Big parts, big challenges

Aerospace Manufacturing hears how Triumph Structures–Wichita keeps itself at the leading edge of machining technology in order to meet customers’ requirements for quality and on-time delivery.

When you’re making monolithic structural parts for commercial and military aircraft, few CNC machining centres are big enough for the job.

It’s why the company invested in the first Makino A6 in the US. With this 5-axis aluminium machining centre in production, Triumph says it has exceeded its goals in three ways: Lowered cycle times by more than 50% for aluminium parts previously processed on a gantry-style vertical machining centre; Reduced part changeover and setup times from hours to minutes on some applications due to the twin automatic pallet changers on the A6; Increased peak metal removal from 1,300cc per minute to more than 8,200cc per minute.

“We strive to be a world-class facility,” begins Kelly Eilerts, applications manager for Triumph Structures–Wichita. “We want not only to deliver on time with good quality, but we also intend to be world class through our processes and the way we cut aerospace structural parts. In order to do that, we obviously need to have world-class equipment to support that dream.”

Triumph Structures–Wichita is a division of Triumph Group, a global leader in manufacturing and overhauling aerospace structures, systems and components. In Wichita, Kansas, Triumph makes a variety of jet aircraft and helicopter parts and transports them to other Triumph facilities for sub-assembly before delivery to OEMs.

Triumph makes complex aerospace parts out of titanium and aluminium. Some of the billets start out as large as 1,360kg and 5.2m long. To machine such massive workpieces, the company continues to invest with Makino. Back in 2017, there were 18 Makinos installed including the A6, three T2 5-axis horizontal machining centres for landing gear trunnions and other hard metal parts, and 14 MAG3 5-axis horizontal machining centres for high-productivity machining of aluminium aerospace parts.

The T2 machines enable Triumph to machine titanium and steel parts at a cutting feed rate of up to 16m/min. They are able to efficiently mill titanium as a result of several advanced technologies, including an active damping system, rigid construction for enhanced performance, a high-torque, high-power spindle and a high-pressure, high-volume coolant system for increased speed and productivity.

The fourteen MAG3 5-axis machines, including both standard and MAG3.EX versions with a larger X-axis and pallet, run at 33,000rpm to machine wing ribs, wing spars, bulkheads, floor panels and stringers. An additional five MAG3 machines have been relocated from another Triumph facility and installed within a Makino MMC2 pallet-handling system to create a cell dedicated to wing ribs.

“With the combination of the MMC2 and MAG3 machines, we’re able to run large aluminium parts 24/7 with an overall equipment effectiveness of 85%,” states Eilerts.

For the largest wing skins, spars and ribs, Triumph had previously relied on a gantry-style vertical mill. While capable of producing parts that meet OEM requirements, the machine limited the company’s ability to grow along with the booming aerospace industry. Specifically, Triumph needed better thermal stabilisation to improve precision. The gantry-style machine is enclosed by four walls, but has no roof on its cabinet and thus no climate control, exposing the spindle, tools and workpieces to temperature changes in the shop. With programs having to be scaled to account for temperature variation, the process is slow and operators must take multiple temperature readings before, during and after processing.

In addition, the gantry-style machine has no external workstation for setting up pallets or a means of changing tools automatically. The spindle must be stopped each time a tool is replaced or parts are loaded and unloaded, resulting in unproductive time. The operators must shut down production and work inside the machining envelope.

What's behind all the power

While parts can be accurately produced on the gantry-style machine, it requires more time than on a high-speed horizontal mill like the A6. The vertical 60kW spindle on the gantry-style machine turns at 25,000rpm. The A6, meanwhile, is equipped with a 33,000rpm/118kW horizontal spindle.

“This speed and power upgrade enables Triumph’s operators to hog out metal on the structural parts in some cases as fast as 26,220cc per minute,” says Ricky Davis, director of operations at Triumph and a veteran of nearly 30 years at aerospace manufacturers in the Wichita area. “I’ve never seen a machine move metal that fast.”

