Ji Cheng Bai

Electrical Discharge Machining (EDM) Phenomena of Insulating ZrO2 Ceramics with Assisting Electrode

Advanced engineering ceramics are more and more widely employed in modern industries because of their excellent mechanical properties such as high hardness, high compressive strength, high chemical and abrasive resistance. These properties limited the machining to the insulated ceramics. This paper investigates the electrical discharge machining (EDM) of ZrO2-based ceramics by assisting electrode method. The theory of assisting electrode method is introduced. The machining phenomena under different electrical parameters were studied. The material removal mechanisms change with the increase in the power of single pulse. Some work-pieces have been machined successful through the assisting electrode method.

Experimental Research on Machining Performance of Electrode Materials in Dry EDM

Electrode materials are important factors affecting machining performances (MP) of electrical discharge machining (EDM). Experiments using different electrode materials were carried out in compressed air aim to realize MP of electrical discharge machining in gas (dry EDM). Experimental results show that a minimum pulse interval exists for given parameters and tool material. Calorific performances of tool materials are main influencing factors of MP on the condition of thorough deionization. Copper achieves the best MP in the experimental tool materials. Experimental results of different workpiece materials depict that material remove rate (MRR) and surface roughness (SR) value increase with increases of discharge energy. SKD61 steel achieves the highest MRR and SR value in the experimental materials. Material holding better performance of heat resistant, such as titanium alloy (TC4), achieves the lowest MRR.

Research on Micro EDM Machine Tool for Machining Micro Array Holes

As demands for the micro array holes in modern industry and the characteristics of micro Electrical Discharge Machining (micro EDM), a new type micro EDM machine tool used to machine micro array holes was designed and manufactured. The machine tool contains following systems: the mechanism system, the control system, the pulse generator system and other auxiliary systems. Each system was studied respectively. Base on a large number of experiments, finally, a sample with 256 array holes was processed by the machine tool. The diameter of single hole is 45µm and precision of the holes is ±1µm. The sample has been successfully applied to R & D test of micro nozzle components

Research of Temperature Field Simulation on Electrode Wire Wear for WEDM

The wire electrical discharge machining (WEDM) technology is widely used in the field of mold industry, aerospace, automobile and so on. However, in the discharge machining, the electrode wire wear will affect the machining accuracy and machining efficiency. There are many factors that affect the electrode wire wear, and cutting many work-piece and precise surveying are needed in the wear experiment, so the whole experiment is complex. This article analyzed the wear mechanism and found the main reason of affect the electrode wire wear by using the ANSYS software to do the temperature field simulation. The simulation parameters and simulation results were verified through experiments. The experiment showed that appropriate ratio of peak current and pulse width and the slow current rise slope can reduce the electrode wire wear significantly.

Investigation of the Effects of Dielectric Inlet Pressure in Inner Jetted Dielectric EDM Milling

In layer-by-layer EDM milling based on inner jetted dielectric, the dielectric inlet pressure is an important process parameter and has great influence on the machining characteristics. So, numerical simulation of the liquid-solid two-phase flow field in discharge gap is conducted. The simulation results of debris concentration reveal that the debris can be evacuated from the discharge gap in time, which increases the machining process stabilization and improves the machining efficiency. Finally, the effect of dielectric inlet pressure on material removal rate (MRR) and tool wear ratio (TWR) were also researched and discussed. The optimum inlet pressure, which maximized the MRR and minimized the TWR, was found through experiment.

Micro-EDM for an Aluminium Matrix Composite

The silicon carbide particle reinforced aluminium matrix composite (SiCp/Al) which is acknowledged as one of the most competitive metal matrix composites is now widely applied in aviation, aerospace and military fields, and its application is extending gradually. As a result of the hard and brittle SiC particles contained, mechanical machining of the material is difficult, but the method of electric discharge machining (EDM) has certain prominent advantages. In this paper, SiCp/Al was machined using micro-EDM. First, a Ф40μm × 4.1mm micro tool electrode of which the aspect ratio is up to 100 was made; and then, through experiment, the impact of open-circuit voltage and electrode material on processing speed and electrode wear was analyzed; finally, 28μm wide micro slits, micro square platform of 34μm long on each side and other micro three-dimensional structure were machined. Research and experimental results show that the use of appropriate micro-machining parameters and reasonable processing methods can improve processing performance to better achieve the micro-EDM of SiCp /Al.

