Table of Contents


    • Use of cold metal transfer technology in the restoration of functional areas

      pg(s) 329-332

      CMT technology provides significant advantages, such as reduced deformation due to high temperatures, high welding speed and a significant reduction in spatter compared to the MIG/MAG method. The experimental work was focused on verifying the possibility of renovating the surfaces of molds for high-pressure aluminum casting using CMT technology. A mold wear analysis was performed and a method of restoring functional surfaces was proposed. Two types of additive materials were used – Thermanit 625 and Thermanit X. The quality of the layers was evaluated by SEM, EDX microanalysis and the coefficients of friction of the layers were determined by the Ball-ondisc method. The renovation layers were also subjected to an immersion test in Al alloy at 680 °C.

    • Determination of cutting forces at drilling medium-alloy carbon steel

      pg(s) 333-336

      This paper presents the application of an experimental method for determining the numerical values of the machinability factors of medium alloy carbon steel in the drilling process. Research conditions are defined, including tools, machine, and machining parameters. The experiment was performed according to a two-factor orthogonal experimental plan, and the values of cutting forces were monitored using a dynamometer through other elements of the information measuring system. Cutting forces were also considered in relation to the drilling depth.

    • Development of Innovative Fully Automatic Processing System for High Energy Efficient Manufacturing of Commercial Cookware

      pg(s) 337-339

      Cookware is one of the indispensable equipment for commercial kitchens. The very large size of commercial cookware (up to Ø1200 mm) requires precision manufacturing processes. In our current manufacturing process, the fact that different processing stations are separate from each other and the processing stages are dependent on the workers, carrying risks in terms of occupational safety (cutting with scissors, grinding, etc.), prevents the product from being obtained with high processing quality and causes high wastage rates arising from the manufacturing process. In addition, it creates negative effects in terms of efficient use of energy and production time, causing an increase in unit costs. Within the scope of this study, the design and prototype production of an energy-efficient and work-safe innovative processing system for commercial cookware, based on R&D systematic studies, is carried out by international standards (EN ISO 12100, EN 614-1, EN 12983-1, etc.) and the results of our current manufacturing process. As a result of this research, occupational safety risks and excessive process steps are reduced, product quality and efficiency are increased, and thus production costs and energy efficiency are increased. Results are promising for further optimization.

    • Comparison of innovative collapsible ceramic hive and traditional non-separable hives made on the basis of natural plastic raw materials

      pg(s) 340-343

      An innovative collapsible frame hive was developed, consisting of structural elements made of technical ceramics containing thermal insulation air chambers. Experimental prototypes were prepared using the slip casting method and based on modified recipe compositions, prepared casting molding masses, original gypsum matrices and optimal heat treatment mode. A comparison was performed between the main operational characteristics of the experimental samples and the traditional non-separable hives which have existed throughout history and made primarily of various plant materials and natural plastic raw materials (clays).

    • Arm microcontroller learning kit

      pg(s) 344-347

      The Arm Microcontroller Learning Kit is built with the STMicroelectronics STM32H750VB microcontroller. The device is a small development system based on an Arm Cortex-M7 microcontroller. It has a modern modular design. The kit includes the most necessary peripherals to illustrate the capabilities of the microcontroller and it also supports a large amount of external peripherals. The cost of the kit is low due to the built-in periphery and the small number of additional external elements. The software uses a small fraction of the libraries provided by the microcontroller manufacturer and can be upgraded. This makes the device suitable for learning an ARM family of microcontrollers by beginners and advanced students.

    • Consolidation of discrete metal fibers using fine powder

      pg(s) 348-349

      Information is given on the study of the process of obtaining two-layer copper permeable powder-fiber materials, based on the activation of the fiber sintering by finely dispersed powder particles process, which are also used to form a thin filter layer. It has been confirmed that the activation of the fiber sintering process by finely dispersed powder particles ensures high-quality consolidation of metal fibers. The optimal ratios between copper fibers, polyvinyl alcohol used for applying fine particles to the fibers, and copper powder have been determined.

    • Designing a Forensic Molecular Genetic Laboratory in Institute of Forensic Sciences and Legal Medicine, as a Prototype

      pg(s) 350-353

      Proper laboratory design is a key element in minimising the risk of contamination in the laboratory. In most countries, ISO/IEC 17025 is the standard for which most labs must hold accreditation in order to be deemed technically competent, and the studies for meeting the requirements of this standard starts from the design, especially in Forensic Genetic Laboratories. Contamination is the top concern in Forensic Genetic Laboratories. In the laboratories designed according to this standard, particular attention is paid to the physical separation between the post-PCR, PCR and pre-PCR area, avoiding the back-movement of samples and material from the post-PCR area to the pre-PCR area. Separate physical spaces for the processing and analysis of known and questioned samples must be guaranteed, and simultaneity must be avoided in the processing and analysis of high and low DNA content samples. In this study, a Forensic Genetics Laboratory has been designed regarding the requirements of 17025 standard. This is the first study demonstrating a prototype of a Forensic Genetics Laboratory design from an internal architectural point of view, regarding the compliance with the ISO/IEC 17025 standard, including some recommendations for the new Forensic Genetics Laboratories planned to be built.

    • Opportunities for the development of the automotive industry in Bulgaria in the second half of the XX century in terms of collaboration with the West and close cooperation with the East

      pg(s) 354-357

      In the mid-1960s, the construction of production facilities for automobile manufacturing began in our country. After multi-million capital investments, a modern base for the production of cars and trucks, and buses, as well as assemblies and aggregates for them, is being created in our country. Licenses and technical documentation acquired by leading Western companies guarantee high quality of Bulgarian production and mark a huge growth in the export of production for the automotive industry. The cooperation opens up perspectives for the complete absorption of the samples produced in our country and cooperation in the industry with countries that are members of the COMECON. The possibility of using foreign experience and gradually preparing the necessary personnel leads to hitherto unknown concentration and specialization in the industry and to extremely high labor productivity.