When Saab-BAE Systems needed to redesign the Gripen fighter landing gear and streamline its assembly for the export market, it found that simulation proved even more powerful than it imagined. Brian Tinham explains.
Saab-BAE Systems, the aerospace and defence joint venture set up in December 1999, reckons its saved tens of thousands of pounds and hundreds of hours of assembly time on landing gear for the Saab Aerospace-developed Gripen swing-wing supersonic jet fighter, recently redesigned for the export market.
With six now built at BAE Systems’ Brough site, the company says it has proven substantially new design and manufacturing concepts, and achieved even more than the anticipated benefits all the way from concept to streamlined assembly for the new aircraft. It also met tight delivery schedules for first orders, and took Bronze medal in the company’s Chairman’s Award for Innovation.
The design and construction of the Gripen landing gear are critical: they are complex assemblies, involving large numbers of components (including an integral fuel tank) and lengthy assembly times. The story starts back in January 1996 when BAE at Brough took on the Gripen main landing gear build work as part of an exchange with Saab in Sweden, using existing drawings and legacy components.
“We could see the potential for cost savings even then,” says project leader Andy Davidson, manufacturing and engineering specialist with BAE Systems. And indeed when Saab began to push the fighter into the export market, costs started coming under more scrutiny. So in 1997, BAE Systems began an exercise aimed at cutting the cost of the airframe by 30%. Davidson: “We had our own high speed machining experience, so we set up a small team led by myself and set out to reduce the parts count and the manufacturing time.” It meant first reviewing the components themselves to design less, but larger, more complex components.
The project then developed. “We wanted to halve the parts count and cut cycle time for the whole unit by about 20%,” explains Davidson. “And as this was supposed to be a fourth generation fighter we wanted to design it on Catia using modern 3D solid modelling techniques.” Coincidentally, to launch the fighter for sale around the world, Saab also needed to increase its guaranteed flying hours from 4,000 to 8,000, so Davidson’s redesign work was easily justified on the requirement to improve structural integrity.
At the end of 1998 Davidson’s team of three from Brough and three from Saab Aerospace got the go-ahead. “We knocked up schematics on Catia, then showed these to our high speed machining experts,” he says. “We went through the whole redesign phase like this, involving manufacturing and engineering together. And we modelled everything, including the legacy components that weren’t going to change, in 3D on Catia.”
At this stage Davidson knew that simulation would be useful from a design to manufacture point of view. “You can model components in space in Catia,” he comments, “but you can’t see how you would assemble them or how you would get the tooling in there. And any errors or problems, like collisions during construction, would have meant ‘job stopped’.” Which is expensive: a delay in the landing gear assembly not only costs time and money while problems are investigated and remedial work undertaken, but can also hold up construction of the rest of the aircraft.
It was at this point that Davidson stumbled across Tecnomatix simulation software at Saab: it had been used to do a nose cone fit on the Saab 340, he says, although not much else. “In 1999 we got agreement from the Board to use it to streamline the assembly process of the Gripen landing gear, and make it a real showpiece project,” he says.
Early last year, the team began creating the simulation, with the Catia models being imported into Tecnomatix’s eM-Workplace ‘virtual factory’ system. “It was a very, very large simulation. We had good help from Tecnomatix: they’d never used it in anger for this size and complexity of simulation – 200 components and all the tooling showing the whole unit being assembled from start to finish. So there was a lot of information, and we helped them to refine their software as we went.”
In all, it took six weeks to develop, verify and optimise the new build philosophy. “Then we stumbled on another benefit,” says Davidson. “Estimating: our estimating man saw what we had done and said that would be brilliant for him – more accurate and cut out the ‘guessing’,” which on something of this size and complexity could make a significant difference.
It did: “He estimated cost of the materials, the tooling and the impact of the learning curve for its assembly on the shopfloor – and on the first unit he came in within hours on a job that took many hundreds!” Indeed, the system is now being used more widely in BAE Systems’ manufacturing – for improving over manual methods in estimating time to complete an assembly and for investigating different scenarios to optimise build processes.
But there was still more. Since the new design and build approach was going to be a complete change for the fitters (who by then had produced about 70 of the old Gripen assemblies), Davidson’s team also harnessed the simulation software to produce PC-based 3D graphical self-help training and assembly aids on CD-ROM, with a view to cutting down the shopfloor learning curve.
“We involved the shopfloor fitters and assembly guys, and said ‘does it look OK to you? What do you think?’ They thought it was great. It was going to be much better than just new drawings being dumped on them. They would have pictures available at a PC right on the jig: so we got their ‘buy-in’. They were amazed at being able to see 3D components on the screen – it made them so much easier to identify. And we were able to optimise the detail in the simulation for them.”
In June last year the first unit was built. Davidson says the result was excellent. Component count was cut to 40% (from 350 to 160), 2,000 fasteners eliminated (with further savings in specialised sealing for the fuel tank) and assembly processes were right first time – all collisions and job-stop situations had been identified and dealt with prior to hitting the shopfloor. Also, manufacturing cycle times had been reduced by 18%. “It was more than 100 hours; a massive saving.”
Davidson says shopfloor managers and staff are delighted with the combination of paper drawings and the mpeg animations from the ‘virtual factory’ simulations. The team describes these as ‘an automated Haynes manual for assembly’, he says. The ability to visualise components on the shopflor has given them a much better insight into what’s required.
Altogether, Davidson says it was a project to be proud of. “The scale of innovation wasn’t just the simulation; it was BAE Systems, Saab Aerospace and Tecnomatix all working together to build this package for a large complex assembly and the whole manufacturing process – and installing it on the shopfloor on PCs.”
Author: Brian Tinham