In an exemplary dynamo-electric machine, such as a turbine-generator, it is desirable to form certain components as one piece. This is generally done for such parts as turn insulation, rotor channels, and slot cells. As a result, relatively sizable presses are required for molding these components. For example, rotor turn insulation is often formed in one piece on a press which is about forty feet (40 ft.) (12M) in length. Such long presses require large shop areas for work and storage, and the length of these machines entails a higher cost for maintenance and repair. Also, any design changes to the length or other characteristics of the part to be molded requires the manufacture of long tool sections, which are expensive to manufacture and inconvenient to store.
Another process, step-molding, would eliminate many of these difficulties, by enabling lengthy parts to be molded using a shorter press. In step-molding, adjacent portions of a continuous part are sequentially molded, or "stepped" along, to produce a single, long molded component. However, attempts to use a step-molding process to form these particular generator components have not been completely successful.
Generator turn insulation, rotor channels, and slot cells are typically formed with a heat-curable material being associated with the component. The work piece, which initially has a soft, pliable composition, is formed or molded by placing the component within a press, and then heated as pressure is applied to form the component into the desired shape. After the component has been "cured" in the press and allowed to cool, it is then ready for installation in the generator. When elongated work pieces are step-molded, in conventional presses, a bulge of material can be formed in a section of the component immediately adjacent the press. As the uncured part is pressed and heated, so as to cure the heat-curable material associated with the work piece, the pressure causes this bulge to form. Heat from the press is sufficient to cure this bulge of material into an inadvertent, permanent "bump" in the work piece. Once cured, this bump may not be entirely flattened out in subsequent step-mold pressings as the remainder of the component is placed in the press. This can result in an unsatisfactory, unevenly molded part.
It is therefore an object of the present invention to provide a step-molding process and apparatus which will prevent the inadvertent curing of material adjacent to the press, to hinder the formation of a permanent bump in generator components.