What is EDM?
Electrical discharge machining, or EDM, is a non-traditional method in which material is removed from a workpiece using thermal energy. Much like processes such as laser cutting, EDM does not need mechanical force in the removal process. This is the reason why it is considered non-traditional contrary to, for example, the processing with cutting tools.
In tool and mould making, EDM is very popular due to its applicability especially for hard materials like titanium or for particularly complex shapes that are hard to achieve with milling.
How Does EDM Work?
Wire electrical discharge machining is a method of cutting metals, in which a traveling wire disintegrates material in a controlled manner.It uses an electrically charged thin brass wire, which is moved by computer control, close to, but not touching, the part to be cut. The wire and the work piece are either fully submerged, or the part is vigorously flushed with a dielectric liquid. The small gap (anywhere from .0005 to .020 inch) creates a spark, which vaporizes small particles of the work piece as the wire advances. The disintegrated particles are flushed away by dielectric fluid, and the wire is able to advance further. The wire itself is traveling – advancing from a large spool, and after use as an electrode, into a spent wire bin. The travel of the wire is determined by the machine’s computer program.
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Wire EDM Specifications
EDM micromachining technology provides higher cutting accuracies and tighter tolerances than standard cutting processes:
5-Axis
Wire Dia .006~.012 in
Tolerance 0.0005
Max Taper angle 15º @ 8 in material thickness
Position accuracy 0.0001 in. (0.003mm)
Feature and contour accuracy +/- 0.0001
Kerf width 0.0065 in ~ .0125in
Maximum workpiece size 11.8 x 13.7 x 19.7 inches
Benefits Of EDM
Material hardness has little effect on EDM wire cutting rate and doesn’t limit possible part geometries. Tungsten carbide, tool steel, Inconel and any metal harder than RC38 are all good candidates where conventional machining is slow and expensive.
A particular benefit is the ability to bring parts to their final size after heat-treatment. This takes out distortion brought about by hardening and stress-relieving.
Why Choose ASTEORD for EDM?
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EDM Materials
ASTEORD works with a variety of materials for wire EDM machining. Virtually any conductive material can be cut using Wire EDM. This would include all metals, including steel, aluminum, brass, titanium, and alloys and super alloys of all types. The hardness of the material is not a factor.
Available Surface Finishes
In the conventional cutting of metals, the surface roughness achieved is inversely proportional to the power and speed of the cutting. In other words, higher quality finishes are achieved by slower cutting. With wire EDM, subsequent passes tend to go faster than the ones that came before.
When you require high-quality cutting and finishing with wire EDM, it is a normal procedure to make the workpiece go through a rough cut and one or more skimming cuts. With each pass, less and less material is removed as it gets closer to the finished edge.
For example, if we take a .010” diameter wire, the first pass may remove 0.013” of material with the overburn. The next skim could remove 0.0015”. The next one takes 0.0004”, and finally 0.0001”. Clearly, more passes can result in very smooth surfaces, but there is also a link to the density of the material being cut. The denser the material, the smoother the finish can be with fewer passes.
With several passes through wire EDM, it is possible to completely avoid any secondary processes, like grinding, that many metal products need to be put through when cut by other means.
Because wire EDM allows such precision in cutting, along with no directionality of the cuts, wire EDM is a great choice when you need a high-quality surface finish.
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