Accurate prediction of tool life is crucial for reducing production costs and enhancing quality in the machining process. However, such predictions often rely on empirical knowledge, which may limit inexperienced engineers to reliably obtain accurate predictions. This study explores a method to predict the tool life of a cutting machine using servo motor current data collected during the initial stages of tool wear, which is a cost-effective approach. The LightGBM model was identified as suitable for predicting tool life from current data, given the challenges associated with predicting from the average variation of current values. By identifying and utilizing the top 50 features from the current data for prediction, the accuracy of tool life prediction in the early wear stage improved. As this prediction method was developed based on current data obtained during the very early wear stage in experiments with square end-mills, it was tested on extrapolated data using different end-mill diameters. The findings revealed average accuracy rates of 71.2% and 69.4% when using maximum machining time and maximum removal volume as thresholds, respectively.

This study investigates the influence of various cone cavity sizes on the flow characteristics and vibration behavior of the gas film flow field in aerostatic bearings with conical chambers under operational conditions. Utilizing a fluid-structure coupling approach, the vibration performance of the conical cavity shaft under external excitation is analyzed. Experimental tests are conducted to evaluate the vibration characteristics of the conical cavity bearing. To facilitate this, an aerostatic bearing test bench is designed to assess the shaft's vibration response under load impacts. The experimental results are compared with simulation outcomes to validate the reliability of the simulation model. The findings indicate that when the height of the conical cavity is 0.1 mm with a 50° angle, there is no supersonic airflow present in the bearing's internal flow field, and the vortex effect is minimal. Conversely, at a conical cavity height of 0.2 mm and a 50° angle, the amplitude of the shaft's response to external excitation is reduced, and the response time is notably short. Overall, the experimental results align well with the trends observed in the simulation data. This research offers valuable theoretical insights for the high-precision machining of aerostatic bearings.

The disc cutter is a main cutter to break rock in the Tunnel Boring Machine (TBM), but its abnormal state will increase the wear and may even cause the damages to the cutter head. But the cutter wear can only detect the limit of tool use, Therefore, real-time monitoring of the rotational speed of the disc cutter has become an urgent technical problem needed to be solved for TBM. This paper analyzes the disc cutter’s structural feature, and the periodic characteristics of disc cutter presented in the rotation process. Then, a monitoring system of disc cutter rotation speed is proposed based on the wear of the disc cutter detected by the eddy current sensor. The wear signal of disc cutters is sampled at a certain period for a long time. Through Fast Fourier Transform (FFT), the frequency character of wear signal is extracted. The rotational speeds of actual disc cutters under different installation distances and different rotational speeds are verified by similar disc cutters in the laboratory. In an engineering project, the rotational speeds of two edge disc cutter on an atmospheric cutter head with a diameter of 15 meters is monitored to verify the method. Results show that the cutter speed could be detected accurately and effectively when the wear amount is less than 20mm.

To realize a human-centered society, it is essential to develop advanced display technology that can artificially recreate tactile sensations for users. However, because the mechanoreceptors in human skin are microscopic, it is challenging to stimulate these receptors with currently available actuators. Thus, to cover the limitations of current actuators, we focused on the tactile illusion known as the velvet hand illusion (VHI), in which a sensation of smoothness occurs when people rub two parallel wires between the palms of their hands. In addition, it is known that a smooth sensation similar to the VHI can be induced using a dot matrix display when two lines composed of pins move in an apparent reciprocating motion on the palm. It is interesting that this smooth sensation is created by the uneven stimulation of the pins. To apply this sensation, it is necessary to elucidate the mechanism behind it. Therefore, in this study, we conducted psychophysical experiments and brain function measurements to determine whether this sensation produced by a dot matrix display is the VHI, and to clarify how sensations differ between displays. First, in the psychophysical experiments, we used the semantic differential method and factor analysis to construct tactile dimensions to investigate the characteristics of the VHI sensation. As a result, it was found that the stronger the VHI, the greater the sense of smoothness and softness. This characteristic was also confirmed in the VHI induced by the dot matrix display. Next, we used functional near-infrared spectroscopy to investigate brain activation related to VHI generation. The investigation confirmed that the strength of the illusion is related to the activity level of the hand area in the left primary somatosensory cortex for both the wire display and the dot matrix display.

