BMF are a world leader in the machining of rotor blades for the aerospace and industrial turbine sectors using high tech CNC grinding & milling machines. Parts up to 1 metre and 25kg are currently typical.

The special alloys used for hot gas path turbine components require unique machining processes not found in conventional machining facilities. Continual investment has been made in state of the art CNC Grinding machines costing up to £1m. These highly complex machines require up to 10 axis of programming in order to generate the complex forms required.

Two grinding techniques are used. Continual Dress Creep Feed (CDCF) grinding using aluminium oxide wheels which are formed using diamond coated rollers. The wheels are continually dressed during the machining process to ensure the profile is maintained and he component specifications are achieved. Steel wheels coated with Cubic Boron Nitride (CBN) are also used.

Latest generation CNC 5 axis milling machines are used where component geometry or a particular casting alloy prevents machining by grinding. High machine rigidity and high torque at low speeds are a special requirement of such milling machines.

Two basic processes are required in the machining of rotor blades

EDM die sinking

Conventional machining techniques cannot produce narrow, enclosed features such as sealing slots used to prevent the hot gases in a turbine leaking between components. Here an Electrical Discharge Machining (EDM) process is used where a male form ‘electrode’ of the shape required is produced in copper or graphite. Electrical current is then passed between the electrode and the component and electric sparks used to erode the required female form. Over 15 CNC EDM machines are used in the production of industrial gas turbine components.

EDM Hole drilling

The same generic process is also utilised to machine cooling holes. Here specialist machines use conductive fluids pumped through hollow electrodes and pulsed electrical signals to achieve quicker machining cycle times.

Finished components require a variety of sub components such as cooling air inserts, Boroscope inspection bushes etc to be permanently assembled. BMF has a capability for all assembly processes including TIG Welding. TIG welding is also used to hard face aerospace products for which we hold NADCAP approval.

Currently parts can be supplied to customers in an “engine ready condition” using the following additional processes:-

• Mass Airflow Inspection
• Water Flow Inspection
• Static Frequency Testing
• Mass Moment Weighing