A 3D finite element program, PLAST3, has been developed for the dynamic simulation of the ironing process. The code is based on a dynamic explicit method, designed for large deformations, non-linear material behaviour and uses a forward Lagrange multiplier method for the contact treatment between deformable bodies. The presented contact algorithm uses contactor nodes and target surfaces described by four-node quadrilateral elements, as the 3D element used is an isoparametric hexahedra. An elementary target surface defined by four nodes is decomposed either into four triangular facets with a CO continuity or into a bicubic Ferguson patch with a C-1 continuity across the adjacent boundary. The problem formulation, the contact algorithm and the target surface discretisation are detailed. Later simulations of ironing process are carried out in order to investigate the influence of the various friction coefficients and target surface interpolation used. Results of the global forces on the sheet, the local normal and tangential contact stresses and the equivalent plastic deformation during ironing are presented.