Electro-Chemical Machining (ECM)

Electrochemical Machining (ECM) is a special process that rapidly removes material by anodic dissolution. BNI is one of the few companies in the world that make use of this process that is particularly suited to shape materials that are hard to machine with conventional methods. BNI routinely uses this process to machine turbine blisks, turbine nozzles and internal complex shapes for the aerospace, defense, energy, and medical industries.

U.S. Navy photo courtesy of Huntington Ingalls Industries by Ricky Thompson/Released

ECM Turbine Wheel

ECM is the only process that can accommodate single piece blisks (bladed turbine disk) with the extremely close spacing shown here utilizing high-strength nickel alloys needed for high-temperature turbines.  It provides the following advantages.

  • No stresses introduced to the part during the process
  • High power density turbine design not constrained by large spacing needed for milling tool sizes and deflection
  • Consistent and accurate reproduction of turbine blade shapes and other fine features with tight spacing
  • No wear of the machine tool
  • Fine surface finish exceeds performance needs with no subsequent processing.

Turbine Nozzle Rings

ECM can also be used to make complicated internal shapes at shallow angles in high-strength materials as shown in the rocket engine turbopump nozzle rings.  These nozzles would be incredibly difficult to mill conventionally at such a shallow angle and would take significantly longer than with ECM.

 

Thrust Reverser Actuator for the JT9D Engine

ECM is used to produce the Thrust Reverser Actuator for the JT9D Engine which is used on a variety of civilian aircraft including the Boeing 747.  The ECM tool shown is used to remove material from the center of each of the three helical lobes on the Thrust Reverser Actuator. Removing the material from the center of the lobes reduces the weight and inertia of the rotor. ECM is the only process that can perform this operation at a reasonable cost.

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