US 4,900,890 AGranted

Electric discharge machining method and apparatus for machining a microshaft

AssigneeMatsushita Electric Industrial Co., Ltd.

InventorsTakeshi Masaki, Takeshi Mizutani, Katsutoshi Yonemaochi, Akemi Tanaka

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Abstract

An electric discharge machining system of machining a microshaft by electric discharge made between the microshaft and a conductive wire used as a working tool. The microshaft is vertically supported by a bearing to be rotatable about its own axis and movable up and down in directions of the axis by a microshaft driving device and the wire is arranged to travel in a direction of its own axis and to be movable in directions close to and away from the microshaft by a wire driving device, whereby the wire is relatively movable with respect to the microshaft in horizontal and vertical directions. On the electric discharge machine, a control unit controls the microshaft driving device and wire driving device so that the wire is moved up to a predetermined position horizontally away by a first predetermined distance from a first reference point in the horizontal directions that the axis of the wire intersects the axis of the microshaft and the microshaft is moved vertically by a predetermined distance with respect to the wire with the wire travelling in the direction of its own axis and the microshaft being rotated about its own axis. As a result, the microshaft is machined to have a diameter equal to twice the first predetermined distance and the machined portion of the microshaft has a length corresponding to the second predetermined distance.

Claims18

Dependent claims

An electric discharge machining method of machining a microshaft by means of electric discharge made between said microshaft and a conductive wire through an electric discharge circuit, said microshaft being vertically supported by supporting means to be rotatable about its own axis and movable up and down in directions of the axis by means of microshaft driving means and said wire being arranged to travel in a direction of its own axis and to be movable in directions close to and away from said microshaft by means of wire driving means, whereby said wire is relatively movable with respect to said microshaft in horizontal and vertical directions, comprising the steps of:

(a) determining a first reference point in the horizontal direction that the axis of said wire intersects the axis of said microshaft;
(b) driving said wire driving means so that said wire travels in the direction of its own axis;
(c) rotating said microshaft and machining the lower end surface of said microshaft by said wire so that the lower end surface thereof becomes perpendicular to the axis thereof to determine a second reference point in the vertical direction on the basis of the position of the machined end surface thereof;
(d) shifting said wire up to a predetermined position away from said first reference point in the horizontal direction by a first predetermined distance;
and
(e) moving said microshaft with respect to said wire in the vertical directions by a second predetermined distance between said second reference point and a predetermined point with said microshaft being rotated and said wire travelling so that said microshaft is machined to have a diameter substantially equal to twice said first predetermined distance and the machined portion of said microshaft has a length corresponding to said second predetermined distance.

3 more elements

An electric discharge machining apparatus for machining a microshaft by means of electric discharge, comprising:

mandrel means for holding said microshaft;
bearing means for supporting said mandrel;
first drive means for rotating said mandrel means so that said microshaft is rotated about its own axis;
second drive means for moving said mandrel and said microshaft so that said microshaft is relatively movable in directions of its own axis with respect to a conductive wire used as means for machining said microshaft;
third drive means for moving said wire in a direction of its own axis at a machining position with said wire being guided by wire guiding means;
fourth drive means for moving said wire so as to be closed and separated to and from said microshaft;
electric discharge circuit means for generating electric discharge between said microshaft and said wire;
and
control means for controlling said first to fourth drive means and said electric discharge circuit means so that said wire is moved by said fourth drive means so as to be separated by a first predetermined distance from the axis of said microshaft, said microshaft is rotated by said first drive means, said wire is moved in the direction of its own axis by said third drive means, the electric discharge is made by electric discharge circuit means between said wire and said microshaft, and said microshaft is moved by said second drive means by a second predetermined distance in the direction of its own axis, whereby said microshaft is machined so as to have a predetermined diameter corresponding to said first predetermined distance and the machined portion of said microshaft has a length corresponding to said second predetermined length, and after the termination of the electric discharge machining of said microshaft, said control means controls said electric discharge circuit means so that the polarities for said wire and said microshaft are switched to be reversed and further controls said second drive means so that said microshaft is moved in the direction opposite to the direction in which said microshaft has been machined by the electric discharge.

6 more elements

Dependencies are inferred from the claim text.