In this paper, a deburring tool with 3-axis compliance is presented for deburring using a robot manipulator. Compliance is provided with beam structures instead of pneumatic pressure, which enables integrated 3-axis force sensing and variable stiffness. Two radial compliances were achieved using 4-PSS (Prismatic-Spherical-Spherical) legs, with P joints composed of cantilever beams. The one axial compliance was configured with two ball bushings and a linear spring. Strain gauges were attached to cantilever beams and a load cell was mounted between the linear spring and the universal joint to perform force sensing. The stability of vibrations and force sensing were verified through deburring experiments using the proposed deburring tool. Additionally, experiments on automatic offset for applying a constant force during deburring were conducted and results were validated by comparing the workpiece before and after the deburring process.
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Stress Analysis of a Robot End-Effector Knife for the Deburring Process Jeong-Jin Park, Jeong-Hyun Sohn, Kyung-Chang Lee Journal of the Korean Society of Manufacturing Process Engineers.2025; 24(6): 42. CrossRef
Stress Analysis of a Robot End-Effector Knife for the Deburring Process Jeong-Jin Park, Jeong-Hyun Sohn, Kyung-Chang Lee Journal of the Korean Society of Manufacturing Process Engineers.2025; 24(6): 42. CrossRef
Strain wave gears are widely used as reducers in robots, including collaborative and industrial robots. As a key component, they play a crucial role in determining overall robot performance. To enhance their effectiveness, various studies have focused on directly measuring the performance of assemblies or predicting the performance of individual components through analysis. However, there is a notable lack of research that experimentally measures and compares the physical properties of the circular spline, flexspline, and wave generator—the primary elements of strain wave gears. In this paper, we developed equipment to measure the radial stiffness of the flexspline, one of the key components, and validated its reliability through preliminary experiments. Furthermore, we measured and compared the radial stiffness of flexsplines produced by three different manufacturers. These findings are expected to provide valuable insights for improving the performance of strain wave gears and advancing robotics technology.
With the increasing frequency of laparoscopic surgery, interest in the application of polymeric ligation clips as a method for ligating blood vessels has grown. Automatic clip appliers with built-in polymeric ligation clips have been developed to reduce ligation time. As the built-in clip is loaded into the jaw of the applier for ligation, a high spring constant, the elastic property of the clip is required to load properly. As the built-in clip loses its elastic properties due to stress relaxation over time, a polymeric ligation clip with a high spring constant is needed to increase the shelf life of the applier. In this study, four design factors of the cavity at the clip hinge (length, width, eccentricity, and angle of the cavity) were derived and applied to the Taguchi optimization method using finite element analysis to evaluate which factor was critical. The four design factors explained 93.5% of the variation in the spring constant. The factors related to cavity width and eccentricity were significant at p<0.05. Cavity width was the most crucial factor, explaining 70.8% of the variation in the spring constant. The spring constant of the improved clip model increased by 55.4% compared with the existing model.
This study introduces a novel tip-tilt-piston aligner based on aligned folded beam flexure. It was designed to enhance precision positioning by minimizing parasitic motion. Through finite element analysis, we compared this aligner with a traditional folded beam flexure-based mechanism, revealing a remarkable 135% increase in translational stiffness and superior rotational stiffness ratios. These advancements are expected to reduce parasitic motion arising from actuator misalignment and external disturbances, ultimately elevating positioning accuracy. The aligner’s suitability as a guiding device was affirmed and optimal actuator placement positions were determined. This research provides valuable insights into precision positioning mechanism design, underscoring the role of flexure geometry and precise actuator placement in minimizing parasitic motion for improved accuracy.
This paper presents the development of a design optimization module for achieving the best performance of hydrostatic bearings. The design optimization module consists of two components: a bearing performance analysis module and an optimization module that utilizes optimization algorithms. Widely recognized global search methods, genetic algorithm (GA), and particle swarm optimization (PSO) algorithm, were employed as the optimization algorithms. The design optimization problem was defined for hydrostatic bearings. Optimization design processes were carried out to improve load capacity, stiffness, and flow rate. Subsequent experimental validation was conducted through the fabrication of a practical experimental setup. The design optimization model demonstrated superior performance compared to the initial model while satisfying design conditions and constraints. This confirms the practical applicability of the design optimization module developed in this study.
Recently, the demand for lightweight open-pore lattice structures with specific stiffness is increasing in many fields, such as the aeronautical, automotive, mechanical and bone tissue engineering sectors. For each concrete application, there is a need to predict its mechanical properties precisely and efficiently. There are several methods used to analyze the mechanical properties of lattice structures. Among them, the asymptotic expansion homogenization method is a more advantageous approach over the experimental, theoretical, and finite element methods, because it handles some of their limitations such as the time-consuming process, size effect, and the high amount of computational resources needed. Therefore, in this work, we use the asymptotic expansion homogenization method to perform a systematic parametric study to calculate the effective stiffness of different open-pore lattice structures. In addition, the designed models were fabricated using an SLA 3D printer, and the effective stiffness of the fabricated specimens was tested via UTM experiment to validate the numerical results computed by the asymptotic expansion homogenization method. Consequently, it was proved that this method is precise and effective for predicting the mechanical properties of lattice structures.
