Aerospace is among the more demanding applications for tube bending with manufacturing tolerances becoming tighter. Yet it’s still commonplace to see older-style hydraulically actuated benders in use. All-electric bending equipment from Unison Ltd. has helped GKN Aerospace produce tubular parts with as many as 19 bends, complex shapes with multi-radius coils, and bending titanium tubing with wall thicknesses (up to 2.6 mm) to cope with the high pressure systems on its customer Airbus’ latest double-deck A380 aircraft.
The tube bending facility fabricates around three to four thousand parts per week, using tubing ranging from a few millimeters in diameter to over 100 mm. The materials used include titanium, aircraft-grade aluminum, and corrosion-resistant steels which are expensive.
The company now uses a 65 mm diameter all-electric tube bender. The precision and repeatability of set-up with the servomotor-controlled architecture nearly eliminates scrap. The machine paid for itself in three months.
Bends are typically made to 1 mm 3D envelope accuracy – sometimes as tight as 0.3 mm.
The ductility characteristics of titanium, and in particular thin-wall titanium tubing, mean that slowing the bending process improves forming.
Servomotor control allows GKN to create bending programs that precisely control all aspects of the tooling’s speed and force, even at very low speeds.
The latest machinery installations are two combined left- and right-hand bending machines, which overcome a long-standing problem with specific component shapes. These include tubular parts with many closely spaced bends, and tubes with coil structures with the mechanical flexibility to accommodate flexing movement during the operation of wing flaps.
Work pieces can be transferred automatically from left to right hand tool heads as many times as required to bend the required shape in a single stage. Batch fabrication times have come down from three days to 1.5 hours for one of the coiled parts, and from 2.5 hours to just 30 minutes for a batch of the multi-bend part that involved switching machines.
Unison pioneered the concept of all-electric tube benders, and is the only UK manufacturer of this advanced type of forming machinery. Unison tube bending machines are available in the US from Horn Machine Tools.