Search

Electrical discharge machining (EDM) has been wildly used in the modern manufacture industry due to its advantage over the traditional manufacture method of some hard-to-cut materials. However, compared with the traditional manufacture method, the EDM process was inefficient and environmentally hazardous due to the decomposition of the dielectrics, especially in the case of sinking EDM which used oil-based dielectric. In order to improve the EDM performance, and for the other hand, alleviate the environmental impact of the process, a new type of dielectric, water in oil (W/O) emulsion was proposed as the working fluid. This work presents a systematical study on the performance of this new type dielectric based on the orthogonal and additional single factor experiments. Statistical analysis of the results show that discharge current (I) and water content of the emulsion significantly influence the machining performance of sinking EDM. The study also analyzed the influence of the emulsion temperature and flushing condition on its EDM performance. It was observed that both MRR and EWR decrease with increasing temperature of the emulsion. Experiments results indicated that W/O emulsion can be used as the working fluid of sinking EDM and alleviated the environmental impact of the process. [ABSTRACT FROM PUBLISHER]

In this paper, a new type of sinking electric discharge machining (EDM) dielectric-water-in-oil (W/O) emulsion is proposed, and the machining characteristics of W/O emulsion are investigated by comparing with that of kerosene. In the experiments, machining parameters such as the dielectric type, peak current, and pulse duration are changed to explore their effects on machining performance, including the material removal rate (MRR), relative electrode wear rate (REWR), and surface roughness. Experimental results revealed that W/O emulsion could be used as the dielectric fluid of sinking EDM and adopting long pulse duration and large peak current could lead to obtaining higher MRR than kerosene. Compared with kerosene, W/O emulsion is observed to cause lower carbon adhered to the electrode surface. Therefore, its REWR is higher. Statistics of the discharge waveform show that more stable discharge processes can be obtained by using W/O emulsion compared with kerosene. Furthermore, W/O emulsion is more economical and more environmentally friendly than kerosene, and it could be an alternative to kerosene in sinking EDM application. [ABSTRACT FROM AUTHOR]

Water-in-oil emulsion has been proposed as the working fluid of die-sinking electrical discharge machining in our previous research. Compared with the traditional mineral oil–based working fluid, the water-in-oil emulsion was more environmentally benign and efficiency. This study presents a new method of die-sinking electrical discharge machining that uses oxygen-mixed water-in-oil emulsion as the working fluid. Experimental results showed that the material removal rate can be highly improved, and the relative electrode wear ratio can be significantly reduced by mixing oxygen into the water-in-oil emulsion. The recast layer was much thinner with this oxygen-assisted machining method. [ABSTRACT FROM AUTHOR]

The influence of several factors on the electrostatic dehydration process of water-in-model oil emulsions in high-frequency electrical field has been studied using conductivity technique. The ascending and the descending periods of the observed conductivity versus time curves were fit to sigmoid and power function, respectively, which revealed the model parameters that were used to quantify anew dehydration efficiency (DE) index. Experiments results shown that not only water content, surfactant concentration, salt concentration in the aqueous phase and temperature but also homogenization were all found to play a non-negligible role in the electrostatic dehydration process. [ABSTRACT FROM AUTHOR]

This work presents a comparative study on the performance of three types of dielectrics at different electrical discharge machining (EDM) parameter combinations favorable for generating porosity. The characteristics of the porosity formation in the recast layer formed in water/oil emulsions (W/O) were investigated by comparing them with those present in the recast layer formed in kerosene and deionized water dielectric. The results showed that the porosity characters were influenced significantly by the dielectric type. The formation mechanism of the porosity in different dielectrics is presented in this article. [ABSTRACT FROM AUTHOR]

Abstract: Although the concept of optimum frequency had been proposed many years due to the various dielectrics, electrical and rheological properties of the water-in-oil (W/O) emulsion, the frequency of the pulsed DC electrical field was still kept constant during the electrical dehydration process in most of the industry application up to now. Taking into consideration of the increment of the droplets’ diameter and variation of various dielectric and rheological properties of the dispersion system during the dehydration process, the dehydration efficiency of pulsed DC electrical field with changing frequency during the dehydration process was investigated in this paper. The results showed that with appropriate combination of the frequencies, the dehydration efficiency of the pulsed DC electrical field can be significantly improved. [Copyright &y& Elsevier]

