SCM selects single source for ball rails, servos and guards

Invited to supply a system that 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 versatile and cost-effective.

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 move between stations.

The processing stations themselves are, in effect, large heat treatment ovens operating at temperatures in excess of 600degC. 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 25-30m and at each processing station they need to be raised by around 400mm to allow entry into the oven.

Low speed, smooth motion and high accuracy

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.

Another 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 system, the engineers at SCM Materials Handling decided to base their design on products from Rexroth.

Alan Watkins of SCM Materials Handling states: "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.

"Another very important factor in our decision was that Rexroth could supply all of the key components we needed for the project. 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 is 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 versatile Rexroth 45mm wide ball rail system. This provides high load handling capacity in all directions and, thanks to a special design with four ball circuits, very low operating friction. It is also 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 28m length of the installation. The systems devised to raise the products vertically at each processing station are also implemented using Rexroth 45mm ball rails.

Standard products for harsh conditions

Alan Watkins comments: "In spite of the high operating temperatures, we were able to use standard ball rail products. 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 is provided by rack-and-pinion drives used in conjunction with Indradrive compact servo drives, 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 as standard, which can be used as building blocks when developing application software.

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 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.

Alan Watkins concludes: "This is a prestigious project for one of the world's leading engineering companies. 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 are looking forward to working with the Bosch Rexroth team on future contracts."

About SCM Materials Handling

SCM designs and manufactures a range of bespoke materials handling equipment for a wide range of manufacturing industries. Furthermore, the Service and Installation department can install machines to the highest professional standards and provide maintenance contracts. See www.scmhandling.com.