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The development of 3D printing technologies has introduced new possibilities in producing multi-material parts, and Fused Filament Fabrication (FFF) is one of these technologies. Typically, multi-material parts are made of different blends of the same material, also known as multi-color 3D printing, or from materials with good chemical compatibility. Conventionally, a simple face-to-face bonding interface between part components and chemical bonding between thermoplastics define the mechanical performance of multi-material components. In this regard, the paper aimed to investigate the contact interface strength of multi-material specimens using a geometric approach. Therefore, several geometrical interfaces, such as dovetail, omega, T-shape, and others, were used to interlock pars of low-compatibility thermoplastic polymers, styrene-acrylonitrile acrylic (ASA), and thermoplastic polyurethane (TPU). In the case of one of these interfaces, modeling by the finite element method was resorted to obtain additional information regarding the processes that develop at the interface level between the two components of the joint during the tensile loading. The results showed that the macroscopic interlocking interfaces significantly improved the mechanical properties of the multi-material specimens.

In industrial practice, there are situations where friction processes are developed, one of the components involves in the process being made of polymeric materials. In such situations, it may be necessary to know more information regarding the magnitude of the friction coefficient for polymer–polymer or polymer–metal material pairs. A relatively simple equipment is designed and materialized, starting from the idea of moving a sled on which there is a strip of known material and on which a sample of the material to be tested is pressed with a force of known magnitude. The processing of the results of some experimental tests carried out on this equipment, using specialized software, allows the determination of an empirical mathematical model to highlight the influence exerted by some input factors in the experiment on the size of the friction coefficient. It is thus found that, for the available experimental conditions, the nature of the couple of materials in contact and the thickness of the polymer layer deposited by 3D printing exert the greatest influence on the magnitude of the friction coefficient. [ABSTRACT FROM AUTHOR]

To evaluate the sound insulation capacity of small panels made of polymeric materials by 3D printing, a Taguchi L18-type factorial experiment with eight independent variables was designed and materialized. The independent variables were the panel thickness, polymer material type, 3D printing speed, infill percent, infill pattern, layer thickness, frequency, and sound volume. Empirical mathematical models were determined through the mathematical processing of the experimental results using specialized software. These empirical mathematical models highlight the meaning and intensity of the influence exerted by the input factors in the process on the acoustic pressure level of the energy absorbed after the passage of sounds through the small panels manufactured by 3D printing from polylactic acid and polyethylene terephthalate glycol. The factor with the strongest influence was the frequency of the sounds, with a maximum of the sound pressure level for a frequency of 13,000 Hz. A polylactic acid panel between the sound source and the sound-receiving sensor reduces the sound pressure level by about 45% from 95.8 to 65.8 dB. The power function type mathematical model in the case of the energy absorbed by the panel highlights the fact that the highest values of the exponents are those attached to the sound frequency (exponent equal to 1.616) and, respectively, to the thickness of the panel (exponent equal to −0.121). [ABSTRACT FROM AUTHOR]

It is known that ceramic–polymer composite materials can be used to manufacture spherical bodies in the category of balls. Since balls are frequently subjected to compression loads, the paper presents some research results on the compression behavior of balls made of ceramic composite materials with a polymer matrix. The mathematical model of the pressure variation inside the balls highlights the existence of maximum values in the areas of contact with other parts. Experimental research was carried out on balls with a diameter of 20 mm, manufactured by 3D printing from four ceramic–polymer composite materials with a polymer matrix: pottery clay, terracotta, concrete, and granite. The same ceramic–polymer composite material was used, but different dyes were added to it. A gravimetric analysis revealed similar behavior of the four materials upon controlled heating. Through the mathematical processing of the experimental results obtained by compression tests, empirical mathematical models of the power-type function type were determined. These models highlight the influence exerted by different factors on the force at which the initiation of cracks in the ball materials occurs. The decisive influence of the infill factor on the size of the force at which the cracking of the balls begins was found. [ABSTRACT FROM AUTHOR]

