Turbomolecular pumps (TMPs) are the enabling technology for ultra-high vacuum (UHV) — the pressure regime below 10⁻⁸ mbar where semiconductor fabrication, thin-film coating, surface analysis, and particle accelerators operate. A TMP achieves this by stacking multiple stages of rapidly rotating blades interspersed with stationary stators, imparting momentum to individual gas molecules. Rotor speeds of 30,000-90,000 RPM are typical, with blade tip velocities approaching the speed of sound. The CNC machining of these blades demands extreme precision, specialized materials, and a deep understanding of high-speed rotor dynamics.
Free DFM Analysis Before Production
To ensure the success of complex TMP rotor projects, we provide Free Design for Manufacturing (DFM) analysis before production begins. Our engineering team reviews your CAD files to identify potential machining risks, such as tool access limitations in narrow blade channels or thin-wall sections prone to deflection. By optimizing the design early, we help reduce manufacturing costs and prevent lead-time delays.
Blade Geometry: Where Fluid Dynamics Meets Manufacturing
Turbomolecular pump blades operate in the molecular flow regime, where the mean free path of gas molecules exceeds the characteristic dimensions of the pump. Each blade row is an array of thin, precisely angled airfoils arranged radially around a central hub. The geometry is unforgiving: blade angle errors of even 0.5° can measurably reduce pumping speed for a given gas species.
Key Geometric Parameters
- Blade angle (α): The angle between the blade chord and the plane of rotation. Varies from ~10° at the inlet stages to ~40° at the exhaust stages.
- Blade chord length and solidity: Determines the probability that a molecule strikes a blade.
- Blade thickness: Typically 0.5-2.0 mm at the root, tapering to 0.2-0.5 mm at the tip.
- Hub diameter ratio: Maximizes blade area and pumping speed.
Material Selection
| Material | Density (g/cm³) | Tensile Strength (MPa) | Application |
|---|---|---|---|
| Aluminum alloy 7075-T6 | 2.81 | 510-570 | Most common TMP rotor material. High strength-to-weight ratio. |
| Titanium alloy Ti-6Al-4V | 4.43 | 900-950 | Used for higher strength or corrosion resistance. |
CNC Machining Approaches
Integral Bladed Rotor (IBR) Machining
The modern approach to TMP rotor manufacturing is to machine the entire rotor from a single aluminum or titanium forging, eliminating joints and improving dynamic balance.
Quality Verification & CMM Inspection
Precision is verified through rigorous Post-Machining CMM Inspection. We utilize high-precision Coordinate Measuring Machines equipped with small-diameter probes (0.3-0.5 mm) to verify blade profiles, angles, and thickness at multiple radial stations. This ensures that every rotor meets the strict dimensional tolerances required for high-speed stability and vacuum performance.
- Blade geometry measurement: Reported profile deviation and angle accuracy.
- Surface finish inspection: Typical Ra 0.2-0.4 µm for optimal gas molecule scattering.
- Dynamic balancing: Balanced to ISO 1940 G0.4 or better.
- Burst testing: Spin-tested to 110-115% of maximum operating speed.
Tik Precision machines turbomolecular pump rotor blanks and stators on our 5-axis CNC platforms. Contact us to discuss your TMP component requirements and receive your free DFM review.
