TPT May 2007

T ube B ending, H ydroforming & E nd- Fo rming

88

Bending sleeves are cut to size and placed into the tube assembly along with grounding spacers using a proprietary set- up method. Following the bending process, tubes are visually inspected for defects. They are then degreased and cleaned, the inner tube ends are trimmed to length and fittings are installed. Results with Wolfbend are much more consistent than for hot wax and scrap rates are closer to single wall tubing,

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The sleeve is a proprietary Teflon formulation that is very good in compression and also stretches and cold flows well in tension

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primarily because the physical characteristics of the bending sleeve are better suited to the purpose. The sleeve is a proprietary Teflon formulation that is very good in compression and also stretches and cold flows well in tension. Combined with the self lubricating properties of Teflon, this leads to good tube wall flow and consistent bend support. Typical design gap is 1 / 8 ", ie a 1.00 OD inner tube requires a 1.25 OD outer, and smaller gaps can also be bent. Bend defects such as wrinkles and ovality tend to mirror between tubes, simplifying

› Wolfbend technology uses a bending sleeve that fills the gap between tubes but remains in place after bending

Wolfbend™ was developed for aircraft fuel lines but it has already found new applications meeting SFAR 88 safety requirements for wiring conduits in fuel tanks. Its design, safety and manufacturing advancements may find application outside aerospace in industries such as petrochemical and pharmaceutical process piping, heat exchangers, and submarine and ship systems. Davis Aircraft Products Co Inc is the exclusive Wolfbend marketing licensee and it is currently used under sublicense by Bombardier, Cessna, Mitsubishi Heavy Industries, Aerospace Industrial Development Corporation (Taiwan), Aero Arc (Torrance, California), BHW Components Ltd (Lancashire, UK), GE Elano Canada, and OSM Partners LLC (Savannah, Georgia). This article was supplied by Mr Rick Rohrberg, vice president of Engineering at Aero Arc Inc, and Mr Larry Wolf, president of Wolfbend LLC. Davis Aircraft Products Co Inc – USA Fax : +1 631 563 1117 Email : ddavis@davisaircraftproducts.com

inspection and eliminating the need for X-ray. The processing time for Wolfbend is typically a few hours. Aero Arc Inc, USA, manufactures double wall tubing for the Boeing 717 and C17 using the hot wax process and for Bombardier Regional Jets using Wolfbend. Mr Rick Rohrberg, vice president of Engineering at Aero Arc, says, “The Wolfbend bending sleeve is much better than hot wax because it’s fast, easy to use, and works well. The phenolic spacers used with hot wax are only in straight sections and fit loosely which can allow the tubes to resonate. The Wolfbend sleeve is secured tightly by bending and gives support in the bends where it’s needed. The Wolfbend™ grounding spacers are also a great feature. The hot wax method requires the tubes to be independently grounded with straps at installation. With Wolfbend the grounding is incorporated and it really simplifies things.” Aero Arc Inc, based in California, is an aerospace component manufacturer specialising in tube bending, sheet metal, machining, and welding since 1982. Aero Arc also manufactures PMA licensed tube and duct assemblies for MD/Boeing aircraft.

Aero Arc Inc – USA Fax : +1 310 381 0173 Website : www.aeroarc.com

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M ay /J une 2007