Faster inspection of aerospace fabrications

When Gardner Aerospace won the contract to supply the outer fan duct assembly for the new Honeywell AS907 engine it needed a new method of inspecting the complex machined aluminium casing.

When Gardner Aerospace - Ilkeston won the contract to supply the outer fan duct assembly for the new Honeywell AS907 engine that powers the Bombardier Continental executive plane, the company needed to find a new method of inspecting the highly complex machined aluminium casing.

Not only was its size - 1040mm diameter by 775mm long - too large for the existing manual co-ordinate measuring machine (CMM) on site, but in any case several days would have been needed to record all the measurements.

So in September 2001, a new LK G90-C CMM with a 2000 x 1500 x 1000mm measuring capacity was installed for taking the 1200 inspection points automatically, a task which it completes in under two hours.

A further reason for upgrading the inspection equipment was the insistence by GKN Aerospace and Honeywell on using the Catia model as a master.

In addition, SPC reporting was a future requirement.

Both requirements are easily met using the relevant software packages from LK.

From the outset it was decided that the new CMM would be part of the shop floor environment and driven by the machine tool operators.

When a component is machined, an operator places it on the granite, selects the relevant inspection programme using LK's Launchpad software and goes back to carry on machining the next part.

A couple of hours later he returns to pick up the results.

However if it is a first-off, the results are checked before continuing the batch run, which is typically between five- and ten-off.

Not only does this empowerment increase the level of interest for the shop floor workforce, it also reduces the number of staff needed in the inspection department.

Programming the CMM is carried out automatically from the solid CAD model; it is not practical to inspect older products for which only drawings are available.

In the case of the outer fan duct assembly, Honeywell supplies to Gardner Aerospace a component model in the Catia CAD file format, which LK's software uses to create the part program online or offline.

A like-for-like comparison of the speed of the new CMM versus manual measurement is available.

Chris Hood, Engineering Manager at Gardner Aerospace, said " We have now put further components on the LK G-90C, such as a combustion outer casing assembly made from Inconel and supplied to Rolls-Royce for the Trent 800 engine that goes into the Boeing 777.

"It is 950mm in diameter by 700mm long and previously took up to 3.5h to inspect manually using conventional metrology equipment.

Now the 250 inspection points are taken on the LK in just a third of the time, thanks in part to the 48m/min vector velocity of the machine.

There are 35 assemblies in regular manufacture and all components will eventually be put on the LK, plus subassemblies as well".

After parts have been inspected, a report is printed out that accompanies every part sold.

This is another benefit of the LK package, whose reporting software is able to generate hard copy automatically from the measured results, including graphics taken from the CAD model to maximise clarity of the information.

This helps checking by the operator, who signs to say the part is good, and also assists the customer during routine assessment of delivered components.

Hood concluded, "Installation of the LK CMM will help us to cut delivery lead times to our customers, which include GKN Aerospace Services, Nozaki, Dowty, Alstom Power, Westland Transmissions and Kaveri.

Already in the case of Rolls-Royce we currently meet 85% of their OTIF (on time in full) requirement; and in the specific case of their combustion casing, we have cut the lead time from 46 to 42 weeks".

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