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The unconventional Wire Electric Discharge Machining (WEDM) technology represents a vital manufacturing technology in different industrial branches. This technology is essential because of the possibility to machine difficult-to-machine materials such as sintered carbides. For this reason, this study analyses the machinability of sintered carbides WKP23S, WSM33S a WK1 with WEDM in both water and oil baths. We investigated the influence of the machining parameters, namely, pulse off time, gap voltage, discharge current, pulse on time, and wire feed, on the cutting speed, surface roughness, and defect occurrence. We investigated 9 different roughness parameters, analysed surface morphology with an electron microscope, and also analysed cross-sectioned samples. We found out that machining sintered carbides in oil bath yields better results than machining in deionized water. The oil tank prevents the removal of the cobalt binder, but it doesn’t reduce fissure occurrence in any significant way.

The influence of the surface area by the impact of high temperatures after wire electric discharge machining (WEDM) is a known fact. However, the affected parameters also include a change in microhardness. In order to further investigate this statement, 5 different ferrous and non-ferrous materials were selected, from which three samples were always made with different settings of machine parameters (gap voltage, pulse on and off time, wire feed and discharge current). This examined not only the effect of the machining itself on the material but also whether the change in the microhardness of the material is affected by the setting of the machine parameters. In order to measure the microhardness of the subsurface layer, a metallographic preparation was made from each sample, which enabled accurate measurements always in the same area. Subsequent evaluation revealed that the microhardness may not be affected at all and everything depends only on the type of material being machined. The changes in microhardness affected by setting machine parameters are negligible. Ovlivnění podpovrchové oblasti působením vysokých teplot po elektroerozivním drátovém řezání (WEDM) je známy fakt. Mezi ovlivněné parametry je však zahrnována i změna mikrotvrdosti. Za účelem bližšího zkoumání tohoto tvrzení bylo zvoleno 5 různých kovových a nekovových materiálů, z nichž byly vyrobeny vždy tři vzorky s odlišným nastavením parametrů stroje (gap voltage, pulse on and off time, wire feed and discharge current). Tímto byl zkoumán nejen vliv samotného obrábění na materiál ale také to, zda je změna mikrotvrdosti materiálu ovlivněna nastavením parametrů stroje. Za účelem měření mikrotvrdosti podpovrchové vrstvy byl z každého vzorku vyroben metalografický preparát, který umožnil přesné měření vždy ve stejné oblasti. Následným vyhodnocením bylo zjištěno, že mikrotvrdost nemusí být vůbec ovlivněna a vše závisí pouze na druhu obráběného materiálu. Změny mikrotvrdosti ovlivněné nastavením parametrů stroje jsou zanedbatelné.

Heat resistance, heat stableness and corrosion resistance are properties that predispose nickel superalloys such as Inconel 625, Mar-M247, Nimonic C 263 and B1914 to a very wide range of applications. Due to their mechanical properties, their machinability by conventional technologies is relatively difficult, so wire electrical discharge machining (WEDM) is widely used, where only one condition is placed on the material being machined, which is at least minimal electrical conductivity. Despite the fact that the main element of which these superalloys are always composed is nickel, their machinability by WEDM is quite different. For this reason, an extensive study comparing the machinability of the four above-mentioned nickel superalloys using WEDM was performed, examining the effect of setting the machine parameters on the cutting speed as well as on the quality of the surface and subsurface layer. It was found out that the cutting speed is different for individual materials with the same set of machine parameters and so that it is possible to significantly increase the quality of the machined surface for individual materials.

The paper presents a method for measuring and recording the forces involved in the coal cutting process. Moreover, a method for visualization of all forces involved in the cutting process was described. In the following part, the construction and principle of operation of a device for determination of forces involved in the cutting process (coal mining), referred to by the author as POU-BW/01-WAP, are presented. Resistance extensometry was used to measure the forces. This is the only device in the world that determines two of three force components that take part in the cutting process. For this purpose, two independent measuring blocks were used, which are strain gauges of force: cutting (Fs) and knife pressure (Fd). In order to register these forces, a real mining knife used in longwall shearer drums was applied – i.e. tangential-rotary. The equipment has the ATEX certificate allowing for operation in real conditions as a device intended for use in potentially explosive atmospheres – in accordance with the directive 94/9/EC. It has received many awards at world fairs for inventions and innovative solutions.

