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Because the fabrication of three-dimensional (3D) microelectrodes is quite challenging, microelectrodes with a simple cross-section are usually used in micro-electro-discharge machining (micro-EDM) to perform layer-by-layer scanning machining for machining 3D microstructures. In this study, we used pure copper powder as the raw material to prepare 3D queue microelectrodes through selective laser melting (SLM). The influences of laser power and laser scanning speed on the densification rate of the 3D microelectrodes were investigated. Moreover, the effects of the temperature and temperature holding time on the conductivity and EDM performance of the 3D microelectrodes during heat treatment were also analyzed. In order to improve the geometric accuracy of the 3D microstructure, 3D microstructures were subjected to micro-EDM with 3D queue microelectrodes: the first microelectrode was used for rough machining and the remaining microelectrodes were used for fine machining. In addition, to ensure a high surface quality of the 3D microstructure, multiple EDM were conducted to eliminate unmelted copper powder and layer defects on the surface of the 3D queue microelectrode. Finally, by applying the 3D queue microelectrodes in micro-EDM, a 3D microstructure with a height error of 1 µm and surface roughness of 1.685 µm was obtained after three repeated discharges. [ABSTRACT FROM AUTHOR]

Micro-stepped holes have been widely used in the fields of micro motor, precision mold, medical device, and so on. YG8 cemented carbide is widely used for machining micro-stepped hole because of its high hardness and good wear resistance. However, it is difficult to realize high-quality machining of micro-stepped holes on YG8 cemented carbide by turning and milling. Micro-EDM has no macroscopic cutting force and is not limited by material hardness, so it is the mainstream technology for machining microstructures on superhard materials. To address the above problems, the paper proposed to adopt micro-EDM to process the micro-stepped hole by using a micro milling cutter. Firstly, micro-EDM was carried out on YG8 cemented carbide with a high-speed rotating micro milling cutter to obtain the basic micro-hole structure. In the process of micro-EDM, the length of micro milling cutter was reduced due to wear. Secondly, micro-EDM was performed on the YG8 cemented carbide using the micro milling cutter with wear in length as the tool electrode, which was made to shake around the central axis of the basic micro-hole, so that a secondary basic micro-hole was machined on the basic micro-hole and a micro-stepped hole was formed. In the process of machining the secondary basic micro-hole, micro milling cutter with no wear would produce a secondary basic micro-hole with the same depth as the basic micro-hole, and no micro-stepped hole would be formed. In this paper, the wear of micro milling cutter in the length direction was transformed into a favorable factor. With the micro milling cutter shaking, a micro-stepped hole was obtained using the same micro milling cutter in different stages of EDM. Through a large number of machining experiments, the main process parameters were optimized and the experimental results were analyzed in this paper. Finally, the micro-EDM of YG8 cemented carbide was carried out with a micro milling cutter with a diameter of 400 µm at 2000 RPM rotational speed n, 90 V machining voltage V, and 0.5 duty ratio R, and a micro-stepped hole with good quality was obtained. [ABSTRACT FROM AUTHOR]

Aiming at the problem of complex path planning in the processing of curved surface workpieces of body-in-white, a hybrid path planning method based on a memetic algorithm is proposed. The method is divided into two parts: welding sequence planning and welding path planning between weld points. By establishing the kinematic model of a spot welding robot based on the pipper criterion and z-y-z Euler angle solution method, the motion constraints of path optimization are analyzed. Under the framework of the memetic algorithm, the improved A-star algorithm with redundant node deletion and a post-smoothing process is used to obtain the smooth collision-free optimal path set between weld points and to construct the objective function of travelling all weld points with the shortest path length and highest smoothness. The multiobjective elitist-simulated annealing genetic algorithm (MESAGA) is used to achieve the welding sequence planning of all weld points. The variable neighborhood search method improves the mutation operator; the elitist strategy is introduced to improve the probability of elitist individual crossover and mutation operation, and a simulated annealing algorithm is used to jump out of local search to obtain the global optimal solution. According to the motion constraints, the joint space path is obtained by the optimal path in Cartesian space. Simulation analysis results demonstrate that the hybrid path planning method based on the memetic algorithm can effectively optimize the path of spot welding robots and lay the foundation for control and trajectory planning during welding processes. [ABSTRACT FROM AUTHOR]

