Optimised to perfection

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Starrag Group’s ‘Turbine Technology Days’ annual gathering does what it says on the tin. If turbine blade or blisk machining is your interest, this is right on target, and aerospace is a central theme. Andrew Allcock reports (extended version)

Located in Rorschach, Switzerland, at the eastern end and on the southern bank of Lake Constance some 50 miles due east of Zurich, machine tools, the design and manufacture of cutting tools, fixturing and development of CAM software fall within this factory’s area of expertise.

Starrag (https://is.gd/akakav) is just one of several brands in the group, however; the others are Berthiez, Dörries, Droop+Rein, Ecospeed, Heckert, Scharmann, SIP and TTL, but this event is very much a Starrag affair. On the turbine blade/blisk machining technology side, there were a number of displays highlighting latest developments (see box item below), these taking in the company’s first automated blisk machining line (currently a proposal), multi-stage blisk machining, a new angle-head solution that boasts automatic toolchanging and adaptive roughing strategies to achieve best fit and eliminate air cutting for forged blades.

But above these specific technology elements, other themes were also aired on topics that included Starrag Group developments, customer partnerships, the Serviceplus machine service/purchase plan and the company’s take on Industry 4.0.

The group, which posted sales of CHF405 million (£310 million) for 2017, representing a rise of over 9% on the previous year that saw it celebrate a record order intake of CHF480 million (£367 million), has just appointed a new CEO – Swiss national Christian Walti (50). Taking on the new role on 1 June, just a couple of weeks before Turbine Technology Days, his immediate previous position was with another capital goods maker, Bosch Packaging Systems, Beringen, Switzerland.

“The reason I came here is that I believe in the company and the set-up in general,” opens Walti in conversation with Machinery. “The challenges and main topics are more or less the same [as in his previous industry], but the intensity varies, of course. Starrag has a long history and is a group of companies with a very broad product portfolio, which is an advantage. The company also has a certain size; it is not a big group, but neither is it small. So, I believe, in a very general way, having great products and a certain size, I am definitely sure we have a great starting position.”

As with all companies, he says that growth is a mid-term requirement, but that it “is not a major issue”, and that growth could come from both organic and acquisitive activities. But the more immediate task is to better exploit group strengths. “The group has to find more synergies. We are as we are because we have certain companies in the group, a certain product portfolio and a certain knowledge, and on this we will build. If we find more things in common, maybe processes or market appearance [‘one brand strategy’], this will give benefit to the customer, I believe.”

He already has a strategy to pursue, in fact, the established Starrag Group ‘2020 Strategy’, and Walti lays out its three main themes. First is a high innovation rate that results in “sustainably great products”, measured by market share or new business won. The company invests 7% of revenues in R&D. Second is increased global footprint/size, with the US and Asia markets mentioned as having more potential, but that even in its strong European market there is yet more to go after, he suggests. This business is segmented in the 2020 Strategy as falling within aerospace and energy, transportation and industrial components, precision engineering and, finally, customer service (original segmentation announcement: https://is.gd/iralam). Across these, the group’s 2017 annual report stated that there is a market potential of around CHF 4.5 billion (£3.44 billion) – more than 10 times the current sales revenue. And third is operational excellence – being more efficient, getting more out of the group and better collaboration between sites. That does not mean portfolio or site reduction, the new CEO emphasises, but sharing of technology modules, or supply chain or overhead exchange, for example.


As for aerospace, with ever-increasing demands and with Starrag already at the “top of the ladder” in being able to satisfy existing needs, the new CEO sees nothing but opportunity in this particular sphere. And a guest speaker at the event, Italy’s Pietro Rosa TBM, underlined how and why Starrag is its production technology partner. Pietro Rosa TBM traces its roots to 1887 and New England Airfoil Products (NEAP) Inc, acquired in 2016, hails from 1955 and was, interestingly, set up by George Einstein, nephew of Albert Einstein.

