Stretch Roll Forming

V. Madhavan, P. Swaminathan, M. Kashani, A. Shah
Fairmount Technologies, US

Keywords: green, flexible, digital, discrete parts manufacturing


Stretch Roll Forming is a novel digital, flexible, green, CNC metal forming process. It is an extension of the three roll forming (or slip-roll) process, wherein many pairs of roller-like dies mounted on positioning slides are used to approximate the instantaneous geometry of the part being formed, and are used to guide the formation of extrusions and sheets into desired shapes. The revolutionary enhancement is that, a stretch force sufficient to induce tensile yielding of the entire section is superimposed on the work piece while it is being formed, by applying appropriate traction forces on the work piece at each of the contact points. Tensile stretching avoids bucking of the section, and increases the strength of the part while reducing spring back and residual stresses. A further revolutionary improvement arises from replacing rollers with short die segments around which belts are driven to apply the traction. The shape of the die can be changed to accommodate different cross-sections of extrusions. Dynamic changes in the location of the die can be used to produce parts with varying curvature along the length of the part.