A process currently under researchers' attention in terms of making holes is the so-called friction drilling. The process is based on pressing a conical-shaped tool, driven in rotation, into the workpiece to be drilled. The analysis of the process highlights that there will be a variation of the axial force to the physical-mechanical properties of the workpiece material. To highlight the axial force variation, it was necessary to select, among several alternatives, a device that would make this possible. In this sense, the method of analytic hierarchy process was used. It was possible, thus, a justified selection of the device intended to allow obtaining additional information on the friction drilling process [ABSTRACT FROM AUTHOR]

The surfaces of the mechanical parts involved in friction processes are made using different processing methods. Each of these processing methods leads to a certain profile of the asperities of the generated surfaces. When such surfaces are subjected to friction processes, it is possible to produce a change in time in the magnitude of the friction coefficient. For experimental research, the outer cylindrical surfaces of some steel test samples were generated using various machining methods such as turning, grinding, ball and diamond burnishing, and vibroburnishing. Later, using a device adapted to a lathe, experimental tests were carried out following the time variation of the value of the friction coefficient under conditions of dry friction and lubricated friction, respectively. The results of the experimental tests were processed mathematically, being determined by empirical mathematical models that highlight the influence of the final processing methods of the surface, the presence of the lubricant, and the test duration on the variation of the friction coefficient. It was found that first, there is an increase over time in the values of the friction coefficient, and then the values of this coefficient stabilize at certain values. The increase in the coefficient of friction until reaching the stabilization value takes place in a proportion of approximately 148–305%. [ABSTRACT FROM AUTHOR]

Increased interest in the study of plastics has led to the development of processing technologies using such materials. The variety of plastics has led to a diversification of the technical processes through which the finished plastic products can be obtained. We approached the idea of designing plastic injection equipment, considering that various research could be made on the phenomena involved during the process, as well as the observation of the technological properties of the plastics. To design such equipment, some known methods used in conception processes could be applied. Optimizing the equipment design process is one of the elements that can ensure high efficiency of the entire injection molding process. Thus, the method chosen in this case was the analytic hierarchy process (AHP) method, which is one of the methods that offer the possibility to choose a solution when there are many alternatives. The relative simplicity and precision of this method are some of the arguments behind this method. The combination of required equipment and application of the AHP method allowed the choice of an optimal solution for testing injection molding. The result of design activity was an alternative to equipment that can be used for developing future research.

When a technical problem is approached, as a direct consequence of analyzing certain distinct existing solutions, an improved solution of the problem could be elaborated. Over the years, some methods able to help the designers were identified and developed. The purpose of this paper was to take into consideration and to develop a succinct comparison of some creative considered methods of solving research problems in the field of industrial processes. The first group of analyzed design method was based on the initial use of the so-called ideas diagram. The results of the analysis were used to propose solutions concerning a device for investigation of the effects developed on sharp peaks by the electrical discharges. The axiomatic design was applied as a creative design method in the case of equipment for the investigation of degradation in time of the subsystems of the computers. The reverse engineering method was considered in the case of a device for supporting the tablet in a convenient position for the user. A final succinct comparison of the three ways of synthesizing an improved solution of a technical problem from the field of industrial processes highlights the essential characteristics of the approached methods.

Within the university study program that trains of the future engineers in the field of manufacturing engineering, in the Romanian technical universities, there are matters that aim at familiarizing students with the way of solving certain problems of constructive and/or technological design. Such a matter, called cold pressing technology, has been included in the last years of the license studies. In the context of the project activity at this matter, as a theme to be solved, the student usually receives the responsibility of designing a mold for the cold-pressing of pieces of various shapes, for large series production, starting from sheet type workpiece. The passing of successive design stages gradually leads the student to elaborate a project that includes an assembly drawing and some mechanical drawings as final documents related to the received project theme. It was considered that by using some principles of axiomatic design, it is possible to investigate and define more clearly the objectives of the project activity in the field of cold pressing technology. The analysis allowed a clearer definition of functional requirements and the identification of solutions to improve the quality of future engineer training activities concerning to project activity in the field of cold pressing technology.

