MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL <p align="JUSTIFY"><em>MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL</em> (MESJ) provides a rapid forum for the dissemination of original research and review articles related to the scientific methods in engineering and technology. It is a peer reviewed international journal published twice annually (for the time-being) using an open access publication model. The journal aim is to foster research in the fields of science, engineering and technology, as well as to provide review coverage of the technical developments that shape our world. It is devoted to publication of original research articles, related to theory and/or applications that have not been published (or submitted simultaneously), at any language, elsewhere. Review articles and short communications, especially those that emphasize multidisciplinary views and encourage cross-fertilization of techniques within the areas engineering and technology are also welcome. <span style="position: absolute;left: -43123px;">Stay productive with Adobe Acrobat Pro - <a href = ""></a>. Always enjoy the latest features in PDF software.</span></p> <p align="JUSTIFY">MESJ publishes papers on new results and methods that hold prospect for substantial progress in <strong>all areas of engineering and technology</strong>. The Journal has been published for the last 30 years.</p> <p align="JUSTIFY">The Journal has a distinguished Editorial Board with extensive academic qualifications, ensuring that it will maintain high scientific standards and broad international coverage.</p> Faculty of Mechanical Engineering, Ss.Cyril and Methodius University inSkopje, North Macedonia en-US MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 1857-5293 666.CONTRIBUTION ON INVESTIGATING THE POSSIBILITY OF USING TWO-PARAMETER FREQUENCY ANALYSIS IN EXPERIMENTAL PARAMETER IDENTIFICATION OF TORQUE VIBRATIONS OF VEHICLE CARDAN SHAFTS During exploitation, motor vehicles are subjected to vibration loads that lead to fatigue of their users and materials of their aggregates. Therefore, vibrations must be studied from the earliest stage of development, using mathematical models, experiments, or their combinations. In theoretical studies, vibrations of concentrated masses are usually observed, although, with the development of numerical methods (especially finite element method), attention is paid to vibrations of elastic vehicle systems. Then, idealizations are usually made, especially regarding operational conditions and relationships between motor vehicle aggregates. In this paper, an attempt was made to de-velop a method for identifying real vibration loads of elastic vehicle cardan shafts under operational conditions. Namely, 2D Fourier transformation was used for two-parameter frequency analysis. The possibility of the procedure's application was demonstrated on an idealized elastic cardan shaft. The research showed that two-parameter frequency analysis can be used to generate torsional vibrations of elastic vehicle cardan shafts in laboratory conditions. Miroslav Demić Copyright (c) 2023 MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 2023-12-28 2023-12-28 41 2 75 81 10.55302/MESJ23412666075d 667.ENERGY EFFICIENCY OF INDUSTRIAL CONCENTRATORS WITH EJECTOR THERMOCOMPRESSION Research on the energy characteristics of systems with ejector thermocompression applied in industrial concentrators is presented in this paper. Ejector thermocompression achieves a significant increase in energy efficiency. The heat pump cycle in ejectors is realized through the compression of a portion of the waste steam from the solution being concentrated, which, together with motive steam from a boiler or another heat generator, is used as the driving steam for the concentration process. Thermocompression realized with thermal energy can represent a sig-nificant advantage over mechanical thermocompression. A setup for the production of concentrated sodium hydroxide (NaOH) solution with two ejector thermocompressors is presented, as well as a polygeneration system with a gas engine – electricity generator, and an ejector thermocompression system. The proposed solutions have high energy efficiency. By implementing thermocompression systems in the production of concentrates, the energy production costs are sig-nificantly reduced, which positively affects the cost of the produced concentrate. The surplus of electrical energy, as well as steam not used in the thermocompression processes, is used to supply energy for the needs of consumers in the production facilities. Gjerasimovski Aleksandar Gjerasimovska