Titanium alloy has been widely applied in industrial fields because of its excellent material properties. Electrical discharge machining (EDM) is commonly technology for processing titanium alloy. When titanium alloy was processed by EDM, a recast layer was inevitably be produced on its surface, which can adversely affect the surface quality and working life. Focus on the above problem, this paper proposed to add B4C powders into the spark oil and cooperate with the tool electrode sloshing for powder mixed electrical discharge machining (PMEDM) of titanium alloy, which can reduce the thickness of the recast layer and thereby improve the quality of the machined surface. Firstly, B4C powders were mixed in the spark oil and the PMEDM of the titanium alloy was carried out. In this step, the thickness of recast layer was preliminarily reduced and the quality of machined surface was improved. Secondly, when the PMEDM of the titanium alloy was nearly completed, the tool electrode sloshed along the machine tool spindle within the EDM gap. Combining PMEDM with the tool electrode sloshing, the recast layer on the machined surface was further eliminated and the quality of machined surface was further improved. By adding 3000 mesh B4C powders into the spark oil, the paper carried out the PMEDM of titanium alloy combining with the tool electrode sloshing. Under the action of appropriate process parameters, the micro-groove structure with surface roughness Ra of 0.205 μm was obtained in the titanium alloy and the recast layer on the machined surface was almost invisible. [ABSTRACT FROM AUTHOR]

Ti-6Al-4V alloy has been widely used in industrial fields. Electrical discharge machining (EDM) is a commonly used technology for machining Ti-6Al-4V alloy. During EDM of Ti-6Al-4V alloy, the thermal and physical characteristics of tool electrode have an important influence on processing characteristics. In order to study the influence of different electrode materials on the processing characteristics of Ti-6Al-4V alloy, brass electrode, copper tungsten electrode, and tungsten electrode were used to perform EDM of Ti-6Al-4V alloy. In this paper, electrodes with V-groove array structures were designed to carry out powder mixed electrical discharge machining (PMEDM) of Ti-6Al-4V alloy, and the machining results were evaluated based on four indicators: microstructures morphology, tool electrode wear (TEW), material removal rate (MRR), and recast layer thickness (RLT). The processing results show that copper tungsten electrode is recommended to machine Ti-6Al-4V alloy because it has the highest reproduction rate (75.2%), a smaller TEW (139 μm), the highest MRR (255.39 mm3/min), and a thinner RLT (3.35 μm). [ABSTRACT FROM AUTHOR]

To promote the development and application of ultra-thin heat dissipation devices, Cu/grapheme (GR) composite foils with hierarchical microscale structure were prepared by ultrasonic-assisted composite electrodeposition, and chemical etching and plasma oxidation treatment were applied to obtain superhydrophilic. The study found that the hierarchical multi-scale structure on the mold electrode surface can be replicated on the foil surface. Ultrasonic refines the grains and reduces the internal defects, while an increase in the GR content not only further refines the grains but also makes the microstructure multi-directional. The combined effect of ultrasonic and GR significantly improves the microhardness of the foils up to 125 HV0.01. Without any surface treatment, the contact angle (CA) of foil gradually increased with the introduction of ultrasonic and GR, the wettability developed towards hydrophobic, and the highest CA reached 98.43°. Chemical etching can change the submicron-scale structure of the foil surface, and then make the wettability towards to hydrophilic, but not enough to reach the superhydrophilic state. After plasma oxidation treatment, a large number of nanoscale CuO and Cu2O particles are generated on the surface of the chemical etching foils, which not only further enriches the multi-scale structure, but also improves the surface energy. As a result, the wettability of foil surface is further improved, showing a superhydrophilic state, and the CA is less than 5°. Moreover, with the introduction of ultrasonic and the increase of GR content, the hydrophily of the foil surface also tends to improve, and the minimum CA can reach 1.89°. [ABSTRACT FROM AUTHOR]

