Four lathes are assisting the Machining Research Centre at South Bank University in research into understanding the behaviour of high temperature alloy materials during machining.

The Machining Research Centre at South Bank University is one of the UK's leading specialists in research into understanding the behaviour of high temperature alloy materials during machining and the interaction between the machine tool, tooling and materials. Based at the South Bank University Faculty of Engineering Science and Technology in Southwark, it has become an international 'centre of excellence' which has recently been awarded European Community funding for a 2.1/2 year project investigating high speed steel/ceramic composite tooling under interrupted cutting conditions. The Centre under Professor Emmanuel Ezugwu, Director Machining Research is also pursuing dry machining, high pressure coolants, high speed cutting and is even developing its own self-propelled rotary turning tool.

Central to its research and machining trials are four (Colchester) lathes (supplied by Colchester Sales' Southern Technical Centre, RK International of Erith, Kent) which include a two-axis Tornado 310 CNC lathe, an electronic Mastiff and two centre lathes.

Says Professor Ezugwu: 'These machines definitely help in the way we do business and combine the rigidity, power, swing and speed range we need for our trials.' Originally formed in 1993, the Centre began providing research services into high temperature alloy machining in 1995.

Since then it has provided consultancy, worked in collaboration and become an unbiased development arm of leading aerospace, tooling and steel stockholding companies.

It has also been closely involved with sectors of industry that manufacture components produced from difficult materials such as those used in gas turbines and jet engines.

Collaboration with leading American universities on the high speed machining of aerospace alloys is currently being pursued and the Centre is carrying out research for the US joint strike fighter project.

In order to obtain meaningful results, the rigidity and capability to deliver a consistent cutting condition were important elements in the selection of the machine tools being used.

Following turning trials, which often involved monitoring to obtain tangential, radial and axial force data through a Kistler Piezoelectric dynamometer, test pieces are often subjected to analytical study using scanning electron microscopy to examine surface integrity, look for cracks, folds in materials, material substrate and evaluation of micro-hardening.

'Any variation in the performance of the machine would therefore influence the critical results of the turning operation,' maintains Professor Ezugwu.

Typical research projects involving turning on the Colchester machines include the effects of cutting tool geometry on tool performance as well as the mechanisms responsible for tool failure when using single and multi-coated PVD carbide grades at high cutting speeds on C263 super alloys.

From the study, the best machining parameters were identified to ensure minimum damage to the machined surface and the data gathered was used to populate software for determining acceptable cutting conditions involving the minimal use of energy, cutting force/power consumption and cutting speed.

Research into future tooling development is also being carried out at the Centre on the Colchester machines involving European funding to monitor the results of a new tool material which combines the fracture characteristic of high speed steel with engineered microstructural modifications of ceramics.

The objective of the new tool material is to increase hot hardness and significantly improve abrasive wear resistance when machining difficult to cut alloys under higher speed conditions.

As an example of the levels of success, Professor Ezugwu refers to research into the use of high pressure (200 bar) coolant when machining inconel 718 super alloy with carbide tooling.

As a result of the trials, tool life capability was raised by around 700 per cent.

The research and monitoring involved investigation of tool performance, failure modes, chip breakability, surface finish and surface integrity on the material machined.