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

A multiwire electric discharge machining method for performing electric discharge machining of a workpiece having a curved surface by causing a wire electrode to travel, the wire electrode being wound multiple times, 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, the multiwire electric discharge machining method comprising:

• starting the electric discharge machining in a state where the curved surface except for an end point is in contact with a contact surface of a dummy workpiece, the end point 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
• pressing the workpiece against the dummy workpiece by moving a pressing portion from another side in the first direction toward the workpiece to bring the pressing portion into contact with the curved surface of the workpiece while the electric discharge machining is continuing.

(canceled)

A semiconductor wafer manufacturing method for manufacturing a plurality of semiconductor wafers by cutting the plurality of semiconductor wafers from an ingot having a curved surface by electric discharge machining in which a wire electrode is wound multiple times and caused to travel, and a voltage is applied between each of a 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, the semiconductor wafer manufacturing method comprising:

• starting the electric discharge machining in a state where the curved surface except for an end point is in contact with a contact surface of a dummy workpiece, the end point being to be reached by the plurality of cutting wire sections when machining of the ingot is completed, the dummy workpiece supporting 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
• pressing the ingot against the dummy workpiece by moving a pressing portion from another side in the first direction toward the ingot to bring the pressing portion into contact with the curved surface of the ingot while the electric discharge machining is continuing.