1. Anti electrolysis (BS) pulse power supply for slow wire processing
Water quality working fluid is used in low speed WEDM. Water has a certain conductivity, even after deionization treatment, reducing the conductivity, but there is a certain amount of ions. When the workpiece is connected to the positive electrode, under the action of the electric field, OH ions will continuously gather on the workpiece, resulting in the oxidation and corrosion of iron, aluminum, copper, zinc, titanium and tungsten, and the ionic state of the binder cobalt in the cemented carbide material dissolves in the water, forming a “softening layer” on the workpiece surface. The measures of increasing resistivity (from tens of thousands of Ohm? Cm to hundreds of thousands of Ohm? Cm) have been adopted to reduce the ion concentration as much as possible. Although they have played a certain role in improving the surface quality, they still cannot solve the problem of “softened layer” effectively. Anti electrolysis power supply is an effective technical means to solve the “softening layer” of workpiece. The anti electrolysis power supply adopts alternating pulse and the average voltage is zero, which makes the OH – ion electrode wire in the working liquid in the state of oscillation between the workpiece and does not tend to the workpiece and electrode wire, so as to prevent the oxidation of the workpiece material. The surface modification layer can be controlled below 1 μ m by WEDM with anti electrolysis power supply, which can avoid the precipitation and dissolution of cobalt in cemented carbide material and ensure the service life of cemented carbide die.
2. Nanosecond high peak current pulse power supply for slow wire processing
There are two kinds of metal erosion in EDM, melting and gasification. The wide pulse duration is long, which is easy to cause melting processing, poor surface morphology of the workpiece, thickened metamorphic layer, increased internal stress, and easy to produce cracks. When the pulse width is small to a certain value, the action time is very short, forming gasification processing, which can reduce the thickness of the modified layer, improve the surface quality, reduce the internal stress and avoid cracks. The pulse power supply used in the advanced low speed WEDM machine is only tens of NS in pulse width, and the peak current is more than 1000A, forming gasification erosion, which not only has high machining efficiency, but also greatly improves the surface quality.
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