Printed circuit board (PCB) can provide assembly support and electrical connection for components in electronic systems. The machining of micro-holes in PCB is a necessary process and key step for its application in electronic components. Therefore, micro-holes are the key structures of PCB. At present, high-speed drilling based on micro-bit is the key supporting technology for machining PCB micro-holes. However, when the copper foil layer in PCB is machined by this technology, the micro-holes are prone to defects such as hole mouth burr and hole nail head, which could seriously affect the performance of PCB. Focusing on the above problems, this paper proposed to use micro electro-discharge machining (micro-EDM) for assisted machining of PCB micro-holes. With this method, the copper foil layer in PCB was machined by micro-EDM, so as to remove hole mouth burr and hole nail head. The paper detailedly studied the influence of micro-EDM voltage, pulse width and pulse interval on hole mouth burr and hole nail head. Finally, under the effects of 10,000 rpm rotational speed, 40 V voltage, 80 ns pulse width and 160 ns pulse interval, the micro-bit with diameter of 200 μm was used to carry out micro-EDM-assisted machining of the copper foil in PCB. From the machining results, it can be found that the hole mouth burr and the hole nail head were basically eliminated and PCB micro-holes with good quality were obtained by the proposed method. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) has been widely used in the machining of mechanical parts. However, the parts obtained by EDM have recast layers and micro-cracks on their surface, which seriously affect their mechanical properties. In order to remove the recast layers and micro-cracks resulted from EDM, this paper proposed to combine micro-EDM with negative polarity micro-EDM. First, the mechanical part was machined using conventional EDM, after which the surface of the part had a distinct recast layer and micro-cracks. As the conventional EDM was nearing completion, the power supply was replaced by a micro-EDM power supply and then the part was processed by micro-EDM to reduce the thickness of the recast layer. After micro-EDM, the part was processed by negative polarity micro-EDM, which can remove the recast layer and the micro-cracks on the surface of the part. Conventional EDM was performed on 304 stainless steel using a copper electrode with voltage of 250 V, pulse width of 7 ms, and pulse interval of 5 ms. The experimental results showed that the recast layer and micro-cracks on the surface of the part were obvious and the surface quality of the part was poor. After that, the same part was sequentially subjected to micro-EDM and negative polarity micro-EDM with voltage of 110 V, pulse width of 0.5 μs, and pulse interval of 15 μs. The experimental results showed that the recast layer and micro-cracks on the surface of the part were almost invisible and the surface quality of the part was greatly improved. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) microelectrodes can be fabricated by laminating multilayer copper microelectrodes. When the 3D microelectrode is used for micro electrical discharge machining (micro-EDM), the 3D microstructure can be obtained with an up-and-down reciprocating motion. The process is simple and the machining efficiency is high. In micro-EDM process, the 3D microelectrode has wear, which affects the shape accuracy and dimensional accuracy of the microstructure. To obtain the wear characteristics and predict the wear of the 3D microelectrode, the paper discretized 3D microelectrode into several microelectrodes with square cross-sections. The discretized 3D microelectrodes comprised a number of α-type electrodes, β-type electrodes, and γ-type electrodes. The wear of these microelectrodes was studied by numerous experiments, and the wear characteristics of individual microelectrodes were integrated to obtain the wear characteristics of the 3D microelectrode. The study found that the wear of these three types of electrodes was linearly related to the machining depth. The fit slope of the α-type electrode was equal to − 0.24071, and it had the most wear. The fit slope of the β-type electrode was equal to − 0.21524, and it had the second-highest wear. The fit slope of the γ-type electrode was equal to − 0.19767, and its wear was the lowest. Finally, a 3D microelectrode with semi-cylindrical features was used for micro-EDM to verify the correctness of the wear characteristics. The experimental results were compared with the theoretical calculation, and the theoretical calculation of the 3D microelectrode wear was basically consistent with the experimental results. The maximum error between the theoretical calculation and the experimental results was 21.85 μm, and the minimum error was 3.16 μm. [ABSTRACT FROM AUTHOR]