In general, rotor inertia has an inversely proportional relationship with proportional gain and bandwidth in a turret speed control system of machine tools; thus, this system has a disadvantage, such as weak disturbance caused by a decrease in the damping ratio and an increase in bandwidth due to low rotor inertia. This paper proposes a damping compensator that is resistance to disturbances in order to improve the above problems. The proposed damping compensator reduces the residual vibration induced in the transient state by using a digital high-pass filter. The experimental results showed that the overshoot was reduced by about 5.5% in the speed response and by about 20% in the torque response in the no-load condition. Under the load condition of 4.8 N.m, the torque response showed that the undershoot was reduced by about 26%.
With advancements in semiconductor manufacturing processes and the development of precision processing technology, flexure hinge-based ultra-precision positioning stages are widely used. In the flexure hinge, axial and bending stiffness properties greatly influence positioning performance. This study examined the stiffness properties of elliptic and parabolic 2-degrees-of-freedom (DOF) hinges, which have not been extensively discussed. The Timoshenko beam theory was applied to derive the stiffness equations for the axial and bending directions of each hinge. The stiffness properties were examined in several design conditions by comparing theoretical and finite element analyses. Based on the results of the analyses, an empirical formula in exponential form for the design of an elliptic hinge was constructed through surface-fitting. The elliptic hinge was found to be a better alternative to a circular hinge under certain design conditions by adjusting two design parameters. In the future, we will develop sophisticatedly designed hinges with improved axial and bending stiffness properties compared to the existing circular and elliptic hinges.
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Derivation and Verification of Novel Phenomenon-based Theoretical Formulas for the Axial Compliance of Circular Flexure Hinges Jun-Hee Moon, Hyun-Pyo Shin Journal of the Korean Society for Precision Engineering.2025; 42(1): 47. CrossRef
The bone scaffold is artificial mechanical support, that is implanted on collapsed bone microstructure. The clinical field has become interested in that, because it is free of immunological rejection. However, few studies have analyzed quantitively the mechanical interaction with the surrounding bone tissue, when the bone scaffold is implanted. Thus, the purpose of this study was to analyze structural behavior variance, according to porous structures of the bone scaffold. This study set the proximal femoral head as the implantation skeletal system, and defined bone scaffolds (i.e. triangular, rectangle, circular, honeycomb) with four porous structures. Then, structural behavior variance was analyzed, caused by the implantation of bone scaffolds. As a result, it was quantitatively confirmed that a porous structure such as a normal bone that can transmit and support an external load is important.
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Computational comparison study of virtual compression and shear test for estimation of apparent elastic moduli under various boundary conditions Jisun Kim, Jung Jin Kim International Journal for Numerical Methods in Biomedical Engineering.2024;[Epub] CrossRef
Quantitative Load Dependency Analysis of Local Trabecular Bone Microstructure to Understand the Spatial Characteristics in the Synthetic Proximal Femur Jisun Kim, Bong Ju Chun, Jung Jin Kim Biology.2023; 12(2): 170. CrossRef
Topology Optimization-Based Localized Bone Microstructure Reconstruction for Image Resolution Enhancement: Accuracy and Efficiency Jisun Kim, Jung Jin Kim Bioengineering.2022; 9(11): 644. CrossRef
The main shaft of a mechanical press inevitably includes significant stress concentrations that can trigger severe mechanical damage and finally lead to failure under repetitive use. In this study, an efficient procedure to quantitatively evaluate the fatigue life of the shaft system including the main shaft and its support bearings, based on the macroscopic failure analysis of the main shaft broken during actual use, was investigated. For this purpose, the bearing support was modeled as an elastic foundation, and the elastic foundation stiffness value was varied to determine the optimal value that best simulates the failure behavior, especially with respect to the failure location and failure sequence, of an actual shaft. While the finite element mesh size was kept the same, only the effect of elastic foundation stiffness was investigated. The optimum value for the main shaft investigated in this study was approximately 60 N/mm³, and the fatigue life of the shaft was evaluated based on the conventional maximum principal stress theory. Based on this, two modified designs to enhance the fatigue life of the existing shaft are proposed.