Silicon carbide (SiC) ceramics have found a variety of engineering applications due to their superior properties. However, the manufacture of SiC ceramics is not an efficient process. A new process of machining SiC ceramics using end electrical discharge (ED) milling is presented in this research. End ED milling employs a turntable with several small cylindrical rods as the tool electrode, and uses a water-based emulsion as the machining fluid. This process is able to effectively machine a large surface area on SiC ceramic. The machining principle and characteristics of the technique are introduced. The effects of tool polarity, pulse on-time, pulse off-time, peak voltage, and peak current on the process performance such as the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR) have been investigated. In addition, the microstructure of the machined surface is examined with a scanning electron microscope and an energy dispersive spectrometer. [ABSTRACT FROM AUTHOR]

Abstract: Electrical discharge machining (EDM) caused a recast layer to form at the machined surface of the workpiece. The characteristics of the recast layer have a great relationship with the type of dielectric. The research work in this paper aims to acquire a profound knowledge of the recast layers of a surface machined by sinking EDM using water-in-oil (W/O) emulsion as dielectric. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrograph (EDS) and micro hardness analysis were performed. The characteristics of the recast layer formed in W/O emulsion were investigated by comparing them with those of the recast layer formed in kerosene and de-ionized water dielectric. It was found that the recast layer formed in W/O emulsion exhibited larger surface roughness, thickness and micro hardness compared with that formed in kerosene and de-ionized water. Both carbide and oxide were detected in the recast layer formed in W/O emulsion whereas only carbide was detected in the recast layer formed in kerosene. Due to the higher supersaturation of gases in the melted material, the recast layer formed in W/O emulsion was found to possess more micro-voids than that formed in kerosene and de-ionized water. [Copyright &y& Elsevier]

Abstract: The influence of several operational variables on the electrostatic separation of water-in-oil emulsions is investigated in a Perspex cell equipped with a high-frequency pulsed DC generator using conductivity technique. The ascending and the descending periods of the observed conductivity vs. time curves were fit to the sigmoid and power function, respectively, which revealed the model parameters that were used to quantify dehydration efficiency (DE). Experiment results show that DE increases with decreasing inter-electrode distance, and at a given inter-electrode distance, DE increases with decreasing frequency. Furthermore, at a given pulse interval, DE increases with increasing pulse duration. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) ceramics have been widely used in modern industry. However, the manufacture of SiC ceramics is not an efficient process. This paper proposes a new technology of machining SiC ceramics with electrical discharge milling and mechanical grinding compound method. The compound process employs the pulse generator used in electrical discharge machining, and uses a water-based emulsion as the machining fluid. It is able to effectively machine a large surface area on SiC ceramics with a good surface quality. In this paper, the effects of pulse duration, pulse interval, peak voltage, peak current and feed rate of the workpiece on the process performance parameters, such as material removal rate, relative electrode wear ratio and surface roughness, have been investigated. A L25 orthogonal array based on Taguchi method is adopted, and the experimental data are statistically evaluated by analysis of variance and stepwise regression. The significant machining parameters, the optimal combination levels of machining parameters, and the mathematical models associated with the process performance are obtained. In addition, the workpiece surface microstructure is examined with a scanning electron microscope and an energy dispersive spectrometer. [ABSTRACT FROM AUTHOR]

The production of dried probiotic bacterial cells that are shelf stable at room temperature remains challenging. In this work, the potential of encapsulation of probiotic Lactobacillus reuteri using heteroprotein complex coacervation (type-A gelatin/sodium caseinate, GE/Cas) was compared to a protein/polysaccharide complex coacervation (type-A gelatin/gum arabic, GE/GA). The optimal pH and GE/Cas ratio for formation of water-in-water emulsions were found to be pH = 6.0 and GE/Cas = 2.0. L. reuteri TMW1.656 survived spray drying without loss of viability; the survival after simulated digestion, heating and ambient storage decreased in the order GE/Cas ≥ Cas > GE/GA > GE. The improved protection of the GE/Cas matrix was related to a reduced hygroscopicity, solubilization and wettability, and may be caused by the relatively higher hydrophobicity of GE/Cas heteroprotein coacervation system. To the best of our knowledge, this is the first study employing heteroprotein coacervation to encapsulate probiotics. Image 1 • Heteroprotein coacervation with W/W emulsion structure was firstly reported. • GE/Cas coacervation provided better probiotic protection than GE/GA coacervation. • Microcapsule properties were related with cell survivals under different stresses. [ABSTRACT FROM AUTHOR]