The paper investigates the influence of some 3D printing conditions on some physical–mechanical and technological properties of polycaprolactone (PCL) wood-based biopolymer parts manufactured by FDM. Parts with 100% infill and the geometry according to ISO 527 Type 1B were printed on a semiprofessional desktop FDM printer. A full factorial design with three independent variables at three levels was considered. Some physical–mechanical properties (weight error, fracture temperature, ultimate tensile strength) and technological properties (top and lateral surface roughness, cutting machinability) were experimentally assessed. For the surface texture analysis, a white light interferometer was used. Regression equations for some of the investigated parameters were obtained and analysed. Higher printing speeds than those usually reported in the existing literature dealing with wood-based polymers' 3D printing had been tested. Overall, the highest level chosen for the printing speed positively influenced the surface roughness and the ultimate tensile strength of the 3D-printed parts. The cutting machinability of the printed parts was investigated by means of cutting force criteria. The results showed that the PCL wood-based polymer analysed in this study had lower machinability than natural wood. [ABSTRACT FROM AUTHOR]

Among the interesting thermal properties of polymeric materials is questionable their ability to transfer heat. The last decades have shown a significant expansion of manufacturing parts from polymeric materials using 3D printing processes. It is known that these processes allow changing the values of some input factors in the 3D printing workflow, which also leads to a change in the way the polymer material is arranged in part and, therefore, to a change in the capacity of the polymer material to transmit heat. To better understand how the variation of some input factors in the 3D printing process can change the way heat is transferred in test samples of polylactic acid (PLA) manufactured by 3D printing, a relatively simple device is designed whereby one of the surfaces of the test sample comes into contact with an aluminum alloy part heated using electrical resistance. Recording images using an infrared video camera helped to complete the information on how heat is transmitted through the test sample. [ABSTRACT FROM AUTHOR]

In some cases, industrial practice requires the production of walls or parts with a thickness of less than one millimeter from a metal workpiece. Such parts or walls can be made by milling using disc cutters. This machining method can lead to the generation of residual stresses that determine the appearance of a form deviation characterized by bending the part or the thin wall. To evaluate the suitability of a metallic material for the manufacturing of thin walls by milling with disc cutters, different factors capable of exerting influence on the deviation generated by the residual deformation of the walls were taken into account. A test sample and an experimental research program were designed for the purpose of obtaining an empirical mathematical model. The empirical mathematical model highlights the magnitude of the influence exerted by different input factors on the disc cutter milling process regarding the size of the deviation from the form, and the correct position of the wall or thin part, in the case of a test sample workpiece made of an aluminum alloy. Input factors considered were cutting speed, feed rate, cutter thickness, wall or part thickness, thin wall length, and height. To rank the input factors whose increase leads to an increase in shape deviation, the values of the exponents attached to the factors in question in the empirical mathematical model of the power-type function were taken into account. It was found that the values of the exponents are in the order 0.782 > 0.319 > 0.169 for wall height, feed rate, and wall width, respectively. It was thus established that the strongest influence on the residual deformation of the thin wall is exerted by its height. [ABSTRACT FROM AUTHOR]

The paper aims to highlight the significance and place of information-seeking in finding improved solutions in the design of innovative products. The observation method was used to identify a way to increase the efficiency of searching for information needed when pursuing a creative solution to a design problem. The study was based on the experience gained in professional activities in higher education for industrial engineering and in the classes held for two academic subjects, when students' creativity was stimulated, including in the search for information. One conclusion is that an experienced designer or researcher should make sketches and notes immediately after formulating the design objective. In this way, the possible inhibitory influence exerted by the results of a deep search for information could be avoided. In the case of a novice designer, it may be necessary to have a minimum collection of general information in the design topic field to familiarize the designer more with the problem addressed. The novice designer could thus develop a few sketches and notes and then go through a deeper stage of information-seeking. Another conclusion was that a certain minimum amount of scientific and technical knowledge is necessary to use technical creativity effectively. [ABSTRACT FROM AUTHOR]

