flange

To flange means to deform sheet metal or pipe by bending a portion of material outward at a right angle or shallow angle to the main body, creating a protruding lip or rim. The resulting feature, also called a flange, serves structural or functional purposes: it may strengthen a component, provide a mounting surface, direct flow, or create a seal interface. The operation is performed on material already formed into basic shape, not as the initial shaping step.

Flanging is executed using press brakes, flanging machines, or specialized die sets. A typical setup uses a V-shaped or compound die to grip and bend the metal edge. For small batch work, manually operated machines with foot pedals control the ram stroke. For production runs, hydraulic or mechanical presses automate the process. The amount of material drawn into the flange (the draw depth) determines the final flange width; deeper draws produce wider flanges but require more material and greater forming force.

Common flanging problems

Sheet metal cracks at the inner edge of the bend if draw depth exceeds material ductility or if the radius is too sharp. Thin-walled tube flanges can wrinkle or buckle if unsupported during forming. Spring-back, the elastic recovery after forming, means the flange angle closes slightly after the tool releases, requiring allowance in die design. Flanges on high-strength alloys demand higher force and may require annealing between passes if drawn deeply.

The term comes from the flange itself, a 19th-century term for any projecting rim or collar. In piping, a flanged fitting joins sections with bolted flange connections. In automotive and aerospace manufacture, flanging reinforces cutouts and edges. Sheet metal workers distinguish between simple flange bending (edge flaring) and channel or box flange work (drawing material into a recessed area), which are more complex and demanding in terms of force and tooling.