The true magnitude of XXL

< Back to Magazine No. 02-2026

industrial

The true magnitude of XXL - What sets modern heavy machinery manufacturing apart

The media loves rankings – the world's largest cruise ships, the fastest sports cars or the tallest skyscrapers. These days, even when it comes to smartphones or coffee makers, hardly any product is introduced without being ranked on a list somewhere.

Even the trade press is following this trend. A few weeks ago, a well-known mechanical engineering magazine published an overview of the world’s largest milling machines. The Droop+Rein FOGS HD from Starrag was also included in the rankings – in an outstanding second place. But size isn’t just measured in meters, metric tons, or kilowatts – in reality, there’s much more to it than that. At Starrag, “XXL” doesn’t refer to the dimensions of a single machine, but rather to the variety of tasks it can handle.

From a turbine blade specialist to an XXL system provider

The real breakthrough into the world of large components began in 1956. With machines for machining turbine blades, Starrag entered the fields of energy technology and aerospace, where the highest precision and ever-larger workpieces go hand in hand. Ultimately, the targeted expansion of the corporate group paved the way for today’s range. Specialists such as Dörries, Droop+ Rein, and Berthiez systematically expanded the range. Starrag consolidated these capabilities into the Large Parts Machining Systems (LPMS) business unit, which combines milling, turning, and grinding for large workpieces.

Landing gears ensure safe landings

In the aviation industry, Starrag demonstrates its XXL expertise not only with massive workpieces but also with critical safety components, where reliability and precision play a key role in manufacturing them. These include landing gear components, which are the parts of a commercial aircraft that are subjected to the greatest stress. They must safely support the entire aircraft weight during every landing while withstanding extreme shock loads, lateral forces, and changes in direction. The requirements for materials, geometry, and manufacturing quality are correspondingly high. New landing gears are made of high-strength titanium or steel alloys; in the future, they may also be made of stainless steels that are difficult to machine. Typical examples include blanks with a machining ratio of over 80% and machining strategies in the micrometer range. Machining involves up to 40 steps and includes complex external contours, multiple holes with tight tolerances, and subsequent heat treatments. The geometry of the components poses a particular challenge. As soon as machining features extend beyond the cylindrical base body, turning alone is no longer sufficient. In that case, Droop+Rein FOGS machining centers handle the entire machining process in a single setup. The high rigidity of the machines makes it possible to manufacture even safety-critical landing gear housings cost-effectively and with the highest precision. Starrag’s solutions are proving popular.

Aerospace suppliers around the world are already using approximately 60 Droop+Rein machining centers specifically for the production of aircraft landing gear. They are a prime example of how “XXL” is not just a matter of meters or metric tons, but also of precision, process reliability, and the ability to reliably machine highly complex components.

Starrag Technology Talk - When the turning diameter grows and grows

When machines themselves are XXL

In the wind power industry, too, the interplay of size, precision, and productivity is key. Not only are the workpieces enormous here – the machine tools are, too. As part of a manufacturing network, a Droop+Rein large-scale machining center and a Dörries vertical lathe both machine rotor housings and brake discs for 14- to 15-megawatt-class offshore wind turbines. Both machines weigh about 870 metric tons, which is roughly equivalent to the weight of 140 fully grown bull elephants. The components already have diameters of around nine meters and are manufactured with a precision of ± 0.1 millimeters. The Dörries vertical lathe used is even designed for workpieces with a swing diameter of up to 15 meters. This means that manufacturing capacity is already in place that is ready for the next generation of even more powerful offshore wind turbines.

Precision down to the last micrometer

However, the machining of large workpieces does not end with milling or turning. It is only during the final finishing process that they achieve their final precision. For this purpose, vertical rotary grinding machines from Dörries and vertical grinding machines from Berthiez are used. For example, Berthiez machines process main bearings with workpiece diameters of up to 4,700 millimeters by combining turning and grinding in a single setup. This reduces the processing time from three to four days to just four to five hours. Dörries machines, on the other hand, were specifically redesigned for machining the larger roller bearing rings of the future. Among other features, they include an enlarged gantry with expansion options for collet chucks up to 7,000 millimeters in diameter, a completely redesigned turning/drilling support, and an integrated HSK-100A drilling spindle. This means they are prepared to machine even larger roller bearing rings in the future.

Step by step to the summit

Modern aerial tramways and gondola lifts demonstrate that XXL is also in demand in the cable car industry. A well-known company in the industry uses a 135-metric-ton Droop+Rein FOGS D40 with a working area of 20,000 × 9,400 × 6,900 millimeters to manufacture drive and idler pulleys.

It processes segments up to 13 meters long for the pulleys of large cable cars. A spectacular example is the two nine-meter- wide pulleys at a modern valley station.

Despite their size, the segments must be machined in a single setup with an accuracy of only 20 to 25 micrometers. The key factor here is the machine’s high rigidity. It ensures that even workpieces of this size are machined with the highest precision – a fundamental requirement for the safe and reliable operation of modern cable cars.

Sometimes the workpiece requires a new machine

Sometimes the requirements are so specific that existing machine designs reach their limits. This applies, for example, in tool and mold making, where users must rough-machine heavy press tools with high cutting performance and then finish them to achieve the highest surface quality and dimensional accuracy. To address this challenge, the Droop+Rein FOGS HD – a new high-gantry concept – was developed, combining the advantages of a traditional portal machine with the dynamics of a gantry machine. With travel ranges of 15,000 × 5,000 × 2,000 millimeters, a torque of up to 7,500 Nm, and separate work areas, multiple workpieces can be machined in parallel and set up simultaneously. The machine performs finishing operations about 20 to 30% faster than conventional portal machines and is suitable for both heavy-duty roughing and high-precision finishing.

With volumetric measurement, climate control, and a volumetric compensation system, this machine design achieves accuracies of 15 to 20 micrometers. This is also evident in the tool and mold making industry: XXL doesn’t just mean large dimensions, but above all the ability to handle a wide variety of manufacturing tasks with maximum precision and productivity. The following example in particular makes it clear – for Starrag, “XXL” doesn’t necessarily mean a larger machine, but rather, above all, a solution tailored to the specific task at hand. Paraphrasing the Starrag slogan, one could therefore say: “Engineering XXL – precisely what you value.” Or, in other words – it’s not the size of a machine that matters, but how precisely it delivers the value the customer actually needs.