2021 № 94 Різання та інструменти в технологічних системах

Постійне посилання колекціїhttps://repository.kpi.kharkov.ua/handle/KhPI-Press/77628

Переглянути

Зараз показуємо 1 - 16 з 16

Influence of the geometric characteristics of the discontinuous profile working surfaces of abrasive wheels for precision and temperature when grinding
(Національний технічний університет "Харківський політехнічний інститут", 2021) Yakimov, A.; Bovnegra, L.; Tonkonogyi, V.; Vaysman, V. O.; Strelbitskyi, V.; Sinko, I.
Grinding is the most common finishing method for hardened steel parts. Grinding is accompanied by a large heat release in the cutting area, under the influence of which structural changes appear in the thin surface of the processed parts, tensile stress and even microcracks, which significantly reduce the operational reliability of machines that include these parts. The use of abrasive wheels with an intermittent working surface makes it possible to reduce the temperature in the area of contact of abrasive grains with the material of the workpiece and, as a consequence, stabilize the quality of the surface layer of the workpieces. High-frequency vibrations in the elastic system of the machine, accompanying the work of an intermittent wheel, are a positive factor that reduces the energy consumption of the grinding process. However, under certain conditions of dynamic interaction of the tool with the workpiece, parametric resonance may occur, which worsens the geometric and physical-mechanical parameters of the quality of the surface layer of the processed part. The aim of the work is to realize the possibility of predicting the quality parameters of the surface layer of parts during intermittent grinding by studying the influence of the design features of the macrotopography of the working surface of abrasive wheels and processing modes on the nature of the dynamic interaction of the tool with the workpiece and the heat stress in the cutting area. It was found that the parametric vibrations of the elastic system of the machine tool can be shifted to a more stable area, due to an increase in the number of interruptions of the working surface of the abrasive whee l with a constant ratio of the length of the protrusions and depressions. The increase in the number of breaks on the wheel also contributes to a decrease in temperature in the cutting area. It was found that to maintain the stable operation of the elastic system of the machine, it is necessary to reduce the number of cavities on the grinding wheel with an increase in the cutting speed. However, both of these actions are accompanied by an increase in the heat stress of the grinding process. It has been experimentally established that for ordinary (pendulum) grinding, it is possible to achieve an increase in processing productivity by increasing the speed of the longitudinal movement of the table.
Simulation of the machined surface after end milling with self-oscillations
(Національний технічний університет "Харківський політехнічний інститут", 2021) Dyadya, S.; Kozlova, Ye.; Germashev, A.; Logominov, V.
Thin-walled parts are widely used in the aviation industry. It is mainly carried out with end mills and is accompanied by self-oscillation during rough milling.They negatively affect the quality of the machined surface. Therefore, it is important to model it taking into account the dynamics of the milling process to predict the accuracy. In the early works of the authors, the mechanism of the profile forming of the machined surface was determined. In this case, the identity of the shape of the cutting surface and the oscillogram of part’s oscillations during milling is taken as a basis. The first wave of self-oscillations takes part in the shaping of the machined surface during cut-up milling with self-oscillation, and during cut-down milling - the last wave. The change in the distances of the cut depressions to the position of the elastic equilibrium of the part is periodically repeated from the maximum value to the minimum. Based on this, when modeling the waviness pitch of the machined surface after cut-up milling, it is necessary to know the feed rate and how many cuts were made by the tool from the largest to the smallest depression. When modeling the machined surface after cut-down milling, you need to know the length of the cutting surface. It is calculated based on cutting speed and cutting time. The formula for determining the waviness pitch after cut-down milling is derived taking into account the tool feed. The waviness height of the machined surface after cut-up and cut-down milling is determined as the difference between the largest and smallest depressions. To determine the size of the pitch and the height of the waviness, formulas are derived for converting electrical and time values of oscillograms into linear ones. These formulas also allow you to determine areas of the oscillogram with oscillations of the part during cutting and the resulting surface areas on the profilogram. The methods for modeling machined surfaces were tested after cut-up and cut-down milling with self-oscillation. In this case, the pitch and height of the waviness on the profilograms were compared with those calculated from the results of measurements of the oscillograms. Based on their analysis, refined formulas for calculating the waviness height have been derived. The error between the measurements of the waviness pitch and height and the calculated values is within 6%.