The three-dimensional topography of machined surface induced by machine tool vibration has a great impact on the optical performance of ultra-precision optical components. This paper aims to explain the formation mechanism of the wavy topography of the machined surface of ultra-precision flycutting. Firstly, a dynamic model of the machine tool was built based on finite element method (FEM) considering the fluid-structure interaction (FSI) effect. Then, a mathematic model for simulating the machined surface topography was built based on the FEM model of the machine tool. The machined surface topography was simulated, and the spatial periods of waviness errors were analyzed based on power spectral density (PSD) method. The reason of waviness errors on machined surface was revealed by investigating the internal relationship between the spatial period of waviness error and the dynamic performance of the machine tool. Moreover, the method for controlling the spatial period of waviness error was discussed, which provides guidance for improving the optical performance of large size optical component. [ABSTRACT FROM AUTHOR]

Based on a planned process design path, a foil queue microelectrode (FQ-microelectrode) is applied sequentially in micro-electrical discharge machining (micro-EDM) in which the micro-EDM results can superimpose to produce the 3D micro-structure. However, in this process, each foil microelectrode (F-microelectrode) inevitably experiences wear, and the wear has an unfavorable effect on the machining accuracy of 3D micro-structure. In this study, the wear of F-microelectrodes for different technological parameters is studied in detail. The experimental results show that the first three pieces of the F-microelectrodes exhibit serious wear, and the wear values are all over 7 μm. As the processing proceeds, the wear of the microelectrode gradually decreases to 2 μm, as a result of an improvement in the processing environment. To ensure the machining accuracy of 3D micro-structure, this paper compensates the wear of the first three pieces of the F-microelectrode through rough and finish machining. Finally, based on the experimental results, a 3D micro-structure with good form accuracy can be fabricated in cemented carbide with pulse width Ton = 80 ns, pulse interval Toff = 160 ns, and machining voltage V = 100 V. [ABSTRACT FROM AUTHOR]

3D micro-electrode is fitted out by multilayer 2D micro-structures, so the steps inevitably occur in the 3D micro-electrode. When the 3D micro-electrode is used in micro-EDM, steps are replicated onto the surface of the 3D micro-structure, which have an adverse impact on the shape precision of the 3D micro-structure. Focus on this problem, this paper proposed to eliminate the steps of the 3D micro-electrode based on skin effect and point discharge. Then, the paper detailedly researched the impact of machining voltage, machining depth, and processing numbers on the elimination of 3D micro-electrode’s step effect and its micro-EDM results. In order to verify the feasibility of this method, the paper designed a 3D micro-cavity structure which has slopes in the X and Y directions with slope angle of 45°. Finally, under workpiece of 304# stainless steel, pulse width of 800 ns, pulse interval of 4200 ns, machining voltage of 110 V, and machining depth of 650 μm (250 μm larger than the design depth), the step effect of the 3D micro-electrode was effectively eliminated and its micro-EDM result has a dimension error within 7 μm and slope error within 3°. [ABSTRACT FROM AUTHOR]

Applying 3D micro-electrodes in micro-electrical discharge machining (micro-EDM) can process a 3D micro-structure with up and down reciprocating machining method. However, this method has some shortcomings, such as the formation of ridges on 3D micro-structure surface and a relatively low processing efficiency. To resolve these shortcomings, this study fabricated 3D micro-electrode and applied it in micro-electrochemical machining (micro-ECM). Based on the principle of electrolytic polishing, the ridges on the 3D micro-structure surface were basically eliminated and make the ridges have little influence on the 3D micro-structure surface. Moreover, with a feeding speed of 50 μm/min, it takes only 8 min to process a 3D micro-structure (360-μm depth) by using micro-ECM. With the improvement of surface quality and processing efficiency, it is believed that this study could improve the application possibility of 3D micro-electrodes in industrial fields. [ABSTRACT FROM AUTHOR]

Correct selection of cutting parameters is one of effective approaches to achieve optimum machining process, including reducing energy consumption. For the close relationship between cutting parameters and energy consumption in machining process, energy consumed is modeled and to be reduced based on analyzing the energy consumption in this paper. According to the different requirements in roughing process and finishing process, corresponding multi-objective optimization functions are formulated considering energy consumption. Taking the optimization of milling operations on aluminum alloy as an example, experiments are carried out to analyze the energy consumption and production rate with sets of optimized/un-optimized cutting parameters for different objectives. The experimental results show that the objectives of low consumed energy and high production rate can be simultaneously achieved by optimization of cutting parameters. [ABSTRACT FROM AUTHOR]