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Документ On the surface roughness of 3D printed parts with FDM by a low-budget commercial printer(Національний технічний університет "Харківський політехнічний інститут", 2022) Christodoulou, I. T.; Alexopoulou, V. E.; Karkalos, Nikolaos E.; Papazoglou, E. L.; Markopoulos, Angelos P.As additive manufacturing machines price is decreasing, while, at the same time, the expertise in the relevant field is rising, it is essential to test and evaluate the low-budget machines that are available for commercial use. Whilst low-budget machines are widely utilized for rapid prototyping and experimentation, they are not capable of producing parts with high surface quality and achieve high levels of repeatability due to low quality hardware and not optimized software. Having said that, the main aim ofthe current study is to experiment with a low budget Fused Deposition Modeling (FDM) 3D-Printer, and evaluate the surface roughness of the printed parts in respect to the angle from the print plate. Polylactic Acid (PLA) was chosen as filament material, while the printed parts surface roughness was measured according to the ISO ASTM 52902-2021 standard. The surface roughness was estimated in terms of the Ra and Rz values, while a statistical analysis was implemented in order some interesting conclusions to be deduced regarding the correlation between part orientation and surface quality.Документ On the machining of aluminum alloy AL6063 with EDM(Національний технічний університет "Харківський політехнічний інститут", 2020) Papazoglou, E. L.; Karkalos, Nikolaos E.; Markopoulos, Angelos P.; Karmiris-Obratański, P.Electrical Discharge Machining (EDM) is a non-conventional machining process, which allows the machining of any electrical conductive material, regardless its mechanical properties, with high dimensional accuracy, and in complex shapes and geometries. EDM widely utilized by modern industry, taking advantage of its unique inherent capabilities. Aluminum alloys find extensive use in numerous applications, and their machining consist an interesting topic, with tangible industrial interest. The current study presents an experimental investigation of machining Al6063 alloy with EDM. A full scale experiment was conducted, with control parameters the pulse-on current and time. The productivity of the process calculated based on the Material Removal Rate (MRR), while the Surface Roughness of the machined surfaces was estimated in terms of Ra and Rt. For these performance indexes Analysis Of Variance was performed and semi-empirical relations that correlate machining parameters with obtained results were proposed. Finally, the cross sections of the specimens were observed inoptical microscopy, in order the formation of the White Layer to be studied.Документ Experimental study on surface roughness of face milled parts with round insert at various feed rates(Національний технічний університет "Харківський політехнічний інститут", 2020) Kundrák, János; Nagy, Antal; Markopoulos, Angelos P.; Karkalos, Nikolaos E.; Skondras-Giousios, D.In the present paper, the variation of surface roughness of machined parts during symmetrical face milling is investigated. During this experimental work, the effect of using a milling insert with a round geometry under various feed rate values on the topography of milled parts is examined. For that purpose, both 2D and 3D surface roughness measurements were performed in three planes parallel to the feed direction, with one of the planes being on the symmetrical plane and the other two being at the same distance from it but in opposite sides. The analysis of the experimental results indicated that although surface roughness increases gradually with increase of feed rate, a considerable increase of surface roughness occurs for feed rate values over 0.4 mm/tooth. Moreover, the overall higher surface roughness values were found to be on the symmetrical plane, which was also more affected by the increase of feed rate than the other two planes.Документ Face milling with a round insert at various cutting speeds and feed rates(Національний технічний університет "Харківський політехнічний інститут", 2019) Makkai, Tamas; Kundrak, Janos; Karkalos, Nikolaos E.; Markopoulos, Angelos P.Face milling is frequently used for the rendering of flat surfaces with a high degree of precision. With this machining process, high material removal rate is possible to be attained but management of cutting forces values is also desirable, in order to avoid excessive power consumption, tool wear or vibrations. This can be achieved by selecting the process parameters within an appropriate range for each case. In the present study, an experimental investigation is conducted with a view to determine the effect of two important process parameters, namely cutting speed and feed on the cutting forces and the specific cutting forces during face milling, in cases where a round insert is used.Документ Investigation of surface roughness on face milled parts with round insert in planes parallel to the feed at various cutting speeds(Національний технічний університет "Харківський політехнічний інститут", 2019) Kundrak, Janos; Nagy, Antal; Markopoulos, Angelos P.; Karkalos, Nikolaos E.In this paper, the roughness of the surface produced by symmetrical face milling is examined. During the research work, the effect of the use of a round milling insert on the surface topography was studied at different cutting speeds. 