Hemispherical stretch-expanding of aluminum sheet by computerized numerically controlled incremental forming process with two path method.

In order to reduce a tool-path schedule for hemispherical stretch-expanding of sheet metal, a CNC incremental forming process with two path method in which a hemispherical shell is stretch-expanded from a flat blank by means of conical stretch-expanding and the following hemispherical stretch-expanding in two continuous tool-path stages has been devised. Hard and soft aluminum sheets were stretch-expanded to hemispherical shells with diameter of 68 mm by using CNG incremental forming machine, and the deformation behavior was experimentally investigated. Experimental results showed that the success of the process depended much on the preventing condition of rupture and large deflection during the stages. It was, therefore, concluded that the proposed two path method was very useful for reduction of the tool-path schedule for CNC incremental hemispherical stretch-expanding of sheet metal.