Manufacturing: Metal Forming

Sheetmetal Forming - Stretch Forming

Stretch forming is a very accurate and precise method for forming metal shapes, economically. The level of precision is so high that even intricate multi-components and snap-together curtainwall components can be formed without loss of section properties or original design function. Stretch forming capabilities include portions of circles, ellipses, parabolas and arched shapes. These shapes can be formed with straight leg sections at one or both ends of the curve. This eliminates several conventional fabrication steps and welding.

The stretch forming process involves stretch forming a metal piece over a male stretch form block (STFB) using a pneumatic and hydraulic stretch press. Stretch forming is widely used in producing automotive body panels. Unlike deep drawing, the sheet is gripped by a blank holder to prevent it from being drawn into the die. It is important that the sheet can deform by elongation and uniform thinning.

The variety of shapes and cross sections that can be stretch formed is almost unlimited. Window systems, skylights, store fronts, signs, flashings, curtainwalls, walkway enclosures, and hand railings can be accurately and precisely formed to the desired profiles. Close and consistent tolerances, no surface marring, no distortion or ripples, and no surface misalignment of complex profiles are important benefits inherent in stretch forming. A smooth and even surface results from the stretch forming process.

This process is ideally suited for the manufacture of large parts made from aluminum, but does just as well with stainless steel and commercially pure titanium. It is quick, efficient, and has a high degree of repeatability.