Process Method for Improving the Surface Quality of Wire Cutting EDM
Using molybdenum wire electrode or brass wire
1.Using narrow pulse width precision processing
The use of narrow pulse width precision quasi-machining is an effective process for obtaining the required surface quality. As we all know, whether it is a low-speed wire(molybdenum wire)feeder or a high-speed EDM wire feeder, high cutting speeds can be achieved by selecting a larger pulse width and quasi-electrical parameters for wire cutting, but the quality of the machined surface is relatively poor, not only rough in the roughness value, but also the thickness of the surface layer changes, and even a microscopic crack appears on the surface. If a narrow pulse precision quasi-electrical parameter is used, although the cutting speed is reduced, the machined surface quality is good, not only the roughness value is small, but also the surface structure change layer is small, so the surface micro cracks are not generated.
If the pulse parameters are selected too small, or the workpiece is thicker, the use of narrow pulse widths for precision processing will be difficult and even impossible to process. At this point, multiple cutting techniques should be considered. Rough cutting should be done using the coarse gauge electrical parameters, leaving a certain amount of finishing allowance, and then using the narrow pulse width to finely adjust the parameters, and even fine tuning can be used to repair light many times, in order to obtain the required surface processing quality.
2. Elimination of strips in EDM wire cut using gold molybdenum wire or brass wire.
The WEDM process is easy to produce cutting stripe, especially for the high-speed WEDM cutting machine using molybdenum wire. (where to buy molybdenum wire? and want to know molybdenum wire price? Please visit www.edm-taguti.com. The generated reciprocating walking wire cutting streaks seriously affect the quality of the wire cutting and cutting surface. The operator must take some effective measures to limit or eliminate the surface cutting stripe generated by the wire-cutting according to the actual conditions during the processing. The commonly used methods are:
(1) Adjust the balance of the stock tube to improve the stability of the threading process.
(2) Eliminate the axial turbulence and radial jumping of the guide wheel, replace the worn out guide wheel and bearing in time.
(3) Minimize the loss of the wire diameter of the wire during the process. Use a coarse molybdenum wire (or dove-aluminum wire) with high tensile strength and low elongation, and tighten the wire periodically according to the tightness of the electrode molybdenum cutting wire. Reduce the Jitter amplitude of the electrode wire. The use of a more sensitive tight wire device helps to tighten the wire and reduce the jitter of the wire.
(4) High-speed wire cutting machines shall adopt over-tracking feed control to allow a small amount of short-circuit waveforms between the poles. This helps to suppress the vibration of the molybdenum wire electrode and improve the quality of the wire-cut surface.
(5) Using a spiral nozzle, to make the working fluid evenly ejected along the axis of the electrode wire, reducing the influence of the lateral impact force of the electrode wire and improving the smoothness of the movement of the electrode wire.
(6) Select a strong cleaning fluid to keep the cutting area clean and improve the quality of the wire cutting surface.
(7) Under the premise of ensuring stable processing, properly lowering the moving speed of the electrode wire (may or may not molybdenum wire) can improve the smoothness of the electrode wire movement and improve the surface quality of wire cutting EDM machining.
(8) Ultra-short path reciprocating cutting technology helps to eliminate the black and white cut fringes produced during high speed wire reciprocating cutting.
(9) Using multiple cutting processes, first perform high-speed cutting with coarse gauges, then fine-regulate the shape with precision and fine-grained specifications, and obtain a good surface quality.
3. Control the concentration of the working fluid and keep it clean
The working fluid has a great influence on the surface quality of WEDM using molybdenum wire). In the WEDM process, the type and concentration of the working fluid must be properly selected, and the cleanliness of the working fluid must be maintained to improve the surface quality of the wire cutting machine.
(l) Use a good cleansing emulsion as a diuretic fluid and strictly control its formulation concentration. During the on-line cutting process, splashing of the working fluid, evaporation of water, and contamination of the electroplating product often change the concentration of the emulsion. The operator is customarily added with water to dilute. However, if water is added too much, the concentration of working fluid solution will be too low, which will reduce the adhesion of the working fluid to the electrode molybdenum wire china and affect the detergency of the working fluid, causing blackening and corrosion of the processing surface thus affecting wire cut surface quality. When the concentration of the working fluid is too low, the soaping oil must be emulsified in water and then added to the working fluid to stabilize the concentration of the working fluid. Or add some detergents and other additives to enhance the cleaning performance of the working fluid as well as the dielectric properties and stability to improve the surface quality. Here, we need to remind everyone that after adding some additives and detergents to some working fluids, the quality of the processing surface has not been immediately improved, and the roughness value will not be lowered immediately, but will only gradually appear after cutting for a certain period of time. This is because the added additives need to be gradually activated under the influence of external conditions, and gradually enhance its detergency, and improve the surface quality of wire cutting machining. However, if the concentration of the working fluid is too large, it will affect its fluidity and the effect of washing and chip removal, and it will affect the surface quality of the wire cutting process using molybdenum wire, and even cause increase of the blackening and roughness phenomenon.
(2) When the oil-containing emulsion is selected as the working fluid, the working fluid may be easily separated from the oil or water, or the oil may be decomposed, and thus it may be easily contaminated, and the surface of the working surface may be blackened or the processing may not be stable. The concentration of the working fluid must be strictly controlled. Excessive or long-term use of the working fluid can make the chip removal difficult and lead to unstable processing. As a result, the quality of the wire cutting surface will be affected, the roughness of the surface will be increased, and even the surface of the workpiece may be blackened.
Therefore, in the WEDM process using molybdenum wire, the type of emulsion must be properly selected according to the requirements of the flying arts, and the concentration of the working fluid should be strictly controlled to keep the working fluid clean for a long time without being contaminated.
(3) The use of a water-soluble working fluid results in a clean white surface. Regardless of which emulsifier is chosen as the working fluid, the carbon will be decomposed during the cutting process due to the presence of grease, and a black sticky substance will be produced on the processing surface, which will easily cause the processed surface to be black or form a distinct black and white cutting stripe; In some occasions, there will also be water and oil separation and pollution. If a water-soluble working fluid is selected, it will contain no grease, and it will not decompose carbon during the process. Therefore, the wire-cutting (using molybdenum wire) surface can be made white and the surface roughness and gloss of the surface can be improved.
For some wire cutting applications, where high surface quality is required, people can consider the use of water-soluble working fluid, in order to improve the surface quality and environmental protection in the cutting process. Using water-soluble working fluid, it is also necessary to control its concentration. Since its use period is longer, the volatilization of water will change its concentration. Attention should be paid to regular water addition and monitoring with a dedicated concentration meter. The water-soluble working solution mentioned here does not refer to pure water, but rather contains certain surfactants, rust inhibitors, detergents and other solvents in pure water. It is a special working fluid for WEDM using molybdenum cutting wire.。
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