Wire electrical discharge machining (WEDM) technology is often used for the final machining of parts to the required surface quality without further finishing operations. At the same time, WEDM has a significant advantage over other machining technologies, and in the fact, it is possible to machine all materials, regardless of their hardness or toughness, it only needs to be at least electrically conductive. Aviation nickel superalloy Mar-M247, which is usually machined to the final form by parts using WEDM, was the subject of research in this study. In order to find the optimal setting of machine parameters (Pulse on time, Pulse off time, and Discharge current) for multicut machining, an extensive design of experiment was performed with a total of 54 circles, which optimized the cutting speed in the first and second cuts and the topography of the machined surface was taken into account in the third cut. Subsequently, an analysis of the topography and morphology of the machined samples was performed, including an analysis of the condition of the subsurface layer. The study also included the analysis of the lamella in a transmission electron microscope. It was found that with the maximization of the cutting speed in the third cut, the surface topography deteriorates proportionally, but it also leads to the complete removal of all cracks formed in the first cut.

The unconventional technology of wire electrical discharge machining is a key engineering technology, designed primarily for machining of conventionally difficult machine materials. One of them is nickel alloys, which are majorly used in the aerospace and energy industries. The subject of research in this study was specifically the B1914 nickel-based superalloy, which was subjected to many analyses leading to an overall optimization of its machining using wire electrical discharge machining. In order to determine the effect of machine parameters setup (pulse off time, gap voltage, discharge current, pulse on time and wire feed) on cutting speed, topography, morphology, surface and subsurface layer quality, an extensive Box–Behnken design experiment consisting of 46 rounds was carried out. The analyses of the condition of the surface and subsurface layers were performed, including their chemical composition and changes caused by wire electrical discharge machining. It was found out that the factors like pulse off time, discharge current and pulse on time have the greatest effect on the cutting speed, although from the point of view of surface topography the parameter pulse off time is not significant. The remaining two parameters cause the cutting speed to act against the surface topography i.e. with the increasing cutting speed, the surface topography gets worse and vice versa.

The basic building block of any electric discharge machine is a generator, which ensures the operation of material separation itself. Not only the erosion rate and electricity consumption but also the quality of the machined surfaces depend on the design of the generator. These key factors for efficient machining have been investigated using a new energy-saving and powerful generator developed for the electric discharge machine (EDM) while machining 1.2363 and 1.2343ESR steels. In order to monitor and model the responses in the form of eroding rate and surface quality, a two-level half-factor experiment was performed with one replication at the corner points and two replications at the central points, for a total of 80 rounds. Both graphite and copper electrodes of sizes 10x10 mm and 100x100 mm were used for eroding and the influence of parameter settings: Open-voltage, Pulse current, Pulse on-time and Pulse off-time was monitored. It was found out that the shape of the electrode and Pulse current have the most significant effect on the erosion rate. The parameters Pulse current, Pulse on-time and their mutual interaction have the most significant effect on the surface topography. Statistically significant factors influencing the occurrence of defects turned out to be Pulse current, Pulse on-time and Material of workpiece, where it can be seen that the material 1.2343ESR is significantly less prone to the formation of surface defects.