2D and 3D surface roughness measurements were carried out in three measurement planes parallel to the feed direction, one of them being the plane of symmetry and the other two planes being at the same distance from it, in both sides. From the analysis of results, it was found that surface roughness decreases significantly for cutting speed values over 100 m/min and then its variation is minimal. Furthermore, higher values of surface roughness are observed in the symmetric plane than the other parallel planes and almost in every case, surface roughness was found to be larger on the entry side plane than the exit side plane.Документ Study on the applicability of coupled Eulerian-Lagrangian formulation in abrasive waterjet machining simulations(Національний технічний університет "Харківський політехнічний інститут", 2019) Dimopoulos, Christos D.; Karkalos, Nikolaos E.; Markopoulos, Angelos P.Non-conventional machining processes are considered as reliable alternatives to the established conventional ones in the case of processing of difficult-to-cut materials. Especially, Abrasive Waterjet Machining (AWJM) is advantageous for this purpose, as it can handle a wide range of workpiece materials and does not cause heat affected zones. In order to study the phenomena occurring during AWJM, numerical simulations should be carried out along with experiments. As machining processes involve significant material deformation, Coupled Eulerian-Lagrangian (CEL) Finite Elements (FE) models have been proven significantly accurate for this purpose, compared to pure Lagrangian models. Thus, in the present study it is attempted to compare the predicted results of CEL and pure Lagrangian models in the case of AWJM and determine whether this method is applicable for the process or not. Simulation cases based on experimental results are employed and discussion on the predicted cutting zone dimensions, stress and temperature field is conducted.Документ Study on mesh dependence of cutting zone dimensions prediction during abrasive waterjet machining(Національний технічний університет "Харківський політехнічний інститут", 2019) Dimopoulos, Christos D.; Karkalos, Nikolaos E.; Markopoulos, Angelos P.Abrasive Waterjet Machining is a non-conventional material removal process, preferred to be used for the cutting of difficult-to-cut materials, due to its ability to remove material without the use of a tool and without causing heat affected zones. Experimentally, monitoring the phenomena taking place in the cutting area is very difficult, due to various reasons such as the high speed of the particles and the obstruction due to the water stream. Thus, a simulation approach, based on experimental data, is required in order to be able to explain these phenomena. In this work, a 3D thermo-mechanical Finite Element model is presented with realistic representation of the positioning of discrete abrasive particles and the dependence of cutting zone dimensions on the mesh size is investigated. After simulation, results are compared to experimental results, mesh independence study is conducted and finally, conclusions on the optimum mesh size are drawn and observed process characteristics are discussed.Документ Investigation of the effect of depth of cut and cutting speed on cutting forces during face milling of steel with a rectangular cutting insert(Національний технічний університет "Харківський політехнічний інститут", 2019) Karkalos, Nikolaos E.; Markopoulos, Angelos P.; Makkai, Tamas; Kundrak, JanosIn metal machining processes, the achievement of a sufficiently high material removal rate is desirable. Material removal rate can be increased to the desired value by an increase of feed rate value and also by increase of cutting speed or depth of cut values. However, as it is also required that surface quality and deformation should be within the acceptable limits, it is necessary to control them by selecting the appropriate process parameters values. In this study, face milling experiments are conducted in order to investigate the effect of using different values of depth of cut and cutting speed on the cutting forces and specific cutting forces. A comparison between the experimental results from cases with constant feed rate and two different depths of cut at four different cutting speed values, ranging from 100 to 400 m/min is conducted. After the subsequent analysis of the results, conclusions on the effect of depth of cut and cutting speed on cutting forces and specific cutting forces are drawn.Документ Influence of depth of cut and cutting speed on cutting forces in face milling under constant chip cross-section conditions(Національний технічний університет "Харківський політехнічний інститут", 2019) Karkalos, Nikolaos E.; Markopoulos, Angelos P.; Makkai, Tamas; Kundrak, JanosIn various high-end industries such as the automotive and the aerospace industry, face milling is one of the most preferred solutions for the fabrication of flat surfaces with high quality. During machining it is desired to achieve the required result with high efficiency. However, attention should be paid so that forces are kept within acceptable limits for maintaining energy consumption and loading of machine tool at relatively low levels. Thus, it is important to determine the influence of process conditions, such as depth of cut or cutting speed, on cutting forces. In this study, this is attempted by conducting experiments at two different depths of cut and four different cutting speeds for cases with the same chip cross-section value. After analysis of obtained results, useful conclusions on the influence of these parameters on cutting forces are presented.