Tribology and topography of hard machined surfaces
(Національний технічний університет "Харківський політехнічний інститут", 2021) Molnar, Viktor
In machining automotive industrial parts by hard machining procedures, the topographic characteristics of high accuracy surfaces have high importance. In this paper 2D and 3D surface roughness features of gear bores machined by hard turning and grinding are demonstrated. The 3D roughness parameters, which are considered as more exact than the 2D parameters, were compared to the 2D ones, which are used more widely in industrial practice. The analyzed machining procedure versions were ranked based on the topographic parameters determining the tribological (wear and oil-retention capability) characteristics of the different surfaces.
The importants of clustering in logistic systems
(Національний технічний університет "Харківський політехнічний інститут", 2021) Veres, P.
Nowadays, the development of higher efficient processes and procedures is the key for success in industrial environment. The companies have machines, production lines, software and hardware tools with high level principles of efficient working. Example: the Industry 4.0 concept use the machines and methods of the near past, upgrade them, and gave them new purpose, as a more efficient tool. Some of the bases of those tools are not as efficient as which many would think, like in group generating or in other word clustering. Clustering is a very hard process, and it is in almost every decision making in every company’s lives. It is important to sometimes examine its significance and flaws. This paper presents the clustering briefly and shows its errors through an example.
Surface roughness modeling during electric discharge grinding with variable polarity of electrodes
(Національний технічний університет "Харківський політехнічний інститут", 2021) Strelchuk, R. M.
The article presents the probabilistic-statistical modeling of surface roughness in the process of electric discharge grinding with the variable polarity of electrodes. The correlation between electric modes of machining and indicators of the quality of the machined surface was established. A probabilistic-statistical model of part surface roughness formed during grinding is obtained, which establishes the correlation between high-altitude surface parameters and electrical machining modes. The developed model makes it possible to calculate the height parameters of the part roughness depending on the electrical modes of grinding. The height of microroughness is determined by the same machining conditions as the depth of erosion pits. It is possible to obtain low roughness if electrical machining modes are reduced.
Finish machining of the cutting inserts from cubic borine nitride BL group composite
(Національний технічний університет "Харківський політехнічний інститут", 2021) Chumak, A.; Klimenko, S.; Klimenko, S.; Manokhin, A.; Naydenko, A.; Kopeikina, M.; Burikin, V.; Bondarenko, M.; Burlakov, V.
Finishing methods of machining of superhard composite’s working elements based on cubic boron nitride BL group are considered. The results of the microgeometry formation research of the cutting inserts’ surfaces during machining by free powders of synthetic diamond, grinding wheels and a method of vibro-magnetic-abrasive machining (VMAM) are presented. It is shown that during VMAM the friction between the inserts’ surfaces and the abrasive particles result in microremoval of the material, which reduces the roughness of the cutting inserts’ surfaces. It is established that additional fine grinding with 14/10 mkm synthetic diamond powder provides the absence of microgeometry defects of the cutting inserts’ surfaces left by pre-machining. The result of high-quality rounding of cutting edges and the formation of surfaces of cutting inserts with less roughness is an increase in strength and wear resistance of metal-cutting tools in high-speed machining under conditions of significant loads.
Modeling the influence of metal phase in diamond grains on self-sharpening of grinding wheels on ceramic bonds
(Національний технічний університет "Харківський політехнічний інститут", 2021) Fedorovich, V. A.; Fedorenko, D.; Pyzhov, Ivan; Ostroverkh, Y.
The article presents the results of theoretical studies using finite element modeling, which made it possible to determine the rational characteristics of diamond wheels based on ceramic and polymer bonds. The effect of the parameters of the diamond-bearing layer on the change in its stress-strain state in the process of microcutting of hard alloys and superhard materials has been studied. It is established that the determining factor in the occurrence of critical stresses during grinding is the temperature in the cutting area, the increase of which in the presence of metal phase inclusions in diamond grains with high values of thermal expansion coefficient can lead to destructive stresses in grains and, consequently, their premature destruction. It is advisable to use diamond grains with a minimum content of metal phase and the use in the manufacture of synthetic diamonds solvent metals with a low value of this coefficient, which will significantly increase the use of potentially high resource diamond grains.
