Shi Chun Di

Fabrication of Micro Parts with Micro-WEDM

A new Micro-WEDM machine is developed in this paper. Therefore, experiment can be done on this machine. Especially, the surface characteristics of work-pieces are analyzed in detail. The Micro-WEDM can machine micro slot easily. In addition, all kinds of micro shaped holes, micro gears, complex micro parts and dies are machined to check its processability. A micro gear can be easily fabricated by micro-forming method with the micro gear dies fabricated by micro-WEDM, and get well performance, which indicates that micro parts machined by Micro-WEDM meet the requirements of micro instrument and device.

Design of Scanning Micro-Arc Oxidation Forming Ceramic Coatings on 2024 Aluminium Alloy

Micro-arc oxidation (MAO), also called plasma electrolytic oxidation (PEO), anodic spark deposition (ASD), or micro-arc discharge oxidizing (MDO), is an effective surface treatment technique which come from anodic oxidation technology. Via increasing the anodic voltage breaking through faraday area to a high stage accompanied by micro-arc discharge phenomenon, It indicated the ceramic coatings thickness increase along with the scanning times increase, while the thickness increment reduces. The phase composition, morphology and element distribution was studied by X-ray diffraction, scanning electron microscopy and line scanning. The morphology of the ceramic coatings shows it divided into compact layer and loose layer. And it composes of α-Al2O3 and γ-Al2O3.

Biocompatibility Research of Medicine Titanium Alloy Coating by Microarc Oxidation

A medicinal titanium alloy hydroxyapatite coating was fabricated by microarc oxidation process, and a kind standard of simulated body fluid was configured, after that the biocompatibility experiment was carried out. The soaked coatings surface morphologies were observed and analysed by scanning electron microscopy,and the coating spectra were simultaneityly researched by X-ray diffraction. The instance of degradation and precipitate were investigated,and the transformation of Ca/P value were measured.

Forming Ceramic Coating on Al2024 by Scanning Micro-Arc Oxidation

Micro-arc oxidation (MAO) is a novel technique to deposit ceramic coatings on the surface of valve metals such as Al, Mg, Ti and their alloys. The oxide films prepared by this technique have a dense structure, high adhesion and excellent integrated mechanical properties. This technique is especially suitable for the surface treatment of machine parts that work at high speed and have a higher demand for resistance to wear and corrosion. There have been many studies in this field in the last few years. The development of micro-arc oxidation and its applications in industrial field was reviewed. Based on conventional micro-arc oxidation, an innovative scanning micro-arc oxidation technology with visible advantages was developed in this paper. Moreover, verification experiment on scanning micro-arc oxidation was carried out, and the experimental results suggested that scanning micro-arc oxidation could be conduced at a high efficiency but low cost way. At last, the effects of scanning times on film thickness were discussed.

Design of the Micro-Arc Oxidation Surface Protection GTAW Integrated Pulse Power

Design a welding and micro-arc oxidation integrated pulse power toward micro-arc oxidation problems of the welding parts of aluminum, magnesium, titanium and its alloy, which can achieve the samples surface protection after welding. Adopting modular design, by adjusting PWM inverter buck and high-frequency inverter boost to get the setting voltage value, the power supplying current and voltage value via chopper inverter to realize. The hardware of system makes STM32 as the core, using CPLD as the basis to design the power control system. Software based on block control strategy applying DA to control the power parameters. Load test proved the feasibility of the power supply design. The power supply can output stable operating parameters. Polarization curve test indicated that the power supply improve the corrosion resistance of the weld joint.

Study about Formation Mechanism of Red Spark Discharge of Micro-Arc Oxidation

Formation mechanism of the micro-arc oxidation spark discharge is always a research problem; so far there isnt a theoretical model for analyzing the spark discharge formation which is widely recognized. Based on analyzing the reaction phenomena and the coating feature in the different periods of the red spark discharge, the formation model of the red spark discharge was established. The spark discharge formation mechanism is shown that it causes the spark discharge formation that the electron bombards the gas layer wrapping the coating in the infancy of red spark discharge stage; at the later period the area of strong electric field generates the spark discharge where the coating of excessive polarization turns out easily.

Research of MEDM Pulse Power Based on the Non-Resonant Natural Oscillation

Aiming to discharge feebly, improving the frequency of MEDM power pulse is an ideal choice. But due to the influence of power resistor, capacitor, inductor with stray capacitance and stray inductance, increasing the higher pulse power frequency met bottleneck. Through the analysis of MEDM discharging circuit and routes, this paper puts forward the theory of not using components, but depending on the natural oscillation of MEDM machine tools and connection line to make MEDM pulse power. Through theoretical calculation and simulation, the oscillation period of discharging circuit can be controlled in 1.5ns, and the pulse width can be less than 750 Ps. It provides theoretical support for making picosecond pulse power and nanometer manufacturing with MEDM.

Fracture Mechanics Study on Porosity Zirnocia/hydroxyapatite Coating Obtained through Microarc Oxidation on Medical Titanium Alloy Surface

In electrolytes TiO2-based complex ceramic coatings containing Ca and P on titanium alloy were ultimately formed containing zirconia/hydroxyapatite by Micro-arc oxidation process. As well as the biomechanics measure experiment of speciments had been done, and the datas were analysised and researched. In addition, the toughening mechanism of reinforced coating was studied in detail, and consists of the second phase toughening, phase transformation toughening and microcrack toughening.The results show that the zirconia /hydroxyapatite coating has advanced biomechanics propertys compared to the individual hydroxyapatite one.

Research on the Electrolyte Service Life of Treating AZ91D by Micro Arc Oxidation

With the development of micro arc oxidation and the growing maturity of the industrialization, the electrolyte service life and stability attract more and more people. In this paper, the electrolyte service life was researched. Under the same technological conditions, it was found that the critical factors affecting the electrolyte service life are the single-processing area and the electrolyte volume. With prolonging the working time of the electrolyte, the gel deposition mass in the electrolyte and the initial voltage always change. The experiment indicates that the electrolyte service life will assume the curve extension when reducing the single-processing area or increasing the solution volume. To some extent, the initial voltage and gel deposition can indicate the active state of the electrolyte, and can be considered as the sign whether the electrolyte service life becomes due.

Study on Stray Capacitance of MEDM Machine Tool

The stray capacitance in the process of MEDM has been the key problem of influencing the processing dimension and precision. This paper puts forward a method of measuring the stray capacitance of MEDM machine tool, through recording the charging waveform of two cases that the RC pulse power is on the machine tool or not by an oscilloscope, and then the measured data are substituted for the capacitance charging formula, we get the stray capacitance value of MEDM machine tool. This paper also tests the cases of different charging voltage and different tool-electrode length, finally we find that the tool-electrode length has a big influence on the stray capacitance.