Search

In micro electrical discharge machining (micro-EDM), the precision fabrication of cylindrical micro rods is difficult to achieve with a high processing efficiency. In order to overcome this challenge, this paper proposes a new processing method, which is denoted as twin-mirroring-wire tangential feed micro electrical discharge grinding (TMTF-WEDG). The machining principle, characteristics, and realization of the new method are firstly introduced. Then, the advantages of TMTF-WEDG in terms of machining efficiency and accuracy are demonstrated. The experimental results have shown that the machining efficiency can be increased to more than 70% in comparison with conventional tangential-feed wire electrical discharge grinding. It has also been proved that a minimum removal of material corresponding to a reduction of less than 1 μm in the diameter of a micro rod can be obtained by TMTF-WEDG. This considerably helps in improving the accuracy and repeatability of the machining process. A deviation of less than 1 μm on the diameter of a micro rod has been obtained in a length range of 800 μm. The process repeatability in machining five micro rods has been established to be below 2 μm. The proposed method is therefore of great significance for improving the machining efficiency and ensuring a high precision in the shaping process of cylindrical micro rods. • TMTF-WEDG method was proposed to improve the machining efficiency and accuracy of micro rods. • An analysis of diameter variation and remove layer thickness characteristics of the micro rods were illustrated. • Compared to TF-WEDG, the TMTF-WEDG can improve processing efficiency by 1.7 times. • A minimum removal layer thickness of less than 1μm was obtained in the experiments. • The uniformity of a single micro rod is <1 μm in the length range of 800 μm, and the repeatablity of micro fods is < 2 μm. [ABSTRACT FROM AUTHOR]

This article describes a new hybrid machining process with combination twin-wire electrodischarge grinding (twin-WEDG) and two electrodischarge circuits to produce microelectrode tools rapidly. The results show that transistor and RC electrodischarge circuits could be jointly integrated into micro-EDM to shape microelectrode tools. Compared to conventional single WEDG technology, the twin-WEDG system utilizing both rough and finished machining combined into only one process can reduce machining time by two-thirds and achieve high efficiency when producing microtools. This high-speed microtool fabrication process can be applied not only to micro-electrode machining, but also to micropunching tool and microprobing tips machining. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, vibration-EDM technology was introduced by the vibrating worktable designed to fabricate noncircular micro-electrodes and micro die-openings using wire electro-discharge grinding (WEDG). Micro punches and micro die-openings with different clearances were fabricated by controlling the spark gap in micro electrical discharge machining (micro-EDM). The micro-punching experiments include producing triangular and hexagonal micro-holes with a side length of 200μm on brass strip. Punching of successive hexagonal micro-holes was also carried out successfully. The micro-forming experiments were conducted on copper and brass, producing cup-shaped protrusions with a diameter of 300μm. All the experimental results show that the modified micro-punching machine is able to perform both micro-punching and micro-forming operations. [Copyright &y& Elsevier]

Abstract: The purpose of this study is to study burr formation in micro-machining using micro-tools. The micro-tools employed are fabricated by micro-EDM using the wire electro-discharge grinding (WEDG) method in the micro-EDM/milling machine we had already developed. Micro tungsten-carbide tool with a minimum of 31-μm in diameter had been fabricated. The simple-shaped micro-tool fabricated is able to perform the micro-machining operation which is a combination of micro-milling and grinding processes. Micro-slot and micro thin-walled structure had been produced on Al 6061-T6 materials successfully. Burr formation in micro-machining is investigated experimentally and classified into four types: primary burr, needle-like burr, feathery burr and minor burr. Formation mechanisms of these burrs and the relationship between their existence and the machining condition are discussed. [Copyright &y& Elsevier]

Abstract: In this research vibration-EDM is realized by the vibrating worktable designed, which is employed in the micro-punching machine we had already developed. It is found that larger feed and better surface finish can be achieved in micro-EDM with vibration machining. Circular and noncircular micro-electrodes of diameter below 200μm were fabricated with vibration-EDM and the setup of u-axis. Experiments to punch micro-holes of diameter 200μm on SUS304 stainless steel and brass strips were carried out. Mass punching of micro-holes on brass strip was performed successfully, using the automatic feeding system developed. The capability of micro-punching and effects of parameters on the quality of punched micro-hole are studied. [Copyright &y& Elsevier]

Abstract: This paper describes the development of a novel micro-punching machine that is capable of producing precision micro-holes. A significant feature of this machine is to fabricate the micro-punch and then the micro-die in the same machine, totally eliminating the eccentricity between the punch and the die when punching is proceeded. By applying vibration machining technique, we can decrease the possibility of electric short-circuiting during the micro-EDM process. The utilization of a proportional solenoid as the power unit of the micro-punching machine and as the source of vibration is found to be a successful attempt. Experiments to punch micro-holes with diameters of 0.1 and 0.2mm on an SUS 304 stainless steel strip with 0.1mm in thickness were carried out. The results show that the performance of this machine and the geometry of punched micro-holes are satisfactory. [Copyright &y& Elsevier]