The phonic pollution is a problem of interest in the mechanical workshops. Various solutions could be applied in order to diminish the intensity level of the sound generated by various noise sources. The research presented in this paper aimed to highlight some aspects concerning the measuring of the sound intensity level in a mechanical workshop and some possibilities of decreasing the sound intensity level by using fences made of distinct materials. The sound intensity level corresponding to the use of a universal lathe was experimentally measured by means of an adequate apparatus. The results of experimental research were mathematically processed and some empirical mathematical models were determined. The analysis of the experimental results and empirical mathematical models highlighted the influence exerted by some factors on the sound intensity level and some possibilities of diminishing the phonic pollution by using various phonic fences.

The vibrorolling could be sometimes applied as a finishing method to diminish the height of the surface asperities. It is expected that the mechanical characteristics of the workpiece material affect in a certain extent the generation of the new profiles corresponding to the surface roughness and distinct values of the surface roughness parameters could be obtained. An experimental research was designed and achieved taking into consideration some vibrorolling process input factors and distinct steels as materials for the test samples. The experimental results were mathematically processed and empirical models were determined. These mathematical empirical models highlight the distinct behavior of the studied steels evaluated by means of the Ra surface roughness parameter.

When the threads are obtained by using turning tools, various factors are able to affect the machining accuracy. In order to reveal the way in which these factors exert influence on the threading accuracy, an analysis of some proper situations of obtaining threads on universal lathes and using turning tools was developed. The analysis showed that the thread profile error could be essentially affected by the position of the cutting tool active edges relative to the workpiece. Taking into consideration the results of analysis, some aspects concerning the requirements to be met during the design of a device that could be used in experimental investigation of influence exerted by some factors on the threading accuracy are presented.

The strength of a joint between the ends of one or more strips can be improved by making the contours of the joint into the shape of either the Greek letter omega or of a dovetail. From the point of view of industrial practice, it is of interest to study the behavior of these joints under stretching demands. The emergence and development of additive manufacturing processes for parts made of polymeric materials has led to the idea of conducting experimental tests to highlight the behavior of omega and dovetail-type joints during the tensile test. For the tensile testing of some test samples in which omega and dovetail joints were used, a Taguchi array of type L18 was employed, with eight independent variables, one variable with a two-level variation, and seven variables with variations on three levels. As independent variables, the type of joint, the couple of polymer materials used to make the two components of the joint, some characteristic dimensions of the joint contours, and some input factors in the 3D printing process were established. The values of average force and average displacement at the peak were considered output parameters. The experimental results were mathematically processed, determining empirical mathematical models of the second-degree polynomial type. These models highlight the influence exerted by the considered input factors on the values of the output parameters. [ABSTRACT FROM AUTHOR]

Electrochemical machining is usually included in the wider group of non-conventional machining methods. This method is based on the material removal from the workpiece as a result of chemical reactions between the electrolyte and the material of the workpiece, under conditions where the tool electrode and the workpiece are immersed in an electrolyte and connected to the poles of a direct current source. Using principles from axiomatic design, specialized equipment was designed. This equipment could be used to experimentally investigate the influence of working gap size on the material removal rate from a test sample made of an electroconductive material. The development of the design matrix led to the observation that, in the proposed version, the condition imposed by the first axiom is not strictly respected. This requires the independence of the functional requirements valid for different components of the equipment, which means that there are possibilities for future improvement of the proposed constructive solution. [ABSTRACT FROM AUTHOR]

Complex surfaces such as helical ones are commonly used in machinery. Such surfaces can be obtained by various machining processes, one of these processes being thread whirling. The influence of machining conditions needs to be better understood to develop a more precise prediction of the specific resulting errors involved in thread whirling. This paper firstly presents the theoretical conditions which generate micro-deviations on whirled surfaces. A theoretical model which considers the geometrical parameters describing the whirling head and cutters and the process's whole kinematics was developed. The threaded surface was described as a complex compound surface resulting from intersecting successive ruled helical surfaces corresponding to the cutting edges of the set of cutters from the whirling head. Numerical simulation results were exemplified and validation experiments were both designed and performed. Empirical mathematical models were established to highlight the influence of the input factors such as thread pitch and external diameter, the ratio between the diameter of cutters' top edge disposal and the thread's external diameter, the rotary speed of the whirling head, and the rotary speed of the workpiece on some accuracy elements and roughness parameters of the threaded surface. [ABSTRACT FROM AUTHOR]

