Boeing's new fuel tanks inspected on LK C.M.M.

Citation

(2002), "Boeing's new fuel tanks inspected on LK C.M.M.", Aircraft Engineering and Aerospace Technology, Vol. 74 No. 5. https://doi.org/10.1108/aeat.2002.12774eab.008

Boeing's new fuel tanks inspected on LK C.M.M.

Keywords: Aerospace industry, Fuel systems, Boeing

Founded in 1909, Cambridge-based Marshall Aerospace is one of UK's leading privately- owned aerospace company, specialising in design, development, maintenance, modification and conversion of military, civil and corporate aircraft. One of its current contracts is to manufacture the auxiliary fuel tanks that are fitted to Boeing's new' Longer Range 747–400' models. To guarantee the quality of the component parts it machines, Marshall inspects them on a computer- controlled CMM (co-ordinate measuring machine) built and supplied by LK (Plate 5).

One tank was delivered to the aircraft manufacturer's Seattle plant in April (2002) and a further four are to be made this year, including two test tanks. This work is typical of the larger assemblies now being produced by the division within Marshall that provides hangar support to in-house projects. Third party manufacture was consolidated three years ago into a separate division which took with it the Stiefelmayer CMM that LK had previously upgraded.

Plate 5 A tank diaphragm for Boeing's new "Longer Range 747400" aircraft being inspected at Marshall Aerospace, Cambridge, on a computer-controlled CMM built and supplied by LK

At the time, hangars were supplied with only relatively small components and assemblies that could easily be inspected using conventional metrology equipment. Any larger parts were sent across to the other division's CMM or subcontracted out for inspection. However, the in-house division's policy was to move into the production of larger size work, to which end it recently purchased a 3-axis DMG vertical machining centre that represents a quantum increase in working envelope compared with the other machines on the shop floor.

An LK CMM was chosen to support the quality control objectives of the division. Marshall's Manufacturing Support manager, Kevin Patterson, commented that this supplier was chosen as a result of recommendations from its customers, in particular Boeing and BAE. LK has installed many computer-controlled CMMs in use by these two aerospace giants world-wide.

Already 20 per cent of parts, around 100 so far, are inspected on the new LK G-90C machine, which has a nominal measuring capacity of 2.5m x 1.5m x 1m. However, after the planned move from single- to two-shift working in the metrology department, that proportion is expected to rise steeply. In addition to inspecting machined components like the Boeing tank diaphragm (pictured), the CMM is also used to reverse-engineer manufacturing jigs and fixtures on which features need to be accurate to less than one thou in this way, exact copies may be made in the future rather than relying on machining the ICY fixtures from the original drawings and risking the introduction of slight variations.

Aircraft component tolerances are generally no tighter than +0, 5 thou, although in the case of parts that are mounted vertically for all-round inspection, such as the diaphragm, limits are in practice tighter. Craig Oglesby, deputy workshop manager, advises that they are effectively working to 2 thou under such circumstances, but even this tolerance does not even begin to tax the new CMM's capabilities, which has a claimed measuring accuracy of 2.5+L/200microns.

LK software supplied with the machines includes the company's proprietary CAMIO package, enabling CAD data, principally from CATIA, to be imported directly to the CMM's. The result is said to be the much faster programming of measuring routines for those components that exist as electronic models rather than drawings. Production of reports supported by graphics is easier and far quicker as they are complied automatically from the inspection results. This is virtually a requirement now in the aerospace industry for first article inspections and during spot check audits by customers. Reports are also useful if there are any out-of-tolerance issues to be resolved, as all concerned can have access to the printout.

Meanwhile over in the "third party" division, Malcolm Roberts, the manufacturing manager who inherited the LK-upgraded CNC Stiefelmayer CMM and another manual measuring machine of the same make, also benefits from CAMIO and reporting software. He agrees that they are ideal for full, first article inspection and help considerably when troubleshooting an out-of- tolerance situation.

Moreover as 1- and 2-offs are the norm, and 15 is well into the realms of a production job for Marshall, the ease of CMM programming from CATIA and occasionally CADDS5 data translates into an enormous time savings over the course of a year.

Concluded Mr Roberts, One of our current projects is the production of BAE Systems Nimrod wings, which we started making three years ago. It was noticeable that when we really got to grips with the capabilities of the upgraded CMM, the wings fitted together better than I have ever seen before.

"The same goes for Airbus A380 and 400M test panels and most other assemblies we manufacture. In fact our CNC measuring machine is in such demand that it has run virtually continuously during the day shift plus regular second-shift working ever since it was upgraded."

Details available from: LK Limited. Tel: +44 (0) 1332 811349; Fax: +44 (0) 1332 850149; E-mail: sales@lkuk.co.uk; Web site: www.lk-cmm.com