Tower
Flanges
Restore tower section flange flatness on-site. No re-fabrication, no transport.
Support Structures & Flange Solutions
Tower
Trusted by wind operators and OEMs across Europe and North America
- Vestas
- Siemens Energy
- NextEra Energy
- GE Vernova
- Enercon
- Nordex
- EDF Renewables
- Welcon
- RWE
- CS Wind
- EEW
- Muehlhan
- Nicon Industries
- Orsted
- Cadeler
- Vattenfall
- Smulders
- Windar
- Titan Wind
- SubC Partner
- Semco Maritime
- LM Wind Power
- Iberdrola
How It Works Tower Flanges.
Tower Flanges.
Controlled Flatness.
Reliable Connections.
Welding distorts tower flange geometry. CNC Onsite restores it with precision flange milling performed after welding, directly in the fabrication line. No re-fabrication. No transport to a workshop. No heat straightening. Flanges leave production flat to OEM specification, with uniform contact surfaces that support correct bolt tensioning.
Machining out what welding puts in
Even small post-weld deviations can lead to uneven bolt preload, local gaps between flange surfaces, increased fatigue loading and unnecessary maintenance over the turbine's lifetime. A mobile CNC flange milling system machines the flange face back to the required flatness and geometry - a controlled, repeatable process in place of manual heat straightening.
Built for serial production
- Integrates directly into the fabrication environment, supporting efficient serial production of large onshore and offshore turbines
- Runs at your factory with our technicians - or we train your own technicians to operate the machine
- A measurement report documents the result at handover
0.21 mmglobal flatness delivered, well below industry requirements
Ø10,000 mmmaximum tower flange diameter
5continents where CNC Onsite has delivered work
Why machining beats heat straightening
Heat straightening is a manual correction method. Controlled CNC machining replaces it with a predictable, repeatable production process - consistent tolerances while improving both quality and production efficiency - contributing to reliable structural connections throughout the lifetime of the wind turbine.
Technical Specifications
Typical duration 1–5 days on site
Diameter range Up to Ø10,000 mm
Flatness tolerance OEM specification
Certification ISO 9001
Equipment Mobile CNC flange milling system
Applications Tower sections
Expected lifetime Similar to original
ISO 9001HIGH PRECISIONOEM TOLERANCESONSITE MACHINING
Reliable Bolt Connections Achieving flange flatness ensures even bolt preload and reduces the risk of fatigue, loosening, and premature failures throughout the turbine's service life.
Sub-Millimetre Precision Controlled CNC machining restores post-weld flange geometry to tight tolerances, ensuring accurate fit-up and repeatable manufacturing quality.
Repeatable Manufacturing Quality Fully CNC-controlled machining replaces manual correction methods with a predictable and repeatable production process.
Built For Offshore Scale Goliath machines monopile and transition piece flanges up to 12 metres in diameter, supporting the increasing size and complexity of offshore wind structures.
How It Works
Our Process
01
Quotation Request
We offer follow-up meetings with the customer. CNC Onsite’s follow-up program is part of our high quality standards.
02
Planning
We plan the technical part of the project, which includes preparation and programming of Goliath, the precision machine that will perform the milling. We plan staff availability and timing, including flexibility to accommodate potential changes to the schedule.
03
Implementation
Our technicians will conduct the precision milling of the flanges at the customer’s factory. Alternatively, CNC Onsite will train the customer’s own technicians for the operation of the machine. The team will use the Goliath machine to mill the flange faces, leaving them flat to within one millimeter.
04
Handover
After machining measurements are made, a measurement report is issued to the customer. Alternatively, the customer or a customer-contracted third party conduct the measurements. Once the measurement are complete, the customer signs off the work.
05
Follow-up
We offer follow-up meetings with the customer. CNC Onsite’s follow-up program is part of our high quality standards.
Talk to our team Get Expert Advice
Get Expert Advice
On Your Project.
Send us your damage report or turbine type and we will respond within one working day with an assessment and indicative quote.
Request received.
An engineer will get back to you within one working day.
“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. We are proud to support the development of the industry and, by securing the tolerances, we contribute to securing the integrity of these large structures and thereby the production of green power for many years.”
Global reach
Wherever your turbines stand
On site within days Worldwide call-out, 24/7. Technicians mobilize within days of a purchase order.
Onshore & offshore The same in-nacelle method works at sea - no offshore crane deployment needed.
Five continents A proven repair track record on wind turbines across five continents.
FAQ
Frequently asked questions
Why does tower flange flatness matter?
Even small deviations caused by the welding process can lead to uneven bolt preload, local gaps between flange surfaces, increased fatigue loading and unnecessary maintenance throughout the turbine's lifetime. Restoring flatness ensures uniform contact surfaces, supports correct bolt tensioning and contributes to reliable structural connections.
How flat can a tower flange be machined?
Flanges are machined to OEM flatness specifications. Across multiple projects, CNC Onsite has consistently delivered flange flatness well below industry requirements, including results down to 0.21 mm global flatness.
How long does on-site flange milling take?
Typically 1 to 5 days on site, depending on the project. Planning includes staff availability and timing, with flexibility to accommodate potential changes to the schedule.
What size tower flanges can be machined?
The mobile CNC flange milling system handles tower section flanges up to 10,000 mm in diameter.
Can we operate the flange milling machine ourselves?
Yes. CNC Onsite's technicians can perform the precision milling at your factory, or we can train your own technicians to operate the machine. After machining, a measurement report is issued and the customer signs off the work.
