More specifically, this invention relates to an apparatus for sealing the lower arm unit in a wire-cut Edm machining which performs submerged machining.

In a wire-cut Edm machining which performs submerged machining, various methods have been proposed for sealing the lower arm unit with the processing tank. For example, as disclosed in U.S. Pat. No. 4,918,279, a slide seal may seal the arm unit when the arm unit moves axially. In such machines, however, particles produced during machining of the workpiece disperse throughout the working fluid and may become deposited onto the arm unit. As a result of these particles, the slide seal may become worn and the sliding resistance of the arm unit varies significantly.

Additionally, such Edm machining may be prone to errors caused from varying temperatures. The temperature inside the processing tank is maintained at a fixed level by controlling the temperature of the working fluid. Portions of the lower arm unit outside of the processing tank, however, would be exposed to the external temperature. Because of the temperature differential, the lower arm unit may expand and cause an error of a few micrometers in the direction. Since the arm's length is about 300 mm-600 mm, a change of 1 degree C. would cause a significant thermal displacement in the axial direction.

To achieve the foregoing and other objects in accordance with the purpose of the present invention, as embodied and broadly described herein, the arm sealing device of this invention may comprise a processing tank having an opening in it which is covered by a slide plate having an opening through which a pipe containing the arm unit passes. Bellows extend from the slide plate to the inserted end of the pipe to provide a seal between the slide plate and the pipe. Machining fluid flows between the pipe and arm unit for maintaining the arm unit at a constant temperature.