Experimental investigation of surface topography of AL7075-T6 alloy machined by EDM
(Національний технічний університет "Харківський політехнічний інститут", 2021) Balanou, M.; Papazoglou, E. L. ; Markopoulos, Angelos P.; Karmiris-Obratański, P.
Electrical discharge machining is one of the most important non-conventional machining processes for removing material from electrically conductive materials by the use of controlled electric discharges. EDM is a non-contact machining process, therefore, is free from mechanical stresses. This paper investigates the machining Al7075-T6 alloy by EDM using a copper electrode. Al7075-T6 alloy was selected, because of its growing use in a lot of engineering applications. The effect of electrical parameters, peak current and pulse-on time, on the surface integrity, was studied. Area surface roughness parameters (arithmetical mean height, Sa, and maximum height, Sz) were measured on all samples and 3D surface characterization has been carried out with confocal laser scanning microscopy. The experimental results showed that the surface roughness is mainly affected by the pulse-on time.
Technological fixtures for machining large-sized thin-walled shells of complex profile
(Національний технічний університет "Харківський політехнічний інститут", 2021) Oliinyk, S.; Kalafatova, L.
The paper analyzes the structure of technological fixtures for the positioning and fixing of large-sized thin-walled pyroceram shells as a factor affecting the dynamic characteristics of the grinding system. The solution to the problem of ensuring the dynamic stability of the «mandrel-workpiece» subsystem is necessary to increase the efficiency of shell machining in present conditions. Studying the vibrations frequency spectrum of the technological system during grinding has made it possible to determine their sources. The magnitude and frequency of vibrations depend on the mandrel structure - the clamping fixture. The study results are the requirements for a new mandrel structure, considering the dynamic stability of the technological system.
The effect of the circular feed on the surface roughness and the machining time
(Національний технічний університет "Харківський політехнічний інститут", 2021) Sztankovics, István
The surface roughness is analysed in different feeds and turning procedures (rotational and conventional) in this paper. Cutting experiments were made on different cutting speeds and feed rates with 2 cutting tool with helical edge geometry and 1 traditional turning tool. The measured 2D surface roughness values were compared between the different cutting tools. The benefit of the circular feed application is showed by the decrease of roughness parameters and machining time.
Evaluation of the forecasted efficiency of performance of rational orientation of the product in the workspace of additive installations
(Національний технічний університет "Харківський політехнічний інститут", 2021) Garashchenko, Yaroslav; Zubkova, N. V.
Preliminary evaluation of the predicted efficiency of the optimization problem of the rational orientation of the product in the working space of layered construction of additive units is proposed to perform based on the analysis of the original triangulation 3D-model of a complex product by its spherical mapping. The condition of reflection on the sphere is that the values of angles in the spherical coordinate system for the faces normal of the triangulated model of product fall into the range of values of a certain triangular face of the sphere model. Examples of evaluation based on the analysis of spherical mapping of the original 3D model of products are considered. Industrial products with different surface complexity were selected as test 3D models. This approach allowed to perform a comparative analysis of the results depending on the design features of the products. The practical implementation was performed in the subsystem of visual assessment of geometric characteristics of triangulated 3D-models, which is part of the technological preparation system for the complex product manufacture by additive methods. This system was developed in NTU "KhPI" Department of Integrated Technologies of Mechanical Engineering named after M.F. Semko.
Interaction of the abrasive medium with the treated surface and the process of metal removal during vibration treatment in the presence of a chemically active solution
(Національний технічний університет "Харківський політехнічний інститут", 2021) Fedorovich, V. A.; Grabchenko, A. I.; Mitsyk, A. V.
