Princípios de corte de fio de descarga elétrica CNC: explicados

CNC Electrical Discharge Wire Cutting Principles: Explained

The electrical discharge CNC wire cutting process mainly includes the following three parts (as shown in Figure a):

(1) Pulsed discharge between the electrode wire and the workpiece.

(2) The electrode wire moves along its axial direction (vertical or Z direction).

(3) The workpiece makes CNC movement relative to the electrode wire in the X, Y plane.

Figure a. Electric Spark Wire Cutting Main Diagram

I. Pulse discharge between electrode wire and workpiece during electrical spark wire cutting

During electric spark wire cutting, the electrode wire is connected to the negative pole of the pulse power supply, and the workpiece is connected to the positive pole. A pulse energy source is applied between the positive and negative poles.

When a pulse arrives, a spark discharge is generated between the electrode wire and the workpiece. The temperature in the middle of the discharge channel can instantly reach above 10,000°C, causing the metal of the workpiece to melt and even a small amount to vaporize.

The high temperature also causes part of the working fluid between the electrode wire and the workpiece to vaporize. This vaporized working fluid and the heat of the metallic vapor expand instantly and have explosive characteristics.

This thermal expansion and local microexplosion expel the melted and vaporized metallic material, cutting the part material by electrical erosion. It is generally believed that the discharge gap between the electrode wire and the workpiece is about 0.01 mm. If the pulse voltage is high, the discharge interval will be longer.

For electrical spark processing to proceed smoothly, it is necessary to create conditions to ensure that each pulse produces a spark discharge, and not an arc discharge, between the electrode wire and the workpiece.

CNC Electrical Discharge Wire Cutting Principles Explained

First, there must be sufficient time interval between two pulses to allow the medium in the discharge gap to deionize, that is, to cause the charged particles in the discharge channel to recombine into neutral particles, restore the insulating force of the medium in the discharge channel. range at this time. discharge point and avoid continuous discharge at the same point, leading to arc discharge. The overall pulse interval must be greater than four times the pulse width.

To ensure that the electrode wire does not burn during spark discharge, a large amount of working fluid must be injected into the discharge opening so that the electrode wire can be fully cooled. At the same time, the electrode wire must move quickly in the axial direction to avoid being burned by continuous spark discharge at a local position.

The electrode wire speed is approximately 7~10m/s. The high-speed moving electrode wire is beneficial to constantly bring new working fluid into the discharge gap and to remove the electrical erosion products from the gap.

During electrical wire cutting, to obtain good surface roughness and high dimensional accuracy, and to ensure that the electrode wire does not burn, appropriate pulse parameters should be selected, and the discharge between the workpiece and the electrode wire molybdenum must be a spark discharge, not an arc discharge.

II. Wire feeding movement in electrical discharge wire cutting

To prevent spark discharges from burning the electrode wire in the same location, which may affect the quality and efficiency of the process, the electrode wire moves along the axis during the cutting process.

The principle of wire feeding is illustrated in Figure b. The molybdenum wire is wound neatly on the wire storage drum, forming a closed loop. When the wire feeding motor drives the rotation of the wire storage drum, the molybdenum wire moves along the axis through the wire guide wheel.

Figure b. Wire feed mechanism schematic diagram

III. X, Y coordinate worktable movement

The workpiece is mounted on the X, Y coordinate worktable of the upper and lower layers, each driven by a stepper motor for numerical control of movement. The trajectory of movement of the part in relation to the electrode wire is determined by the wire cutting programming.

Figure c. Upper bench transmission schematic diagram

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