Cutting & Tools in Technological System

ANALYSIS OF THE EFFECT OF VARYING THE CUTTING RATIO ON FORCE COMPONENTS AND SURFACE ROUGHNESS IN FACE MILLING

2023-11-02T12:07:10+02:00

Traditional machining processes, such as face milling, still play a very important role in the production of machine parts and are the subject of ongoing research. One important area of research is the investigation of high-feed milling processes. However, due to the increased feed per tooth value fz, it is advisable to reduce the depth of cut (ap) in order to maintain the cutting forces at an appropriate level. In this way, the ratio of these two technological parameters, the so-called cutting ratio, changes and we can move into the range of inverse machining, where ap / fz < 1. In this paper, the consequences of this change is investigated on the surface roughness and the components of the cutting force, and it is discussed how the optimal cutting ratio can be found.

ALTERATION OF THE CUTTING FORCE COMPONENTS IN TANGENTIAL TURNING

2023-11-02T14:01:12+02:00

In the development of cutting procedure, the study of the cutting force is important to evaluate the possible loads and elastic deformations in the machining system. The unusual relative position of the cutting tool leads to a changing characteristic of the cutting force in tangential turning. Therefore, it is particularly important to study the values and ratios of the cutting force components in different setups in this finishing procedure. In this paper the depth of cut, feed, and cutting speed are changed, and the effect of these parameters are analysed on the major cutting force, feed force and passive force. The full factorial design of experiment method is applied in the selection of setup parameters and the evaluation of the results. The maximal values and the ratio of the force components were analysed by the determination of equations.

ACTUAL CONTACT AREA ON THE WORN CLEARANCE FACE OF THE CUTTER WITH THE ROUND KYBORITE INSERT

2023-11-03T19:47:07+02:00

For a tool equipped with a circular cutting insert, a dependence is proposed for calculating the nominal area of the contact area on the back surface. It is proved that the actual area of the contact area of the tool differs significantly from the nominal one due to the presence of a system of micro-irregularities, which makes a difference in the assessment of machining process parameters. Using the example of a tool equipped with a circular cutting insert made of polycrystalline cubic boron nitride ciborite, an approach to determining the actual contact area of the back surface with the workpiece during finishing turning of hardened steel is considered. The possibility of taking into account the influence of the system of irregularities in the contact area, determined by the parameters of its topography, on the size of the actual area is shown, and the ratio of the actual and nominal areas of the contact areas of the tool is determined, and it is found that, depending on the degree of development of the microrelief, the ratio of the actual and nominal areas of the contact surface of the cutter differs by at least 20%. It is shown that the actual contact area is also related to the total length of the main and auxiliary cutting edges, determined by the maximum values of the main and auxiliary angles in the cutter plan, and the size of the wear chamfer on the back surface of the cutter.

TOPOGRAPHIC ADAPTABILITY IN THE DIAMOND GRINDING ZONE OF SUPERHARD MATERIALS

2023-11-02T18:53:55+02:00

A comprehensive theoretical and experimental analysis of technological topographic adaptability is carried out, based on an idealized description of the topographic parameters of the working surface of the grinding wheel, their changes during its wear and experimental laser scanning of the working surface of the grinding wheel and the processed superhard material (SHM). It has been established that the protrusion height of diamond grains affects the intensity of destruction (removal) of stock through a change in the number of working grains and the actual contact area of the SHM with the working part of the grinding wheel surface. In a controlled grinding process, it is possible to stabilize the working height of the grains in any of the 3 stages of their wear intensity, equating this intensity with the intensity of removal of the intergranular bond. A method has been developed for determining the actual contact area of the working surface of the grinding wheel and changing its technological adaptability. It has been established that in the process of topographic adaptability, the actual contact area can change by several orders of magnitude, respectively, the specific pressure at the contact of diamond grains with the SHM will change, and, consequently, the nature and intensity of their mutual destruction.

INVESTIGATION OF ELECTRO DISCHARGE MACHINING OF TOOL STEELS BASED ON THE ROUGHNESS OF THE MACHINED SURFACES

2023-11-03T12:22:33+02:00

In electro discharge machining (EDM or spark erosion) the roughness of the machined surface plays a very important role in the applicability of the process. This paper deals with a comparative study of the electro discharge machining of tool steels based on the roughness characteristics of the machined surfaces. Another aim of the research is to investigate which tool materials (electrode material, copper, or graphite) are most effective to achieve the best possible surface microgeometry. Based on the data of the performed cutting experiments and the subsequent measurements, conclusions will be drawn regarding the machinability of the tested tool steels and the applicability of the electrode materials used.