The gear has a wide range of transmitted force as various gear ratios are possible using a combination of teeth. It can transmit power reliably and cause relatively little vibration and noise. For this reason, the application of reducers of electric vehicles is being expanded. Vibration noise generated from gears is propagated into the quiet interior of a vehicle, causing various claims. In most gear studies, transmission error has been pointed out as the main cause of vibration noise of gears. Transmission errors have various causes, including design factors, manufacturing factors, and assembly factors. In general, when predicting transmission error through finite element analysis, design factors play an important role without considering manufacturing factors or assembly factors. In this study, relationships among important design variables (gear module, compensation rate, load torque, and transmission error) in gear design were investigated using analytical and experimental methods. In addition, a method of predicting gear meshing stiffness through the predicted gear transmission error was proposed to obtain variation of meshing stiffness due to changes of gear design parameters.
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Development of a Prediction Model for the Gear Whine Noise of Transmission Using Machine Learning Sun-Hyoung Lee, Kwang-Phil Park International Journal of Precision Engineering and Manufacturing.2023; 24(10): 1793. CrossRef
Flexure hinges are widely used as joint linkages for precision stages applied to lithography processes. Among them, precision stages with 3 DOF (Degrees of Freedom) of x, y and θz prevail in semiconductor manufacturing and they have been adopting single directional flexure hinges as mechanical linkages without backlash and debris. However, new technologies including nano-imprinting, which replaces lithography, needs more than 3 DOF precision positioning stages that adopt cylindrical flexure hinges. In this study, the cylindrical flexure hinges with circular notches were analyzed using the Timoshenko beam theory and FEM (Finite Element Method), with focused on their directional stiffness. Based on the analysis and result comparison between theoretical equations and FEM, several practical suggestions for determining important design variables are provided in the conclusion of this study.
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Derivation and Verification of Novel Phenomenon-based Theoretical Formulas for the Axial Compliance of Circular Flexure Hinges Jun-Hee Moon, Hyun-Pyo Shin Journal of the Korean Society for Precision Engineering.2025; 42(1): 47. CrossRef
Analysis on Elliptic and Parabolic 2-DOF Flexure Hinges for Spatial Positioning Stages Hyun-Pyo Shin, Jun-Hee Moon Journal of the Korean Society for Precision Engineering.2023; 40(3): 229. CrossRef
The purpose of this study was to investigate the excitation force that generates the vibration of the reduction gear case for railroad vehicles. This excitation force is difficult to measure directly. The inverse stiffness method was used using the acceleration response measured in the experiment and the vibration response function derived from the finite element analysis. It was assumed that the excitation force acting on the reduction gear operates in the X, Y, and Z directions for each bearing, and a total of 12 excitation forces were investigated. When deriving the excitation force, singular value decomposition was applied to the vibration response function to increase the accuracy of the result. The results of the excitation force according to the number of degrees of freedom of the response were compared. Additionally, the magnitude of the estimated excitation force according to the singular value category used was compared, and it was confirmed that a too low singular value indicates a different excitation force.
This paper presents the characteristics of tapered roller bearings (TRBs) taking into consideration the effects of tapered roller angle error which may occur during manufacturing. To this end, a TRB model including tapered roller angle errors was developed. The effects of tapered roller angle error on the contact load distribution, bearing stiffness and fatigue life were investigated with respect to changes in the tapered roller angle error. A statistical analysis of the fatigue life of TRBs was also provided with respect to tapered roller angle error. Simulation results show that the tapered roller angle error changes the load distribution of the rollers and causes angular misalignment in TRBs, and subsequently, influences the bearing stiffness and fatigue life. The statistical analysis shows that the Weibull distribution is an acceptable method to represent the statistical fatigue life for the practical range of tapered roller angle errors.
The magnetorheological material changes its characteristics according to the external magnetic field. Magnetorheological elastomer existing in the solid phase has micrometer-sized magnetically responsive particles inside. When a magnetic field is applied by a permanent magnet or electromagnet nearby, it can exhibit stiffness that changes according to the strength of the magnetic field. Many previous studies focused on verifying the variability of the material"s characteristics. However, this study newly proposed a variable stiffness joint for the suspension system of railway vehicles using a magnetorheological elastomer, as a basic study of magnetorheological elastomer for a mechanical component. Based on the characteristics test of the magnetorheological elastomer, the variable joint was designed to have the same structure as the conventional guide arm joint of a railway vehicle. Particularly, to overcome the low magnetic field strength, which may be a problem in the previous research, and to implement uniform magnetic field distribution, the electromagnet was designed to make direct contact with the magnetorheological elastomer. A mathematical model was established and a finite element method verified the model, resulting in an average magnetic flux density of 300 mT, which means 30% stiffness change at 15% shear strain.
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Investigation of wheel-rail wear reduction by using MRF rubber joints with bidirectional adjustable stiffness Ning Gong, Jian Yang, Weihua Li, Shuaishuai Sun Smart Materials and Devices.2025;[Epub] CrossRef
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