Wire electrical discharge machining (WEDM) is an unconventional machining technology that can be used to machine materials with a minimum electrical conductivity. The technology is often employed in the automotive industry, as it makes it possible to produce mould parts of complex shapes. Copper alloys are commonly used as a electrodes for their high thermal conductivity. The subject of this study was creating mathematical models for machining optimization of Ampcoloy 35 with different thicknesses (ranging from 5 to 160 mm with a step of 5 mm) using WEDM to improve the surface properties of mould parts.The Box-Behnken type experiment was used with a total of 448 samples produced. The following machining parameters were altered over the course of the experiment: Pulse on and off time, Discharge current, and material thickness. The cutting speed was measured and the topography of the machined surfaces in the centre and at the margins of the samples, were analysed. The morphology and subsurface layer were also studied. What makes this study unique is the large number of the tested thicknesses, ranging from 5 to 160 mm with a step of 5 mm. The contribution of this study to the automotive industry and plastic injection mould production is therefore significant. The regression models for cutting speed and surface topography allow for efficient defect-free machining of Ampcoloy 35 of 5-160 mm thicknesses, both in the surface and subsurface layer. Elektroerozivní drátové řezání (WEDM) je nekonvenční technologie obrábění, kterou je možné použít pro obrábění všech alespoň minimálně elektricky vodivých materiálů. Své uplatnění nalézá také v automobilovém průmyslu, kde je díky ní možné vyrábět díly forem složitých tvarů obvykle z měděných slitin a to kvůli jejich vysoké tepelné vodivosti. Předmětem této studie byla optimalizace WEDM obrábění měděné slitiny Ampcoloy 35 o tloušťkách 5-160 mm s krokem 5 mm pomocí plánovaného experimentu typu Box-Behnkenova, kdy bylo vyrobeno celkem 448 vzorků. V průběhu experimentu byly měněny tyto vstupní parametry nastavení stroje: Pulse on time, Pulse off time a Discharge current a také tloušťka materiálu. Byla měřena rychlost řezání, analyzována topografie obrobených povrchů ve středu i na okrajích vzorků a také byla studována morfologie a podpovrchová vrstva. Sestavené regresní modely pro rychlost řezání i topografii povrchu umožňují efektivně obrábět tloušťky 5-160 mm materiálu Ampcoloy 35 bez defektů a to jak v povrchové tak podpovrchové vrstvě.

Electrical discharge machining (EDM) is an unconventional machining technology. It allows machining of at least at least electrically conductive materials. The trend of miniaturization of industrial products is obvious. However, the required quality and accuracy must be maintained, which can be achieved with micro-EDM. One of the industrial products is also optical devices used for testing cars. These contain miniaturized parts, which are, however, necessary for their proper functioning. For this reason, this study was performed, which focused on the production of a precise slot measuring 5000 × 170 µm in a copper foil with a thickness of 125 µm. The same copper foil was used as a tool, which represents an advance in the production of micro-parts.The use of the same semi-product for the production of the slit as well as the tool itself has not yet been presented in any similar study. A design of experiment Box and Behnken Response Surface Design was performed for a total of 15 rounds, monitoring the effect of machine setting parameters (Pulse current, Pulse on time and Voltage) on responses in the form of Erosion rate, corner radius, slot length and width. Using multi-criteria optimization, the optimal setting of the machine parameters for the production of a given slit was determined, which is Pulse current = 2.1 A, Pulse on time = 40 µs and Voltage = 238.8 V. Micro-EDM technology has been found to be suitable for the production of miniaturized slits.

This article discusses plasma cutting technology and its influences on the quality of the resulting cut. Plasma or a plasma arch consists of positive and negatively charged particles, excited and neutral atoms and molecules. As it contains free particles, it is electrically conductive and thus subject to the effects of the electrical and magnetic field. The basis of CNC machine design is described in the article, which has at least 3 axes (x, y, z), but there are also more technologically demanding applications, such as pipe cutting, profile and cutting using chamfer to prepare surfaces for welding, where these multi-axis devices are frequently used. The principle of plasma cutting and the plasma cutting phase is described in this article. The materials that can be divided by a plasma arc are described in detail, including graphs displaying the dependence of sheet thickness on the cutting speed. The article describes and lists the gases that are used in plasma-arc cutting, such as oxygen, argon, hydrogen and nitrogen. Important components of plasma cutting technology are the parameters that can be adjusted and set before the cutting so that the cut is of good quality. The most comprehensive chapter deals with the influences that affect plasma cutting quality. Cutting quality can be influenced by a number of factors. Everything starts with the proper choice of a CNC machine and a plasma source. The quality also depends on the expertise and experience of the machine operator and the setting of the plasma cutting parameters. This issue of influences on the plasma cutting quality is based on long-term experience in the field of the thermal cutting process.

