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Electrical discharge sinking

Process in which an electrically charged die creates a cavity in the work piece through controlled spark discharges.

Illustration of Electrical discharge sinking

The process

The tool consists of a die [1] with the inverse shape of the desired cutting.

Connection via power source allows adjustable mold to act as cathode and workpiece as anode. When the lower mold is brought close to the workpiece, intermittent spark discharges occur, which means that the workpiece is melted and vaporized. The discharge is assisted by a dielectric liquid [2], which helps to cool the process and carry away removed material in the meantime the die is lowered to the desired depth.

The spark gap [3] makes the machined surface slightly separate from the outer contour of the tool.

Advantages and disadvantages
In comparison with alternative methods
Exotic materials can be cut
little or no polishing required
Can process thin complex products without causing harm
Tight tolerances, good surface finish
Slower material removal rate