Multiwire electric discharge machine, multiwire electric discharge machining method, and semiconductor wafer manufacturing method

A multiwire electric discharge machining method, comprising:

• performing electric discharge machining of a workpiece having a curved surface by causing a wire electrode to travel and applying a voltage between each of a plurality of cutting wire sections and the workpiece, the plurality of cutting wire sections being sections of the wire electrode traveling in parallel with each other,
• wherein the wire electrode is wound multiple times around a plurality of guide rollers,
• wherein the electric discharge machining is started in a state where the curved surface except for an end point of the workpiece is in contact with a contact surface of a dummy workpiece, the end point of the workpiece being to be reached by the plurality of cutting wire sections when machining of the workpiece is completed, the dummy workpiece supporting the workpiece from one side in a first direction, the first direction being a direction in which the plurality of cutting wire sections moves with respect to the workpiece, and
• wherein the electric discharge machining of the workpiece includes pressing the workpiece against the dummy workpiece by moving a pressing portion from a side opposite to the dummy workpiece toward the workpiece to bring the pressing portion into direct contact with the curved surface of the workpiece.

A semiconductor wafer manufacturing method, comprising:

• manufacturing a plurality of semiconductor wafers by cutting the plurality of semiconductor wafers from an ingot having a curved surface by electric discharge machining by causing a wire electrode to travel,
• wherein the wire electrode is wound multiple times around a plurality of guide rollers,
• wherein the wire electrode includes a plurality of wire cutting sections,
• wherein during the electric discharge machining, a voltage is applied between each of the plurality of cutting wire sections and the ingot, the plurality of cutting wire sections being sections of the wire electrode traveling in parallel with each other,
• wherein the electric discharge machining is started in a state where the curved surface of the workpiece except for an end point of the workpiece is in contact with a contact surface of a dummy workpiece, the end point of the workpiece being to be reached by the plurality of cutting wire sections when machining of the ingot is completed,
• wherein the dummy workpiece supports the ingot from one side in a first direction, the first direction being a direction in which the plurality of cutting wire sections moves with respect to the ingot, and
• wherein the electric discharge machining of the workpiece includes pressing the ingot against the dummy workpiece by moving a pressing portion from a side opposite to the dummy workpiece in the first direction toward the ingot to bring the pressing portion into direct contact with the curved surface of the ingot while the electric discharge machining is continuing.