Wind Turbine Hubs CNC Machining for Wind Energy

Yes. We offer flexible manufacturing capabilities including:
Rapid prototyping for design validation
Low-volume production for specialized applications
High-volume production with consistent quality control
Full structural and dimensional verification at every stage

As for the hubs, we obtain the main shaft bore within ±0.020 inches because it’s critical for bearing clearance. The blade mounting surface flatness allowance is 0.030 inches across the 1 to 3 meter bolt circles for even load distribution. The bolt hole positions are within ±0.015 inches for alignment of the blade root flanges. The pitch bearing seat diameter is ±0.025 inches for bearing fit. We achieved shaft bore and blade mounting faces to ±0.040 inches perpendicularity. And the overall hubs, being large castings of over 2 meters, we attained ±0.050 inches tolerances.

CNC machining hubs are large-format centers with a horizontal spindle up to 5 meters in diameter which machine the bodies. Precision boring achieves the main shaft bore with a diameter of 300 to 800 mm which fits bearings with a tolerance of ± 0.020 inches. Face milling creates flat surfaces that are flat to within 0.030 inches across the 1 to 3 meter diameter bolt circle. The coordinates are drilled to produce the blade bolt patterns with a positional accuracy of ± 0.015 inches for holes M30 to M64. The threads are milled to pitch for bearing mounting. The fabricated hub sections are welded together, the welds being full penetration and the seams inspected by ultrasonic testing. The seams are shot-peened for the fatigue resistance of the hub and protective coating pharmaceuticals are applied for an overall dry film 500 microns thick.

Ductile iron grades 65-45-12 and 80-55-06 have excellent fatigue strength and yield strengths 310 to 380 MPa, allowing them to support bending moments on blade root for mid-size turbines 1.5 to 3 megawatts, have superior castability for complex geometry, including internal pitch bearing cavities, good machining, dampening vibration and reducing drivetrain loads, and are inexpensive. For ductile cast GS-52 steel, it has 350 MPa tensile strength cast steel which correlates to more compact designs, great weldability for integrated parts, and reliability of the structures. The 42CrMo4 forged steel has maximal strength through grain refinement, the fatigue life exceeds 10^8 load cycles and is used for offshore turbines that are 8 megawatts or more. For prototype and small-series fabrications, welded steel has the advantages of flexibility of the design, lower lead time, and lower costs.

Wind turbine hubs are structural components that connect 2 or 3 rotor blades to the main shaft which transmits aerodynamic torque that can range between 100 kilonewton-meters for small turbines to 10,000 kilonewton-meters for 10+ megawatt offshore turbines. Different types include fixed-pitch hubs which are stall-regulated turbines that have blades with permanent angles, variable-pitch hubs with hydraulic or electric motors that allow blades to be adjusted between minus 5 to plus 90 degrees for power adjustment and emergency braking, teetering hubs that allow to oscillate the rotor and lessen fatigue loads on two-blade turbines, and direct-drive hubs which specialize in gearless designs that house the generator to the rotor, modular hubs that allow blade replacement without nacelle access and offshore hubs which have improved corrosion resistance for marine environments.