M. Fonte, Tufts University, Medford, MA

Summary:

Flowforming is an advanced, net shape, cold metal forming process employed for the manufacturing of dimensionally precise, rotationally symmetrical, hollow components. The process is of particular interest in the manufacturing of precision tubular components that have large length to diameter ratios, made with thin walls and require high degree of dimensional accuracies.

With the price of materials substantially increasing, being able to form to net shape makes sense, now more than ever. Alpha-beta Titaniums, nickel based alloy, high strength steels and high strength aluminums are excellent flowformable materials. The process substantially reduces input material requirements, while reducing secondary machining operations. Much less material is required with flowforming, allowing for cheaper parts even with the more expensive materials.

A cylindrical work piece “preform” is attached to a rotating mandrel. Three CNC-controlled rollers, spaced 120 degrees apart, hydraulically compress against the outer diameter of the preform. The rollers, mandrel and preform are all rotating. The desired geometry of the flowformed tube is achieved when the preform wall thickness is compressed above its yield strength and plasticized “made to flow” in the longitudinal direction onto the surface of the inner mandrel. As the preform material is thinned out and lengthened onto the mandrel, preforms are formed into seamless, very round and concentric tubular-shaped products; with increased mechanical properties from the cold work, refined and realigned grain structure, oriented crystallographic texture and excellent surface finishes, all with repeatable accuracy.