Papers by Author: Zhen Long Wang

Abstract: A multi-axis micro-EDM machine tool for small hole is developed. It mainly includes marble base, precision servo and linear-motor platforms, RC pulse power supply, CCD microscope and so on. Superiority of linear motor used on the Z axis is analyzed. Primary experiments, in which small electrodes with different materials are used to machine 3mm thickness TC4, are carried out. Histograms of open-circuit voltage and capacitance to machining efficiency and electrode relative wear and small-hole samples are given. Influence rules of open-circuit voltage and capacitance to machining efficiency and electrode relative wear are analyzed according to experimental results.

Abstract: The dimension of micro turbine engine is usually only few millimeters, so the centrifugal structure is usually adopt. It must be designed by transonic speed for the higher single pressure ratio. The speed of the ration axis can reach 105r/min, so the gas bearing is adopt because the general rolling bearing is impossible. This paper designs a new wedge structure for the micro gas journal bearing. First the feasibility of this structure is verified by using the FLUENT software simulation. Comparing the simulation results with various parameters, finally major optimization parameters are confirmed.

Abstract: A micro-EDM equipment which can fabricate three-dimensional micro-structures is developed. A method of electrode wear compensation on-line which is very important to micro 3D structures machined by micro-EDM is presented. In this method, the wear of electrode can be predicted by the statistics law of open rate of discharge status, therefore, its precise model which is very difficult to build as well as the special CAD/CAM system is hardly necessary. At the same time, the micro-EDM CAD/CAM technology which applies the universal CAD/CAM software for milling is also researched and experienced on Unigraphics (UG). At last, micro 3D structures, a micro hemisphere with diameter ∅150+m and a micro 3D beam which is very popular in MEMS, are machined on silicon wafer by this way, which proves the wide useful of this method and the promising application in MEMS.

Abstract: This paper presents a new kind of multi-axis electro-discharge machining (EDM) computer numerical control (CNC) system which is based on RT-Linux platform. Binary kernel structure of EDM CNC System is proposed to handle real-time task and time-sharing task separately. The system is divided into three parts: CNC kernel module, CNC driver module and CNC user module. CNC kernel module implements CNC control function in of the software system, and implements the move control to the NC machine. CNC driver module is just as device driver level. CNC user module is user manage procedure. The experiment of rimed turbine blisk validates the performance of the system. The performance implied that the system is real-time, stable and reliable.

Abstract: The performance and stability of output of electrical discharge machining (EDM) are determined by the output of EDM pulse power supply. In order to resolve disadvantages of conventional pulse power supply, such as undesirable efficiency and low power factor, the prototype design of energy-saving EDM pulse power supply is developed. It is composed of such three stages as a single-phase active power factor correction (PFC) pre-regulator, a full-bridge phase shift zero voltage switching (FB-PS-ZVS) converter based on complex control paralleled of machining current closed-loop and voltage closed-loop at period of spark gap insulation, and a pulse generator based on machining sequence control. The PFC pre-regulator contributes to a great increase to about 0.95 in its power factor. The efficiency of the new system is considerably increased to about 70% due to design of ZVS. The pulse generator contributes to the pulse machining current without a tail. Experiment results demonstrates that the prototype is capable of low electrode wear, high speed, stable machining.

Abstract: A new process of fabricating microstructures through micro electrochemical milling (micro EC milling) is proposed. By utilizing side wall of simple micro tool electrode rotating at high speed like micro mechanical milling and controlling the movement track on NC three-axis feed worktable, microstructures with high precision can be milled by micro-ECM under high-frequency short-pulse current. Micro EC milling can greatly improve the machining status in the tiny machining gap and thus make machining stable by simple rotary column electrode. The influence factors on the accuracy of micro-EC milling were investigated through process experiments, such as feed speed, machining voltage and kind of electrolyte. The process of the NC generating micro-ECM integrating CAD/CAM technology is studied. G code for machining complex microstructures can be generated by the universal CAD/CAM of traditional milling based on UG software. Last, Microstructures with complex shape were milled by this process, for example the micro bend beam with width of about 50μm, and its aspect ratio is about 6.

Abstract: Micro electrical discharge machining (EDM) with block electro discharge grinding (BEDG), is explored and assessed as a method for developing micro electrode, for wire electro discharge grinding (WEDG) has shortcoming of low working efficiency, especially in the case of micro machining. For fabricating micro electrode by BEDG, mechanics of initial clamping errors are analyzed, the technology of electrode movement is proposed to compensate the clamping errors and control the finish size of micro electrodes. On the basis of a great deal of experiments, the effect of working voltage on machining efficiency has been found out and been analyzed theoretically, threshold value of working voltage is determined to be about 30V.As shown by result with the technology, at a high machining speed, the minimum diameter of micro electrodes reaches 3*m, its slenderness ratio is more than 5.

Abstract: Developed with micro technology, the microelectrode is the key manufacture technique. The micro electrical machining, mainly including micro electrical discharge machining (EDM) and electrochemical machining (ECM), is one of the important technologies of microelectrode fabrication. Firstly, the microelectrode was fabricated with a counter block of EDM while the cylindrical tungsten electrode fed along radius and its axis. Then the fabrication technology of ECM was also introduced. The pulses power supply and the non-passivation electrolyte were used. The cylindrical tungsten electrode also can be served as the probe of the scanning probe microscopy, which fabricated by ECM. Through comparisons, the surface roughness, machining efficiency, and machining capability of the microelectrode fabricated by ECM are better than those of the microelectrode fabricated by EDM, but the shape and the microhardness are worse than those of the microelectrode fabricated by EDM. Both of them can fabricate the cylindrical tungsten microelectrodes with several micrometers diameter.

Abstract: Experiments of combining micro EDM with USM are carried out to enhance the machining ability and flexibility of the micro EDM, improve the machining state, and increase the productivity and aspect ratio of the micro holes. Basing on RC pulse power supply and workpiece vibration, the micro holes are drilled. The results of comparing experiments indicate that in the processes of both micro EDM without USM and micro EDM with USM, the machining velocity and the wear of the electrode increase with the increase of open voltage and loop capacitance. The experiment results of amplitude influencing on the machining process indicate that with the increase of ultrasonic amplitude, the machining velocity heightens and the aspect ratio of the micro holes augments; at the same time, however, the wear of the electrode and the extensive magnitude of the holes increase. Micro holes with some cross-section and accurate profile are drilled steadily.

Abstract: Based on analysis of the mechanism of Electrical Discharge Machining (EDM) and the characteristics of deposition processing, the processing conditions of micro EDM Deposition (micro EDD) are determined. Micro EDD is a new EDM method taking air as machining medium, using narrow pulse width, long pulse interval, low discharge current and connecting the tool electrode with the anode of pulse generator. Using EDM shaping machine and brass, tungsten and steel as tool electrode respectively, micro cylinders are deposited on high-speed steel surface. And then the microstructure of deposit is analyzed detailedly. Results show that elements of the deposited material distribute uniformly, whose components depend on the tool electrode material. As the high cooling rate of the solidification process, the deposit grain size refines obviously, which leads to the hardness of tungsten or steel deposit increasing. Moreover, the Metallurgical bonding has occurred on the interface between deposit and high-speed steel base, whose thickness is about 5μm.