Cutting edge advance for aerospace engineers

Manufacturers are realising that there are virtually no limits to what ultra high-pressure water jets are capable of cutting and machining.

And rapid advances in practice and knowledge of the technology have been achieved since Europe’s first state-of-the-art, water-jet machining technology centre was established at the University of Nottingham, central England.

The university’s School of Mechanical, Materials & Manufacturing Engineering joined forces with Rolls-Royce’s aerospace/engineering group, the East Midlands Development Agency and the Midlands Aerospace Alliance to establish the 1.1 million pounds centre. Among its objectives is exploring how the technology can be used to create parts for the aerospace industry.

Water-jet technology

In the UK, early use of the process had been predominantly limited to flat-bed techniques - cutting two-dimensional (2D) objects from sheets of raw material. But engineers at the new centre are using a six-axis, water-jet machine, capable of cutting three-dimensional parts from blocks of metal to develop new processes and techniques.

“It is a method that is particularly suited to aerospace engineering,” said Professor Ian Pashby who leads the project. “The metals used within the industry are difficult to cut and to machine using other methods. Water-jet technology is very precise and adaptable - it can even be used to cut food” he added.

The water-jet process is said to be more environmentally friendly than other machine-cutting techniques. The six-axis water jet can be used to create pockets within blocks of metal that are essential to the manufacture of aerospace parts.

Currently, corrosive acids are used to do this and that must then be disposed of separately. The water-jet machine uses just water and grit and “which is not as nasty as the chemicals used elsewhere,” said Professor Pashby.

Rolls Royce

Stephen Burgess, Rolls-Royce Manufacturing Process & Technology Director, added: “Water-jet manufacturing can be and has been used to reduce the cost and environmental impact of producing and refurbishing our components. It is suitable for many commodities in our supply chain as well as processing next-generation materials and structures. The machine at Nottingham University will allow us and the aerospace industry to research and develop solutions to a range of manufacturing challenges.”

A grant from the East Midlands Development Agency was used to buy new equipment. Rolls-Royce and the university are supporting technical development at the centre that is unique in UK engineering and is the first time the technology has been used for the aerospace industry outside of the United States.

It is a method that is particularly suited to aerospace engineering

Professor Ian Pashby

Project Leader

It will be an important resource for the engineering and manufacturing businesses based in the East Midlands, making them more competitive within the global aerospace market.

Mike Carr, the regional development agency’s Executive Director of Business Services, commented: “In a global economy where the scope to compete on a cost basis is increasingly limited, innovation is crucial in maintaining the competitive advantage. We are pleased to support this project, and recognise that Rolls-Royce and Nottingham University - alongside other universities and businesses in the East Midlands - are leading the way in developing new and exciting technologies, contributing to the vision of a flourishing region by 2020.”

Machine shops of all sizes are realising greater efficiency and productivity by implementing ultra high-pressure water jets in their operations.

What makes them so popular? Water jets require few secondary operations, produce parts with no heat-affected zone, heat distortion, or mechanical stresses caused by other cutting methods, and can provide better use of raw material.

Abrasive jet cutters mix abrasive garnet to a pressurised water stream to cut harder materials. Examples are stainless steel, titanium, glass, ceramic tile, marble and granite.

Water-jet metal-cutting machines yield very little heat, therefore no heat-affected zone and hence in most cases will not require further heat treatment. Water-jet machining is also considered as a “cold cut” process and therefore is safe for cutting flammable materials such as plastic and polymers.

The process has already been put to some unexpected uses. Chocolate makers Thorntons, for instance, needed equipment capable of cutting out designs for polycarbonate moulds for their new designs in Easter eggs. But no one could find a way of carving perfect shapes in the moulds without melting or damaging the plastic.

Philip Shipway said: “The attributes of water-jet technology make it the method of choice in certain circumstances, particularly when heat and high forces need to be avoided. When we were approached by Thorntons, we could see immediately that we had a technology that fitted the bill. That’s not to say there weren’t challenges to be overcome, but a combination of ingenuity and hard work by all involved has enabled us to deliver a first-class solution.”

Founded in the early 1900s, Thorntons has grown into an organisation with a turnover in excess of 180 million pounds sterling. “But this proved to be one of the most interesting challenges in their search for chocolate creativity”, said chocolatier David Brealey.