Case Studies: Mobile Metrology Evolves
Airbus-Broughton manufactures every wing variant in the Airbus product line, including the new A380, at its site near Chester, UK. Around 140,000 jobs are generated in the UK by Airbus wing work, directly and indirectly through supplier contracts. Providing work for more than 7,000 people, Airbus is the largest employer in Broughton, North Wales.
Over the past decade most of the Airbus tooling has been designed using a 3-D CAD package. Using digital CAD models has allowed the company to go gageless and recertify these tools using noncontact measurement systems such as the laser trackers. More than 100 laser trackers manufactured by Leica Geosystems (St. Gallen, Switzerland) are in use at 16 Airbus production facilities in France, Germany, Italy, Spain and the UK. The Broughton plant alone uses seven laser-tracking systems to perform recertification and modification jobs.
A laser tracker is an industrial metrology system used for manufacturing and engineering applications, such as design validation, build-and-inspect, confirmation of close tolerance work, part alignments and part mating, and on-demand data acquisition. The device is a light, portable coordinate measuring machine (PCMM) with tracking facilities that reside on a specially designed cart. A high-speed tracking, 3-D laser interferometer and precision angular encoders deliver a measuring rate of up to 3,000 points per second, with a measurement distance up to 40 meters when used with a corner cube reflector.
The Leica portable measurement systems are distinguished by their stability and minimal maintenance requirements. These characteristics support mission critical goals at Airbus like honoring delivery dates.
"One hour of equipment downtime may only cost me £45 in labor costs, but one hour of downtime to a major airline is worth many thousands of pounds due to the lost revenue if the aircraft is not in service," says Graham Tudor, tooling operations manager at Airbus.
The wings on any aircraft are extraordinarily complex and the most crucial element in the entire construction.
Tooling requirements are immense due to the number of the complex parts going into a wing assembly, and the need to maintain extremely tight tolerances of about 0.25 millimeters over the entire length of the wing. The wing assembly takes place in large jigs that can reach the height of several stories. Individual jigs may have hundreds of tooling points that must be in perfect alignment with each other.
To meet the challenges of precision alignment, part mating and quality assurance, Airbus added a Leica T-Probe to their metrology arsenal. This wireless, handheld probe with six degrees of freedom can be used to accurately measure inside deep parts and tools. The probing device works in tandem with a laser tracker to provide a streamlined approach to data acquisition and dimensional control in assembly tools.
"Leica equipment has taken us away from the conventional tooling business and has made recertifications and modifications our core competence," says Tudor. "We are using the laser trackers plus the new Leica T-Probe for that innovation, and are registering savings in the region of 30 to 50% in both time and money.
"Recently, we had to rework an A340 wing. We were requested to move the wing back into the jigs to repair the fault, which had never been done before. We had recertified the jigs using the Leica laser technology and were able to put the wing into a different jig other than the one in which it was originally built. Bringing the wing into a different jig with absolutely no modifications or adjustments was only possible because of the tolerances we had achieved when we did the recertification," concludes Tudor.
Alan Minshul, Airbus tool engineer, adds, "One of the frustrations has been that our legacy tooling still has to be checked using conventional methods. With the introduction of the Leica T-Probe, we can go gageless there as well, thus allowing us to recertify these tools up to 50% quicker. In a way, the probe is the evolutionary missing link that we have been waiting for all along."
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