Abstract: This research presents a novel process using micro electro-discharge machining (micro-EDM) combined with high-frequency dither grinding (HFDG) to improve the surface roughness of micro-holes. Micro-EDM is a well-established machining option for manufacturing geometrically complex small parts (diameter under 100μm) of hard or super-tough materials. However, micro-EDM causes the recast layer formed on the machined surface to become covered with discharge craters and micro-cracks, resulting in poor surface quality. This affects the diameter of the micro-hole machined and undermines seriously the precision of the geometric shape. The proposed method that combines micro-EDM process with HFDG is applied to machining high-nickel alloy. As observed in SEM photographs and surface roughness measurement, HFDG method can reduce surface roughness from 2.12 to 0.85μm Rmax with micro-cracks eliminated. Our results demonstrated that micro-holes fabricated by micro-EDM at peak current 500mA followed by HFDG at 40V can achieve precise shape and good surface quality after 6–8min of lapping. [Copyright &y& Elsevier]

This paper describes a new hybrid technique combining wire electro-discharge grinding (WEDG) technology with one-pulse electro-discharge (OPED), to fabricate multi-micro-spherical probes. The results show that a burnished micro-spherical probe with diameter of about 40 μm could be formed instantaneously, which is not available with conventional machining methods. The unevenness of the radius is about 3 μm with repeatedly machining at the same conditions and the center shifting tolerances of the sphere is about 1 μm. Compared with micro-discharge electro-machining (EDM), the surface roughness of the probe is much smaller than discharge crater. [Copyright &y& Elsevier]

With the development of the WEDG (wire-electrodischarge-grinding) it became possible to produce very small electrodes or products like e.g. ejection pins or cores for mould inserts. A new field for the WEDG is the production of milling tools for micro-cutting. The Institute of Production Science (wbk) of the University of Karlsruhe and the Institute of Industrial Science of the University of Tokyo, Center for International Research on MicroMechatronics, developed together a way to produce these milling tools in tungsten carbide with CNC-controlled EDM machines. This research has shown the potential of the machining of micro-cutting tools with a diameter smaller then 100 μm—which is at the moment the size of the smallest commercial milling tool in tungsten carbide—by micro-EDM. [Copyright &y& Elsevier]

With this method a rod electrode with negative polarity is rotated and fed into a plate electrode to form holes. After the rod electrode returns to the initial position, the axis of the rod electrode is off-centered from the center of the hole at a certain distance. The polarity of the rod electrode is then reversed, and the rod electrode is fed into the plate electrode, either with or without rotation. Since holes are formed by the rod electrode itself, the rod electrode can be machined very precisely. Since this method does not need initial positioning of the tool electrode with respect to the plate electrode, the operation is easy and short. [Copyright &y& Elsevier]

• Key technologies were proposed to improve the diameter uniformity and repeatability of micro-shafts fabricated by TMTF-WEDG. • The critical factors of TMTF-WEDG system were analyzed, which affects the the diameter uniformity and repeatability of micro-shafts. • New strategies were proposed for improving the performance of TMTF-WEDG. • A micro-shaft with a diameter of 45μm and uniformity of ± 0.5μm was successfully fabricated. • For five repeated fabricated micro-shafts, the diameter repeatability was controlled within ±1 μm. The new method of micro-shaft fabrication, named twin-mirroring-wire tangential feed electrical discharge grinding (TMTF-WEDG), is mainly characterized by the tangential feed strategy and the narrow slit formed by twin-mirroring-wire to achieve the diameter control of micro-shaft. The critical factors of micro-shafts accuracy and repeatability include processing position offset of micro-shaft, front edge position fluctuation of wire electrodes, and asymmetry of the twin-mirroring-wire electrodes, which cause the deviation of the tangential feed path and fluctuation in narrow slit width. The diameter of the micro-shaft was smaller than the theoretical value with processing position offset, which is not conducive to the control of the micro-shaft diameter. The front edge fluctuation of the wire electrodes caused the variation of the micro-shaft diameter to be around ±3 μm in the axial direction. The asymmetry of the twin-mirroring-wire electrode is the key factor affecting the tangential feed path which further affects the controlling the repeatability of the micro-shafts. New strategies were proposed, including the determination of the initial machining position achieved by tool setting, improvement of the twin-mirroring-wire system, the determination of the feed path, and improvement of feed strategy for trimming the taper of micro-shafts. The processing results show that a micro-shaft with a diameter of 45 μm and uniformity of ± 0.5 μm was successfully fabricated. For five repeated fabricated micro-shafts, the diameter repeatability was controlled within ±1 μm. [ABSTRACT FROM AUTHOR]