Nataša Šarevski Vasko Copyright (c) 2023 MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 2023-12-28 2023-12-28 41 2 83 88 10.55302/MESJ23412667083g 668.ENERGETIC AND ECONOMIC ANALYSIS FOR UTILIZATION OF BIOGAS FROM PIG FARMS IN NORTH MACEDONIA Today, when the world is facing an increasing need for energy, and therefore, the exploitation of natural resources is increasing, the problem of environmental pollution and global warming grows. The question of finding and using alternative and clean energy sources, imposes itself. The problem of environmental pollution and the need for renewable energy sources have increased the interest in allocating more funds for scientific research work for the use of biodegradable waste, so that in many countries more and more plants are being built that use biomass for biogas production. Biogas is a very interesting and important source of energy. All organic matter originating from mowing the lawn, cutting branches, farm waste, plant biomass from agricultural production, can be used as raw material for biogas production. Macedonia has large quantities of this type of waste, so there is a good precondition for eco-nomical use of them and to get electricity and heat from them. The paper focus is on assessment of the economic viability for utilization of biogas in pigs farms in Macedonia through integration of cogeneration power plant. The economic analysis is performed with method of benefit to cost ratio. Also sensitivity analysis is performed as a function of levelized cost of energy in regard of 7 critical factors: capital cost (amount of capital investment cost), interest rates (D is equal to 0%, 5%, 10 % and 15%), capacity factor (plant size), fuel cost (cost of procurement, preparation and transport of the substrate), cost of capital, debt ratio and net plant efficiency. The results indicate that the payback period could be in less than 9 years. Kliment Angelov Šešo Igor Copyright (c) 2023 MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 2023-12-28 2023-12-28 41 2 89 98 10.55302/MESJ23412668089a 669.METHODOLOGY DEVELOPMENT AND PERFORMANCE TESTING OF AN ACOUSTICALLY ISOLATED BOOTH USING THE ISO 23351-1:2020 STANDARD An acoustically isolated meeting booth is a specially designed structure used to isolate and reduce the level of speech. This pod is made in order to create a sound-isolated space, where you can work, record or perform sound in conditions of minimal noise and interference. Acoustically isolated pods are used for various applications such as music recording studios, movie theaters, conference rooms, and wherever it is important to limit sound transmission and ensure a quality acoustic environment. In this type of acoustically isolated rooms, acoustic characterization of all types of sound sources, as well as sound receivers, usually sound sensors, is carried out. The main objective of this research is to develop a methodology using the ISO 23351-1:2020 standard and test the performance of an acoustically isolated cabin. In addition to the primary goal of research, an additional goal is the analysis of the accuracy of the results obtained from a low-cost noise sensor through its comparison with a class 1 sound meter. The obtained results provide an opportunity for research and application of standardization that enables the development of a methodology for measurement and assessment of the characteristics of an acoustically isolated booth. In particular, the focus is on applying the methodology, measuring and comparing the results of noise measurements between a class 1 sound meter and a low-cost sensor unit. Nakova Elena Stojanovski Ivica Sakova Haritina Domazetovska-Markovska Simona Maja Anačkova Copyright (c) 2023 MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 2023-12-28 2023-12-28 41 2 99 107 10.55302/MESJ23412669099n 670.DESIGN AND IMPLEMENTATION OF SELF-BALANCING MOTORCYCLE In this research paper, an investigation was conducted into the development of mechatronic systems for two-wheeled vehicles, with a primary focus on a self-balancing motorcycle. The self-balancing motorcycle, which is currently in the developmental phase, has a primary objective of enhancing traffic safety by eliminating the require-ment for external assistance. The study delves into its design, programming, and potential for further enhancement and eventual commercial utilization. Fundamental equations of bicycle dynamics were derived, and a PID controller, guided by MEMS sensor data, was employed for steering control. The paper encompasses the presentation of experimental tests and refinements to the feedback