This paper presents an optimization of energy distribution in hydraulic hammer forging based on the three actuals which are (1) actual place, (2) actual product and (3) actual situation. For the automation in the hydraulic hammer forging, “billet jumping” during the forging process is a fatal defect. It is much difficult to simulate the billet jumping through numerical simulation. Thus, it is important to determine the optimal energy distribution without using numerical simulation. To successfully determine the optimal energy distribution in hydraulic hammer forging, first, several experiments based on the latin hypercube design sampling are conducted. Then, multi-objective optimization minimizing total energy and billet thickness is performed. In this process, the billet jumping is numerically evaluated through the experiments and is handled as the design constraint. Surrogate-based optimization using radial basis function network is performed to determine the optimal energy distribution considering the billet jumping. Through the experimental result, the hydraulic hammer forging using the optimal energy distribution is successfully conducted without the billet jumping.

Low-frequency vibration cutting (VC) is a machining technology wherein a tool periodically vibrates to break cutting chips. However, VC produces tool paths that include air cuts to break up chips, which deteriorates surface roughness and roundness. This study aims to address these limitations. Low-frequency vibrations are applied to both the upper and lower turrets of a multitasking lathe. To improve surface roughness with simultaneous VC, this study presents a theoretical method to calculate the optimal values for frequency and amplitude of VC and the starting positions of the Z-axis of two upper and lower turrets. Simulations and actual machining experiments were conducted after adjusting VC frequency and amplitude and the starting positions of Z-axis of both turrets. Results show that the surface roughness improves with two-turret simultaneous VC compared to one-turret single VC in stainless steel and brass machining experiments, while succeeding in breaking up cutting chips. Furthermore, the surface roughness of simultaneous VC is improved to a level close to that of single and simultaneous conventional cutting (CC) results in stainless steel. Although there is some variation in material, the roundness of simultaneous VC is generally improved compared to single VC and CC. For the machining of brass, the roundness results of the simultaneous VC were better than those of single CC, VC, and simultaneous CC.

In turning processes, effective chip control is crucial for preventing machining issues such as tool damage, workpiece surface defects, and equipment malfunctions caused by cutting chips. This paper introduces a novel chipbreaking method using a triangular tool path to enhance chip management without compromising surface quality. The technique involves creating a triangular motion in the cutting tool, enabling intermittent air cuts that effectively break chips. This approach can be implemented easily by modifying existing CNC programs, without requiring specialized tools or equipment. Experimental results show that the proposed method successfully breaks continuous chips into smaller segments, significantly reducing chip-related risks. Surface roughness remained comparable to conventional turning, demonstrating that this method preserves surface quality. However, a drawback of the triangular tool path is the increased machining time due to extended tool movement. To mitigate this, higher feed rates were applied during rough-cutting stages, reducing machining time without affecting surface roughness or roundness. This study highlights the potential of a triangular tool path as a practical solution for chip control in unmanned and automated machining environments. Although further optimization is needed to improve machining time, this method offers a flexible and cost-effective option for enhanced chip management.

This study presents a state stabilizing mechanism that can maintain consistent axial tension in the ball screw feed drive systems used within machine tools, even when the screw shaft is elongated due to thermal expansion. The proposed mechanism is structured as an attachable unit for the end of the screw shaft in a feed drive. During a machining cycle, the heat generated from the rotation of bearings within the unit is then used as an intrinsic energy source to expand hydraulic fluid sealed within a pressurized chamber. By minimizing the variation in pressure within the chamber, the mechanism autonomously maintains stable axial tension in the feed drive. After modeling pressure within the chamber and comparing calculated results with trends in actual test data, the proposed mechanism was confirmed to maintain stable axial tension even in the presence of shaft elongation. Results in preliminary tests validate the mechanism as a solution that may be considered during the design stage.