Computer systems supporting the management of machines operation and maintenance in companies have been successfully applied in many branches of industry. Over the last few years these systems have been considerably transformed. It also seems that using them for operating mining machines in hard coal mines is inevitable, as maintenance generates high production costs. If implemented, the systems will allow for optimization of stocks, spare parts and materials, supplies, outsourced services as well as maintenance-repair works. Application of a system supporting the management of mining machines/equipment will also enable a better, more effective use of employees. As a result of these actions, the time needed for preparations and repair will be shortened, which will translate directly into the economic effects of mines.

Electrical discharge die-sinking machining (EDM) is one of the indispensable unconventional technologies enabling the machining of all materials that are at least minimally electrically conductive. Due to the clear trend of miniaturization of products, it is necessary to ensure their quality and accurate production, also with the help of micro-EDM. It is the optical instruments used for testing car lights that contain these miniaturized parts necessary for the correct functioning of the device. For this reason, this study was performed, which focused on the production of a precise slot measuring 5000x170 µm in a copper foil with a thickness of 125 µm. The same copper foil was used as a tool, which represents an advance in the production of micro-parts. A design of experiment Box and Behnken Response Surface Design was performed for a total of 15 rounds, monitoring the effect of machine setting parameters (Pulse current, Pulse on time and Voltage) on responses in the form of Erosion rate, corner radius, slot length and width. Using multi-criteria optimization, the optimal setting of the machine parameters for the production of a given slit was determined, which is Pulse current = 2.1 A, Pulse on time = 40 µs and Voltage = 238.8 V.

Wire electrical discharge machining is an unconventional machining technology that is crucial in many industries. The surface quality of the machined parts is carefully monitored, but the condition of the subsurface layer also plays a crucial role, especially in case of defects occurrence such as cracks or burnt cavities. The subsurface layer of individual materials is affected differently due to wire electrical discharge machining. For this reason, this study was carried out focusing on a detailed analysis of transmission electron microscope (TEM) lamellae made of Ti-6Al-4V titanium alloy, AlZn6Mg2Cu aluminium alloy, pure molybdenum, Creusabro 4800 steel, and Hardox 400 steel. The attention was first of all paid to the concentration and distribution of individual elements in the recast layer and also in the base material, which was often affected by Wire electrical discharge machining. Further, a diffraction analysis was performed for each TEM lamella in the adhesive area and in the area of the base material. In order to assess the macro-effects on the machined material, the analysis of the topography of the machined surfaces and the morphology analysis were performed using electron microscopy. Elektroerozivní drátové řezání je nekonvenční technologie obrábění, která je klíčová v mnoha průmyslových odvětvích. Jakost povrchu takto obrobených dílů je pečlivě monitorována, nicméně stav podpovrchové vrstvy hraje také klíčovou roli a to především při vzniku defektů v podobě trhlin či vypálených kavit. Podpovrchová vrstva u jednotlivých materiálů je v důsledku elektroerozivního obrábění ovlivněna odlišným způsobem. Z toho důvodu byla provedena tato studie zabývající se detailní analýzou TEM lamel vyrobených z hliníkové slitiny AlZn6MgCu, titanové slitiny Ti-6Al-4V, čistého molybdénu, oceli creusabro 4800 a oceli hardox 400. Pozornost byla věnována především koncentraci a rozložení jednotlivých prvků v oblasti recast layer a také v základním materiálu, který byl často účinky WEDM také ovlivněn. Dále byla u každé TEM lamely provedena difrakční analýza v oblasti přílepku i v oblasti základního materiálu.

