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Electrical discharge drilling

Abrasive machining method in which a controlled spark discharges from an electrically charged electrodes creates a small hole in the workpiece.

Illustration of Electrical discharge drilling

The process

The tool consists of a narrow lance [1].

Connection to power supply allows the lance to acts as cathode and the workpiece as anode. When the electrode, that is, the lance is brought close to the workpiece, intermittent spark discharges, which causes the workpiece to be melted and vaporized.

The discharge is assisted by a dielectric fluid [2], which is flushed through the cavities of the lance, which helps to cool the process and carry away removed material during the time the lance is lowered through the work piece. The spark gap [3] allows the produced hole diameter to be slightly larger than the diameter of the lance [4].

Advantages and disadvantages
In comparison with alternative methods
Can create microscopic holes for example, lubrication and fuel systems
Can drill small holes in extremely hard materials
quick process
can drill holes angled towards the surface
Electrode wear
Small speed for large holes
A through-hole is difficult to control