Traction bending

Abstract

A traction bending apparatus bends workpieces (such as tubes and aluminum extrusions) with good thickness and wrinkling control, in circular arcs or in shapes clearly distinct from circular arcs, with cold forging of the workpieces for springback control, with smooth symmetric bending of symmetrical parts, and with smooth bending of non-symmetrical parts, without jaw marks. The apparatus can readily effect multi-point bending and can be used with workpieces of any length. A stationary die support mounts a die adjacent a first end of the support, and has first and second control arms pivotally mounted to the die support second end. The first and second linear actuators, preferably hydraulic cylinder assemblies with piggyback pneumatic cylinder assemblies, are connected to the control arms to provide powered pivoting movement thereof. First and second traction arms are pivotally mounted to the control arm and have first and second workpiece engaging rollers. Third and fourth linear actuators, preferably hydraulic cylinders, are pivotally connected to the die support at an intermediate section, and to the traction arms. A stripper linear actuator is mounted to the die support to effect movement of the workpiece bent by the apparatus away from the die support, and a clamping linear actuator clamps the workpiece for good thickness and wrinkling control. A computer control mechanism (e.g. PLC) provides control of the linear actuators to effect desired bending.