system, providing valuable insights into the system's overall performance. The research embarks on the intersection of technology, vehicle dynamics, and safety, laying the groundwork for future developments in these interconnected domains. Vasilevski Damjan Pecioski Damjan Domazetovska-Markovska Simona Copyright (c) 2023 MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 2023-12-28 2023-12-28 41 2 109 113 10.55302/MESJ23412670109v 671.PROCEDURES OF WELDING METAL PRODUCTS WITH MIG/MAG ROBOT WELDING This research paper describes robot welding programming and different approach of three appli-cations in manufacturing processes by welding. It gives an overview of robot manipulator and its main components. For the experimental work a 6-axis robot arm is used and three different welds are made. Detailing of programming for every example with or without synchronization with the positioner and the trajectory is discussed. The paper presents steps of software development for online programming of a robot arm with or without synchronization. Krstevska Aleksandra Zdraveski Filip Bogatinoski Zoran Copyright (c) 2023 MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 2023-12-28 2023-12-28 41 2 115 121 10.55302/MESJ23412671115k 672.ENHANCING MANUFACTURING EFFICIENCY: A LEAN INDUSTRY 4.0 APPROACH TO RETROFITTING Industry 4.0 technologies are already affecting global supply chains by revolutionizing how com-panies manufacture and distribute their products and services. Many companies are affected by this transformation, especially small and medium-sized enterprises (SMEs) that are keen to enhance their market competitiveness as quickly and easily as possible. The transformation from traditional approaches to Industry 4.0 can bring many benefits, how-ever, this transition involves adopting technologically advanced machinery with a high level of digitalization and com-munication. The cost and time to replace old machines could be unsustainable for many SMEs and that is why these enterprises seek alternative solutions for the digitalization of their legacy machines, such as retrofitting. This paper conducts a review of both retrofitting and Lean Industry 4.0 (Lean 4.0) to identify the challenges and benefits of both concepts and explore how they can interact and merge with each other to help SMEs to increase their market competi-tiveness. Argilovski Aleksandar Vasileska Ema Jovanoski Bojan Copyright (c) 2023 MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 2023-12-28 2023-12-28 41 2 123 129 10.55302/MESJ23412672123a 673.EXPERIMENTAL RESEARCH OF THE MECHANICAL PROPERTIES OF THE INJECTION MOLDED PARTS IN MOLDS PRODUCED BY ADDITIVE MANUFACTURING In this study, additive manufacturing emerges as an innovative technology for concurrent engine-ering in the design and production of molds for injection molding processes. The primary objective is to conduct expe-rimental research on the mechanical properties of injection-molded parts using a non-conventional mold produced through additive manufacturing technologies. The state-of-the-art additive manufacturing technologies provide various methodologies and techniques for designing and printing parts. Utilizing these diverse technologies significantly ex-pands the possibilities for rapidly creating molds, thereby enhancing the scope of rapid tooling in the molding process. The study begins by designing and fabricating SLA mold inserts according to the relevant tensile testing standards. To evaluate the mechanical properties, a series of tensile tests are conducted and a comparison is made between the pro-perties of the molded parts produced with SLA mold inserts. The results demonstrate that SLA mold inserts made with additive manufacturing can effectively produce injection molded parts with comparable tensile strength to those ma-nufactured using traditional steel molds. Tuteski Ognen Kočov Atanas Copyright (c) 2023 MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 2023-12-28 2023-12-28 41 2 131 140 10.55302/MESJ23412673131t Under Cover Under Cover Jovanovski Bogdan Copyright (c) 2023 MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 2023-12-28 2023-12-28 41 2 71 71 Impresum Impresum Jovanovski Bogdan Copyright (c) 2023 MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 2023-12-28 2023-12-28 41 2 72 72 Table of Contents Table of Contents Jovanovski Bogdan Copyright (c) 2023 MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 2023-12-28 2023-12-28 41 2 73 74 INSTRUCTIONS FOR AUTHORS INSTRUCTIONS FOR AUTHORS Jovanovski Bogdan Copyright (c) 2023 MECHANICAL ENGINEERING – SCIENTIFIC JOURNAL 2023-12-28 2023-12-28 41 2 141 144