The use of environmentally friendly, lubricant-free plastic seals in the rotating parts of robots and machines is on the rise. However, variations in seal geometry and operating conditions can influence the contact pressure between the seal and shaft, potentially leading to poor sealing performance, premature wear, or debris ingress. Therefore, advanced design optimization is essential. In this study, we conduct a parametric study and sensitivity analysis to enhance the performance of plastic seals. Finite element analysis (FEA) is carried out using a 2D axisymmetric model with interference fit contact conditions to accurately simulate the behavior of the seal and shaft. We verify the reliability of the analysis by comparing the deformation of the seal diameter before and after shaft insertion with experimental measurements obtained using a 3D tactile measurement device. We analyze four design variables: pressure, temperature, seal diameter, and coefficient of friction, considering seal contact pressure as the objective function. Sensitivity analysis is performed to determine the impact of these design variables on contact pressure and to identify trends.

Recently, large-scale accidents caused by minor damage from fatigue failure and impact on structures have been frequently reported. Therefore, a real-time damage monitoring system of structures is considered to be one of the most important technologies to ensure safety in various types of research. The piezoelectric sensor, which has an advantage of converting deformation of a structure into an electrical signal without using an additional power source, has been reported as one of the most suitable methods for real-time monitoring systems. This review aims to describe the structural monitoring system utilizing piezoelectric paint sensors. First, we present the concept of a piezoelectric paint sensor with the advantages of flexibility and piezoelectric performance. Then, factors affecting the performance of the piezoelectric paint sensor are introduced. Finally, an overview of piezoelectric paint sensors for structural monitoring, such as vibration detection and impact monitoring, are provided. The state-of-the-art of the application of the piezoelectric sensor is also introduced, providing feasibility in industrial fields.

In this study, design for additive manufacturing (DfAM) of release agent injection manifold for hot forging has been performed to achieve weight reduction and flow path optimization. The weight reduction of 53.5% was achieved, thereby enabling the application of stainless steel 316L, which has high strength and corrosion resistance. Lightweight manifolds using Al-Mg-10Si and SUS316L materials were fabricated by PBF-type metal 3D printer. The feasibility test showed that mold life was improved by 14% by solving residual release agent problem. In addition, the flow path optimization results suggested that the flow standard deviation of each outlet dropped sharply from 264 to 75 ㎤/s. This approach demonstrated that DfAM for release agent manifold could be applied to increase mold life and improve product quality and productivity for hot forging.

Precision positioning stages are devices for precisely positioning objects according to required degrees of freedom and performance. Precision positioning stages are classified into serial and parallel mechanisms. Except for specific applications, the parallel mechanism is preferred. In serial mechanism, dynamic characteristics such as resonant frequency are clearly different from axis to axis and the first resonance frequency is distinctly low compared to the second. These make the control performance different for each axis and incurs limitation in control. In this study, the first and second resonant frequencies in a serial 2-DOF precision positioning stage were increased while maintaining their approximal value. Compliance analysis for the stage was performed by applying the matrix based method. A new concept of resonant frequency isotropy (RFI) was introduced and design optimization was performed in which first and second resonant frequencies almost coincided. This optimization allowed for the design of a serial 2-DOF precision positioning stage with enhanced first resonance frequency by 50.8% and RFI by 80.2% compared to the initial design. This paper is expected to increase the use of precision positioning stages based on serial mechanism and apply the concept of RFI to the positioning stages with more than 2-DOF.