Windtech International - Precision flange milling introduced for Vestas 15 MW turbine towers

Jun 24, 2025

Want to read full articles?

Sign up free of charge and login and read the full text of published articles on our website.

You can use your email or username to login

FOLLOW US AT

Follow us at BlueSky

CNC Onsite has delivered its custom-built Goliath milling machine to tower manufacturer Welcon, where it is now in use machining 97 bottom tower flanges for Vestas' 15 MW V236 turbines. The turbines are intended for offshore wind projects in Germany and the Netherlands.

The milling process is a critical step in ensuring the tower and transition piece form a flat, stable and fatigue-resistant mechanical joint. The bolted connection requires high precision to guarantee structural integrity under load. The Goliath machine, designed by CNC Onsite, has achieved a global flatness tolerance of 0.21 mm on the first flange — well below the required 1 mm for this project.

Welcon has adopted flange facing as a standard production process, replacing the traditional heat straightening method. Heat straightening uses controlled heating and cooling to correct welding-induced distortions, but can be time-consuming and less accurate.

Mounted directly onto the flange, the Goliath machine uses adjustable legs with hydraulic cylinders or electric actuators to adapt to various flange sizes. In its standard configuration, it can mill flanges from 6.5 to 10 metres in diameter, and it can be adapted for larger components. The fully CNC-controlled system mills flat, tilted and double-tilted surfaces, and can also machine additional features such as gasket grooves.