CNC Turbine Blade Grinding, Polishing and Finishing Machine

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The SPE turbine blade finishing machine is suitable for a wide range of aerospace and energy materials:

• titanium alloys
• nickel-based alloys and superalloys
• chromium-nickel steels
• stainless steels
• non-ferrous metals

The wet belt grinding process ensures cooling of the blade surface, reduces the risk of thermal damage and helps contain harmful grinding dust.

One of the major advantages of the SPE 6 CNC is that turbine blades can often enter finishing with a rougher milled surface. Instead of generating the full surface quality on an expensive 5-axis milling machine, part of the surface preparation is shifted into a controlled CNC belt finishing process.

This can reduce milling time, cutter wear, tooling cost and manual rework while maintaining repeatable surface quality and stable blade geometry. For many customers, this balancing of milling and CNC finishing is one of the biggest cost levers in the entire turbine blade production process.

Typical customer example: a turbine blade airfoil entering the finishing process at approximately Ra 1.4 µm (55 µin) after milling can often be brought to around Ra 0.6 µm (24 µin) or finer in a single CNC finishing cycle with a suitable abrasive such as A45 (P400), depending on material, geometry and target specification.

Where required, downstream processes such as stream finishing, tumbling or blasting can still follow afterwards. However, these operations are often shorter because the SPE 6 CNC has already created a more consistent starting surface.

Typical surface roughness requirements for turbine blade manufacturing range from Ra 1.2 µm (≈ 47 µin) to Ra 0.6 µm (≈ 24 µin) for steam turbine blades, and from Ra 0.6 µm (≈ 24 µin) down to Ra 0.4 µm (≈ 16 µin) for gas turbine blades, guide vanes and aircraft engine blades.

Under production acceptance conditions, the SPE 6 CNC achieves surface finishes down to Ra ≤ 0.05 µm (≈ 2 µin) using two-step abrasive processes. In customer acceptance tests, values of Ra ~0.03 µm (≈ 1.2 µin) were demonstrated during customer acceptance tests (FAT) with a leading OEM. These results confirm the suitability of the SPE 6 CNC for high-end aerospace and industrial gas turbine applications. 

The first step removes milling marks using structured abrasive belts such as A45 (FEPA P360–400), followed by ultra-fine finishing with A16 (FEPA P1200) belts to obtain superfinished blade surfaces while maintaining profile accuracy.

Such a process can reduce or eliminate downstream finishing operations in selected turbine blade production environments.

For a complete overview of turbine blade grinding, polishing and finishing processes, see our turbine blade production process (manual & CNC). For processing larger turbine blades and vanes, the MTS 6 CNC turbine blade grinding machine for large turbine blades provides a dedicated solution.

The SPE 6 CNC uses Siemens Sinumerik One control and supports fast NC program creation through CAD/CAM software.

Advantages include:

• standard industrial CNC platform
• easy operator acceptance
• fast program generation from 3D data
• high repeatability in serial blade production
• optional adaptive processing based on measuring data

• constant blade quality
• excellent and repeatable surface finish
• highly reproducible material removal
• reduced manual grinding effort
• easy programming through offline software
• savings in upstream 5-axis milling processes
• controlled polishing of leading and trailing edges
• coolant-based process for thermal protection and dust control
• proven machine concept for turbine OEM applications worldwide 

In addition to conventional CNC parameters such as cutting speed (S) and feed rate (F), the SPE 6 CNC uses contact pressure (H1) as a fully programmable and feedback-controlled process parameter.

This allows precise control of material removal on complex blade geometries such as leading and trailing edges.

The result is a stable, quantifiable and repeatable finishing process with consistent surface quality — independent of operator influence.

• improved repeatability compared with manual polishing
• reduced measuring effort after airfoil grinding and polishing
• shorter milling cycles through balanced stock removal
• consistent blade quality across multiple rows
• well established amongst OEMs and turbine blade manufacturers - see case studies 

For recurring turbine blade geometries and established finishing processes, CAD/CAM-supported programming enables efficient and repeatable NC program generation.

The IMM CAD/CAM workflow is based on Mastercam with a dedicated turbine blade finishing module, allowing reliable programming of airfoil surfaces, leading edges and trailing edges.

This gives programmers a familiar CAM environment and avoids the need to learn completely different programming systems. Compared with many robotic finishing solutions, no separate programming environment or complex path teaching is required. 

A key advantage is that SPE and MTS use the same CAD/CAM logic and workflow. This allows customers to transfer proven programs and process strategies across different machine platforms and blade sizes.

For a broader comparison between CNC and robotic turbine blade finishing approaches, see our turbine blade production overview.  

While the SPE 6 CNC is widely used in turbine blade production, its core technology is not limited to this application.

The combination of 6-axis interpolation, programmable contact pressure and CNC-controlled finishing enables the processing of a wide range of complex freeform geometries.

• Medical components such as surgical instruments and implants 
• Orthopedic components (e.g. knee joint surfaces) 
• Precision parts made from stainless steel or titanium 
• Complex aerospace components beyond airfoils 
• Any geometry requiring controlled and repeatable surface finishing

In previous projects with leading German medical technology manufacturers, demanding geometries such as laryngoscope blades and knee implants were successfully processed on the SPE platform.

This demonstrates that the SPE is not only suitable for turbine blades, but also for high-precision applications in the medical and general industrial sector.

Rather than being a dedicated turbine blade machine, the SPE should be understood as a flexible CNC finishing platform for applications where precision, repeatability and defined surface quality are critical. 

Example components:

•  Laryngoscope blades 
•  Orthopedic implant surfaces 
•  Complex stainless steel, titanium and ceramic components