INTRODUCTION OF FLOW FORMING
Flow forming is a chipless cold forming method which is used to manufacture dimensionally precise, round seamless hollow components.
In flow forming; a hollow axis symmetric preform is fitted to a mandrel. After both are made to rotate, compression forces are applied to the outside diameter of the preform by hydraulically-driven or ballscrew-driven CNC-controlled rollers. For most applications three rollers are used.
By a pre-calculated amount of wall thickness reduction, in one or more passes, the material is compressed above its yield strength, plastically deformed and made to flow. The desired geometry of the workpiece is achieved when the outer diameter and the wall of the preform are decreased and the available material volume is forced to flow longitudinally over the mandrel.
Cross-sectional wall reductions for most materials are in excess of 90% of the starting wall thickness. Typically, the preform can be flow formed up to six times its starting length before a need for reannealing of the metal is required.
The inside surface quality of the finished workpiece is almost same with the outside surface quality of the mandrel.
Flow forming process has two typical types which have been appeared due to fixing necessities of preform shapes.