Pietro Rosa TBM group produces LP and HP compressor blades, blisks and fan blades for the aerospace sector – for Rolls-Royce, GE and Pratt & Whitney – in the range 20 to 1,000 mm and which operate at -70 to 550 °C; it produces blades for other sectors, too. In Italy, this is high-mix, low-volume at a rate of 150,000/year, while the US sister site manages 250,000 in a low-mix, high volume setting and has an ambition of 500,000/year, says Mauro Fioretti, CEO of the family-owned Italian group. The $70 million turnover, 350-employee operation has four Starrag machines in the USA and six in Italy, having worked with the machine tool firm since the 1980s, following the addition of machining to its forging capabilities during that decade. With an order book of $600 million stretching forward 15 years and operating under cost-down pressures, it is working closely with Starrag on improving machining processes for its increasingly high value products.

Starrag's new CEO, Christian Walti, left, discusses turbine business with Pietro Rosa TBM group's CEO Mauro Fioretti

Pietro Rosa TBM group chief technology officer Andrea Maurizio highlighted a few key technology challenges. Hotter engine temperatures call for materials for compressor blades that are more difficult to form, machine and polish; more complex surface profiles and transitions, especially in compressor blades, call for advanced CAM programming skills within the company –

“a big part of the value of a machine is in the software that accompanies that”; advanced machine technology is required to meet the relatively new ‘surface abuse’ requirements, such as no distorted or torn grains, or recast swarf on the surface; that last one requires tooling that is “always in good shape, with sharp cutting edges and with tool life management important”; and, finally, automation, which is “key for cost competitiveness”. In terms of business challenges, Pietro Rosa TBM must support its customers with faster new product introduction that allows them to win in the available window of opportunity.

To deliver on all that and more, continuous innovation is necessary, Maurizio says, adding that for a company that is not a huge OEM, this requires the support of key technology partners, one of which is Starrag. And he characterises Starrag as a company that: offers “best in class” in this manufacturing technology area; has “a very responsive and experienced technical support”; can design and manufacture cutting tools in house and has “impressive” CAM programming and software capabilities. Summing up, he says that, regarding precision, he is “absolutely stunned about the results we can get from the machines”. And for high volume manufacturing of 100,000s of blades that is an increasing need, this will require methods that are even more special than before, calling for minimal human intervention and demanding that everything be fool-proofed, he says, adding that Starrag is again the right partner.

Maurizio also highlighted that for the future in such high volume production, machine-located sensors will be required to provide data that will support process stability. An Industry 4.0 theme, this is something Starrag machines already boast and have done for some five years now, with the focus on just that, maintaining a stable process such that all parts are good parts. This takes in sensors for spindle vibration, chatter detection, collision detection, temperature measurement/compensation and even strain gauges to identify tool push-off, for example.

Pietro Rosa TBM group chief technology officer Andrea Maurizio gets into some detail at the June event

Its Service plus service/machine purchase offering also falls within the Industry 4.0 world and rests on machine component lifetime performance knowledge, in-built sensor-derived information, Siemens CNC software (axis drive power consumption, auxiliary function time variation [tool change time] and frequency response) and so-called fingerprint tests (circularity, for example). Serviceplus sees companies offered three, five or eight-year contracts where no upfront machine investment is required, but where regular payments are made to Starrag, who has responsibility for maintenance and spares availability (high risk spares kept on site). An uptime guarantee, supported by a downtime penalty paid to the customer when established performance parameters are not met, operates. This approach is possible both for new and existing machines, the latter subject to a condition check. Globally the company has some 50 machines running like this in eight-10 customers, says Martin Finkeldei, head of customer service.


Another part of the company’s Industry 4.0 offer is its Integrated Production System (IPS), which has seven modules (https://is.gd/ayefiy). These range from the high level – its ERP-interfacing cell management software – to more detailed things – its Process Quality Control that avoids collisions via a 3D-modelled machine environment. But, as managing director Bernhard Bringmann explains, Industry 4.0, taking in such things as machine sensors, must solve customer problems, not just aim to fit the Industry 4.0 tag. “It’s really about functionality of the machine and customer benefits. For us, there are challenges where we see, for example, that we need to have higher process stability or quality. We undertake tests and see what the variation is, where does it come from, the dominant factor, then we develop countermeasures. Sensors and software are part of the toolkit that we use.”

