Wire cut Electrical Discharge Machining (WEDM) belongs to the category of electrical processing. When the former Soviet Union Lazarinko and his wife studied the phenomenon and causes of the corrosion damage of the switch contacts by spark discharge, they found that the instantaneous high temperature of the electric spark can make the switch contacts damaged. The local metal is melted, oxidized and corroded, thus creating and inventing the electrical discharge machining method.
my country was the first country to use it for industrial production. The basic physical principle is that free positive ions and electrons accumulate in the field and quickly form an ionized conductive channel. At this stage, a current is formed between the two plates. This leads to numerous collisions between the particles, forming a plasma zone, which quickly rises to a high temperature of 8,000 to 12,000 degrees, instantly melting some materials on the surfaces of the two conductors, and at the same time, due to the vaporization of the electrodes and the dielectric liquid, a bubble is formed, And its pressure rules go up until very high. Then the current is interrupted, and the temperature suddenly drops, causing the bubbles to explode inward, and the generated power throws the melted material out of the crater, and then the corroded material re-condenses into small spheres in the dielectric liquid, which is expelled by the dielectric liquid. Then, through the monitoring and control of NC control, the servo mechanism executes, so that this discharge phenomenon is uniform and consistent, so that the processed object can be processed, making it a product with the required size and shape accuracy.
Wire EDM can be divided into high-speed reciprocating wire EDM (Reciprocating type High Speed Wire cut Electrical Discharge Machining commonly known as "wire cutting machine"), low-speed unidirectional wire EDM ( Low Speed one-way walk Wire cut Electrical Discharge Machining commonly known as "slow wire")
Wire cutting machine composition
The CNC wire cutting machine consists of three major parts: mechanical, electrical and working fluid systems.
1. Mechanical part
The mechanical part of the wire cutting machine tool is the foundation, and its accuracy directly affects the working accuracy of the machine tool, and also affects the full play of electrical performance. The mechanical system consists of machine bed, coordinate table, wire transport mechanism, wire frame mechanism, taper mechanism, lubrication system, etc. The machine bed is usually a box-type structure, which provides the installation platform for various components, and is closely related to the accuracy of the machine tool. The coordinate table is usually composed of cross carriage, rolling guide rail, screw motion pair, gear transmission mechanism and so on. It is mainly the relative movement with the electrode wire to complete the machining of the workpiece. The wire conveying mechanism is composed of a wire storage drum, a motor, a gear pair, a transmission mechanism, a reversing device and an insulating part. The electrode wire is neatly wound on the wire storage drum. The wire rack is divided into single-column cantilever type and double-column gantry type. The single-column cantilever type is divided into upper and lower arms. Generally, the lower arm is fixed, and the upper arm can be moved up and down. The guide wheel is installed on the wire frame to support the motor wire. The taper mechanism can be divided into swing type and cross drag plate structure. The swing type is completed by the rotation of the upper and lower arms through the lever, which is generally used in large taper machines. The cross carriage type is completed by moving the electrode wire to expand and contract, and it is generally suitable for small taper machines. Lubrication system is used to relieve mechanical wear, improve mechanical efficiency and reduce power loss. It can play the role of cooling, corrosion inhibition, vibration absorption and noise reduction.
2. Electrical part
The electrical part includes machine tool circuit, pulse power supply, driving power supply and control system. The machine tool circuit mainly controls the operation of the wire transport motor and the working fluid pump, so that the electrode wire can continuously cut the workpiece. The pulse power supply provides spark discharge energy between the electrode wire and the workpiece to cut the workpiece. The driving power supply is also called the driving circuit, which consists of a pulse distributor, a power amplifier circuit, a power supply circuit, a preamplifier circuit and other control circuits. It is a special power supply that provides power to the stepper motor, and is used to control the stepper motor. The control system mainly controls the movement of the table carriage (track control) and the discharge of the pulse power supply (processing control).
3. Working fluid system part
The working fluid system is generally composed of a working fluid tank, a working fluid pump, a liquid inlet pipe, a liquid return pipe, a flow control valve, a filter screen cover or a filter element. The main function is to concentrate the discharge energy, take away the discharge heat to cool the electrode wire and the workpiece, and remove the galvanic corrosion products.
Processing principle of wire cutting machine
(1) Wire cutting - short for CNC wire EDM. (2) Working principle: The moving wire is used as the tool electrode, and the pulse current is passed between the wire and the workpiece, and the workpiece is cut by the corrosion effect of the pulse discharge. (3) Since it uses wire electrodes, it can only be used for contour cutting. (4) The working principle is shown in Figure 2.
Figure 2 Processing principle of wire cutting machine 1-- numerical control device 2--wire storage 3--guide wheel 4--electrode wire 5--workpiece 6--nozzle 7--insulating plate 8--pulse generator 9- - Hydraulic pump 10 - Water tank 11 - Control stepper motor
(5) When the gap between the workpiece and the wire electrode is enough to be broken down by the pulse voltage, a spark discharge occurs between the two to cut the workpiece. (6) The stepper motor 11 is controlled by the instruction issued by the numerical control device 1, and the two pallets X and Y are driven to move, and workpieces with arbitrary curve contours can be processed.
Wire cutting machine safety operation rules
1. Check the switch knob of the circuit system, turn on the AC stabilized power supply, turn on the power switch first, then turn on the high-voltage switch, and connect it to the negative line after 5 minutes. 2. After turning on the power switch of the console, you should first check whether the output data of the regulated power supply and the neon light digital tube are normal, input the information for about 5 minutes, and perform a trial operation. 3. The high-frequency power switch for wire cutting should be placed in the off position before processing. When the molybdenum wire is running, the high-frequency power can be turned on, and it should be kept at 60-80 volts. The high-frequency power supply should be turned off before parking. 4. When cutting, coolant should be added. When the molybdenum wire is in contact with the workpiece, check whether the voltage and electro-hydraulic value of the high-frequency power supply are normal, and must not be processed in the case of arcing. 5. If a fault occurs, the high-frequency power supply should be turned off immediately, and the reasons should be analyzed. Other items, especially metal equipment, are not allowed to be placed in the electric box. 6. Do not touch the electrode wire or workpiece with hands or conductors. Do not touch switches or other electrical parts with wet hands.