Effect of Micro-EDM on Diameter Consistency of Micro-Hole Arrays

The inkjet template is an important part of digital printing equipment. The diameter of hole arrays on the template determines the consistency of the ink droplet and thus affects print quality. To improve the printing performance of digital printing equipment, this study investigated the effect of micro-electrical discharge machining (micro-EDM) on the diameter consistency of micro-hole arrays on an inkjet template. Combining block electrical discharge grinding and wire electrical discharge grinding enabled the online processing of the fine tool electrode, whose diameter can be stably controlled at less than 45 μm, whose maximum diameter deviation was about 1 μm. The tool electrode can also be used to process micro-hole arrays. Subsequently, the relationship between the discharge energy of micro-EDM and the erosion material was theoretically analyzed, as was the effects of the diameter consistency of the micro-electrode itself on that of the micro-hole array processed by the micro-electrode and the relationship between processing parameters and the discharge gap between the micro-electrode and the workpiece. Experimentations were conducted on the effect of the flow rate, flush angle, and rotation speed of the electrode and the resistivity of de-ionized water to the diameter consistency of the micro-hole arrays. On the optimized parameters, a 16×16 micro-hole array with a diameter deviation of less than 2 μm was successfully processed, and the average diameter of the holes, about 44 μm, was used for the inkjet template. Beside, an electrode with a diameter of 14μm is also machined and it was used to process a 8×8 micro-hole array, whose diameter deviation is 0.9μm and average diameter is less than 20μm. Large number of experiments show that by the proposed method, one electrode can stably machined 800 holes with diameter less than 50μm, and their diameter deviation is less than 3μm. The digital printing equipment with these holes can meet the current demand for components with micro-hole arrays.

Noncircular Tool Fabrication by WEDG Using Electrode Jump Motion and Noncircular Array Holes Drilling

Electrode jump motion strategy was adopted to fabricate noncircular tool using wire electrical discharge grinding (WEDG). The machining procedure and electrode jump motion strategy for noncircular tool fabrication were determined through experiments. This approach has been verified by successfully machining of rectangular electrode (38μm×38μm, 700μm length) and D-shaped electrode (diameter 45μm, height 42μm, 500μm length). D-shaped array holes of 6×6 matrix were drilled using corresponding single noncircular tool which was manufactured by the adopted machining approach. The array holes have tight diameter tolerance and height tolerance which are both less than 2μm, and positioning errors are both less than 1μm in the direction of the X, Y-axes.

Study on Modeling and Simulation of Wire Vibration in WEDM

The wire electrical discharge machining (WEDM) has been widely used in the field of metal cutting, mold industry, aerospace and so on. However, in the discharge machining, it is very important to restrain the wire-tool vibration for the improvement of machining accuracy. In this paper, it is created a model of the wire vibration with double-ended fixed, established the differential equation of vibration, and derived its full theoretical solution to analysis the vibration factors. Simulations of the wire vibration with ANSYS Transient dynamics analysis were given. An orthogonal design of the wire vibration using L9 orthogonal table was made, and the experiment found that minimize the servo voltage, reduce the pulse width, and select the appropriate wire tension and pulse interval, which can reduce the wire vibration.

Study on Powder Mixed EDM of an Aluminium Matrix Composite

The powder mixed electro-discharge machining (PMEDM) technologies of silicon carbide particle reinforced aluminium matrix composites (SiCp/Al) are researched in this article. SiCp/Al is widely acknowledged as one of the most competitive varieties of metal matrix composites, firstly applied in the aviation, aerospace and military fields, and gradually extended. Because of the hard and brittle SiC particles contained in this material, mechanical machining is difficult, but EDM does have some advantages. To the same kind of moderate volume fraction (45%) SiCp/Al material, a comparative test was conducted using two kinds of processing methods, traditional EDM (the former) and PMEDM (the latter). Effects of the electrical parameters of both processing methods on the material removal rate (MRR) were analyzed and compared. After processing, the surface roughness value of the former is Ra1.386μm while the latter is Ra0.406μm which is only 29.3% of the former. The surface hardness was also tested by the MTS nano indenter: the former is about 1.7GPa, and the latter is about 2.2GPa which is 1.3 times of the former. Finally, to the machined surface, the micro-topography and the component of ‘white point’ were observed and analyzed by using scanning electron microscope (SEM) and energy spectrum respectively. Experiments and investigation results show that the PMEDM has a better performance compared with traditional EDM in improving the roughness, hardness and so on. So PMEDM will have a great potential in the processing of aluminium matrix composites.