Перегляд за Автор "Kundrak, Janos"
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Документ Analysis of the change in roughness on a face-milled surface measured every 45° direction to the feed(Національний технічний університет "Харківський політехнічний інститут", 2021) Nagy, Antal; Kundrak, JanosIn this article, we analyze the difference (inhomogeneity) of the roughness values measured on a nonalloy carbon steel surface milled with a parallelogram-shaped (κr = 90°) insert as a function of the the tool movement direction and the relative position of the examining points on the workpiece surface. The characteristic distribution of roughness and the magnitude of the deviations were examined by measuring at selected points along several planes on a surface characterized by the movement conditions of the workpiece and the symmetrically arranged tool perpendicular to the machined surface, which formed double milling marks. The selected points mark the lines with specified inclinations with respect to the feed direction, and their measured values were compared. In these directions, the magnitude of the difference in roughness measures was obtained.Документ Comparative analysis of CBN cutting inserts with different edge geometries(Національний технічний університет "Харківський політехнічний інститут", 2019) Kundrak, Janos; Sztankovics, Istvan; Gevai, MartinaIn this paper the experimental results of newly developed cutting inserts with special geometry and position for machining of hardened surfaces are summarized. The design of the tool holder and cutting insert allows the increase of the applied feed values in hard turning. Experiments are carried out at increased feed in bore turning procedure and the results are compared with the nowadays used conventional turning technology.Документ Comparison of finish machining procedures on the basis of material removal performance(НТУ "ХПИ", 2011) Kundrak, Janos; Deszpoth, I.It is suitable to compare the economy of procedures so much different in material removal – like abrasive machining and machining with edges – on the basis of material removal rates. The comparison of different hard cutting procedures was carried out in compliance with the evaluation criteria that were the quality requirements in producing the workpieces. In this paper the economic efficiency of the machining procedures – grinding, turning, and combined procedures – is analysed on the basis of the machining times, the surface rate and the material removal rate.Документ Comparison of hard machining procedures on the basis of the amount of the used up coolant and lubricant(НТУ "ХПИ", 2011) Kundrak, JanosThe application of coolants and lubricants (CL) considerably contributed to the increase of the efficiency of material removal in metal machining procedures. Both the cooling and the lubricating effect reduces the load on the tools, thus facilitates the partition of the material and the formation of a better surface quality. This article seeks to ascertain whether given production task – namely the machining of a hard surface – can be fulfilled with the same accuracy and economic efficiency if using less CL.Документ Decision support method for the applicability of hard turning(Національний технічний університет "Харківський політехнічний інститут", 2022) Kundrak, Janos; Deszpoth, Istvan; Molnar, ViktorIn this study the applicability of hard turning is analyzed in the case of disc-shaped parts (gear wheels). The relevance of such parts has been increasing in the automotive industry; therefore, the efficiency of large series or mass production has high priority. The novelty of this paper is the collection of factors that has to be considered in preparation for applicability decisions of hard turning in order to ensure efficient machining. This can be the basis of the IT support, i.e. an automation solution for technologists. The introduced process is elaborated on the basis of theoretical considerations and production shop-floor experience.Документ The effect of tool wear on chip formation in hard turning(НТУ "ХПИ", 2011) Szabo, G.; Kundrak, JanosThis paper compares the cutting process characteristics depending on the extent of the tool flank wear. The research was executed with Finite Element Method analysis. The researched cutting process was hard turning, when case hardened steel 16MnCr5, 62±2 HRC was cut by a cubic boron nitride tool insert (CBN). The examined data were the main cutting force, the passive force, the cutting temperature and the chip segmentation morphology.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 Finite element modelling of shear in hard turning(НТУ "ХПИ", 2010) Kundrak, Janos; Szabo, G.; Varga, Gy.The major problem of a choice of optimum finishing operation is solved at processing internal surfaces tempered of steels. Parameters by means of which it is obviously possible to carry out a choice of optimum operation turning or grindings are offered. The comparative analysis of efficiency of application of these operations has shown, that turning operation internal apertures at which the attitude of length to diameter does not exceed 1,1 is preferable.Документ Increasing productivity of combined procedure by reducing grinding allowance(Національний технічний університет "Харківський політехнічний інститут", 2019) Kundrak, Janos; Deszpoth, Istvan; Molnar, ViktorExperiments were carried out to determine the minimal extent of acceptable grinding allowance on case-hardened workpieces machined by combined procedure. The extent of acceptable or unacceptable allowance was determined by a “painting” method. After bore grinding tests for 2D roughness, roundness and 3D topography measurement were carried out. It was found that a 0.03 mm allowance in the bores of gearbox wheels of cars is satisfactory and also necessary to obtain the required level of topography when combined machining was applied and when no white layer formed in the turning procedure. This is a significant finding, because the usual allowances of 0.05 mm or higher (in many cases significantly higher) can be decreased to 0.33 mm and the machining time of bore grinding can be reduced in proportion to this extent.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.