Papers by Author: Ji Cheng Bai

Abstract: 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.

Abstract: 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.

Abstract: 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

Abstract: Micro-EDM technology has the advantages of no-contact and no-cutting force, it has been used in many fields. In order to use micro-EDM to machine proprietary micro array holes, which needs high precise of hole spacing and consistent hole diameter, a new macro-micro dual-drive system of micro-EDM have been made. It uses macro drive to move to a place, measures the error with the high precise grating, and uses micro drive to compensate the error. Online measurement proved that this method has important value if it will be used in micro-EDM.

Abstract: 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.

Abstract: 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.

Abstract: In Wire Electro Discharge Machine (WEDM), as the big randomicity of electro discharge, single discharge energy is various. In this paper a resistor-less and half-bridge power supply is investigated based on pulse width modulation(PWM), whose single discharge energy is equal , adopting discharge control strategy of breakdown waiting. And the experiment shows the cutting speed and surface roughness of this isopluse power supply is superior to that of traditional isofrequency power supply.

Abstract: In this paper, a novel Pulsed-Width-Modulated (PWM) half-bridge High Speed Drilling Electrical Discharge Machining (HSDEDM) power supply has been developed. This power supply has excellent features that include minimal component count and inherent protection. This topology has an energy conservation feature and eliminates the output bulk capacitors and current limiting resistances. Energy used in the erosion process will be controlled by the switched Insulated Gate Bipolar Transistors (IGBTs) in the half-bridge network and be transferred to the gap between the tool and work-piece. The relative tool wear and machining speed of our proposed topology have been compared with that of a normal power supply with current limiting resistances.

Abstract: Super-capacitors are new equipments for energy storage，and they have wide application in practice. At present, blanking is used to machining the electrodes of super-capacitor; however, the disadvantages of the method are burrs, electrode collapse. A new method processing electrode of super-capacitor, wire electrical discharge machining in gas (dry WEDM), were presented in this paper, and the electrode surface morphologies were studied utilizing scan electron microscope (SEM). First, the surface morphologies comparison studies of super-capacitor electrodes processed with different method, such as shearing, blanking and dry WEDM etc., were performed, and research results show that the super-capacitor electrode surfaces machined by dry WEDM achieve flat machining surface, and electrode edges do not collapse. Further surface morphology analysis was carried out based on different pulse durations and air pressure, and analysis results indicate that better machining surface can be achieved when suitable pulse duration and gas pressure are selected. Finally, surface energy spectrum analysis of the super-capacitor electrode processed by dry WEDM is performed, and the analysis result show that alumina are formed on the middle of electrode, aluminum foil, which is favored to the performance of super-capacitor.

Abstract: 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.