Wednesday 5 December 2012

Twister turns!

Unique robotic tube bending system can dramatically speed production

A unique robot-based CNC tube bending machine that provides metal fabricators with unprecedented flexibility for manufacturing complex preassembled tubular parts is now available from Unison.

Known as the 'Twister', the machine combines a high performance multi-axis industrial robot with an exceptionally compact and versatile all-electric tube bending station. It is ideal for companies seeking to streamline their manufacturing operations by eliminating process stages, or wishing to accelerate small batch size production of specialist parts by minimizing tool changeovers.

The Twister robotic tube bender has been launched following the new joint sales and marketing initiative announced by Unison and Rosenberger, which aims to provide customers with the widest choice of all-electric tube bending and allied processing automation on the market, backed by extensive applications support expertise. Both companies are renowned innovators of tube bending automation, and their combined range of all-electric, servomotor-controlled machines now covers tube diameters from 16 to 200 mm.

Conventionally, 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.

Developed by Rosenberger specifically to provide a more flexible solution than conventional systems for bending preassembled tubular parts, the Twister uses a fully articulated six-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 0.05 degrees, with a repeatable feed accuracy of just 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 210 degrees. Changeover of tools and part programs is simple and can be accomplished in less than five minutes. Like the robot, the bending heads are driven by high accuracy, energy-efficient servo motors, and offer fully programmable speed profiles for optimum control of material flow.

All machine setup 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, capitalizing 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.

According to Alan Pickering of Unison, "Rosenberger has an installed base of over 1000 bending machines, with a particularly significant presence in the automotive industry. To date, the company has supplied 40 Twister machines to this sector, for manufacturing a wide range of parts including seat brackets, head restraint frames and preassembled components such as hydraulic power transmission lines. We believe that the machine's use of a robot as an intrinsic part of the bending process, rather than just for handling, has considerable merit for a wide range of tube bending applications. The Twister can easily be integrated with other process automation such as cutting or end-forming machines, and is readily scalable to suit large automated manufacturing cells."

Unison currently offers 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.

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