Basics of Wire EDM: Pros, Cons and Steps of CNC Wire Electrical Discharge Machining

Wire EDM or WEDM generally refers to Wire Electrical Discharge Machining. Its basic working principle is to use the continuously moving fine metal wire (called electrode wire) as the electrode to etch the metal and cut the workpiece by pulse spark discharge. What are the advantages and disadvantages of wire EDM? What steps are involved in the process of CNC Wire Electrical Discharge Machining?

Advantages of Wire EDM

– Wide range of application: no matter the thickness and hardness of the material, it can be processed. As long as it is a conductive material, it can be processed from a thin plate to cemented carbide, regardless of the thickness, size, and hardness of the material.

– It can process complex shapes: in addition to linear cutting, it can also be cut into arcs and process complex shapes, such as the combination of straight lines and arcs. Taper machining can also be carried out by moving the upper and lower metal wires respectively.

– High accuracy: the accuracy of wire cutting is comparable to that of grinder (0.005 mm unit).

– Burr-free: since burr removal is not required, peripheral equipment such as a chip conveyor belt is not required, and the process can be shortened.

– No need for special tools: since relatively cheap brass (brass) wires can be used to replace consumable tools such as cutting tools for rotation and cutting, there is no need to replace the tools and the cost of consumables can be reduced.

– Reduce material damage: because wire cutting is a non-contact process, the load on the material will not be too large, and the thermal deformation is also very small.

Disadvantages of Wire EDM

– Cannot process with the bottom: because wire cutting is a wire saw, it cannot be processed with the bottom. If you want to carry out EDM at the bottom, the sinking die EDM machine is the best choice.

– Slow processing speed: it cuts while gradually melting the workpiece, so it is slower than cutting and is not suitable for mass production. Its speed is a few millimeters per minute, and it can hardly be seen to move with the naked eye.

– Non-conductive materials cannot be processed: Although conductive materials can be processed regardless of their hardness, non-conductive materials cannot be processed.

– Cannot process horizontally: because the line stretched vertically is processed like a saw, it cannot be processed horizontally.

Steps and Process of Wire Electrical Discharge Machining

Wire cutting discharge is used to accurately cut metal materials for high-precision machining. Wire cutting is usually used to process block materials, such as molds and gears, precision fixtures, and post-treatment of hardened parts requiring high machining accuracy, rather than cutting sheet materials.

The general processing steps of WEDM are briefly described as follows.

1. First, put the workpiece to be processed on the workbench. Of course, you can cut it from the end of the workpiece, but usually, at the beginning of wire cutting, the starting hole (line) is usually connected to the workpiece to avoid deformation due to the internal stress of the workpiece. When the workbench (or metal wire) moves in the XY direction (on the plane) according to the pre-entered NC data, processing starts. Because it operates continuously through NC control, it can be processed unattended even if there is no operator. After cutting, it will be automatically cut into the specified machining shape according to the NC machining data. When cutting workpieces, they will not touch each other, while maintaining a constant distance of tens of microns (tens of microns).

2. When the distance between the workpiece and the wire electrode in the insulating state in the working fluid is close to dozens of microns, the insulation between them is destroyed, and spark discharge occurs, resulting in the instantaneous flow of pulse current. In the high-density discharge state called the arc tower, several thousand degrees of high temperature is generated locally and the metal (workpiece) melts.

3. In addition, the temperature of the working fluid around the arc column immediately rises and vaporizes, causing rapid volume expansion, thus causing an explosion between the workpiece and the electrode surface. This blows out metal debris.

4. Then, when the pulse current is cut off and flows into the surrounding clean water, the molten metal cools and turns into fine debris, which is washed away, and the insulation between the electrodes is restored again, waiting for the supply of the next pulse voltage.

In this way, the metal (workpiece) is melted and removed under each voltage pulse and repeated hundreds of thousands of times per second to cut the workpiece by wire cut EDM.

Basics of Wire EDM: Pros, Cons and Steps of CNC Wire Electrical Discharge Machining

Advantages of Wire EDM

Disadvantages of Wire EDM

Steps and Process of Wire Electrical Discharge Machining

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