Saturday, May 4, 2013

Manufacturing Technology - Aerospace's Secret Sauce

Manufacturing Technology - Aerospace's Secret Sauce:
When we on Aviation Week mention advanced manufacturing, we tend not to explain what we mean in much detail, or show what some of these technologies look like in action, so I thought I would take the time to walk through some of the main advances in composites and metallics manufacturing that are changing how aircraft are made.
One of the first of these was automated tape laying (ATL - video below), which has taken over from time-consuming manual lay-up for large carbon-fiber components that are flat or have simple curves. An ATL machine lays down a single, wide carbon-fiber prepreg tape, the machine head pressing the tape against the tool to consolidate the layers of material.

More recently, manufacturers have made increasing use of automated fiber placement (AFP), which does not deposit material on the tool as fast as ATL but can be used to make smaller, more complex parts more precisely. AFP (video below) uses narrow carbon-fiber tapes called tows, which can be steered across the tool to align the fibers with the loads.

Moving over to metallics, perhaps the most noticeable shift over the years has been away from riveting together many sheet-metal parts to machining single-piece structures out of solid metal. Where sheet metal is still used, techniques have been developed to minimize the manual assembly task and so reduce the time and cost to produce a component.
Airbus has pioneered the use of laser beam welding (video below) to join stringers to skins to produce fuselage panels, speeding up the joining process from 0.15-0.25m/min for riveting and sealing to 8-10m/min for welding. Skins and stringers are formed to shape before welding, but Airbus has developed advanced aluminum alloys than can be welded flat then creep-formed to final curved shape.

Chemical milling has been used for decades to remove metal from sheet-metal panels to reduce their weight, but environmental issues with the hazardous chemicals and the need to reduce cycle times to increase production rates is driving a shift to machining. This requires specialist machines (video below) that can support one side of the curved panel while material is being removed from the other.

Throughout aircraft manufacturing, there is a trend towards automation and the use of robots. Large fixed auto-riveting machines are common, and industrial robots are beginning to be used to join aircraft sections in final assembly.  But one unusual application is a small crawling-drilling-riveting robot (video below) used by Airbus in the assembly of fuselage sections for the A380.

Developed with Spain’s MTorres, the so-called Flexible Drilling Head “walks” over the curved fuselage panel, holding itself in place with suction cups on its feet. The 220lb robot locks itself into position, drills a hole, inserts a rivet, then releases itself to move at a speed of 3.5mm/min to the next position. The machine is used to drill 8,500 holes in fuselage Section 19.
Thanks to MTorres for the videos (if you can excuse the music!).
Read more about new advances in manufacturing technology in the latest issue of Aviation Week & Space Technology. One of the technologies featured is linear friction welding (LFW), which is a technique to join metal parts by forcing them together and oscillating them until they fuse into a single component. LFW already is being used to join blades to disks to produce titanium compressor blisks for turbine engines, dramatically reducing the final machining required.
Linear friction welding also is being developed as a way of producing near net-shape preforms that can reduce substantially the material waste and machining time involved in producing complex structural parts from expensive aerospace alloys. LFW is used to fuse together simple waterjet-cut shapes to produce a tailored blank that is them machined to final shape, as this Aviation Week video illustrates.

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