Wire EDM Machining
Wire Electrical Discharge Machining, Wire EDM, is a machining process that utilizes a wire filament that carries an electrical charge through the wire and is used to cut away the hard metal elements.
There are two major components required for the wire EDM machine, not the least of which is the wire used to remove the metal in order to shape the product being manufactured. The degree of precision and the amounts of materials that can be removed through successive passes are greatly determined by the composition of the wire, typically copper wire, as well as the type and strength of the electrical current. Certainly, the greater the diameters of the wire, the more material that can be cut with each pass; however, the trade-off with the larger diameter wire is that the degree of precision is decreased.
Most wire EDM machines today are CNC-controlled tools. The acronym CNC stands for “Computer Numerical Control.” Rather than rely on the somewhat inaccurate and imprecise “eyeball” approach, modern wire EDM machines rely solely upon computers to guide the wires to cut away only the metal that needs to be removed.
In order to cut designs with greater precision and in order to create 3D objects, wire EDM machines have wires that occupy not only the traditional X and Y axis but also the U and V axis for a standard 4-axis tooling but can also have a 5th access for even greater precision.
The second component of wire EDM is that the metal being worked is commonly inserted and tooled in a tub of fluid, typically a Deionized water which controls the conductivity of the wire for a better cut as well as to help keep the core temperatures down. As is commonly understood, electrical currents passing through metals increase internal temperatures and metal tooled in higher heat environments becomes less rigid and have a loss of tensile strength. An additional advantage of tooling in water is to help remove chips and particles from the work area decreasing the amount of accidental scoring of the finished product as well as to decrease the overall “heat affected zone.”
One final advantage to machining in fluid is that it helps to extend the life of the wire itself. Wire EDM machines are high maintenance. The wires must be checked for pitting, scoring, breaks, and other failures on a regular basis. Evidence of any of these if left uncared for, can cause improper tooling of the object, loss of precision or even damage to the machine. By tooling in fluid, the wires are kept cooler and the electrical charges passed through the wires are maintained at a steady rate, thereby extending the wire lives.
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