Using a mould for thermoforming produced by fused filament fabrication implies several limitations, such as thermal damage due to the low thermal conductivity properties of the plastic material. For the cooling of the plastic mould, many different approaches and influencing factors can be considered. This paper identifies those factors, and based on statistical DOE, adequate experiments have been conducted to analyze the influence of process variables. The results reveal that by using the Voronoi pattern performs an optimum, uniform, and effective cooling. By using the PLA material, the lowest temperatures are obtained in the case of moulds with Conformal Cooling channels. [ABSTRACT FROM AUTHOR]

Polylactic acid (PLA) is a plastic material used occasionally for thermal insulation. Thus, information is required with respect to the thermal insulation property specific to various types of PLA. On the other hand, the development of 3D printing processes has led to ensuring the conditions for manufacturing PLA parts, with properties that can be modified by varying the input factors of printing process. The proposed experimental research method uses the measurement of temperature variation on one surface of PLA panel, while applying a cooling process on the opposite surface. Several panels with different characteristics are tested. The experimental results are processed using a specialized software and an empirical mathematical model is developed. The model highlights the influence of panel thickness, cooling duration, infill, and deposited layer thickness with respect to the temperature of the panel surface opposite to the cooled one. [ABSTRACT FROM AUTHOR]

The thermal properties of parts obtained by 3D printing from polymeric materials may be interesting in certain practical situations. One of these thermal properties is the ability of a material to expand as the temperature rises or shrink when the temperature drops. A test experiment device was designed based on the thermal expansion or negative thermal expansion of spiral test samples, made by 3D printing of polymeric materials to investigate the behavior of some polymeric materials in terms of thermal expansion or contraction. A spiral test sample was placed on an aluminum alloy plate in a spiral groove. A finite element modeling highlighted the possibility that areas of the plate and the spiral test sample have different temperatures, which means thermal expansions or contractions have different values in the spiral areas. A global experimental evaluation of four spiral test samples was made by 3D printing four distinct polymeric materials: styrene-butadiene acrylonitrile, polyethylene terephthalate, thermoplastic polyurethane, and polylactic acid, has been proposed. The mathematical processing of the experimental results using specialized software led to establishing empirical mathematical models valid for heating the test samples from −9 °C to 13 °C and cooling the test samples in temperature ranges between 70 °C and 30 °C, respectively. It was found that the negative thermal expansion has the highest values in the case of polyethylene terephthalate and the lowest in the case of thermoplastic polyurethane. [ABSTRACT FROM AUTHOR]

Wire electrical discharge machining (WEDM) is a process that is used when it is necessary to manufacture small-width slots with a micrometer accuracy or to precisely detach parts with complex contours from metal workpieces in the form of sheets or plates. The fact that the wire electrode rests only in the working zone in two of its guides allows it to achieve micrometric oscillations, leading to the generation of an error from the flat shape of the slot surfaces that gradually develops into the workpiece. The slot widths are influenced by several factors, such as the workpiece thickness, pulse-on time, pulse-off time, the wire tension force, the current, and the wire movement speed along its axis. Some theoretical assumptions about the behavior of the wire electrode were first considered. An experimental research plan was then designed to obtain additional information on the influence of the mentioned factors on the slot width in different positions of the cross-section through the slot. The statistical processing of the experimental results led to the elaboration of empirical mathematical models that highlight the order of influence and the intensity of the influence exerted by the factors mentioned above. [ABSTRACT FROM AUTHOR]