Interaction of working medium granules with the processed surface of the part is considered. It is noted that the processing methods are characterized by the dynamic interact ion of the abrasive medium with the processed surface. It is indicated that during vibration treatment there is an impact contact of the abrasive granule with the surface of the part, which leads to the formation of characteristic traces during the formation of the surface relief. The types of impact of abrasive grains of working medium granules on the surface of the processed part are identified. It is indicated that the effect of abrasive grains depends on the geometric parameters of the tops of the grains and the working contour of the granule as a whole. The alternation of the operation of abrasive grains in the connection with the nature of the motion of the granule over the surface of the part is shown. The interaction of surfaces of bodies during vibration treatment is considered. The distinctive features of the vibration treatment method from other analogs are indicated. The conditions for the formation of the surface layer of the part during vibration processing are given. The analysis of the mechani cal-physicochemical model of the micro-cutting process in the presence of a chemically active solution is carried out and a comparison of the intensity of technologies for vibration treatment of steel parts is given.
Technological provision of the accuracy for the thread form of rod pumps
(Національний технічний університет "Харківський політехнічний інститут", 2021) Yakovenko, Igor; Vasilevskyi, Yu.; Basova, Yevheniia; Edl, Milan
Aspects of thread manufacturing used in downhole rod pumps are considered. Technological defects of distortion of lateral surfaces of a thread profile arising in the course of processing on CNC machines are described, and the factors which most influence formation of these defects are established. The influence of profile defects on the reliability of the threaded connection during the operation of rod pumps is analyzed, as well as the research on the dynamics and oscillations of machine systems is analyzed. With the performed analysis the mathematical model of real techn ological system in the course of machining process is created and investigated. The main technological factors that have the greatest influence on the occurrence of error in the shape of the thread surface are identified. With the help of software for analysis of dynamic systems, the necessarily calculations were performed and the behavior of the dynamic system in the process of forming the thread profile was considered. Based on the analysis of the obtained results, a system for managing the parameters of the technological process of threading and technological solutions formulated. The introduction of which had a positive impact on the stability of the machining process and reduce the frequency of the above defect.
Quality management of cutting tools on heavy machines
(Національний технічний університет "Харківський політехнічний інститут", 2021) Klymenko, G. P.; Vasylchenko, Y.; Donchenko, Ye.
The work is devoted to improving the efficiency of cutting tools on heavy machines by developing a quality management system for its operation, determining rational operating regulations and developing general machine-building standards for cutting. The developed model of the tooloperation control system for the first time allowed to systematically consider the structure and relationships of all components of the process. The qualimetric approach to the tool operation process made it possible to develop methods for quantitative assessment of the process quality and substantiate the structure of the preparatory information subsystem.
Automatic control of temperature and power conditions during rough grinding of slabs
(Національний технічний університет "Харківський політехнічний інститут", 2021) Tihenko, V.; Lebedev, V. V.; Chumachenko, T.
The production of high-quality rolled products (slabs), the formation of its surface phase-structural composition, texture, stress state during rough grinding depends on the temperature in the area of contact between the wheel and the slab. During processing, due to geometric errors of the rolled surface, as well as due to local changes in hardness, periodic fluctuations of the instantaneous depth of cut occur, which can be determined indirectly by controlling one of the technological parameters, for example, the power spent on grinding, with subsequent recalculation it to online temperature values. The grinding temperature is described as a control object in the form of an aperiodic link. Computer simulation has confirmed the efficiency of the system for maintaining the specified temperature of slab grinding under various operating conditions that simulate the situations of real production.
Investigation of the effect of areal roughness measurement length on face milled surface topographies
(Національний технічний університет "Харківський політехнічний інститут", 2021) Nagy, Antal
Surface roughness is of great importance in the manufacturing industry, as it affects surfaces’ tribological properties (wear, friction, lubrication, etc.), corrosion resistance, fatigue strength and appearance. Areal roughness measurement, which provides a more comprehensive characterization of surfaces, is becoming increasingly popular, but systematic studies are still lacking, so measurements are often analyzed differently. In this paper, the effect of the measurement length is analyzed in the main measurement direction on areal roughness of face milled surface topographies, which were measured with a confocal chromatic sensor.