ROUGHNESS INVESTIGATION OF SINGLE AND DOUBLE CUTTING MARKS ON FACE MILLED SURFACE

2023-11-03T15:24:45+02:00

In 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.

LASER MEASUREMENTS IN CUTTING PROCESSES

2023-11-05T11:52:13+02:00

Laser measurements are used chiefly for experiments during metal cutting. The recent development of laser technology offers chances that are advisable to take advantage of machine manufacturing. This article presents some measuring applications for metal cutting. Its purpose is to show separate literature on each technology to provide insight into the possibilities of laser measurements.

PURPOSE AND TECHNOLOGICAL PROPERTIES OF GRANULAR MEDIA FOR VIBRATION FINISHING AND GRINDING PROCESSING

2023-11-05T13:40:25+02:00

The purpose and characteristics of granular working media used in vibration processing operations are given. It is indicated that the purpose of granular media is their contact interaction with the processed part surface under conditions of various energy parameters. This interaction is accompanied by elastic-plastic deformation, micro-cutting, adhesion and mechanic-chemical processes. Indicators of technological and operational properties for various types of granular media are given, including the intensity of material removal from the processed surface, cutting ability, wear resistance and achieved surface roughness. The physical and technological parameters of granular media have been established, including deformability, hardness during finishing and hardening operations and surface roughness of the media granules. The influence of the parameters of processing media granules on the productivity of vibration treatment has been determined. It is shown that such parameters are the binding of the granules material, its wear resistance, grain material, granulation and the shape of individual granules. It is noted that the choice of granule sizes depends on two main factors such as: the necessity to obtain a given roughness and high productivity of vibration operations. It was revealed that to ensure high surface cleanliness, the use of small granules of the medium is required, but to obtain high productivity, the use of large granules is required. Approximate dependencies have been determined that relate the size and weight of granules of the processing medium and the processed parts. It is indicated that the best results in achieving high quality of the processed surface and sufficient productivity are provided by granular media with a shape close to a sphere. It is noted that granules in the form of cones, pyramids, prisms and other forms are used for the successful processing of hard-to-reach places in the form of small holes, straight and sharp angles in the interface of the surface of parts, niches or pockets. Such granules are specially manufactured from a mixture of grinding powders of various grain sizes and an inorganic binder based on clays. The features of the physical and technological parameters of processing media are given.

ARITHMETIC MEAN HEIGHT AND MAXIMUM HEIGHT OF THE ROUGHNESS PROFILE IN HONING WITH DIFFERENT FEEDS

2023-11-05T15:58:26+02:00

The achievable surface quality is an important factor even in roughing procedures; however, it is most relevant in finishing. Two commonly measured and analysed characteristics of the machined surface roughness profile are the Arithmetic Mean Height and the Maximum Height of the Roughness Profile. In this paper these parameters were studied in bore honing. Cutting experiments were carried out, where the feed rate and the applied honing tool are varied. After the evaluation of the measured 2D surface profiles, the following conclusions were drawn: the effect of the feed rate is not linear; the lowest values of the analysed roughness parameters were achieved by the application of 50 mm/rev. feed rate and a honing tool with 80 grain size and ceramic binder; the difference between the studied roughness parameters was 6.5-8.0-fold.

ANALYTICAL ANALYSIS OF THE THEORETICAL SURFACE ROUGHNESS IN THE CASE OF BURNISHING OF CYLINDRICAL WORKPIECE

2023-11-05T15:05:10+02:00

In the last decade, ensuring the highest possible surface quality of manufactured parts has been given a major priority, so more and more emphasis is being placed on the examination and development of finishing treatments that can effectively ensure increasingly stringent surface roughness. For this purpose, diamond burnishing - which is a widely used cold plastic technology - can be used productively as it can improve the surface roughness of the material. But even though due to the development of engineering technology, new possibilities and methods are constantly being developed to examine individual material structure changes, the ability to plan the surface roughness is very difficult. This paper focused on the determination of theoretical roughness to establish a mathematical model that can predict and analyse the relationship between experimental process parameters and surface roughness parameters. To validate the model, real experiments were performed, where the surface roughness were measured before and after the application of burnishing process on low alloyed aluminium shaft pieces.

