Wire EDM

Principles of EDM

EDM is a controlled metal removal process that is used for removing metal by means of electric spark erosion. An electric spark is used in this process cutting tool for cutting (eroding) the workpiece to produce the finished part to the desired shape.

The metal removal process is carried out by applying a pulsating (ON / OFF) electric charge of value high frequency current through the electrode to the workpiece. It removes (erodes) very small pieces of metal from a workpiece with controlled speed.

EDM process
EDM spark erosion is the same as for an electrical short circuit that burns a small hole in a piece of metal with which it comes into contact. In the EDM process, both the workpiece material and the electrode the material must be an electrical conductor.

The EDM process can be used in two different ways:

1. A pre-shaped or formed electrode (tool) is usually formed, usually made of graphite or copper to resemble the shape of the recess. The formed electrode is fed vertically downwards and the reverse electrode shape is eroded (fired) in the solid workpiece.

2. A continuous vertical wire electrode with a small needle diameter or smaller has a diameter controlled by a computer to follow a programmed path to erode or cut a narrow socket through the workpiece to get the required shape.

Conventional EDM
In the process of EDM, an electric spark is used to cut the workpiece, which takes shape opposite to the cutting tool or electrode. Both the electrode and workpiece immersed in a dielectric fluid, which is generally a light lubricating oil. servomechanism maintains a space about the thickness of a human hair between the electrode and work, preventing them from contacting each other.

In frame or weight machining, EDM can be a relatively soft graphite or metal electrode is used for cutting hardened steel and even carbide. A slightly larger cavity is formed in the EDM process than the electrode because of a cut.

Wire cutter
The wire cutter is an unloading machine that uses CNC movement for production desired contour or shape. It does not require a special electrode, instead uses continuous live wire like an electrode. Electroerosion electrode has a thickness about a small diameter needle, the path of which is controlled by the machine computer to obtain the required shape.

Dielectric fluids - conventional EDM
During the erosion process, the workpiece and electrode are immersed in the dielectric oil, which is an electrical insulator that helps control arcing. Dielectric oil ensures flushing, it is pumped through the arc gap. This removes suspended particles of the workpiece material and the electrode from the working cavity.

One of the most important factors for successful EDM surgery is removal metal particles (chips) from the working gap. Leaching these particles from the distance between the workpiece to prevent the formation of bridges causing short circuits.

Flushing Ram EDM
Rinsing is the most important function in any electrical discharge operation.

Flushing is the process of introducing pure filtered dielectric fluid into a spark gap.

Incorrect use of rinsing can cause irregular cuts and poor machining conditions.

There are many rinsing methods used to effectively remove metal particles while assisting in the machining process. Too much fluid pressure will remove chips earlier can assist in cutting, resulting in slower metal removal. There will be too little pressure do not remove the chips quickly enough and this may cause a short erosion process

EDM wire dielectric fluids
The dielectric fluid must circulate under constant pressure to flush (wash away) the fluid metal particles and support the machining or erosion process. If red sparks occur during sparking cutting operation, water supply is insufficient. To overcome this problem, increase the flow of water until blue sparks appear.


The Servo Mechanism

Wire and vertical EDM machines are equipped with a servo control mechanism automatically maintains a constant distance of about the thickness of human hair between electrode and workpiece. For both types of machines it is important that they are not physical contact between the electrode and the workpiece, otherwise an arc can damage the workpiece and break the wire. The servo moves the electrode to the workpiece as the operation progresses, detects and controls the wire spacing to maintain the correct arc gap that is necessary for successful machining operations.

Advantages of EDM

Conventional EDMs can be programmed for vertical orbital machining, vector, directional, spiral, conical, rotary, spin and indexing machining cycles. This versatility gives electric discharge machines many advantages over a conventional machine gear.

● Any electrically conductive material can be cut using the EDM process.
● Hardened parts can be machined, eliminating heat deformation treatment.
● X, Y and Z axis movements allow programming of complex profiles using simple electrodes.
● Complex die sections and molds can be produced accurately, faster and at lower costs.
● The EDM process is burr-free.
● Thin delicate sections such as ribs or ribs can be easily machined without deformation.

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