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This application is a divisional of U.S. patent application Ser. No. 09/528,328 filed on Mar. 20, 2000, now U.S. Pat. No. 6,510,601, presently allowed.
The present invention relates generally to Invar tool fabrication. More particularly, the invention relates to a method for fabricating an Invar tool including the step of superplastically forming an Invar facesheet to match or to approximate a predetermined contour of the tool.
Modern day aerospace, defense, and high tech research applications typically require complex, high precision, and close tolerance tooling. Thermal expansion is an area of particular concern in the aerospace industry with regard to tooling. For example, most military aircraft applications stipulate that tools exhibit minimal dimensional changes when subjected to extreme temperature variations.
In the campaign to control thermal expansion, a useful material has been developed under the tradename of Invar 36. Invar 36 (“Invar”) is a nickel-iron alloy that has a rate of thermal expansion that is approximately one-tenth that of carbon steel at temperatures up to 400 degrees F. Invar therefore has a particular attractiveness in fabricating tool components, including a header, which serves as a “frame” for a tool, and a facesheet, which is welded to the header.
Several of our first approaches in developing the present invention were labor and material intensive. One such approach involved a stretch forming technique as shown in
A preferred method of the present invention for fabricating an Invar tool includes the step of providing a tool header defining a predetermined contour. An Invar facesheet is then superplastically formed to match, accurately or substantially, the predetermined contour of the tool header. Normally, the method further provides for welding the Invar facesheet to the tool header. Forming the Invar facesheet in this way results in less scrap, and therefore substantially reduces material costs. Forming the Invar facesheet in this way also leads to reduced labor costs.
The present invention further provides an Invar tool. The Invar tool includes a tool header defining a predetermined contour, and one or more Invar facesheets welded to the tool header. The Invar facesheets are formed with an SPF diaphragm driver to substantially match the predetermined contour of the tool header.
Further in accordance with the present invention, a method for molding parts on Invar tooling is provided. The method includes the step of making an Invar tooling surface from a sheet of Invar with SPF diaphragm forming. The sheet is placed on a tool header, and a part is formed against or on the tooling surface.
The various advantages of the present invention will become apparent to one skilled in the art by reading the following specification and sub-joined claims and by referencing the following drawings in which:
Thus, the Invar facesheet
It is preferred that the die
Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification and the following claims.