Sustainability has become a major concern in many countries and is leading to strict regulations regarding the impact of products and services during their manufacturing, use, and disposal. Power consumption monitoring in manufacturing companies can lead to a reduction of machine tools energy wastes and consequently to lower expenses. To this end, a complete transparency of energy usage among the entire manufacturing facilities is required. Despite the small volume of material processed, micro manufacturing processes are energy intensive and the optimization of energy usage becomes critical for manufacturing sustainability. Electrical discharge machining (EDM) is considered an attractive solution for the manufacturing of microcomponents. In this paper, a low cost and modular data acquisition system, based on open-hardware and open-source software, for online energy consumption monitoring, is presented. The system described is applied for energy efficiency analysis of the micro EDM milling process by using a state of the art commercial machine tool. A number of sensors is connected to the data acquisition system to measure the energy consumption of the main sub-systems of the machine tool, data is recorded through a microcontroller, and sent to the main computer via Wi-Fi for data storage and analysis. Results show that the process efficiency depends on machine parameters but it is always far below 0.01 %. Solutions are suggested to improve the energy efficiency of the machine tool considered in this work.
COBISS.SI-ID: 13851931
In this paper the optimization of the spool and housing geometry in a small hydraulic seat valve to enable the reduction of the axial flow forces to a minimum value is described. Non-optimized hydraulic valve geometry is usually the main cause for many problems related to response time, actuation force and energy consumption. To overcome these limitations and problems we have done a thorough numerical and experimental analysis of a seat valve. The main influential geometry parameters of the seat valve are defined for numerical analyses. In the next step the basic theory of the numerical simulation, including the 3D modelling, meshing and parameterization, is explained. The reduction of the flow forces in a small hydraulic seat valve is treated in detail by using a commercial simulation tool, Ansys CFX. The validation of the numerical fluid model of the valve is done by comparing simulation and experimental results obtained with the test rig for axial flow force measurement. With the validated numerical fluid model of the valve new fluid models are built taking into account all influential geometry parameters of the valve for the purpose of the final optimization of the valve geometry. The results of the simulation analyses show that the axial component of the flow forces can be reduced significantly just by modifying the geometry of the valve spool and housing. Thus the valve dynamic characteristics, such as response time, are significantly improved while the necessary actuation force and power consumption are reduced.
COBISS.SI-ID: 13766683
This paper describes some possible methods for the reduction of the axial static flow forces in hydraulic sliding-spool and small on/off seat valves. These forces increase with the increase in the volume flow and the pressure difference and thus determine higher actuation forces for the control of the valve unit. This results in the necessary use of more powerful actuators for the direct control of hydraulic valves. The topic is therefore very relevant from the energy consumption point of view regarding the actuation of hydraulic valves. To make the use of low-power actuators for the control of directly actuated valves possible also for higher hydraulic power the flow forces acting on the valve piston in the axial direction must be reduced. This paper presents one of the possible solutions with such a design of the hydraulic valve housing and the spool that the flow stream of the fluid through the valve causes minimal axial static forces. The main influential geometry parameters of the sliding-spool and seat valve are defined and analysed in detail using the CFD (Computational Fluid Dynamics) simulation tool Ansys CFX and experimental analysis for the validation of the numerical fluid model of the valve. The results of the research are very promising and prove that the axial component of the flow forces and therefore the necessary actuation force can be reduced significantly just by modifying the geometry of the valve housing and spool. Thus the power consumption of the actuator is minimised and the valve dynamic characteristics are improved at the same time.
COBISS.SI-ID: 13974811
In this paper, the cutting front development during abrasive water jet (AWJ) cutting is studied using a two-dimensional cellular automata (CA) model, hence the striation formation phenomenon is studied indirectly. To calculate the shape of the cutting front, the CA model uses the following inputs: cutting velocity, AWJ intensity and material type. The cutting process is described by simplified material removal and AWJ propagation models in the form of CA rules. The rules encompass AWJ ability to erode the workpiece material and, inversely, the workpiece materialʼs resistance to the erosion process. The proposed CA model is validated by checking the trend of the cutting front development at various input parameters. The simulation results are in good agreement with experimentally obtained trends and thus confirm the proper setup of CA rules. This gives a better insight into the AWJ cutting mechanism.
COBISS.SI-ID: 13974043
This study describes in detail the mechanical properties of polymethylmethacrylate (PMMA) denture base resins with regard to fabrication procedures, moulding and thermoforming. The investigation included eight specimens of each group of the materials, made separately for each experimental protocol (moulding and thermoforming). Analysis of the mechanical properties of the tested resins was comprised of tensile and 3-point bending strengths, elongation, fracture toughness and micro-hardness tests. Data obtained from the mechanical tests were statistically processed by using one-way analysis of variance (ANOVA) with Tukeyʼs post-hoc test and with the significance level Alpha=0.05. Triplex cold specimens showed the lowest bending strength, fracture toughness and micro-hardness as well the highest standard deviations. Biocryl C in a thermoformed condition exhibited higher tensile and bending strength in comparison to the same material but in the as-received condition (before thermoforming), while the results are opposite for fracture toughness and micro-hardness. Compared to Triplex hot, thermoformed Biocryl C had statistically non-significantly higher values for bending strength and micro-hardness, but significantly lower ones for fracture toughness and tensile strength. In contrast, the lowest dissipation of testing results in all mechanical tests was recorded for Biocryl C fabricated by a thermoforming process, meaning that this material has the highest predictability of the materials tested. The mechanical properties of thermoformed PMMA materials are comparable to cold and hot polymerized PMMA materials. Standard deviations obtained for thermoformed PMMA material are lower than those obtained with cold and hot polymerized PMMA materials.
COBISS.SI-ID: 13894939