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Mills CNC has revealed that Smith and Nephew Orthopaedics has recently invested in its tenth Doosan multi-axis mill-turn centre – the MX 2000ST.

The machine was installed at the company’s Advanced Bearing Systems facility in 2009 and is being used to manufacture complex, high-precision orthopaedic ball (femoral) and socket (acetabular) components used in BHR (Birmingham Hip Resurfacing) surgical procedures.

BHR hip resurfacing uses low-wear, metal-on-metal bearing resurfacing technology and is a procedure where the articular surfaces of the femur and acerabulum are replaced, leaving the femoral head substantially preserved.

BHR components are made from cobalt chrome castings (an extremely hard and durable material), and part accuracy repeatability, and surface finish requirements are demanding (roundness tolerances are generally less than 2micron; surface finish requirements are in the region of 0.015micron Ra).

Smith and Nephew began using Doosan multi-axis mill-turn centres in 2004.

Paul Footman, manufacturing and production manager at Smith and Nephew, said: ‘We wanted to reduce cycle times to meet demand, reduce lead times and increase productivity, and standardise our method of production.

‘To acquire the machine tools to help us to do this, we invited three machine tool manufacturers to produce sample batches,’ he added.

Smith and Nephew’s trial was not limited to identifying the optimum machine tool – instead the company was also looking for a full turnkey manufacturing solution, involving tooling, fixturing, coolant and so on, to be replicated in its manufacturing cell at its Leamington facility.

The MX machine, with its high-torque main and sub-spindles; +/-80mm Y-axis for performing mill/drill operations across the centre line; B-axis rotation capability on its milling spindle (240-deg/0.001 increments) for machining complex angled features; large servo-driven bottom 12-station turret (5.5kW 4,000rev/min); and large-capacity ATC provided Smith and Nephew with the power, flexibility and reliability required.

The performance of the MX machine, combined with Mills CNC’s technical and applications support, resulted in Smith and Nephew continuing its investment in MX2000ST machines in 2005.

Five years on, a further eight MX machines have been purchased and all are performing well.

Machine cycle times are being reduced and the lean manufacturing strategies introduced by the company have helped improve quality and productivity still further.

All of Smith and Nephew’s Doosan MX machines are covered by Mills CNC’s ‘360’ service contracts for maintenance and service.

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