In the aviation and energy sectors, many turbine manufacturing companies rely on Starrag machines. This is true not regarding the manufacture of engine blades and blisks, but also turbine housings. Decades of experience have supported the development of the wide range of Starrag machines designed for the entire turbine housing machining process.
The housings and casings for aircraft engines and steam/gas turbines are available in small and large sizes. These complex components are becoming ever-more complex and increasingly manufactured from difficult-to-machine materials. These factors usually demand the deployment of several processing technologies, ideally combined into one machine or flexible manufacturing systems.
Thanks to its breadth of machine tools, Starrag says it can meet all requirements. The Starrag STC series, for example covers a large area of turbine casing applications, with its various sizes and designs capable of handling casing diameters up to 3.3 m. The machines are predestined for the economical, five-axis, heavy-duty machining of sophisticated casings made from titanium or Inconel.
For machining smaller casings, Starrag offers the Heckert X series in MT design. These models support high-precision turning and milling on a single machine platform. The five-axis X variants of this compact series add another option: the positioning axis in the rotary swivelling table is suitable for angled holes, as are often required in casings.
If a huge steam/gas turbine housing with a diameter of up to 12 m requires machining, Starrag can recommend its correspondingly large Droop+Rein portal machining centres, which are built at the site of Starrag Technology GmbH in Bielefeld. The plant also produces large vertical Dörries lathes, which again see use in the machining of steam/gas turbine housings.
Vertical turning and grinding processes are also the speciality of the Berthiez machines from the Starrag plant in St Etienne, France, which are mainly used in aircraft construction.
For ultra-precise fine boring and milling, as well as precision grinding, Starrag has the SIP horizontal or vertical jig boring machines, manufactured in Vuadens in Switzerland.
Also built in Vuadens are Bumotec CNC turn-mill centres, which produce small, high-precision and complex parts in five axes and with accuracies of just a few microns. In the production process of casings, Bumotec models see use in the machining of mounted components, such as injection nozzles.
The UK subsidiary TTL, which handles maintenance, repair and overhaul (MRO) tasks, plays a vital role in the turbine housing sector. TTL specialises in Siemens NX CAM software, a tool common in the turbine industry and as a process developer for adaptive milling. After build-up welding and precise milling, the cost-intensive housings are restored to almost new condition.
Alexander Fitz, sales director for aerospace and turbine at Starrag AG, explains: “Machine tools are one of our core competencies, which no other company in the world can offer in terms of their technological breadth and varying sizes. We also have an in-depth technical understanding of the entire process chain required to manufacture ready-to-install turbine housings.”
This expertise enables Starrag to combine various machining operations in one machine. Klaus Struebel is segment sales manager for aerospace and turbines at Starrag with decades of expertise in the field of turbines. He points out that the integration of milling, turning and grinding with self-developed angle and other machining heads can reduce clamping positions and increase productivity.
“If one machine is not sufficient for machining, we can combine our different product ranges in flexible manufacturing systems: a Starrag STC with a Berthiez vertical turning-grinding centre, for example,” he says. “Standardised interfaces and pallets allow us to accelerate the process and increase accuracy. If required, we integrate additional washing, drying and measuring processes.”
Starrag in Rorschacherberg has for many years been developing and grinding carbide milling cutters for aircraft and turbine components made from difficult-to-cut materials such as titanium, Inconel or high-alloy steels. In most cases, the cutters are customised products adapted to the respective machining process, namely the component, machine, material and other concomitant circumstances. Starrag says its cutters ensure faster machining and have a longer service life than standard tools – an important contribution to a stable, repeatable process.
Machining expert Struebel cites the required bores: “The internal bores represent a particular challenge in the machining of turbine housings. We develop special interchangeable angle heads for this purpose, which must also cope with the limited space available.”
The design requires a great deal of experience, as does deep-hole drilling with very small diameters in titanium or Inconel. Tight tolerances must be maintained for the drill holes so that add-on parts – such as blades – fit precisely.
Another of Starrag’s strengths is the gear spindle manufactured in Rorschacherberg, which remains thermally and mechanically stable and is highly durable even when processes run for 80 hours. The gear spindle is used on STC machining centres and Droop+Rein gantry machines. For the latter, different special heads are available, including angle heads in various lengths, with different torques and speeds.
Struebel summarises: “We provide our customers with higher productivity by looking at the entire process. We don’t just sell a product, we make sure the machine fits the machining application in terms of size, technology, axis configuration and kinematics, and then optimise the process with the appropriate peripherals.”
This activity usually takes place at the ATCC (Aerospace Turbine Competence Centre) in Rorschacherberg, which offers the best conditions for the process. Covering an area of around 2000 m2, the ATCC features the latest four- and five-axis Starrag machining centres. Developers and application specialists are also on call. The ATCC is also able to produce test runs and small series batches for customers.
More information www.starrag.com
