TPT January 2024

ARTICLE

Schwarze-Robitec GmbH

geometries, the CNC 40 Rotary with an independent axis for the bend die is used. The option of flexibly moving the bending head to the left or right side is used for around 20 per cent of the components. Thanks to modern CNC technology, multidimensional tube systems can be produced precisely and reliably without welding in a single work step. This way, coiled tubing and pocket tubes are produced in the shape of an angular U, for example. Such tubes are used frequently in aircraft to compensate for expansion and vibration. Demanding material Requirements for production are exacting. Not only do tubes with relatively large diameters and very thin walls need to be bent, but also the material used is titanium, which has a high strength. This means the bending process must be very slow and at the same time vibration-free. Despite the thin wall thicknesses of 0.56 to 0.88mm, it is important that no cracks or folds occur during bending. “From a purely technical point of view, this is a major challenge,” said Philipp Knobloch, Global sales director for new machinery equipment at Schwarze-Robitec. “A high torque is required to achieve a smooth movement, but the slowness of the motion means there is a risk of vibrations occurring, which can lead to wrinkles.” Special devices such as wiper dies help to counter this. Titanium is lightweight, strong and corrosion-resistant, making it particularly important for aerospace engineering, yet the material is very brittle and can crack easily. Special attention must also be paid to the surface finish, hence the percentage of dents, scratches, wrinkles and notches must not exceed one per cent depth, measured against the tube diameter.

On top of that, ovality must be less than three per cent, as the tubes must have almost perfect roundness to ensure ideal flow properties. The smallest product defects can have fatal consequences. Leaks in hydraulic tubes, for example, can prevent the landing gear from extending and the aircraft from landing. If fuel leaks from a tube and drips onto a hot spot, the worst-case scenario is a fire in the aircraft. Requirement of certification Aircraft manufacturers place high demands on their Tier 1 suppliers in terms of quality and safety. Not only are the components subjected to exacting controls, for example, but the entire production process also has to be validated. The tube manufacturing process at TDM is therefore likewise subject to strict regulations, compliance with which is checked and audited on site on behalf of the aircraft manufacturer. In this context, there are also separate requirements for the manufacturer of tube bending machines. “Thanks to its many TDM uses two Aircraft Edition tube bending machines from Schwarze-Robitec: the single-stack CNC 40 E TB and the CNC 40 Rotary with rotating bending head

years of experience in the aviation sector, Schwarze-Robitec knows the specifications exactly and can meet them without any problems,” explained Mr Viehrig. “In addition, the contact persons have been and continue to be available to advise us at all times and have thus also provided valuable support for the entire certification process.” TDM has obtained numerous qualifications in recent years and also fulfils, for example, the quality management system standard DIN EN 9100, which applies specifically to aviation.

For particularly complex geometries such as coiled tubing, the CNC 40 Rotary is used with an independent axis for the bend die

The special feature of the CNC 40 Rotary, which allows the bending head to be moved flexibly to the left or right side, is used for approximately 20 per cent of the components

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JANUARY 2024