Unison and Rosenberger’s Twister produces complex preassembled tubular parts

Initially, Unison is offering three versions of Twister, capable of bending steel tubes with outside diameters of 20, 30 and 50 mm. The 20 and 30 mm models can handle tube thicknesses up to 2 mm, while the larger model can accommodate a tube thickness of 4 mm. However, Unison and Rosenberger's combined range of all-electric, servomotor-controlled machines now covers tube diameters from 16 to 200 mm. They believe they can provide customers with the widest choice automated bending solutions available on the market and this will be backed by extensive applications support expertise. The Twister can be easily integrated with other process automation such as cutting or end-forming machines, and is readily scalable to suit large automated manufacturing cells. Unison reports that Rosenberger has already supplied 40 Twister machines to the automotive sector for the manufacture of a wide range of parts including seat brackets, head restraint frames and preassembled components such as hydraulic power transmission lines. In conventional systems, most tube bending operations are performed on straight sections of tube, and other components that make up the final assembled product such as tube fittings or other rigid tubes or hoses are added after bending in subsequent process stages. To a large degree, this manufacturing sequence is dictated by the tube bender, which grips the tube with an in-line collet to progressively push it past the bending head and rotate it for any out-of-plane bends. As a consequence, the tube material needs to be straight and free from obstructions, and bends can only be made in an order that corresponds to the direction of tube advancement. The Twister has been developed by Rosenberger specifically to provide a more flexible solution than conventional systems for bending preassembled tubular parts. It uses a fully articulated 6-axis industrial robot for all tube transport, material feed and rotate functions. The robot arm is equipped with pneumatically-powered gripper fingers – which are part-specific and exchangeable under program control – and handles all X, Y and Z axis movement of the tube as it is being bent. All axes are driven by servo motors and capable of extremely precise positioning – tubes can be bent to within 0.05º, with a repeatable feed accuracy of 0.01 mm. Unlike conventional tube benders, the grippers can relinquish their hold and reposition during the bending cycle while the tube is clamped – for example, to hold the other end of the tube – enabling complex shapes to be formed in any desired sequence. The pedestal-mounted bending station can be equipped with up to five bending heads to facilitate uninterrupted production of parts with multiple bend radii, and is capable of right and left bending to any angle up to 210º. Changeover of tools and part programs can be accomplished in less than five minutes, says Unison. Like the robot, the bending heads are driven by high accuracy, energy-efficient servomotors, and offer fully programmable speed profiles for optimum control of material flow. All machine set-up and operation is controlled via an ergonomic HMI, based on a mobile touch-sensitive panel with an integral PC. Part programs can be generated using the panel PC or any standard office computer, and verified before downloading to the bending machine's PLC-based CNC controller. The software provides a unified environment, capitalising on the tight functional integration of the robot and bending station to ensure that its programming is as simple as a conventional all-electric bending machine.