Keeping things turning

1. December 2022

Large-scale bushings for gearboxes destined for wind turbines all over the world are being produced in Papenburg, Germany, using a machining technology that is unrivalled in Europe. An important contribution to sustainable energy generation and reducing humanity’s carbon footprint.

After machining, the bushings are individually inspected by plain bearings worker Andreas Zobel to ensure that they exhibit the required dimensional accuracy.
(Images: ©Ralf Grothe, 2022)

The cast blanks for these bushings are made at Europe’s largest continuous-casting plant for non-ferrous metals. Rheinmetall operates this facility at the Papenburg plant. The specialists in Papenburg use aluminium bronze for the bushings, which are approximately 60 centimetres long, have a diameter of 44 centimetres and weigh around 105 kilograms.

This material features exceptionally high strength, thanks not least to a high percentage of copper. It is also very corrosion-resistant, making it suitable for use in various climate zones – even in the harshest environmental conditions. Each wind turbine has three large bushings and five small ones, along with twelve thrust washers; different versions of this configuration also exist.


The environmentally friendly task of the gearbox is to convert the relatively slow speed of the wind turbine blades into a very high rotational speed in the attached generator to produce power. Modern offshore wind turbines can generate up to 15 megawatts of power.

After machining, all bushings first undergo thorough cleaning to remove residual particles.
(Images: ©Ralf Grothe, 2022)

The bushings for the wind turbine gearboxes are machined using a complex method that gives them their spherical shape. But before production of the first series could start in November 2021, the Papenburg facility had to be equipped with a state-of-the-art machining centre costing nearly €2 million. An air-conditioned room was needed so that the bushings could be machined at a constant ambient temperature. Extremely low tolerances in the mm range make maintaining a constant room temperature of 20 °C (+/- 1 °C) vital. Even the temperature of the cooling water in the machine tool is controlled.

The same high-precision approach continues in the number of residual particles permitted. After machining, each workpiece is checked individually and then again following a special final cleaning procedure in the laboratory.

“Very few manufacturers in the world are able to achieve the minimal bushing tolerances that the customer requires,” declars Dr Frank Buschenhenke, head of Industrial Engineering. Forming the curvature of the bushings in the mm range was the biggest challenge the team faced, even though the staff at the plant have a wealth of machining experience. “Our customers can confirm that we’re the only supplier in Europe that can manufacture this product,” adds Buschenhenke.

Even during machining, the dimensions of the bushings required by the customer are continuously rechecked. (Images: ©Ralf Grothe, 2022)


The Industrial business unit of the 130-year-old Papenburg company won the order from a well-known German manufacturer of gearboxes for wind turbines. Rheinmetall entered the segment years ago, with the aim of reducing its dependency on automotive plain bearings. Today, in terms of sales, it represents a comparatively small but steadily growing area of business for the plain bearings plant, which forms part of Rheinmetall’s Materials and Trade division. The Industrial segment plans to double its share of sales in the coming year alone.

Although its production capacity for large bushings is in the four-digit range, the Papenburg plant is already working on the next generation of gearboxes for wind turbines. Another aim here – and this comes as no surprise – is to achieve the lowest possible weight in the smallest possible installation space. The world – or should we say the blade – continues to turn for wind turbines too!

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