A method of shaping a tool comprises the steps of defining a shape of an article to be formed with the tool as a plurality of first elements; defining an initial shape of the tool as a plurality of second elements; determining an electric potential of each of the first and second elements; determining an equipotential line between the article and the initial shape of the tool based on the electric potential of the first and second elements; and forming the tool to have a shape coincident with the equipotential line.