Wire electrical discharge machining (WEDM) is an unconventional and very efficient technology for precision machining of the Nimonic C 263 super alloy, which is very widespread, especially in the energy, aerospace and automotive industries. Due to electrical discharge, defects in the form of cracks or burned cavities often occur on the machined surfaces, which negatively affect the correct functionality and service life of the manufactured components. To increase the efficiency of the machining of Nimonic C 263 using WEDM, in this study, extensive design of experiments was carried out, monitoring input factors in the form of machine parameters like Pulse off time, Gap voltage, Discharge current, Pulse on time and Wire feed, the output of which was comprehensive information about the behaviour of such machined surfaces, which allowed the optimization of the entire machining process. Thus, the optimization of the Cutting speed was performed in relation to the quality of the machined surface and the machining accuracy, as well as an analysis of the chemical composition of the machined surfaces and a detailed analysis of the lamella using a transmission electron microscope. A detailed study of the occurrence of surface or subsurface defects was also included. It was found that with the help of complex optimization tools, it is possible to significantly increase the efficiency of the machining of the Nimonic C 263 super alloy and achieve both financial savings in the form of shortened machine time and increasing the quality of machined surfaces. Elektroerozivní drátové řezání (WEDM) je nekonvenční a velmi efektivní technologie pro precizní obrábění super slitiny Nimonic C 263, která je velmi rozšířená především v energetickém, leteckém a automobilním průmyslu. Vlivem elektroeroze často vznikají na obrobených površích defekty v podobě trhlin či vypálených kavit, které negativně ovlivňují správnou funkčnost a očekávanou životnost vyrobených součástí. Za účelem zefektivnění obrábění Nimonic C 263 pomocí WEDM byl v rámci této studie proveden rozsáhlý plánovaný experiment, při kterém byly sledovány vstupní faktory v podobě parametrů nastavení stroje Pulse off time, Gap voltage, Discharge current, Pulse on time a Wire feed, jehož výstupem bylo získání komplexních informací o chování takto obrobených povrchů, což umožnilo optimalizaci celého obráběcího procesu. Byla tedy provedena optimalizace rychlosti řezání v návaznosti na jakost obrobeného povrchu a přesnost obrábění, dále byla provedena analýza chemického složení obrobených povrchů a také detailní analýza lamely pomocí transmisního elektronového mikroskopu. Součástí byla i detailní studie výskytu povrchových či podpovrchových defektů. Bylo zjištěno, že pomocí komplexních optimalizačních nástrojů je možné obrábění super slitiny Nimonic C 263 výrazně zefektivnit a dosáhnout tak jak finanční úspory v podobě zkrácení strojního času tak zvýšení jakosti obráběných povrchů.

When grinding high demands are usually placed on the geometrical tolerances of the workpiece surface. For this reason, the spindles of the grinding machines are normally designed with requirements for a minimum position change of the grinding disks due to external forces and bending moments. The design theory of these spindles is relatively well elaborated, as it represents the most frequently used solution in practice. However, there are also cases where it is necessary to grind some hard-to-reach areas, using a great ejection of the spindle. In these cases, it is necessary to reassess the required geometrical tolerances with regard to its necessity to comply with the minimal changes in the position of the grinding discs due to the great ejection. Where it is necessary to maintain high geometrical tolerances, it is necessary to ensure a greater rigidity of the spindle. This rigidity is usually improved by increasing its diameter. By doing this we also increase the weight of the spindle that is heavily ejected, and thus its deformation can occur due to gravity forces. That is why it is necessary to analyse the deflection of the spindle depending on its ejection in the course of its design. In the case we increase the diameter of the grinder spindle the possible applicable grinding disc diameter decreases, due to the growing size of its housing. Any grinding of hard-to-reach surfaces is therefore done in particular to improve the quality of the surface with low requirements on the geometrical tolerances. This article deals with the design patterns for a spindle used in axial grinding for inner rotating surfaces. The article contains a spindle design solution and an analysis of its deflections, depending on its ejection, and the size of the passive forces.

Die-sinking electrical discharge machining is an unconventional technology that allows to machine all at least minimally electrically conductive materials regardless of their physical and mechanical properties. Despite the fact that it is not a conventional technology, the tool gets also worn out, which is a tool electrode. The wear of the electrode does not only mean its loss but also the degradation of the shapes that are transferred to the resulting workpiece. For this reason, a design of experiments was conducted with 6 input factors, 2 were categorical: the electrode material (copper, graphite) and workpiece material (steel 1.2363 and steel 1.2343ESR) and 4 were numerical: Open-voltage, Pulse current, Pulse on-time, and Pulse off-time. In the framework of this design of experiments, the wear of the used graphite and copper electrodes at their corners and edges was evaluated, which was made possible by the use of electron microscopy and the use of approximation circles. Furthermore, the eroding speed, the topography of the machined samples, and the morphology of the surfaces of the used electrodes were investigated. It has been recognized that the use of a graphite electrode will allow for more accurate workpiece shapes and less wear. Web of Science 20 4 art. no. 130

