First-tier subcontract machinist, JJ Churchill, can now produce turbine blades in-house without the need for fir-tree root-forms pre-ground elsewhere or machined later by another subcontractor.

This follows the installation of a purpose-built VIPER iGrinder at its Market Bosworth factory.

The VIPER is made by Japanese machine tool company, Makino, for grinding tough materials such as nickel alloys and used licensed Rolls-Royce know-how. The machine was supplied by Makino-NCMT Grinding Division, Thames Ditton, sales and service agent in Europe and Scandinavia.

Managing director, Andrew Churchill, explained, "The VIPER process, based on a 5-axis machining centre platform, is accepted as the most cost-effective way of creep-feed grinding nickel alloys for hot-end gas turbine components in a high-mix manufacturing environment.

"It has the extra advantage that milling operations can be performed in the same cycle. So components normally come off the machine finished, unlike with conventional, multiple-machine methods for grinding fir-trees, which have a much larger footprint on the shop floor and create a lot of work-in-progress.

"We also use the iGrinder to produce fir-tree root-forms on compressor blades for the cold end of engines in stainless steel and Jethete, which is quicker than milling and more accurate."

In a conventional compressor blade production route, precision forgings are supplied to the Market Bosworth factory with aerofoil surfaces broadly in their finished state. It remains only to mill the leading and trailing edges and complete any shroud end operations required. In so-called advanced production routes either an oversize blade forging is supplied and profile-milled to the finished aerofoil, or the starting point is sawn round billet from which the entire blade is machined. This includes rough and finish milling the form of the aerofoils, root and shroud.

Supplementing the above machining processes with fir-tree root-form grinding adds considerably more value to the part – around 25% estimates Mr Churchill. The i-Grinder therefore has the potential to increase turnover significantly. Already a second, perhaps larger machine is being considered for 2012.

The initial contract for which JJ Churchill used its new fir-tree grinding capability was in the production of three types of compressor blade for the Olympus turbojet engine, which previously powered Concorde but is now harnessed for industrial and marine power generation. Another job involves making turbine blades in their entirety for cold rig test equipment.

The first aero engine turbine blade on which JJ Churchill will use its VIPER fir-tree grinding capability will be for producing Trent engine blades for Rolls-Royce.