A better understanding of heat transfer through materials used for 3D-printed parts could lead to an extension and an optimization of their use. A topic of interest could be analyzing temperature variation in these materials during cooling processes. Experimental research and equipment were designed to obtain additional information on the surface temperature decrease when the opposite wall surface is exposed to a freezing temperature. Experimental tests were performed on samples made of polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS). An experimental Taguchi L8 program was used, with seven independent variables at two levels of variation. The experimental data analysis with specialized software based on the least-squares method identified a mathematical model of first-degree polynomial type. The coefficients for each input factor involved provide information on the magnitude and trend of the considered output parameter when the input factors' values change. It was found that the thickness of the 3D printing layer, the thickness of the test sample, and the 3D printing speed are the main factors that affect the temperature decrease rate. [ABSTRACT FROM AUTHOR]

The study of residual stresses in metal parts can be performed by making slits where such stresses are assumed to exist. Measuring the width of the slits can provide information on the type and size of residual stresses. The slits must be made by machining processes that do not introduce other stresses in the part's material. One of the methods that can be used in this regard is electrochemical cutting. In the paper, the ideas diagram method was used to analyze the possibilities of contouring some alternatives for the different components of electrochemical cutting equipment. An equipment structure was designed to allow the realization of slits in metal parts to evaluate the internal stresses in parts made of metal. [ABSTRACT FROM AUTHOR]

The liquid crystal display is a resin additive manufacturing process applied in the dental, jewellery, engineering industries or hobby, in applications where surface quality, level of details and dimensional accuracy are the main requirements. This paper identifies and explains issues concerning the dimensional accuracy, which are experimentally identified using printed samples made from dedicated photosensitive resin material and Gw basic software to determinate the optimal printing parameters. [ABSTRACT FROM AUTHOR]

Punching is a cold deformation process by which holes are obtained in the workpiece in sheets or plates. The part of interest is the separate part of the workpiece or that which remains after separating an area from the plate or sheet. A systemic analysis of the punching process was first performed to investigate the punching processes better. The analysis revealed the parameters of interest in the case of such processes and the factors that influence the values of the parameters of interest. The use of the first axiom in the axiomatic design facilitated the identification of some components of a device that would fulfill the different functional requirements of the device. A variant of the device was designed to facilitate a more detailed study of the material's behavior in the area affected by the plastic deformation process. The device considers the specific components of a die, being adaptable to some of the existing universal machine tools in a mechanical workshop. [ABSTRACT FROM AUTHOR]

The wire electrical discharge machining is a nonconventional machining method applied to machine ruled surfaces in plate type workpieces made of electroconductive materials. There are various methods to establish the optimal values for the process input factors in the case of the wire electrical discharge machining. One of these methods is the gray relational analysis that takes into consideration distinct weightings for some of the process output parameters. The method was applied considering the pulse on time, pulse off time and average current intensity as process input factors. The process output parameters were the surface roughness and the machining speed of penetration in the plate type workpiece. In this way, distinct combinations of the process input factors values were established for different weightings of the output parameters. [ABSTRACT FROM AUTHOR]

The wire electrical discharge cutting can be used to separate parts from plateshaped workpieces or to make slots with various contours in electroconductive materials generally characterized by low machinability by conventional machining processes. The analysis of the wire electrical discharge machining process showed that there are many groups of factors able to affect the process results. The axiomatic design principles were used to define the conditions in which experimental research aiming to highlight the factors able to affect the sizes of technological interest in the case of wire electrical discharge machining. To evaluate the influence exerted by some input factors of the wire electrical discharge machining process, namely by the pulse on time, pulse off time, and by the average intensity of the discharge current, on some results of technological interest, an experimental research in accordance with the requirements of a full factorial experiment was designed and materialized. By processing the experimental results, it was possible to determine empirical mathematical models of power type function. [ABSTRACT FROM AUTHOR]

To develop the design activity in the case of a mechanical equipment for a machining process, certain initial conditions should be known and these conditions are sometimes called design requirements. Over the years, various methods were used in to elaborate the design requirements. Within the method of value analysis, better initial information is offered by the product or process functions. When the axiomatic design method is applied, the so-called functional requirements are taken into consideration. In the paper, the value analysis method and the axiomatic design method are used to highlight the design requirements in the case of a polyfunctional minimachine tool. One noticed that if the value analysis method is applied, some functions which are not technical attributes of the product or process are considered, in the case of applying the principles of the axiomatic design method only the requirements that could be materialized by a certain component of the desired product are considered. [ABSTRACT FROM AUTHOR]