CEO Walti agrees – making machines smarter and supporting users are key Industry 4.0 areas for Starrag, but when moving to the management side, MES and big data, cooperation with others is the more likely route. Starrag’s focus is very much on delivering cost-effective, high quality production, where there are large benefits to be had. As Bringmann concludes: “You may have a more-or-less standard process, but if you can optimise it with the right tool, coolant, fixture, strategy and so on, usually you can gain 30-40-50% increases in productivity. With everything under control, there is a gigantic lever for optimisation.”

Extended version from here:

Box item

Technology demonstration details

■First automated blisk cell – an FMS for the production of 2,700 of seven different types of blisk ready for assembly per year has been designed by Starrag that features additionally a cutting tool FMS. Cycle time per blisk is between 22-25 hours. The system takes in: 11 NB 151 machines (500 mm diameter blisk capacity); one component load/unload gantry; a gantry serving CMMs, grinding units, abrasive flow, washing, FPI line, shot peening and an engraving station; and one gantry that serves machines with tools from a central magazine. This central tool store is a critical part of the set-up as up to 40 tools/hour are required – a combination of the number of machines and tool life (some have a cutting life that is less than 12 minutes) conspire to deliver that requirement. Normally, Starrag wouldn’t be involved in this tool provision element of a system, the company advises. The central tool system is an FMS for tools, employing a robot to serve: a tool input/output station where new tools are manually placed for collection by the robot and worn tools placed by the robot for an operator; heat-shrink unit; presetter; two ANCA MX5 Linear tool regrinding units (tools ground while in their holders and measured in machine); plus, the central tool store that it loads preset tools to and unloads worn tools from. A manual tool setting station for high lifetime and uncommon tools also exists. This system will support at least one unmanned shift. There is complete redundancy within the system, with output maintained, should a processing unit fail. Cost for this set-up is approaching SFr30 million (£23 million).

■Blisk machining – an STC 800 MT machine (800 by 800 mm square or 800/1,000 mm diameter pallet, 2,000 or 2,500 kg capacity) was shown machining a multi-stage blisk (pictured). This had 21 aerofoils at 580 mm diameter and 44 at 560 mm. The key challenge was the achievement of a ± 30 micron aerofoil form tolerance and 0.8 micron Ra surface finish. No cutter toolpath step-overs were allowed, either. Special variable pitch Starrag milling cutters and Starrag-designed fixturing were employed. The latter avoided the use of foam infill, which is a method employed to fill space and avoid vibration or distortion.

The blisk machining demonstration highlighted Starrag's expertise in this area

■Toolchanging angle head – when machining casings, typically using an STC-style, ‘nodding-head’ machine, it is often necessary to employ more than one angle-head. With this new development – a joint one with Benz – a single head will now be able to replace multiple units as tools can be exchanged into the HSK-B63 spindle interface unit. The head unit mates with four toolposts on the machine interface side, with hydraulic clamping initiated. There are positioning posts, too. These are all covered during normal operation. In a milling example on 40CrMnMoS8-6, a 20 mm diameter solid carbide end-mill was run at 57 m/min, 0.13 mm/rev, 4.5 mm DOC, 19 mm width of cut to remove 40 cm3/min of material.

■Adaptive roughing for single turbine blades – this makes use of two in-machine probing routines. The first requires three points to be probed and aligns the blade via global axis shifting to give best fit between original forging and finish machined part to deliver more uniform material distribution and so reduce the number of cutting paths and avoid negative material potential. A second routine then identifies where material is, updates the existing Starrag RCS-generated NC program, allowing the first toolpath to be a safe metalcutting one. Use of standard face-mills that use round or square inserts is facilitated, avoiding the need for expensive shell end-mills with 90° inserts.

First published in Machinery, July 2018