The energy revolution will only succeed with the right finish

Climate change can only be stopped if CO2 emissions decrease to net zero. On the way to achieving this target, an important role is being played by new, powerful wind turbines with stronger, quieter and more compact drives that can be operated with or without a gearbox. Their efficiency depends on all of the important drive elements having the right finish – for years now, this has been a speciality of the Berthiez machines from Starrag.

It is a highly challenging task: According to the Global Wind Report 2021, the annual report by the Global Wind Energy Council (GWEC), over the next decade, wind turbines must be installed three times faster than previously to achieve the target of net zero. However, the global wind energy sector is already working to address the problem by investing heavily in new turbines. Yet, while increasing the pace at which the wind energy infrastructure is expanded, quality cannot be disregarded. In all areas of the value creation chain, there is demand for suppliers who really know their business.

However, the construction of new, more efficient wind turbines is possible only in cooperation with the drive sector. Because with or without a gearbox, the conversion of wind – a very volatile energy source – into electricity depends on drive elements that must be manufactured with high precision, such as bearings, gears and other components of the gearboxes. Starrag S.A.S. from Saint-Étienne, France, has established a very positive reputation with its large vertical Berthiez lathes and grinding machines, both in relation to this application and throughout the entire energy sector.

Berthiez RVU 4700/450 with a 177.2 in. (4,500 mm) table diameter. On the new RVU grinding machines, it is possible to grind bearings of any size from 39.4 to 236.2 in. (1,000 to 6,000 mm) in diameter with micrometer precision.

Grinding – A matter of common sense

In particular, grinding plays an important role in the manufacturing of drive elements. “Grinding is primarily a matter of common sense”, explains Jean-Luc Baechlé, Plant Manager of Starrag S.A.S. “Our grinding experts are able, thanks to many years of expertise, to reliably predict how a dimension or a shape can be achieved with micrometer precision”. The France-based specialist is sure that with Berthiez RVU vertical grinding machines, not only is this task possible, but also the high-precision grinding in the μm range on these machines will even have an extremely high level of repeating accuracy at all times. The grinding technology from Saint-Étienne with table sizes of 31.5 in. to 236.2 in. (800 mm to 6,000 mm) is also designed for large wind turbine components. 2,000 workpieces weighing up to 35,274 lb. (16,000 kg) with a maximum height of 39.4 in. (1,000 mm) can be machined.

When building machines for very selective drive manufacturers in the wind energy sector, it is essential to use high-quality drive technology yourself. Saint-Étienne has no concerns in this aspect: The machines of the French Starrag plant have tables with hydrostatic bearings and these tables are equipped with torque motors that, in combination with the highly rigid grey cast-iron construction, provide high machining accuracy and vibration-damped and backlash-free rotation. This set is completed by a support and an electrospindle holder turret equipped with an hydraulic balancing sys-tem, large ball screws,constant balancing of the grinding wheels and precise component temperature control.

2,000 workpieces weighing up to 35,274 lb. (16,000 kg) with a maximum height of 39.4 in. (1,000 mm) can be machined.

Ergonomic help: HMI Berthigrind user interface

A very important aspect of grinding is ease of operation. The magic word is HMI: These three letters stand for Human Machine Interface, which describes a user interface that makes it easier for the specialist staff to operate the machine control system. This is a crucial task, according to Sales Engineer, Sylvain Lhoste: “Because the grinding of components is very complex, we support operators with the user interface Berthigrind.” There is a wide variety of possible applications for the grinding technology from Saint-Étienne. “For all wind turbines we supply machines for grinding the bearing to position the entire wind turbine (nacelle) and the rotor blades. They help the turbine to convert wind energy into electricity in a highly efficient manner”, explains the Plant Manager. “For wind turbines with gearboxes between the main rotating shaft and the generator, our machines are also suitable for machining the high-precision bearings of the rotor shaft as well as the bearings, gears and other components for the generator gearbox. In very large wind turbines that do not have a gearbox, our machines grind the largest bearing that is necessary for these turbines”. Starrag’s grinding technology is popular: For example, it has proven itself worldwide when it comes to manufacturing a wide range of tapered roller bearings, spherical roller bearings and cylindrical roller bearings with a diameter of between 39.4 and 236.2 in. (1,000 mm and 6,000 mm).

Using a double slide: 20% less machining time

A speciality is the machining of bearings for wind turbines. If, for example, users working with the RVU 2800/250 vertical grinding machine use two grinding discs or lathe tools at the same time thanks to the double slide, they can reduce machining times by around 20%. The extension with the second slide also increases the machine capacity tenfold. “This very efficient plant is an example of close cooperation with our customers”, says Plant Manager Baechlé. On the new vertical RVU grinding machines, customers are able to grind bearings of any size from 39.4 to 236.2 in. (1,000 mm to 6,000 mm). in diameter with micrometre precision.

The doubled extended warranty period allows the wind turbine operators longer intervals between instances of expensive and very time-consuming maintenance work.

Doubled extended warranty period reduces expensive maintenance

“The idea behind it comes from one of the world's leading bearing manufacturers, which wanted to double its bearings’ warranty to 24 months for its customers”. Thanks to new, optimized machine technology, the group can now manufacture drive technology that is different from the competition in one very important aspect. The doubled extended warranty period allows the wind turbine operators longer intervals between instances of expensive and very time-consuming maintenance work. This is a very important factor that is popular with many customers, not just the owners of difficult-to-access offshore platforms. However, it is not the technology alone that turns very discerning users into loyal customers. This is where the Starrag philosophy “Engineering precisely what you value” comes into play. This means customers always receive precisely the technology and service that they really need – no more, but also no less. Baechlé: “We try every possible option to develop solutions that meet the customers’ needs precisely”

Despite the COVID-19 travel ban: On time commissioning in China

In this case, what the customer needed was to have a vertical grinding machine quickly and reliably assembled and commissioned in China – in the middle of the COVID-19 crisis. As experts from SaintÉtienne were not allowed to travel to the Far East, technicians from Starrag China took over the difficult task of assembling and commissioning the machine, which had been delivered in a disassembled state, with support from the remote Berthiez specialists. Baechlé: “Assembly and commissioning were accomplished through close cooperation between France and China, to the full satisfaction of the customer and within the prescribed timeframe. This successful experience in very tumultuous circumstances established trust and has led to many new orders”.

Berthiez RVU 2800 grinding machines

The RVU grinding machines set new standards in high-precision machining and are especially suitable for high precision grinding applications in the bearing and aerospace industries. The range can be equipped with up to four water-cooled grinding spindles which can achieve a performance of 60.3 hp at 18,000 rpm. (according to the type of grinding wheel selected)