The Stretch Roll Forming (SRF) technology, embodied in our XtruForm (XF) machines, stretch bends components to the required contour. The process resembles CNC roll bending in the way the contour is produced but adds a longitudinal stretch force to prevent section buckling, reduce springback and reduce residual stresses. SRF works by using two sets of opposing stretch stations, exit and brake stations, that act like players in a tug-of-war game with the extrusion as the rope.
To increase the stretch force at each station beyond what can typically be applied by rollers, belts are used to apply traction forces to the extrusion. Each station has a pair of vise jaws that clamp across the legs of the cross-section and apply traction forces along the length of the part. The cumulative effect of the incremental stretch force applied by each station on the exit and brake sides results in the maximum stretch force in the extrusion occurring between the exit and brake stations.
The bend contour is controlled by moving and orienting the traction stations with respect to the stretch bending plane, to bend the extrusion to the curvature required. Dynamic CNC positioning of the exit stations as the extrusion flows through the stretch bending plane is required to bend it to the curvature required at each point along the length, and to follow the motion of the bent extrusion as it moves through the stations.
XtruForm machines can create contours both in yaw plane and pitch plane, allowing production of complex parts with 3D spline contours.
