This paper aims to explore the shaking forces and shaking moments in single- and multi-engine configurations, with the effect of various ratios of connecting rod length to crank length. The reciprocating engine has 1 to 6 cylinders. The research uses mechanical analysis to highlight critical issues in dynamic analysis and engine design. The shaking forces and shaking moments on the crankshaft are measured through kinetic analysis and free-body diagrams of a reciprocating engine system. Results show that as the U1/U2 ratio decreases, the shaking forces in the x- and y-directions and the shaking moments decrease. However, constraints on the U1/U2 ratio exist, such as rod weight, buckling risks, and engine height. The largest shaking forces acting in the x-direction are achieved by a six-cylinder engine, and the least ones are achieved by a one-cylinder engine. The study was limited to single and multi-cylinder engines. It did not consider the effect of counterweight-based balancing techniques that modify movement dynamics. The paper combines shaking forces and shaking moments analysis in the x and y axes. Prior research has not comprehensively analysed the combined effects of gas pressure, shaking forces, and shaking moments. The gap serves as the primary motivation for the study, which aims to integrate these factors into a unified framework-an approach that has not been previously undertaken.
The aim of the work is to design and numerically analyse a personalised knee protector shell for sports applications. The subject of this research is the outer protective shell, a key element responsible for transferring and dissipating loads from impacts or falls. The work included 3D scanning, geometric modelling of the protector shell, and numerical analysis using the Finite Element Method (FEM). The analysis enables assessment of stress distribution, strain, displacement, and structural behaviour under applied loads, thereby verifying the adopted design assumptions. The protector’s shell is designed as a composite element, made of fibreglass and epoxy resin, with a constant thickness of 3 mm. The use of composite materials is due to their favourable mechanical properties, such as a high strength-to-weight ratio, damage resistance, and the ability to shape complex geometries. Simulation results showed that at a load of At 10 kN, the permissible stress state of the material was exceeded locally at the point where the force was applied, which could initiate composite damage. Based on additional analyses, a safe operating force of 7.5 kN was determined. In this case, the shell layers do not fail, and stresses and displacements remain within safe limits. The obtained analysis results indicate that the designed structure fulfils its protective function under real-world conditions. They can serve as a basis for assessing the effectiveness of the designed shell and its suitability for sports applications. The obtained results confirm the validity of using 3D scanning technology and numerical analyses in the design process for personalised sports protectors and can serve as a basis for further development work, including dynamic analysis, experimental studies, and layered optimisation of the composite.
The review article presents an in-depth analysis of the use of 3D printing in the production of full dentures and also mentions the use of this method in other areas of dentistry, such as implantology and orthodontics. It begins with a general overview of 3D printing in dentistry, including its use to produce tooth replacements, metal elements, and implant templates. The article then compares the conventional method of producing full acrylic dentures with the digital 3D-printing technique. Narrative literature review of PubMed, ScienceDirect and Google Scholar (2001–2025) using keywords on 3D printing in dentistry and (digital) full dentures. The following review allowed us to determine the advantages and disadvantages of each method and to summarise the analysis results in the context of an individual approach to a given case. SLA/DLP and PolyJet are the primary routes for dental models and prosthetic components, while FFF is primarily used for lower‑cost applications. Digital workflows can shorten treatment and enable archiving/reproduction of prostheses, but 3D‑printed complete dentures still show limitations in functional fit (including palatal adaptation), surface quality, and cost; intraoral scanning alone may not capture the functional border moulding needed for full denture retention. The review does not provide meta‑analytic evidence and relies on available heterogeneous studies. More long‑term clinical trials are needed to assess durability, biocompatibility, discolouration, and the impact of printing/post‑curing parameters. The paper helps clinicians and technicians match clinical needs with appropriate printing methods and denture-base polymers (notably PMMA-based resins) and stresses the importance of cleaning and post‑curing to reduce residual monomer risk. It integrates denture-specific clinical requirements with an up‑to‑date overview of additive technologies and polymers, highlighting current barriers and research directions for printed complete dentures.
The purpose of the study is to enhance efficiency and reduce waste in printed circuit board (PCB) manufacturing, a critical sector supporting the electronics and artificial intelligence industries. The research aims to identify inefficiencies in the production process and propose practical solutions to improve productivity and cost-effectiveness. The study employed Motion and Time Study techniques to analyse the workflow in a representative PCB manufacturing facility in Thailand. The ECRS principles (Eliminate, Combine, Rearrange, Simplify) were applied to redesign the process. A roller system was introduced to streamline the return of fixtures to their starting positions, and its impact on productivity and cost was evaluated. The analysis revealed significant time losses due to manual fixture repositioning. Implementing the roller system doubled productivity from 0.23 to 0.46 sheets per baht and reduced fixture arrangement costs from 4.44 to 2.17 baht per sheet. The solution was cost-effective, achieving a payback period of 4.5 months. The study was limited to a single facility, which may affect generalizability. Future research should explore the integration of automation and scalability across different PCB production environments. The findings demonstrate that applying Motion and Time Study with ECRS principles can significantly improve operational efficiency in PCB manufacturing. The roller system offers a low-cost, high-impact solution for reducing waste and enhancing productivity. The research presents a practical case study of applying industrial engineering tools and ECRS principles to PCB manufacturing, offering actionable insights to improve efficiency in a rapidly growing industry.
Evaluation of the potential of a novel electron beam hardening (EBH) process for improving the surface integrity (SI) of C45 steel cylindrical specimens of a normalised initial material structure. An EBH experiment based on the one-factor-at-a-time technique, X-ray diffraction analysis, phase analysis, and SEM microstructural analysis was employed to study the SI characteristics. Compared to the as-received initial structure, EBH of normalised C45 steel specimens produces very similar results for the microhardness (HV0.05), the axial and hoop RSs, and phase and structural changes in the surface layer, but higher roughness (Ra) because of the less pronounced glazing effect. The results and conclusions regarding the effects of EBH on SI characteristics apply to the ranges of EBH operating parameters studied. The results form the basis for a planned experiment that considers interactions among the operating parameters. The novel EBH process is a cost-effective surface-hardening method for shafts and axles made of normalised C45 steel. The study demonstrates, for the first time, the effectiveness of a novel EBH process for the transformation surface hardening of cylindrical C45 steel parts, accounting for the effect of the normalised initial structure.
