Hot blow forming control method
AssigneeGeneral Motors Corporation
InventorsJames Gregory Schroth, Mark W. Verbrugge, John Robert Bradley
Life of this patent
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Abstract
A sheet material is gripped at its edges and hot blow formed by a pressurized working gas against a forming tool surface. The flow characteristics of the material are determined at increasing gas pressures over a range of temperature relevant to the forming operation. A predetermined pressure/time schedule is determined at a reference temperature for rapid shape formation of good parts on a continual basis. The process is then controlled as parts are thus formed by measuring the forming temperature of the parts and correcting the pressure time schedule, using the determined flow characteristics, for the actual temperature to achieve the desired shape evolution of the parts.
Claims10
A method of controlling application of a pressurized working gas against one side of a sheet material workpiece to stretch it into conformance with a heated forming surface as a succession of said workpieces are stretched into conformance with said forming surface, said method comprising:
- predetermining working gas pressure relationships for stretch forming strain rates over a range of temperatures for said forming of said sheet material workpieces into a desired product shape;
- predetermining a forming time-gas pressure application reference schedule at a reference forming temperature for said forming of said product shape;
- and during the forming of said sheet material workpieces;
- continually measuring the temperature at a location selected for controlling the application of gas pressure for forming said sheet material workpieces;
- and
- adjusting the pressure of the working gas applied against said workpiece using a said pro-determined working gas pressure relationship for the measured temperature when said measured temperature differs from said reference forming temperature.
A method of controlling the forming of a heated aluminum sheet metal alloy workpiece during application of a pressurized working gas against one side of the heated sheet metal workpiece to stretch it against a heated forming surface as a succession of said workpieces are stretched into conformance with said forming surface, said method comprising:
- predetermining working gas pressure relationships for stretch forming strain rates over a range of temperatures for said forming of said sheet metal workpieces into a desired product shape;
- predetermining a forming time-gas pressure application reference schedule at a reference forming temperature for said forming of said product shape;
- and during the forming of said sheet metal workpieces;
- continually measuring the temperature at a location selected for controlling the application of gas pressure for forming said sheet metal workpieces;
- and
- adjusting the pressure of the working gas applied against said workpiece using a said pre-determined working gas pressure relationship for the measured temperature when said measured temperature differs from said reference forming temperature.
A method of hot blow forming a superplastic aluminum sheet metal alloy workpiece using a pressurized working gas to stretch said workpiece against a forming surface of a heated forming tool into a product shape as a succession of said workpieces are stretched against said forming surface, said method comprising:
- pre-heating said workpieces to a temperature in the range of 400° C. to about 500° C.;
- predetermining a forming time-gas pressure application reference schedule at a reference forming temperature of said forming surface in the range of 400° C. to about 500° C. for said forming of said product shape;
- and during the forming of said workpieces;
- using an electrical control circuit, and electrical resistance heaters in said forming tool, to heat said forming tool to said reference forming temperature;
- continually measuring the temperature at said forming surface and comparing the measured temperature with the corresponding reference temperature;
- and
- adjusting the pressure of the working gas applied against said workpiece using a said pre-determined working gas pressure relationship for the measured temperature when said measured temperature differs from said reference forming temperature.
Dependencies are inferred from the claim text.