How can you make sure the assembly of any wind turbine runs smoothly when there's only one chance? To make sure the answer is not blowing in the wind, Vestas Nacelles in Lem, Denmark, has a strict quality policy, enabled by high-capacity portable measuring systems from Hexagon Metrology.
No small object has ever left the Vestas Nacelles factory. Hubs, housings or other steel structure elements for wind turbine nacelles can be 3.5m high and weigh up to 16t. For such enormous parts, the quality policy at Vestas Nacelles relies on valid data that enables the monitoring of process performance.
"That means we will be alerted if a process gets out of control by showing evidence of systematic variation," says Ingo Boysen, production quality manager. "By reacting fast in these situations, we have been able to extend our knowledge in terms of processes and items.
"This has given us the possibility of reducing our process variation and thereby improving the process robustness while lowering the cost of poor quality."
Every single part the factory produces is also measured. "We understand measurement is not just inspection of the parts; for us, it is an integral part of production. You could say our production relies on measurement," he explains.
"Our developers define a certain number of points on each object that are critical to quality, the so-called CTQs. So we measure the CTQs on each part as well as a large number of additional characteristics, such as the position of holes or other features on a hub.
"Subsequently, we make sure all single components of the nacelle fit together before the wind turbine is assembled. It is very difficult to correct any mistakes once a part has left the factory, and, in the case of a hub, scrap would cost us €20,000 per piece for just the material.
"Measurement pays off, but not just for us: we are using the measurement data to actively reduce cost to the benefit of our customers."
The quality team at Vestas Nacelles has long experience of metrology. Besides a large stationary CMM, they had used two Leica LT D300 and LT D500 laser trackers for many years. According to Jeppe Nielsen, head of the measuring team, "the time had come to look for new measurement systems".
"The old laser trackers were still working perfectly, however, we wanted to see if there was something faster out there," he says. "A new tool should help us with saving time and effort."
The result of the subsequent benchmark and testing phase led to the conclusion that, thanks to their mobility, measurement range and high accuracy under difficult shop floor conditions, laser trackers were still the ideal solution for Vestas Nacelles' measurement challenges.
Nielsen and his team chose the Leica Absolute Tracker AT901, a high-performance portable metrology tool from Hexagon Metrology. Using two of these advanced laser trackers made measuring large parts considerably more efficient for Vestas.
"Besides gathering data in real time, the PowerLock function impressed us," comments Nielsen. "Because of PowerLock alone, we save two hours' work time per object - in some cases, that means we cut the measurement time in half."
PowerLock is a laser beam technology that helps a laser-tracker operator automatically connect the laser beam emitted by the tracker with the reflector.
"Before, every time the beam was interrupted, it was a long procedure to re-establish the connection - it could even mean we had to climb down the ladder from which we measure some points, get the beam recovered and continue the measurement.
"With PowerLock and a remote control, we can now measure our parts with only one operator - before, it was a two-man task", says Nielsen.
Vestas Nacelles' production in Lem also includes bearing housings, all of which undergo a measurement procedure. For Nielsen, the benefits of being able to bring this in house were obvious.
"We used to have them measured by an external supplier before, which meant transport and lead time," he recalls. "That was too expensive for us, so we looked for our own tool to carry out these measurements. It had to be an additional one, since our two laser trackers are already in constant use. We developed a business case and found out that the ROMER Absolute Arm from Hexagon Metrology would be the best tool for this application.
"Ordering the measurement, sending the part and getting it back took us days before; now, we have the results in ten minutes. The measuring arm paid for itself in less than half a year. In addition, wireless data transmission, the fact that no set-up time is necessary and the robust, carbon fibre construction make it a very convenient and reliable measurement solution."
The five measurement specialists in Nielsen's team use the two Leica Absolute Trackers and the ROMER Absolute Arm every day. Without the metrology equipment, production stops at Vestas Nacelles - that makes reliable systems and efficient support essential.
Boysen is beyond pleased with the choices. "With the Hexagon Metrology systems, we're thoroughly happy," he says. "The cooperation has been good from the beginning. We know that we can count on the arm and the trackers, as well as on the local service in Denmark."
Hexagon Metrology offers a comprehensive range of products and services for all industrial metrology applications in sectors such as automotive, aerospace, energy and medical. It supports its customers with actionable measurement information along the complete manufacturing life cycle of a product - from development and design to production, assembly and final inspection.
With more than 20 production facilities and 70 precision centres for service and demonstrations, and a network of over 100 distribution partners across five continents, Hexagon Metrology empowers its customers to fully control their manufacturing processes, enhancing the quality of products and increasing efficiency in manufacturing plants around the world.