Flexible dieless forming - Incremental Sheet Forming

Incremental sheet forming (ISF) is an umbrella term for a range of processes in which a sheet is formed incrementally by a progression of localised deformation. The key advantage of ISF over conventional sheet forming processes is that specialised dies are not required; a wide range of shapes can be achieved by moving a spherical-ended indenter over a custom-designed numerically controlled tool path. Hence ISF is ideally suited for small-batch-size or customised sheet products. The wide range of potential applications includes bespoke medical implants, architectural features, specialised laboratory equipment and parts for specialist vehicles.

ISF is considered a sustainable manufacturing process because a relatively small and light-weight machine can be used to form sheet metal whilst avoiding the material expense of specialised dies. In addition, ISF can be used as a local production process, avoiding long transportation distances. Re-work or re-forming of old products are further capabilities offered by ISF, which is less energy-intensive than re-melting the material.

One of the most widely researched forms of incremental forming is called ‘single-point incremental forming’ or SPIF, in which a sheet is clamped rigidly around its edges but unsupported underneath and formed by a single spherical-ended indenter. Other variants of the process exist and are widely referred to as ‘two-point incremental forming’ or TPIF, in which the sheet is formed against full or partial dies using one or more indenters. Further variations include the use of a water jet or a combination of water jet with shot as an alternative to the solid indenter, as demonstrated by Iseki. Although TPIF offers the advantage of improved control of the deformation and hence improved geometric accuracy through physical constraint of the sheet, it is less flexible than SPIF because specialised tooling is required. Hence the research at Cambridge University has focussed on improving the capabilities of SPIF, therefore avoiding the use of specialised tooling.