PROBABILISTIC APPROACH TO CALCULATING THE RATIONAL THICKNESS OF THE TOOL`S CUTTING INSERT FOR HEAVY MACHINE TOOLS

2023-11-11T18:23:23+02:00

The paper proves that the development of regulations for the operation of cutting tools on heavy machine tools, the formation of objective functions for optimising the parameters of machining parts should be carried out based on a given level of reliability of the cutting tool. In this case, a large number of indicators are used to determine the tool's reliability, durability and maintainability separately. Based on statistical and theoretical studies of the probabilistic nature of the properties of the cutting tool and the parameter of load distribution on it, quantitative dependencies between the parameters of the scattering of properties and the thickness of the tool plate of a prefabricated tool were obtained. The stochastic nature of the machining process on heavy machine tools causes a large dispersion of the properties of the machined and tool materials and other machining parameters. This leads to the need for a probabilistic approach to determining the design and technological parameters of the cutting tool. The reliability of a prefabricated cutter depends on both its load and the bearing capacity of the tool structure, which is the ultimate stress that characterises the strength of the structure. Using a probabilistic approach to calculating the thickness of the cutting plate of the cutters, a correction factor for the thickness was determined taking into account the level of reliability of the tool. The level of reliability was understood as the probability that the maximum stress arising under the action of the load will not exceed the bearing capacity. Typical structures that are most commonly used at modern heavy engineering enterprises were investigated. The law of distribution of cutting forces was determined on the basis of statistical data on the operation of carbide cutters. The thickness of the cutting element was calculated for the Rayleigh load distribution law, determined on the basis of statistical data on cutting forces during turning for different cutter designs. The distribution of the bearing capacity of the tool material of the tool inserts was determined on the basis of laboratory tests.

SURFACE TEMPERATURES AND VACATION BURNS OCCURRING DURING GRINDING OF CEMENTED GEARS WITH TWO DISHED WHEELS ON DIFFERENT PARTS OF THE MACHINED INVOLUTE PROFILE

2023-11-12T12:27:19+02:00

To increase grinding productivity with the provision of specified physical and mechanical properties of the surface layer of the surface layer of the processed part it is necessary to know the temperature on the surface of the workpiece, since its value depends on the depth of the defective surface layer. In the work theoretically justified the difference of surface temperatures in the initial (at the base), in the middle (on the dividing circle) and final (at the top) points of involute profile of the gear tooth when grinding with two disc wheels on the zero scheme. The difference in temperature at different points of the processed tooth profile is justified by the fact that at different parts of the trajectory of the movement of the heat source acts a different number of thermal pulses. These pulses have different duration and time intervals between the actions of these pulses in different points of the involute profile are also different. The number of thermal actions on a fixed point of the machined profile depends on the length of the heat source, and the duration of heating of the surface at this point is determined by the width of the heat source. The duration of cooling depends on the location of the point on the involute profile. Mathematical models have been developed to calculate the temperatures at different parts of the trajectory of the rolling path of a disc grinding wheel on the tooth being machined. Each of these formulas contains two sums. The first sum determines the temperature increase at a fixed point of the tooth profile under repeated exposure to thermal pulses during the forward stroke, and the second sum - during the reverse stroke. Mathematical models are based on the principle of superposition of thermal fields. It is found that the temperature in the middle part of the tooth is 40% less than at the tooth apex and 20% less than at the tooth base. The engineering method of distribution of the total allowance by passes at multi-pass gear grinding with two dished wheels according to the zero scheme has been developed. The method is based on the experimental dependence of the depth of the defect layer on the depth of cutting, which has a linear character. In the work, calculations were made on the allowance distribution in the initial, middle and final points of the involute tooth profile. The calculations showed that in order to prevent burns on the final machined surface, grinding in different parts of the machined profile should be performed with a different number of passes. The smallest number of passes on the separating circle, and the largest - on the top of the tooth. The proposed methodology of distribution of allowances by passes can be used at the stage of design of gear grinding operation (for optimization of modes) and at the stage of machining (for diagnostics of the operation). It is theoretically substantiated that calculations of allowance distribution by passes should be made only for the tooth head. To increase grinding productivity with provision of the specified physical and mechanical properties of the surface layer of the processed part it is necessary to know the temperature on the surface of the workpiece, as its value depends on the depth of the defective surface layer. In the work theoretically justified the difference in surface temperatures in the initial (at the base), in the middle (on the dividing circle) and final (at the top) points of involute profile of the gear tooth when grinding with two disk wheels on the zero scheme. The difference in temperature at different points of the processed tooth profile is justified by the fact that at different parts of the trajectory of the heat source acts a different number of thermal pulses. These pulses have different duration and time intervals between the actions of these pulses in different points of the involute profile are also different. The number of thermal actions on a fixed point of the machined profile depends on the length of the heat source, and the duration of heating of the surface at this point is determined by the width of the heat source. The duration of cooling depends on the location of the point on the involute profile. Mathematical models have been developed to calculate the temperatures at various parts of the rolling path of a dished grinding wheel on a machined tooth. Each of these formulas contains two sums.

