METHOD OF FABRICATING AN OBJECT WITH A THIN WALL HAVING A PRECISELY SHAPED SLIT

A method of making a structure having a cavity and having a thin wall with a precisely shaped slit. An object having a cavity having two openings, one of which is to be closed by a thin wall with a slit, is placed on the surface of a fixture. The fixture surface has a slot conforming to the size and shape of the slit to be formed in the thin wall, and a shim member is inserted into the slot such that it extends into the slot a distance deeper than the desired thickness of the thin wall and such that it extends above the surface of the fixture and into the cavity of the superposed object. The object and fixture are fixed in position with the slot properly located in the position of the slit to be formed, and the cavity is filled with a molten settable material from its other end. After the molten material has set, the object is separated from the fixture, the shim adhering to the set composition in the cavity of the object. The surface of the object which was adjacent the fixture is then provided with a plated metal layer over the opening to be provided with a thin wall. The plated layer is then machined such that the layer, in the area covering the cavity opening, has the desired thickness of the thin wall being provided. The settable material is then melted out. The shim is then removed by selective etching to produce the desired structure.