning error norm was reduced at all points. [ABSTRACT FROM AUTHOR]