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CNC Onsite Develops Precision Tool for Milling 10-m Wind Turbine Flanges

The increasing dimensions of wind turbines operating in harsher offshore environments create engineering challenges for large flange connections that join wind turbine towers to their foundations.

June 04, 2022. By News Bureau

The increasing dimensions of wind turbines operating in harsher offshore environments create engineering challenges for large flange connections that join wind turbine towers to their foundations. To prevent bolts loosening – an issue often associated with significant repair costs and downtime – the connecting flanges must be flat to within millimeters.

Capable of two-millimeter accuracy, 'Goliath', to be launched by Danish machining tool expert CNC Onsite in autumn 2022, can mill flanges of tower bases, monopiles and transition pieces of up to 10 metres in diameter.

A critical mechanical joint within the wind turbine structure, large flanges are technically complex to mount reliably, requiring pairs of matching surfaces fixed in place with bolts. After the manufacturer has welded the flange into the structure – a process that often warps the flange – the surfaces have traditionally been corrected by hand using heat treatment to produce similar skewness. Goliath, however, achieves fine tolerances as part of the production process post welding by milling, grinding and grooving the flanges to create faces with the required structural fit.

“We constantly develop our manufacturing to ensure we can deliver the right products with the right tolerances that the industry requests. With larger flanges, integrating Goliath into our manufacturing process will allow us to continue to do just that,” says Klaus Munck Ramussen, Senior Vice President, Bladt Industries.

With offshore requirements driving ever-growing turbines, the wind energy industry continues to innovate, integrating suppliers’ technology into their manufacturing processes. As a longstanding supplier of foundations and transition pieces, Bladt Industries exemplifies this trend.

CNC Onsite has applied its long experience in developing and operating flange milling machines to Goliath, making it stiffer, stronger and more precise than the previous machines.

“Obtaining a global flatness of a couple of millimeters on a four to five metre diameter flange can be challenging enough, but obtaining the same result on today’s eight-plus metre flanges is simply not possible with previous methods,” explains Søren Kellenberger, Sales Director, CNC Onsite.

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