Characteristic analysis and problem solving method of proces
At present, most of the wire cutting manufacturers are using fixed conductive block way of electricity, cutting ordinary steel, copper, hard alloy more normal.However, in the process of cutting aluminum, short circuit, broken wire and distortion of cutting track are easy to occur, and the processing efficiency is low.Through the observation and analysis of actual machining, it is found that there are special physical and chemical characteristics in machining aluminum parts by wire cutting.
In the cutting process, the molybdenum wire is slowly close to the aluminum parts. When the positive and negative terminals reach a certain electric field intensity, the discharge meson (emulsion) is punctured.Spark discharge between molybdenum wire and aluminum, and with local instantaneous high temperature, the part near the molybdenum wire cutting channel by melting at high temperature and evaporation, cause local violent explosion, the melting and vaporization of metals is thrown.During this discharge, the water in the emulsion is decomposed into hydrogen and oxygen ions.The partially melted and vaporized aluminum and the oxygen ions generated by the discharge produce alumina, which is carried out of the cutting channel by high-speed moving molybdenum wires and flowing emulsions.In addition, a small amount of aluminum and alumina are attached to the surface of the molybdenum wire and the surface of the cutting channel with the action of electric field.
1. Common problems in wire cutting processing of aluminum parts
1.1 reasons for low efficiency of wire cutting aluminum parts
The melting point of aluminum is lower than steel, copper and hard alloy, the conductivity is lower than copper, higher than steel, hard alloy.Theoretically, the efficiency of using wire cutting to process aluminum parts should be higher than that of steel parts.After field test cutting, the aluminum parts are processed with new molybdenum wire or molybdenum wire cut steel parts. At the beginning, the processing efficiency is 2 to 3 times that of steel parts.However, after a period of time, alumina attached to molybdenum wire gradually. As alumina is not conductive, the conductivity between molybdenum wire and aluminum parts is reduced, so it is not easy to form a discharge channel and the cutting efficiency is reduced.
1.2 reasons for loss of conductive blocks in wire cutting processing of aluminum parts
When cutting aluminum, the conductive block will have a groove phenomenon, aluminum oxide abrasion on the surface of molybdenum wire is one of the reasons.When the new molybdenum wire cuts aluminum, the molybdenum wire slides on the conductive block and has good conductivity.When the alumina on the molybdenum wire gradually attached more and more, the surface of alumina parcel layer molybdenum wire conductivity fell sharply, makes processing is negative, molybdenum wire into a positive, conductive block as the cathode, and between them there is a layer of alumina medium, processing after a period of time will see molybdenum wire and small spark discharge between two conductive block.This discharge causes the conductive block to be electrically corroded out of the groove.
1.3 reasons for short circuit in cutting aluminum parts
Cutting aluminum, alumina adherent molybdenum wire of the electric corrosion and cut the surface of the channel, as oxide layer thickening, result in discharge channel enhanced insulation, corrosion performance degradation, the sampling circuit can't honest feedback the actual circumstances of the plasma channel, the control system can't give machine tool feed the right instructions, failed to correctly adjust feed rate, cause a short-circuit.
1.4 reasons for the distortion of the track of aluminum parts in wire cutting process
When cutting steel and copper parts.The cutting short circuit machine will stop feeding, return to eliminate short circuit phenomenon, and continue cutting.When the aluminum parts are short-circuited, the control system misjudges due to the spark discharge between the molybdenum wire and the conductive block, and the molybdenum wire contacts and bends with the workpiece.The actual machining track is distorted and the workpiece is pulled by molybdenum wire and scrapped.
1.5. The reason why wire breaking is easy for aluminum parts in wire cutting and processing
The bending of upper 1.4 molybdenum wire is too large, which will also cause the molybdenum wire to break when the workpiece is pulled.Molybdenum wire in electric spark discharge loss exist in the cutting process of aluminum, cutting after a period of time, store on the drum to participate in the discharge of the molybdenum wire spark erosion, diameter decreases, and conductive block was cut out of the narrow groove.However, there is a small section of molybdenum wire on both sides of the silk tube, which ACTS as the reversing buffer of the silk tube in the process of processing. These two sections of molybdenum wire do not participate in spark discharge, and their diameter has not changed.Participate in the discharge of the molybdenum wire slip the narrow slot on the conductive block, because of the small diameter is relatively easy, when drum to reversing the buffer storage, glides across the narrow slot molybdenum wire diameter suddenly become bigger, led to the decrease of the electrode wire card or broken wire speed by electrical burn out.When cutting aluminum parts, because alumina and aluminum chips are attached to molybdenum wire, once carried into the groove of the conductive block, it will squeeze the groove to death, the molybdenum wire will be clamped, and the wire will be cut off or the wire speed will be cut off by electricity.
2. Original solutions to problems
2.1 adjust the appropriate electrical parameters and feed speed
2.2 timely adjust the position of the conductive block
2.3 improve the feeding mode to prevent wire breakage (such as power on the wire drum)
2.4 special electrode wire for cutting aluminum parts is adopted
2.5 wire cutting machine tools for cutting aluminum into electrical appliances
The solution of the new invention
Above 1, 2 are common problems and solutions for cutting aluminum parts.According to the above problems, as long as the attachment of alumina to molybdenum wire is solved, the problems of short circuit, broken wire, distortion of cutting track and low processing efficiency can be solved.I changed the output characteristic of high frequency power supply and effectively avoided the attachment of alumina to molybdenum wire when cutting aluminum parts.