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Volkswagen relies on hydroforming for rear axle
Reduced Number of Components
The Volkswagen AG relies on a new hydroforming production system for volume production of rear axle components for the A-platform 4WD models (VW Bora, VW Golf, Audi TT and Audi A3), delievered by Schuler Hydroforming GmbH & Co. KG. In comparison with the conventional rear axle production where welded deep drawn components are used, the automotive industry now enjoys the many advantages hydroforming has to offer. With hydroforming rear axle components such as the main tube, the control arm and the filler tube can be produced at lower cost, better quality and with increased rigidity. In the first year of volume production 750.000 hydroformed components will leave the production line.
The decision to integrate hydroformed components into various models of their VW-A-Platform has been primarily influenced by the advantages these components have to offer: welding operations, which were previously necessary to join the half shells, are eliminated. In the conventional production of the main tube for examples four parts are required, whereas with hydroforming the same component can be produced as one single part. In addition, when test results of conventionally produced components are compared with test results of hydroformed components, the rigidity of the latter is considerably higher. The complete production system consists of: Robot-automated Bending Cell, Hydraulic Hydroforming press complete with water hydraulics and pressure intensifier, Laser cutting station, End trimming and flanging unit.
Bending Process Automated by Robots
The bending unit, in which the tubes are bent prior to hydroforming, is a fully automated production cell. First, the tubes are singled-out in a magazine and are then readied for pick-up, presented with the weld seam in a defined position. The robot, equipped with two grippers to handle straight and bent pipes, picks a positioned tube and transfers it to the bending machine. The robot returns to the magazine, picks the next tube and moves to the bending machine. Here the robot tooling is rotated and the free gripper picks the bent tube from the bender. The tooling rotates once more and places the next tube into the bender. The bent tubing is then transferred to the lubrication station and out of the bending cell. With empty grippers the robots once more returns to the magazine and the whole procedure is repeated. Within the bending cell the bent tubes are transferred and lubricated by the robot.
Hydroforming Press with Moving Bolster
The hydraulic hydroforming press with its water hydraulics and pressure intensifier forms the core of the hydroforming production line. The press into which the pre-bent tubes are manually placed, has a closing force of 30,000 kN (3,350 U.S. ton). The bed is 3,150 x 1,400 mm (124 x 55 in.) and the slide stroke is 900 mm (35 in.). Because three different components and various prototyping jobs are performed in the press, the press has been equipped with a tool change system. The hydroforming line is designed to permit different tooling concepts. The system, depending on the tooling used, supports the following functions: preforming with the tool, pre-forming with internal pressure and finish forming by hydroforming including hole piercing operations. Once hydroforming is complete, the ends of the rear axle components are trimmed by means of a laser cutting unit.
The hydroformed and laser-trimmed rear axle main tubes finally are fed to a special end trimming unit. This consists of a trimming and flanging unit for processing the bushings hydroformed into the main tube. This is necessary because in a subsequent operation rubber metal bearings are pressed into the bushings. Taking this into account, the end trimming station consists of a hydraulic press, eletro-pneumatic trimming unit, feeding unit and control. After trimming of the hydroformed bushing surface, the edges of the bushings are pre-flanged by 45° and in a additional station final flanged to 90°.
Hydroforming Process Control Numeric H
To control the hydroforming process and the press functions and to enable flexible programming, the line is equipped with the new Numeric H Control developped by Schuler Hydroforming GmbH & Co. KG and Schuler SMG GmbH & Co. KG. This provides the operator the possibility to graphically program process sequences via a Windows NT operators interfaced. Thereby, the hydroform process is clearly presented and the 16 programmable axes offer a high degree of flexibility. Each axis can be programmed with a dependence on the respective other axis.
Image 1: Hydroforming press with 30.000 kN closing
Image 2: Hydroforming Press with Double Tool
Image 3: Fully automated bending cell
Image 4: Trimming and flanging unit
Image 5: Rear axle with 3 hydroforming components Main
Tube, Filler Tube and Control Arm
Image 6: VW Golf
Image 7: Audi TT Coupé
With permission by Volkswagen AG and Schuler Hydroforming GmbH
Last update: März 15, 2000
Letzte Änderung: 15 März 2000
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