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RK is working with Robbi, an Italian specialist in cylindrical and internal grinding, to meet the requirements for more challenging grinding solutions for use in aerospace and defence applications.

According to RK, there has been a shift towards specialised cylindrical grinding applications in the UK requiring bespoke solutions for large, high-value, more complex components in difficult and unusual materials.

Owing to the high risk often associated with this type of component, users are also requiring higher orders of production consistency over size, geometry and surface finish, with an increasing need for machine and process reliability over extended periods of production life.

Dick Aldrich, sales director of RK, based in Erith, said: ‘To be successful in providing a viable grinding solution, you have to be able to respond with ever-higher application-specific solutions particularly for aerospace and defence.

‘Due to the level of application expertise and problem-solving capability available through Robbi, this has opened doors to successful installations as diverse as wind turbines, rollers for the food industry and machine-tool bearings,’ he added.

Projects such as these also require greater emphasis on the effective operational life expectancy and reliability of machines as users do not want to be faced with the high costs of replacement or upgrading during the lifespan of the components being produced.

They often require the added flexibility of being able to change over to different components as new developments come into production.

Aldrich continued: ‘The problem with grinding is that the process involves a whole host of variables, including the material being ground.

‘It has to account for varying stock levels, the intricacies of wheel development and progressive in-cycle influence of wheel wear, the setting of feed variation points and dwell times, providing different dressing frequencies and the influence of coolant, filtration and thermal effects,’ he said.

Robbi’s experience in a variety of applications enables RK to create higher-productivity solutions.

Increasingly on the agenda is the application of electronic support to the process with the likes of in-process gauging, automatic wheel balancing and programmable dressing.

In various UK aerospace applications, RK and Robbi have engineered solutions such as the grinding of stellite bearings, ceramic materials and demanding gearbox motor shafts destined for helicopters.

The two companies have also met the increasing requirement for the grinding of carbide wear parts.

RK recently installed a Robbi internal grinder for producing specialised aerospace bearings measuring up to 300mm in diameter by 30mm in depth that had to be concentric within 0.0003mm total indicated run-out (TIR).

Other project areas include the food-related sector, where a recent project involved a Robbi machine grinding 400mm-diameter cast-iron rolls.

The machine, installed in a purpose-designed, temperature-controlled environment, had to maintain 0.0002mm in size over a 3,000mm part length aided by specialised closed-loop measurement and process control.

Machines for producing multi-diameter pump shafts for both the water and the nuclear industry between 300mm and 400mm in diameter by up to 2,000mm in length have been installed, while a recent gas project required a special cylindrical Robbi grinder to produce 1,200mm-diameter components that were 5,000mm long.

Robbi specialises in application engineering using its range of Omicron modular-based cylindrical and sliding-gap machines with a swing-over table up to 995mm and up to 6,000mm between centres.

Its internal IGR-250 grinding machine can be programmed to produce up to eight diameters in the same part, up to a maximum diameter of 355mm.

Robbi also produces a range of complementary bore finishing vertical and horizontal honing machines with a capacity of up to 460mm in diameter by a 2,500mm hole depth.

The Omicron cylindrical range covers conventional machines designated R and E with up to 2,030mm between centres and 455mm swing-over table and with the ability to support up to 300kg between centres.

The semi-automatic Omicron T5 is available in four basic capacities for smaller batch production; it has automatic dressing compensation and up to 995mm swing-over table and 6,000mm between centres.

Meanwhile, for medium- to high-volume production using Siemens 840 Di control, the Omicron Teach-in and full CNC versions have similar capacities to the T5, with the ability to optimise in-process grinding with automatic measuring devices.

With CNC, an additional axis can be added that allows the interpolation of a profile on the grinding wheel to enable high-precision crowning to be produced on a component.

The Omicron T5 universal sliding-gap machine has a capacity of up to 1,000mm in diameter by 2,030mm between centres.

It has two wheel heads each having hydrodynamic spindles that are carried on independent carriages on its cast-iron bed.

It incorporates a split table that also enables long tapers to be ground.

As both wheel heads are independent, they can be applied to separately grind both a face and an OD, with the advantage of applying different wheels and grinding data.

Controlled by the Siemens 810 D, the wheel head can be rotated 180deg with an index swivel of 2.5deg using either manual or auto-positioning.

Using the PLC-based control, up to eight different diameters can be programmed on the same part, each having total independence for setting factors such as speeds, feeds and spark-out routines.

Marposs Micromar E9 can also be incorporated for the precise, closed-loop control of the process.

The machine also has the option to carry an internal spindle for integrated external, face and internal processing.

RK International Machine Tools

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