In addition to a host of developments and innovations in the machining of turbine blades, blisks and casings being demonstrated by Starrag during a recent technology event held at its headquarters in Rorschacherberg, Switzerland, there was a keynote address by Gregor Kappmeyer — Rolls-Royce Deutchland’s manufacturing manager of engineering and technology.
Showcasing a range of machines, as well as complementary software and tooling for world-class turbine engine production, the event attracted customers and partners from as far afield as China and the USA. Adding further interest to the Turbine Technology Days was the fact that machining demonstrations took place in Starrag’s manufacturing area, where a large number of machines were at various stages of build.
Talking about the difficulties to be faced when machining aero-engine components — and factors such as fuel usage that are driving the quest for more-efficient engines — Mr Kappmeyer highlighted a number of product and business challenges that the industry faces.
With regard to products, he said aero-engine manufacturers are having to accommodate more-complex designs, new materials (including high-temperature super alloys and composites), and tighter quality specifications. On the business front, increasingly aggressive cost targets are having to be met, along with improved safety and improved delivery performance.
“To remain competitive, we must continue to adopt new materials and manufacturing technologies, modern equipment and methods, and improve our process understanding — embracing an increased attention to detail by the use
of simulation, tool specification and quality control.”
There was no shortage of developments in any of these areas at the Turbine Technology Days workstations. For instance, there was the single-set-up machining — milling and turning — of aero-engine compressor casings, the 24/7 production of blades on a robot-fed machining centre, and demonstrations of Starrag’s new NB machine’s A/B axis configuration, which significantly reduces the time required for machining blisks.
The milling and turning in a single set-up of a 660mm-diameter x 500mm-high aero-engine compressor (typically Inconel or titanium) saw the workpiece mounted on a Starrag STC 800 MT — a 60kW machine with a spindle speed of 15,000rev/min and a torque of 174Nm.
The machining process, following Vericut simulation, included milling, turning, internal machining with a Benz angle head, back spot facing with a Heule Solo 2 cutter assembly, and measuring with a Renishaw TC53-30 probe. Wall thicknesses down to 5mm were produced.
Non-stop blade production was shown by a Starrag LX 051 horizontal machining centre incorporating robot handling. This machine has a work envelope of 650 x 650 x 680mm, rapid-traverse rates of 62m/min, a 360deg A axis that moves at 200rev/min, and a 360deg (continuous) B axis that rotates at 60rev/min. The LX 051 can accommodate and automatically load/unload 40 blades up to 400mm long, giving an unmanned operating time of up to 10hr. Moreover, the use of modular fixturing means that set-ups can be changed in minutes.
Starrag’s expertise in developing flexible manufacturing solutions was highlighted by a number of illustratations. These included a system for machining forged compressor blades at the rate of 40,000 a year. The system featured integrated inspection and marking, two tool-grinding machines, along with tool shrinking and tool pre-setting stations. Also highlighted was a system for machining forged guide vanes at a rate of 35,000 a year.
This system also featured polishing cells, integrated inspection and marking, plus tool shrinking and tool pre-setting stations.
Another demonstration was blisk machining — 56 titanium blades (30mm long) on a 524mm-diameter blisk — using a Starrag NB 251. This machine has been specifically developed for machining blades using a ‘tip entry’ strategy that requires very small axis movements.
With a B-axis head that intersects with the spindle centre-line and pivots around that intersection by its tool length of 150mm, the resulting minimal compensating movement is reduced by 96%, resulting in machining-time reductions of up to 80%. The NB 251 can accommodate blisks up to 1,100mm in diameter with blades up to 200mm long.
The Turbine Technology Days also demonstrated the capabilities of Heckert HEC machines when machining titanium alloys. For example, an HEC 500 X5 was seen machining titanium alloy hydraulic blocks, while an HEC 800 was shown machining turbine casings. Meanwhile, an HEC 1800 was machining landing-gear components while an HEC 800 X5 was machining structural parts.
There was even a Heckert HEC 630 demonstrating in-cycle friction stir welding. Other areas of note included: adaptive machining for blisk repair (repairs are usually about 60% of the cost of buying new); Haimer tool shrinking and tool balancing; and the latest version (7.4) of Starrag’s RCS software, which has improved routines for trochoidal milling and reducing tool wear. Starrag has a UK subsidiary in Birmingham (
www.starrag.com).