Offshore wind foundation manufacturer CS Wind Offshore has begun operating a custom-built automated milling machine from Danish machining specialist CNC Onsite at its Aalborg plant, replacing manual cutting in the production of cable penetrations in transition pieces bound for one of Germany’s largest offshore wind farms.
Each transition piece requires six cable holes and twelve pressure relief holes. The cable penetrations carry wiring for external workspace lighting and platform cranes, and the edges have to be clean enough for reliable sealing in a saltwater environment. The pressure relief holes prevent structural warping in rough sea conditions.
“We required a tolerance of one millimetre to eliminate micro-gaps and completely isolate the internal electrical routing,” said Flemming Smidt Pedersen, Senior Manager, Production Engineering at CS Wind Offshore. “At sea, this watertight integrity is absolute.” He added that the process achieved 0.3 millimetres and runs dust-free.
The four-axis gantry machine measures 3.6 metres long, 2.3 metres wide and 2 metres high, and weighs 4.8 tonnes. It was developed at CNC Onsite’s headquarters in Vejle, Denmark. Rather than moving the workpiece into a machine tool, the unit clamps onto the component using electromagnets, which hold it vibration-free against the curved surface without marking the high-grade steel or requiring conventional clamping.
“These parts are massive and virtually impossible to move into a standard machine. Therefore, we bring the machine to the workpiece instead,” said Søren Kellenberger, CEO of CNC Onsite. Each transition piece weighs 370 tonnes and spans 7.8 metres in diameter, and has to be rotated on rollers to align the cutting zones; the machine tracks that rotation on a wheeled maneuvering setup.
Cable routing through the structure runs diagonally, so the penetration wall needs a 45-degree angle. The machine’s adjustable machining angle covers 28 to 90 degrees, and it can handle openings from 50-millimetre utility holes up to oval penetrations of 2,575 by 550 millimetres. Founded in 2012 and certified to ISO 9001, 14001 and 45001, CNC Onsite serves both onshore and offshore wind, including flange machining and repair work on yaw rings, blade root inserts and generator shafts.
