Nickel-titanium material is expensive and machining by turning is regarded as very difficult, but innovative lathe control helped to optimise machining conditions to get good results.

The impressive signage adorning Goldring Industries' Trafalgar Works in Cable Street, Wolverhampton, serves a dual purpose. It is first and foremost a highly visible symbol of what in less than 15 years has become an extremely successful engineering business. But it also bears witness to Ivor Dring's determination to overcome redundancy, a circumstance that for some has been known to signal the closing of one door and the slamming shut of the next.

However, for Goldring Industries' founder and managing director, the decision to start his own sub-contracting company, while not without its setbacks, opened the door to a new way of life.

'I initially envisaged running a small machine shop with, say, five or six employees,' he says, 'but there is now a team of more than 30 people and we are still recruiting.

Our 45,000ft2 premises are owned rather than leased, and we provide a one-stop-shop for fabrication, casting, machining, assembly, test and painting.' Ivor Dring's previous experience with NEI's nuclear engineering division, latterly as operations manager, has proved invaluable, enabling Goldring Industries to become a main contractor to the Ministry of Defence and to include on its customer list some of the biggest names in British industry.

'We are an ISO 9002 - 2002 accredited company and we are very good at complying with procedures while still being able to produce work quickly,' he says.

This explains why Goldring Industries is now producing safety critical components for one of the UK's largest generators of electricity.

Machined on one or other of two recently installed XYZ Proturn 425 VL manual/CNC lathes to a diametric tolerance of +/-0.0005 inch, these nickel-titanium alloy components play a key role in avoiding unscheduled shutdowns of expensive generating plant.

However, the machining process is complicated not so much by the varying sizes required within any given batch of components or the tight tolerance, but by the nature of the material.

It belongs to the group of metallic materials known as Shape Memory Alloys, which possess properties of particular relevance to this application.

Although a relatively wide range of alloys are known to exhibit the shape memory effect, only those that can recover substantial amounts of strain or that generate significant force upon changing shape are of commercial interest.

It is the latter quality that is crucial because the component is frozen in liquid nitrogen - extending its length by some 40 per cent and reducing its external diameter accordingly - before being placed in position.

It then returns to its original size as the temperature rises above the transition temperature necessary to trigger the shape memory effect.

The end result is an extremely tight fit, with the component held securely in place.

The nickel-titanium material specified is expensive and machining by turning is regarded as very difficult, while heat treatment after machining, which ensures the necessary changes in the material's structure, must be undertaken in a vacuum furnace to prevent unacceptable oxidation of the alloy.

Prior to heat treatment, the components must be free from grease and other contaminants, particularly chlorides, and must not be handled directly, which demands great care throughout the manufacturing process.

The two XYZ Proturn 425 VL manual/CNC lathes equipped with the innovative Prototrak VL control have shown themselves to be ideally suited to their role in this demanding process.

Although dimensional accuracy and surface finish are the critical criteria, ease of programming and the ability to run through the entire sequence of turning the outer diameter, including the two locating 'nibs', and machining an internal bore before committing to computer control have proved invaluable.

This takes account of the high cost of the material and the numerous variations in the sizes of components specified within each batch.

It says much for Goldring Industries' enhanced turning capability that, having succeeded in obtaining the order, the company's first batch of 42 components was the subject last November of a complimentary letter from its new customer.

'It is gratifying,' he wrote, 'to be able to say that this is the first batch of these components I have ordered [from any supplier] that has had no rejects.