To control thermal variation, which can affect tolerances, the A6 is equipped with its own HVAC system that pumps 45 tonnes of chilled air into the machine enclosure to keep the work envelope as well as the bed casting and the automatic tool changer at 20°C. Coolant is automatically chilled or heated as needed to maintain the spindle, tooling and workpieces at a constant temperature.

“The gantry machine is much larger, but the temperature taken at the beginning of machining is not going to be the same as the temperature taken at the end,” Eilerts explains. “That can introduce a lot of variables. Heat from the machine itself is added as it’s moving. Coolant temperature changes, which affects the temperature of the part. With the A6, all of these variables have been removed. That makes it much easier for us to machine large parts accurately and consistently without having to scale our programs.”

What really influenced Triumph’s decision to invest in the A6, however, are the opportunities the machine creates to improve productivity.

The A6 is equipped with two worktables outside the machine. This design enables operators to set up pallets with any combination of jobs, which currently feature four versions of wing skins and spars for those wings, a wing rib and three versions of helicopter floor panel. Ergonomic worktables are lowered into a horizontal position to enable operators to bolt and pin workpieces into position safely and comfortably. Once setup is complete, the worktable is raised into a vertical position and is ready to be moved into the A6 as soon as processing of another part finishes.

Triumph takes full advantage of this capability. The company runs two 12-hour shifts on weekdays, with one operator scheduled on the A6 during each shift. Before weekend shifts, jobs are set up in advance and are ready to be run by an operator, who is also able to run other machines on Saturdays and Sundays.

“That’s where the multiple tables come in handy, because we are able to use our limited resources on a weekend to unload and reload a part while the machine is still running,” says Nick Raffety, the lead A6 operator.

Equipped with an advanced Makino control, the A6 also can be programmed to shuttle loaded pallets automatically in and out of the machine, freeing up operators to handle other tasks. Triumph also equipped the A6 with Makino’s MPmax software to monitor the machine’s performance, including what programs it runs, cycle times, tool change times and utilisation rates. MPmax can alert operators and managers to issues or when it’s time for a part change. This is just one way in which Triumph’s team is continually learning and implementing new features to expand unattended operation.

High speed, high quality

Investing in an advanced aluminium machining centre with the capabilities of the A6 is a significant business decision. Triumph made the commitment in no small part because of the capacity the horizontal machining centre adds to its Wichita facility. The company had one customer in mind when considering the investment and selecting the A6 to make wing skins and wing spars for a specific commercial platform.

But Triumph now uses the A6 for so much more. In the first four months of production on the A6, the company was able to move additional parts from the slower gantry-style machine onto the A6, as well as win new commercial and military orders. Faster cycle times that result from the speed and power of the A6 in addition to productivity gains from having two pallets are both key.

“We’re able to do things so much faster than we anticipated that we’ve put ourselves in a position to realise a full return on investment within just a few years, faster than we had anticipated,” says Eilerts.

Some of the faster production can be attributed to the control on the A6. Most of Triumph’s T2 and MAG3 machines use the same type of control system, making it easy for operators to learn quickly how to run the A6 without extensive training. Triumph also has standardised on 121 tools in the A6’s magazine and collaborated with Makino’s aerospace engineering team to revise and standardise programming. With Makino’s engineers, Triumph focused on developing new machining methods and manufacturing processes to make full use of the A6’s features. The result is not just speed but also precision and quality, with repeatable tolerances of ± 2.5µm and surface finishes of 32Ra. The need for secondary finishing has been reduced as a result.

“The parts coming off the A6 are in the 30Ra range or better, which is four times better than our customers require. It’s very impressive to hold that kind of surface finish with the feeds and speeds we’re running at,” notes Eilerts.

Because of this combination of speed, precision, repeatability and high quality, the A6 enables Triumph to expand its relationships with customers and to pursue new customers. The A6 keeps Triumph Structures–Wichita on the cutting edge of manufacturing technology and learning new ways to make better aerostructural parts for less cost.

“We have a lot of other parts we could run on the A6 and reduce our cycle times by 40-50%,” Davis concludes. “We’re just getting started.”

NCMT is the sales and service agent for Makino in the UK.

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