Turbine blade manufacturing - grinding, polishing, finishing

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After milling, turbine blades usually require additional abrasive finishing to remove scallop marks, stabilize edge geometry and improve surface quality.

Typical target roughness values include:

• steam turbine blades: Ra 1.2 µm to 0.6 µm
   
• gas turbine blades and vanes: Ra 0.6 µm to 0.4 µm
   
• aircraft engine blades: Ra 0.4 µm and below
   

Using a two-step abrasive process, even superfinished surfaces down to Ra 0.12 µin (0.003 µm) can be achieved under production acceptance conditions.

Compared with manual polishing, CNC turbine blade finishing offers significantly higher repeatability and lower measuring effort.

Production benefits include:

• stable stock removal across multiple blade rows
   
• highly reproducible surface quality
   
• reduced manual grinding effort
   
• shorter milling cycles through balanced stock removal
   
• easy programming through offline software
   
• controlled polishing of leading and trailing edges
   
• coolant-based processing for thermal protection and dust control

 Depending on blade size, geometry and production volume, different machine concepts are used. 

For:

• aircraft engine blades
   
• compressor blades
   
• highly twisted gas turbine blades

For:

• large industrial gas turbine blades
   
• steam turbine blades
   
• heavy compressor blades

For:

• repair work
   
• manual edge correction
   
• flexible abrasive finishing

The finishing process must preserve blade geometry while improving surface roughness.

Particularly critical are:

• leading edge radii
   
• trailing edge thickness
   
• platform transitions
   
• twisted airfoil sections
   

Integrated measuring systems such as Hexagon 3D inspection can validate profile stability directly after grinding.

In industrial production environments, two-step abrasive finishing can significantly reduce downstream superfinishing operations.

First, milling marks are removed using structured abrasive belts such as A45.

In the second step, ultra-fine Trizact belts such as A16 generate superfinished surfaces while maintaining stable blade geometry.

Such process layouts can replace downstream brush finishing in selected blade manufacturing environments.