International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The paradigm of Industry 4.0 pushes additive manufacturing (AM) from rapid prototyping towards the position of series production. Especially in metal 3D printing, increased attention is being paid to the topics of sustainability and resource efficiency. Energy demand during production and the calculation of building times play a decisive role here. Science has developed models for calculating energy consumption based on analytical and empirical approaches. Building time calculators have been introduced using a wide variety of analytical, analogical and parametric approaches. The present review summarizes the results and the state of the art, illustrates the results graphically and thus paves the way for further research approaches. The specific energy consumption per kilogram of processed material has risen over the last decades, which can be explained by higher technical requirements for production machines. Building time calculations continue to be subject to errors, depending on the type of calculation. The introduction of machine learning approaches has the potential to reduce this discrepancy.

Thermal comfort and indoor air quality highly depend on proper design of Heating, Ventilation and Air Conditioned (HVAC) system. These system require large amounts of energy. Efficient use of energy leads to new concept design of HVAC systems. In this article, energy consumption in office building is analysed using Hourly Analysis Program (HAP) software. The aim of this research work is focused in estimation of office building energy consumption considering three different HVAC systems, respectively. Therefore, Variable Refrigerant Flow (VRF) system, HVAC 2-pipe and HVAC 4-pipe system were analysed with respect to energy consumption. A typical office building placed in Tirana, of 5000 m2 of total area is used for this study.

The paper considers the issue of deep tillage, the use of the latest technical advances, in order to develop new tillage implements that provide better tillage and reduce erosion. The main attention is paid to the preservation of soil fertility and the use of funds in organic farming. The aim of the work is to improve the process of mechanical tillage by digging by developing a new working body and the process of interaction of digging working bodies with the soil, which change its physical properties and improve environmental safety. The most promising for deep tillage is the digger in terms of both energy and agronomic indicators (reduction of compaction, preservation and restoration of water and air balance, preservation of humus, preservation of biomass). Rotary diggers with rotational movement of working bodies are more effective in comparison with diggers having oscillating movement of working bodies. As a result of studying the dependence of the angle of the blades, providing the movement of the formation on the surface of the working body, from their position on the trajectory, it was found that the smallest value (5…70) is the angle of inclination after turning the blade deepening. When lifting the formation from the bottom of the furrow to a certain height, the required angle of the blades increases, reaching a value of 28… 300 when overturning the formation at a height of 0.20…0.25 m

Much of the technical equipment in energy, industry, commerce and the public sector (electronic equipment, electric motors, furnaces, chargers, uninterruptible power supplies, etc.) are inherently non-linear loads and are sources of harmonic distortion of currents. Non-linear loads adversely affect all components of the power system: they increase losses in transformers and electric motors by thermal loading their windings, increasing dielectric and/or mechanical losses and generally reduce the efficiency of the electrical system. The paper deals with operation of a power transformer that supplies combined non-linear load in a public building

During the last two decades the Heating Ventilation Air Condition (HVAC) systems have been used to enable heating, cooling and ventilation of buildings with the primary aim of meeting the requirements of thermal comfort and indoor air quality. In this research work, energy consumption in buildings has been analysed by using Hourly Analysis Program (HAP) software. The object of our research work was focused in the Polytechnic University of Tirana. Mathematical models of thermal calculations have been based on the international standard ISO 13790: 2008 on energy use and thermal performance of buildings.

The mathematical model of the polymer plasticization in the reciprocating screw injection molding machine is presented. According to the mathematical model, a computer program was developed. Based on the computer program, simulation studies of the injection molding process were conducted. Next, the experimental studies, evaluating the theoretical model from the accuracy and usefulness point of view, were carried out. Important output quantities, such as the temperature and pressure profiles, the power demand by the screw, the torque on the screw and the screw rotation time were measured. The studies were performed on a specially made
research office. The simulation results were compared with the experimental data measured for the most popular polymers and different operating parameters of the injection machine. The experimental studies have indicated the need to introduce some corrections to the mathematical model. Several modifications have been made to the model, related to the methods of stress determining in the polymer layer. Finally, the output characteristics of the plasticization process in the injection molding are now correctly determined by the model with an average error less than 10%.

Injection moulding is a widespread method of polymer processing. The annual, global energy consumption for injection moulding is comparable to the annual energy production of different European countries. The most energy-consuming stage of the injection moulding is the plasticization process, which needs the energy mainly for the rotational and reciprocating screw motion as well as the heating of the barrel. Both issues were examined by changing various parameters of the injection moulding process, measuring the process characteristics and calculating the corresponding values of SEC (specific energy consumption). Various thermoplastic polymers were examined. It was found that the optimal conditions from the energy consumption point of view is low value of rotational velocity of the screw. Changes of back pressure do not affect the energy consumption of the plasticizing system of the injection moulding machine. Furthermore, an increase of the SEC value with increasing barrel temperature was shown. It was ca. 15% for the average barrel temperature rise of 20°C.

Injection moulding is a widespread method of polymer processing. The annual, global energy consumption for injection moulding is comparable to the annual energy production of different European countries. The most energy-consuming stage of the injection moulding is the plasticization process, which needs the energy mainly for the rotational and reciprocating screw motion as well as the heating of the barrel. Both issues were examined by changing various parameters of the injection moulding process, measuring the process characteristics and calculating the corresponding values of SEC (specific energy consumption). Various thermoplastic polymers were examined. It was found that the optimal conditions from the energy consumption point of view is low value of rotational velocity of the screw. Changes of back pressure do not affect the energy consumption of the plasticizing system of the injection moulding machine. Furthermore, an increase of the SEC value with increasing barrel temperature was shown. It was ca. 15% for the average barrel temperature rise of 20°C.

The goal of this paper is to minimalize the gap between the heat pump’s compressor COP and the system COPs. A water-water heat pump was installed in a family house without piped floor heating, with 13 radiators, together with a 300 litres thermal storage and 200 litres hot water storage tank. Some measurements are published, taken before and after the system optimisation. The measured compressor COP is compared with theoretical data published by the device producer. The results show that the power consumption was decreased by 15 percent after the system optimisation. The influence of the equithermal curve settings and the power of the submersible pump are analysed and the results are presented. The seasonal COP (SCOP) for Bratislava area is calculated. for the system under consideration.

This paper discusses a spring-loaded accumulator with the output rotary link used in drives with energy recuperation for step movements. The basic principles of drives with energy recuperation made using the properties of oscillatory systems, when the energy spent on acceleration of the inertial mass moves from kinetic to potential energy. This drive must be equipped with accumulators of mechanical energy and managed retainers. The creation of such actuators is caused, mainly, by the necessity of increasing speed, large, in comparison with traditional, technical capabilities, when the comparative simplicity of their designs and low cost.