CNC Wire EDM: Your Best Friend in the Workshop

Posted on Nov 11, 2020

cnc wire edm

EDM (Electrical Discharge Machining) is a non-traditional metalworking process that uses spark erosion to remove material from the workpiece. An electrical discharge (spark) is created between the electrode, which is usually a wire, and the workpiece.

Between them is usually a weakly conductive liquid medium, such as deionized water, which is continuously flushed as work progresses.

The wire EDM electrode is moved close to the workpiece, which is then gradually destroyed by electrical discharge. As the workpiece is eroded, the electrode is moved deeper into the workpiece along a computer-controlled path.

Usually, the finished piece goes through several passes, the initial pass is relatively quick and removes most of the material. Subsequent passes will reproduce the cut path at a slower speed and remove less material, but as a result improving the surface quality and adapting the workpiece to the specification. The CNC wire erosion machine is made AFTER heat treatment so as not to affect the finished dimensions.

The cutting wire can be moved in several dimensions and at great angles. This allows the cutting of cones in the workpiece; this is especially useful in the production of extrusion molds. Cutouts and be created by threading the wire through a pre-drilled hole.

Besides metals, other conductive materials such as graphite, diamond and metal alloys can be machined with a wire EDM machine.


Wire EDM Cutting Process

Wire EDM is a specific type of wire EDM process and is one of the most common.

As the wire moves closer to the workpiece, the electric field increases with the square of the distance. Eventually, the dielectric material will reach the point where the electric breakdown occurs and sparks pass through the gap between the wire and the workpiece, thus eroding both components by the current. The wire is used because it can be continuously wound to prevent the electrode from being excessively eroded.

The wire is usually made of a single brass strand and is held at the top and bottom by diamond guides, the guides can move in the x-y plane, and the upper guide can move independently in three axes.

This allows cones and another complex, intricate, and delicate shapes to be processed. The movement of the guides and the workpiece is controlled by a CNC computer.

The typical diameter of the wire is 0.25 mm and occurs in spools about 10 miles long, the cut is larger than the wire diameter because the wire does not actually come into contact with the workpiece and a "cut" occurs due to the spark from the wire to the workpiece.

The "overcut" is predictable and can be programmed in the CNC work steps. If the smallest diameter wire is used, the cut can be accurate to plus or minus micrometers. Modern wire EDM machines often include multiple heads for cutting more than one piece and automatic wire threading.


Applications for Wire Cut EDM

Wire EDM (WEDM) is used to cut toughened metal sheets up to 300mm thick, which are usually difficult to otherwise machine. It is also used when the final piece requires low stress, wire EDM has a low cutting force to remove material and a slight change in mechanical properties is usually observed.

Electrical Discharge Wire is used for the production of extrusion dies, dies and tools.

Electrical Discharge Wire is best suited for relatively small quantities of products that require tight manufacturing tolerances. Industries that use EDM components include the semiconductor industry, medicine, and instrumentation.


Any Benefits of Machining With EDM?

Complex shapes that with traditional cutting tools would otherwise be difficult to manufacture

An extremely hard substance with tolerances that are very close. Quite tiny workpieces where, because of extreme pressure from the cutting tool, traditional cutting tools may destroy the part.

Between the instrument and the workpiece, there is no immediate touch. Hence, without distortion, fragile parts and poor materials may be machined. It is possible to achieve a strong surface finish.


Produce Anything You Can Imagine With Just One Wire Cut

Cut conductive materials, from aluminum and copper to graphite, with an electric spark. EDM technology achieves extreme accuracy in the production of extremely fragile parts at very high cutting speeds. It's not just limited to dying and mold.

Since only one tool is required, it is also an inexpensive alternative to milling, turning, grinding, turning or broaching. Moreover, you can run a whole range of different processes using multi-functional EDM, even unmanned.

With the CNC wire EDM machine, there is no chip or scrap in processes involving expensive materials, Wire Cut EDM has the advantage of not producing chips and generating additional scrap costs.

For CNC wire EDM, there is no special fixture as EDM machines do not require special fixtures for different components and processes - saving money and increasing flexibility. However, to increase the throughput, consider adding an extra robot.

Thanks to the CNC wire erosion machine, no burrs or rework, as no force is applied, the wire cut leaves perfect surfaces. For even finer surfaces or even a mirror finish, there is a micro finish feature that can replace even multiple steps with a single procedure.

Finally, there is the beauty of CNC wire EDM, cutting without force as there is no contact between the cutting tool and the workpiece, EDM allows you to cut very small parts, such as injector pins, watch parts, precision car parts, and medical parts, with the thinnest of the wall. This is an absolute benefit compared to drilling, milling, or lathing.


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