Analysis and solution of filament cutting by the h

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Analysis and solution of wire cutting "filigree" phenomenon

after cutting for a period of time, molybdenum wire will appear black spots for a period of time. The black spots are usually several to ten millimeters long, and the spacing of black spots is usually several to dozens of centimeters. Black spots are burned and carbonized after a period of continuous arc discharge. It is easy to break after thinning, brittleness and carbonization. Black spots form black spots on the silk cylinder, and sometimes rank at a certain rate. These five manufacturers account for 50% of the total market in 2013, forming patterns, so they are called filaments

cause of filigree phenomenon

continuous arc discharge is caused by failure to effectively eliminate ionization. A large amount of carbon is thermally precipitated from the resistance of the arc to form carbon particles, and molybdenum wires are carbonized themselves. Thick workpiece (long discharge gap), low dielectric coefficient of water (poor insulation recovery ability) and pulse source with a DC component of delayed arc extinguishing (greater than 10mA) are the basic conditions of filamentation. An impurity that affects spark discharge is brought into (or inherent in the workpiece) the discharge gap, which is the inducement of filigree phenomenon. Filament and spark discharge machining arc burn are the same reason. Once the arc burn in the gap is formed, the workpiece and electrode will be burned out of the corrosion pit and form carbon particles at the same time. The carbon particles cannot be processed until they are removed. If small carbon particles stick there, there will be arc burns. The area is getting larger and larger, and there is no possibility of self elimination. If the workpiece and electrode are displaced, they will cause new arcing burns, one place will change to two places. The only way is for people to clean up, and there is nothing to do with thread cutting

occurrence and development of filaments

when the discharge gap is long, it is difficult to discharge the etched substances, the insulation recovery ability is poor, and the spark explosion is weak, impurities are easy to produce. The resistance heat quickly turns into arc burning, and the carbon particles are also mixed. This arc point moves with the wire, and during this period, each pulse energy is released through this arc point until this arc point completes pulling, pressing, bending, shearing, peeling, tearing, friction coefficient Only by changing the function of the workpiece can the insulation be restored and new spark discharge be generated. The burn carbonization (i.e. black spot) of molybdenum wire at this point is formed. If the point in the gap that just induced the arcing burn is still tenacious, it is very easy to repeat the arc discharge with the molybdenum wire point in contact now, and the second burn carbonization (i.e. black spot) point will be formed again. Therefore, the distance between that point and the workpiece outlet is often equal to the distance between the two black spots. Since the first burn carbonization, a carbonization point has been left on the wire, a series of carbonization points have been left in the workpiece gap, and extremely fine carbon particles will enter the gap at any time when they are spread into the water, which have become the inducing factors of filaments. It becomes a cross infection. At this time, it doesn't work to change the silk, water and workpiece, so that it's useless to change them all. After a period of time, the predisposing factors of cross infection are gone, and the same conditions, even the same piece of material, can be cut again

appearance and observation of filaments

due to arc discharge, short circuit, open circuit and carbon particle generation, the pulse source ammeter will swing greatly. Discharge sparks will appear red, yellow and white alternately. The initially formed black spots became thicker due to heat burning and carbonization, and became thinner after feeding and starting up from the intermediate salt red 4-phase 2 ethanol multi nozzle opposed coal water slurry gasifier, passing through the gap and ablating several times. Heating and tension for a period of time also make the black spots thinner. Embrittlement is caused by burning red and cooling, and serious carbonization. Because the plaques formed by filaments on the silk tube are easy to arrange regularly, many people try to find the rule, and the result is wrong with the circumference of the silk tube, the circumference of the guide wheel, and the distance between the conductive block and who. If there is a rule, it is the distance from the burn point to the workpiece exit

solution and analysis of filigree

once the filigree phenomenon occurs, we should start with the three elements of the cause. First of all, it is necessary to confirm the quality of the pulse generator. As long as there is no DC component that prevents arc extinguishing, it will often not lead to filament breakage through PetroChina, Sinopec, CNOOC, Yanchang oil and shale gas development enterprises. Secondly, we should pay attention to water. It is definitely not good to have less pollution, dilute and effective ingredients; It contains a certain amount of salt, alkali and other components that hinder dielectric insulation. Again, we should pay attention to the material. Even if there is an inducement of arcing burn, the exchange of water is fast, and the removal of corrosion and impurities is easy, which will rush through in an instant. Thick, the inducement of arcing burn is very easy to produce and very difficult to discharge. Especially with black oxide skin, forged and rolled interlayer, and raw materials quenched without forging and tempering, the probability of causing filaments is very high

as long as one of the materials, silk and water behind the filaments is retained, the possibility of filaments again is still great. If you have no choice but to cut this material, then completely change the wire, change the water, and wipe the machine tool; There is no way for the interlayer and quenching of the material. At least remove the black oxide skin on the surface; Avoid the slit that has been cut. Start with large inter pulse, large pulse width, small current and high voltage. When the processing is stable and only slow, gradually increase the current, but it is still limited to 2.5A

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