STUDYING THE INFLUENCE OF THERMOMECHANICAL PHENOMENA ON GRINDED SURFACE QUALITY PARAMETERS OF PRODUCTS MADE FROM HARD-TO-PROCESS MATERIALS

2023-11-12T14:14:54+02:00

Grinded surface quality state of products made from hard-to-process materials is formed under the influence of thermomechanical phenomena during final machining operations. But grinding causes the formation of burns, cracks, and tensile stresses in surface layers of products. These defects significantly influence reliability and durability of products during their operation. High thermal tension of diamond-abrasive processing leads to the fact that thermophysics of these processes is dominating in formation of quality characteristics of processed surface. Existing grinding methods for products made from hard-to-process materials do not allow to fully eliminate defects that occur in surface layer. Among the factors that conduce these defects are inevitable fluctuations of processing allowance, microheterogenity of the material characterized by the size of grain, packaging defects, structural transformations and dislocations, product warping during thermal treating, insufficiently studied thermomechanical phenomena. The mentioned effects accompany grinding process and cause burn marks, microcracks, structural transformations, residual stresses. Exploration of thermomechanical phenomena that form the quality of surface layer considering preceding machining operations of products, determining their influence on cracks and burns formation based on quality analysis of thermal and stress states and make up the objective of this research. This paper proposes more efficient models for studying quantitative connections between technological system parameters, physical and mechanical properties of processed materials, their structure, and thermomechanical processes during grinding. We have developed optimal technological parameters for processing metals and alloys prone to defects in surface layer based on determined relationships. Such defects encompass defects like cracks, burns, and chips.

INFLUENCE OF RADIAL DEPTH OF CUT ON INITIAL CONDITIONS OF OSCILLATIONS DURING END-MILLING OF THIN-WALLED PARTS

2023-11-15T11:21:58+02:00

Milling is widely used in mechanical engineering and other industries. Optimization of this process can lead to improved quality of machined parts, increased productivity and reduced wear of equipment. The paper investigates an important aspect of the milling process, namely the influence of radial depth of cut on the properties of the tool-part technological system (TS) and the amplitude of vibrations during machining. Vibrations can be a direct cause of reduction of quality and accuracy of machined parts. When the amplitude of vibrations increases, their impact on accuracy becomes critical. The analysis of studies of up and down end-milling with different radial depths of cut in the third speed zone of oscillations shows that with increasing radial depth of cut the cutting time and maximum thickness of the cut layer increases. This affects the length of the cutting surface and the character of the workpiece oscillations during up and down-milling. The length of the cutting surface determines how many waves of accompanying free oscillations of the TS and with what intensity will leave their trace on the cutting surface. In up-milling, the thickness of the cut layer increases with increasing radial depth of cut, while the amplitude of the accompanying free oscillations TS and their period decrease. At down milling the thickness of the cut layer decreases, and the amplitude of accompanying free oscillations of the TS and their period increase. A common characteristic feature of up and down-milling is the shaping of the machined surface in the cutting zone with a small thickness of the cut layer. In up-milling, this area is at the beginning of cutting, when the oscillation conditions are the same for all radial cutting depths. Therefore, the machined surfaces after up-milling with different radial cutting depths have close values of pitch and undulation height. At down-milling with increasing radial depth of cut, the amplitude of accompanying free oscillations of the TS in the profiling zone increases. This leads to an increase in the pitch and height of undulations on the machined surface. When milling in the third speed oscillation zone, it is necessary to select the radial depth of cut so that the cutting time is less than the period of the accompanying free oscillations of the TS. This will avoid undesirable oscillations and improve the quality of machining. The paper provides important results and recommendations for optimizing the milling process, considering the influence of radial depth of cut on TS properties and vibration amplitude. These findings may be useful for professionals working in the field of cutting materials processing to improve the efficiency and quality of production processes.