Danny High

We used to have tools ( templates ) that would lie over the beam and the mechanic would drill the hole by hand , said Danny High , Boeing metrologist.If we had 1 , 000 different beams then we would have to have 1 , 000 different tools..

The drilling machines use a laser to orient the part.This is important because the beams are made from aluminum extrusion that can vary in size and thickness.The aluminum tends to bend and bow when extruded.We found that if the machine is correct and the beam is off , the parts have variations , he said.
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That surface is the floor of the airplane , said High.

After exiting the drilling machines , wire management holes are routed and grommets are installed.A pneumatic tabletop machine used to install grommets replaced a large floor model that required extensive material handling to get the beam to the machine , set up the job and take it back down again.Also , the previous machine wasn't automatic , so inconsistencies crept into the process.

With the automated machine the grommets are all consistent.With the old system , if somebody put them in and drove them by hand they may vary in height.
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If I take the part off and move it to a CMM , we could reject it , even though it is a good part , said High.

To get around this , a touch trigger probe is affixed to an automatic tool changer on the milling machine itself.First the operator qualifies the probe on his machine , said High , and then he verifies hole locations , edge margins and the profile of the part before it goes to skin assembly.The idea is to catch errors before they impact assembly..

The machine also uses sensors on the gantry and other strategic points for real-time thermal compensation.Because aluminum grows twice as much as the steel drilling machine , there had been problems in assembly.We couldn't cut the parts to net because of thermal growth , said High.The machine grew at one rate and the aluminum grew at a different rate.We always cut them to the difference between the two rates.We always had to leave excess on the parts , and then trim it off as part of the assembly process.We can save up to 30 minutes by net trimming the part..

To ensure quality , Boeing uses a philosophy of inspecting the process instead of just the product.
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Also , tests are run daily to monitor the health and accuracy of the fourth and fifth axis of the machine tool , which are usually the weakest axes on any machine tool , said High.Inspecting the product after it is made does not add value , it just tells us if we did a good job , said High.Inspecting the process before we manufacture the part helps minimize errors in the final product..

Putting the pieces together

That extreme accuracy during fabrication pays dividends in assembly.Assemblers start with the cockpit nose section and join it to the top and bottom halves of the fuselage.

To control the temperature in a building that massive would cost millions and millions, said Danny High, quality manager at Boeing.We use sensors to track the temperature changes..

Boeing has taken into account the exact environments in which individual measurements are taken, something that experts say is critical for more accurate measuring.Knowing the characteristics of each area in the factory, even where the machine's exhausts are released, can play a key role in reducing temperature inaccuracies.A large factory may have 10 different environments.