In the industrial engineering field, there are several methods able to be applied in order to materialize a cut contour. Not in all cases, the removable rate of material and cutting accuracy are satisfactory and the costs are sufficiently low. In such situations, some nonconventional processing methods could ensure a fast and appropriate solution for cutting workpieces. Knowing that the surface roughness is a parameter of real interest in almost cases when the accuracy is considered, definitely it will decide the chosen manufacturing process. Due to its influence on the surface properties and on the number of subsequent machining operations, the required roughness value could be taken into consideration when selecting the cutting process. Among distinct nonconventional processes which can be applied, in the present paper, the laser beam procedure was established as being the right choice in order to accomplish certain objectives. A theoretical analysis showed that some of input factors for laser beam process are able to affect the sizes of the surface roughness parameters and could be represented by cutting speed, pressure of the gas sent to the processed area, the power developed in the contact area between the laser beam and workpiece, the process efficiency and the frequency of the laser beam. An experimental research was designed and developed, in order to highlight the influence exerted by the above mentioned factors on the size of the Rz surface roughness parameter. Using the experiments planning, it was developed a series of experiments, in order to show the intensity of effects exerted on the surface roughness by the process input factors. [ABSTRACT FROM AUTHOR]

The electrochemical machining with forced hydrodynamic depassivation allows the material removal from workpiece by electrochemical erosion. The products resulted as a consequence of the electrochemical reactions developed between the workpiece material and electrolyte are removed from the machining zone by forced circulation of the electrolyte. A theoretical analysis led to formulation of several hypothesis concerning the behaviour of some metallic materials when test samples presenting a conical surface are affected by the electrochemical machining process with forced hydrodynamic depassivation. In the paper, the results of some experimental researches developed on test samples from steel, bronze and aluminium are presented. By mathematical processing of the experimental results, some empirical mathematical models were established. The empirical models highlight the influence exerted by the gap size, by the size of angle corresponding to the conical surface and by the voltage applied to the two electrodes on the size of the final gap and on the quantity of material removed from the test piece, for a certain duration of the machining process. [ABSTRACT FROM AUTHOR]

The electrochemical machining process is based on the material removal from workpiece as a consequence of electrochemical reactions developed between the workpiece material and electrolyte, when both tool electrode and workpiece are found in an electrolyte and they are connected in the electric circuit of a direct current supply. Distinct factors could exert influence on the sizes of parameters of technological interest in case of electrochemical machining process. The paper presents the results of some theoretical considerations and experimental researches concerning the evolution of the work gap size and diminishing the test piece mass in case of using a conical active surface of the test piece and an aqueous solution of sodium chloride as electrolyte. The experimental results were mathematically processed and empirical mathematical models were determined. The empirical models and the graphical representations based on these empirical models illustrated the diminishing of the final gap size when the angle of conical surface increases and when the initial gap size is higher; the increase of voltage determines an increase of the final gap size. A similar influence is exerted when the test piece mass is considered as output factor. [ABSTRACT FROM AUTHOR]

The electrical discharge drilling could be applied in order to obtain cavities in workpieces made of materials difficult to be machined by classical machining methods. Distinct factors exert influence on the drilling speed. An experimental research was designed and developed by considering the depth of the cavity achieved by means of a tubular tool electrode. One used a machining scheme involving the achieving of the work movement by test piece to the tubular tool electrode clamped on the machine tool table. In this way, the influence exerted by the spurious electrical discharges facilitated by the presence in the work gap of the metallic particles detached from the two electrodes can be diminished. Empirical mathematical models were determined by mathematical processing of the experimental results and using specialized software. The empirical mathematical models proved a high influence exerted on the drilling speed by the peak current intensity. [ABSTRACT FROM AUTHOR]