Wire electric discharge machining apparatus, wire electric discharge machining method, and control device

A wire electric discharge machining method comprising:

• a voltage applying step in which a power supply device applies a voltage between a wire and a workpiece;
• a machining step in which a machining unit machines the workpiece by relatively moving the wire and the workpiece and forms a product part, which is an inner side portion of the workpiece and a target machining shape, by cutting off an outer frame portion from the workpiece;
• and
• a control step for controlling the power supply device and the machining unit, wherein
• in the machining step, a first boundary region in a boundary between a member to be the outer frame portion and a member to be the product part is machined to leave a part of the boundary as an uncut portion, thereafter, after the member to be the product part and the member to be the outer frame portion are connected by a conductive member, the product part is cut off from the member to be the outer frame portion by machining a second boundary region, which is the uncut portion, in the boundary, and, when the workpiece is machined, a plurality of times of machining is repeated for the first boundary region and a plurality of times of machining is repeated for the second boundary region,
• the second boundary region includes a first region and a second region used as the approach run section when starting a machining of the first region,
• the second boundary region has a side crossing a machining direction in machining the first region, a machining start point of the second boundary region is set on the crossing side, and
• in the control step, when the second boundary region is machined, the machining unit is controlled to start the machining from the machining start point.

A control device comprising:

• a control unit that controls a power supply device that applies a voltage between a wire and a workpiece and a machining unit that machines the workpiece by relatively moving the wire and the workpiece and forms a product part, which is an inner side portion of the workpiece and a target machining shape, by cutting off an outer frame portion from the workpiece, wherein
• the control unit causes the machining unit to machine a first boundary region in a boundary between a member to be the outer frame portion and a member to be the product part to leave a part of the boundary as an uncut portion, thereafter, after the member to be the product part and the member to be the outer frame portion are connected by a conductive member, cuts off the product part from the member to be the outer frame portion by causing the machining unit to machine a second boundary region, which is the uncut portion, in the boundary, and, when machining the workpiece, causes the machining unit to repeat a plurality of times of machining for the first boundary region and causes the machining unit to repeat a plurality of times of machining for the second boundary region,
• the second boundary region includes a first region and a second region used as the approach run section when starting a machining of the first region,
• the second boundary region has a side crossing a machining direction in machining the first region, a machining start point of the second boundary region is set on the crossing side, and, when machining the second boundary region, the control unit controls the machining unit to start the machining from the machining start point.