Deflection Compensations for Tool Path to Enhance Accuracy During Double-Sided Incremental Forming

Abstract

Incremental sheet forming (ISF) is a flexible sheet metal forming process that enables forming of complex three-dimensional components by successive local deformations without using component-specific tooling. ISF is also regarded as a die-less manufacturing process in the absence of part-specific die. Geometric accuracy of formed components is inferior to that of their conventional counterparts. In single-point incremental forming (SPIF), the simplest variant of ISF, bending near component opening region is unavoidable due to lack of support. The bending in the component opening region can be reduced to a larger extent by another variant of ISF, namely, double-sided incremental forming (DSIF) in which a moving tool is used to support the sheet locally at the deformation zone. However, the overall geometry of formed components still has unacceptable deviation from the desired geometry. Experimental observation and literature indicate that the supporting tool loses contact with the sheet after forming certain depth. This work demonstrates a methodology to enhance geometric accuracy of formed components by compensating for tool and sheet deflections due to forming forces. Forming forces necessary to predict compensations are obtained using force equilibrium method along with thickness calculation methodology developed using overlap of deformation zone that occurs during forming (instead of using sine law). A number of examples are presented to show that the proposed methodology works for a variety of geometries (axisymmetric, varying wall angle, free-forms, features above and below initial sheet plane, and multiple features). Results indicate that there is significant improvement in accuracy of the components produced using compensated tool paths using DSIF, and support tool maintains contact with sheet throughout the forming process.