Papers by Author: Ming Rang Cao

Abstract: The mechanism that the magnetic field and the dispersant are helpful to chip removal, to improve the material removal rate (MRR) and to reduce the tool wear rate (TWR) was analyzed in detail.The corresponding experiments were conducted based on theoretical analysis. The experimental results show that adding a certain proportion of dispersant into the dielectric fluid and introducing the magnetic field for high speed small hole drilling by EDM can greatly improve the material removal rate and significantly decrease the tool wear rate.

Abstract: The small hole EDM is one main method of micro holes machining and applied very widely. But it’s machining efficiency is low and machining stability is bad, which is more obvious because of chip-ejection difficulty when the ratio of length to diameter is rather large. Secondary discharge caused by chip-ejection difficulty not only makes the material removal rate reduce, but also causes geometric tolerance and affects product performance. Based on dispersion mechanism study of the water dispersant, the influence of the water dispersant is analyzed to chip-ejection, material removal rate and machining quality of the high-speed small-hole EDM. By contrasting the machining effect on using tap water with disperser dielectric liquid during electric spark small hole machining, adding the certain proportion disperser in water-based dielectric liquid may increase the material removal rate, decrease the tool wear rate, improve the effective impulse numbers, obviously reduce the second discharge number, and the taper of tool electrode and hole becomes small, so the hole machining quality enhances.

Abstract: The two disadvantages of EDM are the low material removal rate (MRR) and poor surface quality. In this investigation, EDM assisted by magnetic field (MFEDM) has been proposed for the first time to overcome above-mentioned disadvantages. Constant magnetic field was applied to the both sides of discharge channel perpendicularly to form a novel process. In experiment, EDM machine tool D703F was used to machine nonferromagnetic materials. The machining parameters discharge current and pulse duration were chosen to determine the effects on material removal rate and surface roughness.Experiment results indicate that the MRR of the combined machining is 1.2~3 times of EDM’s one. Furthermore, the value of surface roughness is also reduced. Therefore, the introduction of magnetic field to EDM has important academic and practical values to the development of EDM.

Abstract: The flow field characteristics have a significant effect on the machining stability in high-speed small hole EDM drilling. Thus, Lagrangian discrete phase model (DPM) has been developed to simulate the gap liquid-solid two-phase flow field. The numerical calculation is based on the standard k-ε turbulent model, and the SIMPLEC algorithm is used in the simulation. All the governing equations are solved by software Fluent 6.2. Through numerical simulation, the pressure distribution, the velocity distribution of the dielectric liquid, traces of debris particles, and the debris particle concentration were obtained. The flow field characteristics under different pressures and drilling depths were obtained through simulations. Finally, experiments were carried out to investigate the effects of the flush velocity at exit obtained through simulation on material removal rate (MRR).

Abstract: The selection of manufacturing conditions is very important in manufacturing processes as these ones determine the material removal rate (MRR) of the so-obtained parts. So in this paper, based on the brief introduction of the experimental principle and the high-speed small hole EDM drilling system, effects of non-electrical parameters on MRR are discussed in detail. The relationships between MRR and these factors are also analyzed. The conclusion can provide an important reference for production in practice.

Abstract: The EDM can machined some superhard conducting material that cannot be handled by the traditional method, such as carbide alloy, tool steel and engineering materials etc., however, it is also accompanied with slow material removal rate(MRR) and poor surface quality (surface roughness). For some fine machining having rigorous criterion on size and surface roughness, the EDM cannot meet the demand. Some researches indicate that the MRR of small hole by electrical discharge machining combined with ultrasonic vibration (UEDM) can increase in certain range, but the surface quality is still poor. Although there are lots of the researches on the UEDM, some debates on machining mechanism and applied scope existed, and technology of UEDM needs the further study. After small hole machined by the UEDM, it is polished by ultrasonic vibrating. Two steps are includes in this technology. In the first place, on a high velocity electro discharge small hole machine with high-pressure dielectric liquid and hollow electrode, a transducer and horn are attached between the spindle and the electrode. The ultrasonic vibration of the tool electrode is implemented by connecting the horn and the tool electrode together with a chucking appliance. The second, after the small hole is complete, with the same machine tool and tool electrode the process of polishing the inwall of the small hole is carried out by accompanying the ultrasonic vibration, revolution and feed of the tool electrode with the abrasive material. In the experiments, the reference point for UEDM is found and the new theory is proposed to explain the increase of the MRR and the decrease of the surface roughness value .The polish with the ultrasonic vibration can improve further the surface roughness. The ultrasonic vibrating polish after the hole by UEDM is an economical and effective technology, which realizes machining of two procedures in one machine tool. So the process for changing machine tool and tool is not needed any more and the efficiency is further improved.