Abstract: An electric discharge machine having an electrode mounting device (42) for mounting a tool electrode, a quill (41) movable in the vertical direction and having the tool mounting device attached to a lower end, at least two linear motor movers (43, 44) attached to the quill and disposed symmetrically about the central axis of the quill, at least two linear motor stators (31, 32), each disposed opposite one of the at least two movers, and a balance device (6) for balancing a gravitational force acting on the quill. The balance device has an air cylinder (60) arranged coaxially with the quill so that a balance force having a force vector aligned with the central axis of the quill is generated. The air cylinder is preferably mounted in a hole formed in the center of the quill and extends in a vertical direction.

Abstract: An electric discharge machining apparatus includes a first movable body (40, 42, 50) movable along the Z axis, a ball screw (34), a motor (30) for causing rotation of the ball screw, a nut (35), attached to the first movable body, threadingly engaging the ball screw, a second movable body (10, 13) movable along the Z axis relative to the first movable body, capable of having the tool electrode attached thereto, and a linear motor (71, 72, 73) for moving the second movable body, for machining a workpiece by moving a tool electrode along a Z axis towards the workpiece while causing an electric discharge between the workpiece and the tool electrode. The linear motor includes a stator (73) attached to the first movable body, and a mover (71, 72) attached to the second movable body. The first and second movable bodies include respective electrode attachment units (50, 13).

Abstract: A wire cutting device (3) for cutting a wire electrode (5), used to generate an electric discharge between it and a workpiece (W), comprising a drive gear (12), a follower gear (13) which meshes with the drive gear and is shiftable in its axial direction relative to the drive gear, an adjustable bias mechanism (17) which presses the follower gear against the drive gear in order to accommodate wire electrode of various diameters, materials and conditions, take-up rollers (10a, 10b) which feed spent wire electrode between the drive gear and the follower gear, and a drive mechanism for driving the drive gear such that the peripheral speed of the drive gear is greater than the speed at which the wire electrode is fed out by the wire take up device.

Abstract: An electric discharge machining apparatus comprises a quill 8 movable in the vertical direction, at least one set of linear motor movers attached to the quill, symmetrically about a center axis of the quill, and a single set of linear motor stators facing the set of movers. An electrode mounting device (9) for holding a tool electrode (6) is attached to a lower end of the quill, coaxially with the quill. Preferably, the set of movers includes magnetic plates (12, 14) attached to the quill and a row of permanent magnets (11, 13, 15, 16) arranged on the magnetic plates, and the set of stators includes a yoke (31, 41) and a coil (32, 42) wound around the yoke. The quill has a hole (8a) in its center extending in the vertical direction, and an air cylinder (61) providing counter balance for the load of the quill is preferably disposed in this hole.