Keeping metal on the move

Citation

(2007), "Keeping metal on the move", Aircraft Engineering and Aerospace Technology, Vol. 79 No. 6. https://doi.org/10.1108/aeat.2007.12779fab.010

Keeping metal on the move

Keeping metal on the move

Invited to supply a system which would reliably and safely transport heavy, high-value products between processing stations used in their manufacture, engineers at SCM Materials Handling found that equipment from Bosch Rexroth was the key to developing a versatile and cost effective solution.

Though simple in concept, the project presented a number of very specific challenges. The transport system needed to be robust enough not only to carry the products, weighing eight tonnes each, but also the two tonne carriages that support the products as they are moved between stations.

The processing stations themselves are, in effect, large heat treatment ovens operating at high temperatures in excess of 6008C. Sections of the transport system would therefore inevitably be exposed almost continuously to high temperatures. In addition to this, aggressive dust is present throughout the operating environment.

During processing, the products are transported over a horizontal distance of 25 230m metres and at each processing station they need to be raised by around 400mm vertically to allow entry into the oven.

The speed of movement required is low – from a product entering the system to leaving – but smooth transport is essential, as is positional accuracy. In spite of their large size and mass, the products must be positioned to within 0.1mm when they arrive at a processing station.

A final but crucial requirement was reliability. With each product costing many thousands of pounds and with the possibility that multiple products would be simultaneously present in the system, interruptions to the normal operation had the potential to be extremely costly.

After carefully assessing the requirements of the application, and surveying the market for equipment that could be used in developing a convenient and cost effective solution, the engineers at SCM Materials Handling decided to base their design on products from Rexroth.

“A big attraction of working with Rexroth was that, through past experience with the company, we knew that we could rely 100 per cent on product quality and also that the company would be willing and able to provide us with any technical support we might need during the project,” said Alan Watkins of SCM Materials Handling.

“Another very important factor in our decision was that Rexroth could supply all of the key components we needed for the project,” he continued. “Having a single source of supply is a very big benefit; not only does it simplify ordering and logistics, it also means that if support should be needed there's never any problem over divided responsibilities”.

The final design, developed by engineers from SCM Materials Handling, working in close collaboration with the Bosch Rexroth customer support team, makes extensive use of the Rexroth 45mm wide ball rail system. This versatile system provides high-load handling capacity in all directions and thanks to a special design with four ball circuits, very low-operating friction. It has also been designed to minimise lubrication requirements, even when used in demanding environments.

Mounted on a heavy-duty fabricated steel framework, two continuous runs of ball rail are used to provide horizontal transport through the full 28-metre length of the installation. The systems devised to raise the products vertically at each processing station are also implemented using Rexroth 45mm ball rail.

“In spite of the high operating temperatures, we were able to use standard ball rail products,” said Alan Watkins. “Providing the high degree of protection against dust ingress we needed was also straightforward as Rexroth products intrinsically offer a high degree of ingress protection and in demanding applications like ours this can easily be enhanced with readily available seal and scraper options”.

Motive power for both the vertical and horizontal motions (vertical ball screw unit) horizontal is provided by rack and pinion drives used in conjunction with Indradrive compact servodrives, all supplied by Rexroth. Implementation of the drive system, which gives users a choice of manual or fully automatic control, was fast and straightforward as the controllers are easy to parameterise. They also incorporate a wide range of internal functions that can be used as building blocks when developing application software as standard.

The drive system is complemented by an electronic control panel (HMI) with a full colour display that makes extensive use of graphics. This not only provides readily accessible information on the status and performance of the transport system, but also gives users full control over it via an intuitive, easy to use interface.

In addition to ensuring the efficient reliable operation of the transport system, SCM Materials Handling was also tasked with providing guards to cover the whole of the area occupied by the installation. For this, the company chose to use the Rexroth EcoSafe protective fence system.

Supplied in the form of modular panels that can be quickly assembled to guard areas of almost any shape or size, EcoSafe provided an efficient approach to fully and securely enclosing the transport system. Standard EcoSafe products, custom finished in line with the end-user's paint colour specification, were used for the majority of the installation but, for those areas of the fence exposed to prolonged high temperatures, Rexroth fabricated and supplied stainless steel panels.

“This is a prestigious project for one of the world's leading engineering companies,” said Alan Watkins. “Products from Bosch Rexroth, and the excellent support we received from the company, made it possible for us to produce an efficient, dependable and cost-effective solution. Our client is delighted with how easy the system is to use and also with its performance. Its reliability, a critical issue, has also proved to be beyond reproach. Overall, this has been a very successful project and we're looking forward to working with the Bosch Rexroth team on future contracts.”

Details available from: Bosch Rexroth; Tel: +44 (0) 1480 223200; Fax: +44 (0) 1480 470789, E-mail: laura.varey@boschrexroth.co.uk; web site: www.boschrexroth.co.uk/