Manufacturing blisk rotors in a single clamping operation

Machining blisks and impellers rapidly and reliably in a single step saves both time and money. Thanks to the five-axis Starrag NB 151, which has been specially designed for such machining processes, users from the aviation, aerospace and energy sectors can benefit from these advantages.

With its NB line, Starrag is developing five-axis machining centers designed especially for manufacturing titanium, nickel-based alloy, and blade-steel blisks and impellers for stationary gas turbines. At the beginning of 2019, the machine tool manufacturer released the NB 151 as a smaller version of the Starrag NB 351 and NB 251. The NB 151 is designed to manufacture workpieces up to 23.6 in in diameter, up to 11.4 in in length and up to 661.4 lb in weight.

Starrag NB 151 users can expect to benefit from short cycle times, reduced tool costs and a low amount of wastage. As with the larger models in this line of five-axis machining centers, the NB 151 can perform all relevant production steps for manufacturing blisks and impellers – from the efficient roughing of components from a single piece of material, to the adaptive machining of friction-welded blisks, right through to the highly dynamic smoothing of flow surfaces in point contact. Such efficiency is possible thanks to a basic design that has already been tried and tested in small horizontal Heckert machining centers and the Starrag LX 051 blade machining center. The mineral cast machine bed has excellent damping properties and a high degree of rigidity, while the compact design still provides easy accessibility to the workpiece thanks to clever positioning of the spindle and fixtures. The high-quality Starrag spindle also ensures high removal rates.

NB 151

The two circular axes are certainly among the highlights of the Starrag NB 151. Specially developed for blisk machining at the Starrag site in Rorschacherberg, they are 100 % made in Switzerland. 

Special circular axes – developed by Starrag and produced in Switzerland

The two circular axes are certainly among the highlights of the Starrag NB 151; specially developed for blisk machining at the Starrag site in Rorschacherberg, they are 100 % made in Switzerland. Without compromise, the axes have been optimized for performance in multi-blade applications, as their layout has been carefully designed to reduce compensating movements of the linear axes to a minimum.

One key factor for successful blisk machining is being able to easily access the component; in the NB 151, this is ensured by the wide 280-degree angle of the B-axis, as well as the incredibly compact A-axis. The machine’s optimized obstacle contour both prevents collisions with the spindle and allows the use of shorter tools. The resulting cutting stability ensures the shortest possible roughing times and perfect surfaces after smoothing.

Head of Development Dr Markus Ess

“With the NB 151, we can provide a service package tailored to blisk and impeller machining that will impress customers with its unrivalled overall performance.”

Its rigidity and excellent damping properties allow higher cutting values, while also reducing tool wear. 

Processing solutions from Starrag

Along with supplying high-quality machinery, Starrag has also become synonymous with providing customers with end-to-end machining solutions for their components. The NB 151 is no exception. This blisk machining center fits seamlessly into the overall package offered by Starrag, which covers the entire process chain from programming and technology to software, tools and machinery. Head of Development Dr. Markus Ess explains: “With the NB 151, we can provide a service package tailored to blisk and impeller machining that will impress customers with its unrivalled overall performance.”

The NB 151 offers customers the chance to improve several aspects of their manufacturing processes, such as productivity. Its rigidity and excellent damping properties allow higher cutting values, while also reducing tool wear. The high dynamics of the machine, resulting from features including a low number of moving masses, also contribute to minimized processing times, while integrated sensors and systems improve process reliability. Markus Ess explains: “Various elements of the machine, for example the spindle, are continuously monitored for vibration, deformation and temperature fluctuations. Corresponding automated compensation processes then ensure machine accuracy.”

As standard, each Starrag NB 151 is also equipped with a measurement fixture which, in conjunction with special Starrag software, allows the blisks to be machined adaptively. This feature automatically measures every single turbine blade on the unmachined part and creates a tailored blade geometry, before generating the relevant NC program and executing it on the machine. This ensures perfect transfers between friction-welded blades and the rotor.