Wire electrical discharge machining (WEDM) is an unconventional technology that is indispensable in almost all industries as well as pure molybdenum, which is used in almost all areas of industry, from energy through chemical, automotive, metallurgical to physical laboratory equipment designed for vacuum. However, due to its energy demands, the effort is to maximize the cutting speed with an emphasis on maintaining the quality of machined surfaces, which also often contain a number of defects in the form of cracks or burnt cavities. For this reason, the aim of this study was to find the optimum setting of the machine parameters using a design of experiment consisting of 33 rounds, with the material of pure molybdenum being examined. An extensive analysis of all machined samples was performed in terms of defects occurrence in the surface and subsurface layers, the analysis of topography and morphology including 3D surface reliefs, the analysis of chemical composition with dependence on diffusion processes and measurement of residual stress in the workpieces. Due to the high occurrence of cracks, the influence of the cut orientation through the semi-finished product was tested, and its fundamental influence on the occurrence of massive cracks was found out. In addition, to minimize the topography parameters and maximize the cutting speed, the machine parameters were set to: gap voltage = 70 V, pulse on time = 6 µs, pulse off time = 30 µs, wire speed 10 m·min−1 and discharge current = 35 A.

The unconventional technology wire electrical discharge machining is widely used in all areas of industry. For this reason, there is always an effort for efficient machining at the lowest possible cost. For this purpose, the following comprehensive study has been carried out to optimize the machining of the copper alloy Ampcoloy 35, which is particularly useful in plastic injection moulds. Within the study a half-factor experiment of 25-1 with 10 axial points and 7 central points of a total of 33 rounds was carried out, which was focused on the response monitoring of the input factors in the form of the machine parameters setup: gap voltage, pulse on time, pulse off time, discharge current, wire speed. Based on the study of the response in the form of cutting speed and surface topography, their statistical models were created, while the optimal setting of machine parameters was determined to maximize the cutting speed and minimize the topography parameters. Further, a detailed cross-sectional analysis of surface and subsurface layer morphology was performed using electron microscopy including the chemical composition analysis. In order to study microstructural changes in the material at the atomic level, a lamella was created, which was then studied using a transmission electron microscope. Nekonvenční technologie elektroerozivního drátového řezání je široce rozšířenou ve všech oblastech průmyslu. Z toho důvodu je vždy snaha o efektivní obrábění s co nejnižšími náklady. Za tímto účelem byla provedena následující komplexní studie, která optimalizuje obrábění měděné slitiny Ampcoloy 35, která nachází své uplatnění především ve formách pro vstřikování plastů. V rámci studie byl proveden poloviční faktorový experiment 25-1 s 10 axiálními body a 7 centrálními body čítající celkem 33 kol, který byl zaměřen na sledování odezev vstupních faktorů v podobě nastavení parametrů stroje: gap voltage, pulse on time, pulse off time, discharge current, wire speed. Na základě studia odezev v podobě rychlosti řezání a topografie povrchu byly vytvořeny jejich statistické modely, přičemž dále bylo určeno optimální nastavení parametrů stroje pro maximalizaci rychlosti řezání a minimalizaci parametrů topografie. Dále byla provedena detailní analýza morfologie povrchu a podpovrchové vrstvy v příčném řezu užitím elektronové mikroskopie včetně analýzy chemického složení. Za účelem studia mikrostrukturních změn v materiálu na atomární úrovni byla vytvořena lamela, která byla následně studována užitím transmisního elektronového mikroskopu.

Kotus M., Andrassyova Z., Cico P., Fries J., Hrabě P., 2011. Analysis of wear resistent weld materials in labo ratory conditions . Res. Agr. Eng., 57 (Special Issue): S74–S78. The aim of the study was the evaluation of the suitability of using filler surfacing materials in abrasion resistant layers according to their material and tribology features. Laboratory analysis of the selected materials consisted of the tests of hardness, microstructure and wear resistance determination. The abrasive wear resistance was defined according to the standard STN 01 5084. On the basis of the results obtained, we can state that using the hard-facing for the background is tenable for the purpose of wear amount decrement where the abrasive wear prevails.