Method and apparatus for hydro-forming thin-walled workpieces

A method for hydro-forming a wall of a workpiece, the wall having first and second opposed faces, comprising the steps of:

• (a) supporting the first face of the wall against a work supporting surface having at least one cavity configured to define a desired protruding feature on the first surface of the wall;
• (b) placing a hollow member adjacent to and spaced from the second face of the wall defining a clearance between the hollow member and the second face of the wall that is open to an external atmosphere, the hollow member having at least one opening therein to supply fluid from inside the member to the workpiece adjacent the cavity;
• (c) applying a fluid through the opening under sufficient pressure and for a sufficient period, to the second face of the wall to hydro-form the desired feature, against the cavity, in the wall of the workpiece;
• and
• (d) maintaining said clearance between the member and the second face of the wall open to said atmosphere, the clearance being sized to provide sufficient pressure drop to maintain the pressure of the fluid, at the portions of the wall to be deformed, high enough to deform the wall during the hydro-forming of the feature while facilitating said placement and removal of the member to and from said adjacency.

A process for hydraulically forming cylindrical tubing into a desired shape, comprising the steps of:

• (a) providing a forming die having a bore sized to receive and support the tubing with an entry in at least one end of the bore and a cavity in an inner surface of the bore configured to define a desired protruding shape to be formed in an outer peripheral surface of the tubing;
• (b) providing a needle having an external diameter that is smaller than an internal diameter of the tubing whereby the needle fits in the tubing with a clearance, between an inner surface of the tubing and an outer surface of the needle, that is open to an external atmosphere and sufficiently small to provide a pressure drop, in the clearance, sufficient to maintain the pressure of the fluid, at the portions of the tubing to be deformed, high enough to deform the tubing, during said forming, while being sufficiently large to facilitate insertion and removal of the needle, the needle defining an opening to allow application of fluid under pressure from inside the needle to the inner surface of the tubing adjacent the cavity;
• (c) positioning the tubing within the die;
• (d) inserting the needle into the tubing forming said clearance;
• (e) applying sufficient pressure to fluid in the needle for a sufficient duration to apply pressure through the opening to deform the tubing into the cavity to form the desired shape while maintaining said clearance open to said atmosphere;
• and
• (f) removing the needle from the tubing and removing the tubing from the die.