Документ Influences of the technological parameters on the surface twist in grinding(НТУ "ХПИ", 2016) Nagy, Nora; Kundrak, JanosThe requirement towards to the functional surfaces of the machine components became higher over the time. The final steps in the machining are supposed to create a surface which ensures wear resistance, longer lifetime and has special features on demand as well. The twist free surface can be considered as a special surface condition. The following paper presents the effect of the grinding parameters to the surface twist.Документ Investigation of face milled surface topography on C45 workpiece assuming movement at 30° and 60° to feed direction(Національний технічний університет "Харківський політехнічний інститут", 2023) Nagy, Antal; Kundrak, JanosWhen surfaces with anisotropic texture are moved in different directions related to their assembled counterpart during operation, the friction conditions change, as they are determined by the lay of the topographies. In the article, contributing to the exploration of this characteristic, we analyze the inhomogeneity of the topography on a face milled plane surface with a symmetrical setting in sections at an angle of 30° or 60° to the feed direction. Roughness profiles are recorded at 13 pointslocated equidistantly from each other in each measurement plane, and the degree and distribution of the roughness deviations are determined on the surface.Документ Investigation of surface roughness characteristics of face milling(Національний технічний університет "Харківський політехнічний інститут", 2019) Nagy, Antal; Kundrak, JanosSurface quality and accuracy affect the integrity and lifetime of machine parts and the operational requirements of the structural (or assembly) units. These are the reasons that the expected surface roughness must be planned based on the operational requirements of the parts. The path of the tool edge, which is defined by the characteristics of the kinematics of face milling, makes the milled surface inhomogeneous, which means the roughness analysis in various directions gives different values. In this paper the effect of increasing the feed rate on surface roughness is investigated. This cutting data is chosen because increasing the feed rate is an effective way to increase productivity.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 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 Investigation on wear and tool life of cutting tools(НТУ "ХПИ", 2011) Kundrak, Janos; Raczkovi, L.The wear of cutting tools is determinant in chip removal and tool life is in economic efficiency of cutting. The reason is that superhard tools are expensive and surfaces or parts machined by them have to fulfill strict requirements referring to the accuracy and quality. That is why investigation on these tools have a major importance. The paper focuses on some wear feature of CBN tools and on determining of tool life.Документ Joint machining: hard turning and grinding(Національний технічний університет "Харківський політехнічний інститут", 2019) Kundrak, Janos; Molnar, Viktor; Markopoulos, Angelos P.The manufacturing of increasingly complex components and, at the same time, production of parts of superior quality is a growing trend in industry today. This tendency is realized through advanced machining processes that take advantage of the capabilities of the new machine tools, the properties of cutting tools and the advancements in control and CAD/CAM/CAE systems available today. However, productivity is important and it is not always possible to reduce machining times, while difficult-to-cut materials, successive processes and tool replacements hinder the desired goal. However, ready-machining of the components is a feasible way to achieve the aforementioned requirements. A possibility for this is machining the workpieces on one machine tool, with only one clamping. The fulfilment of the processing and finishing of parts with one clamping and the application of several processes, i.e. hard turning and grinding, in one machine tool is called joint or combined machining. There are several advantages to this arrangement in manufacturing processes, which are discussed in this paper.Документ Lead time reduction in manufacturing process of toothed parts(Національний технічний університет "Харківський політехнічний інститут", 2019) Molnar, Viktor; Deszpoth, Istvan; Kundrak, JanosIn manufacturing automotive industrial components, the reduction of machining time and operation spare time detected in the cutting operations can be realized by the modification of technological parameters. However, reduction in the total component manufacturing lead time can be realized to a great extent by re-organization of the production process to eliminate unnecessary waiting periods (e.g. storage, in-process storage, etc.). In our study the total lead times of two different types of components were analyzed by mapping the process in a detailed way. The rate of waiting time within the lead time was analyzed; the theoretical and the measured lead times were compared and the effect of operation sequence on lead time was analyzed. Using these calculations and also measurements the problematic operations were identified and suggestions for process improvement were made.Документ Research of plastic strain and chip morphology in hard turning(НТУ "ХПИ", 2011) Kundrak, Janos; Szabo, G.In the case of several surfaces/parts, the turning of hardened materials replaced the machining applied before. The knowledge of strain mechanisms may advance the increase of material removal efficiency this appoint newer fields of application. This paper introduces the morphology and the plastic strain of the removed chip in the case of orthogonal (2D) cutting. The relationship between plastic strain and the change of cutting data has been investigated.Документ Roughness investigation of single and double cutting marks on face milled surface(Національний технічний університет "Харківський політехнічний інститут", 2023) Nagy, Antal; Kundrak, JanosIn machining with defined cutting edge tools, in some rotational tool processes (e.g. face milling) the tool edge may scratch the surface of the workpiece one more time, depending on the cutting conditions, during one revolution of the tool. As a result, the topographies with single or double cutting marks will be different from each other. The deviation, depending on its size, can also affect the functional performance (e.g. friction conditions) of the operating surfaces. In this article, face-milled topographies created with a symmetrical setting and with single or double milling marks are compared according to the magnitude of the roughness and the degree and nature of the inhomogeneity.