A process planning problem typically encountered in flexible manufacturing systems treating laminated material (e.g. metal sheets) is modelled and solved. In such production systems computer controlled clamps hold the material on a work table. Sheet repositioning represents an important proportion of the processing time. The models developed in this paper give, under various operational conditions, a minimal set of repositionings. The first formulation of the model calls for a medium-size mixed-integer programming problem. In a subsequent reformulation, the real life problem is reduced to a set of simpler linear programming problems. Illustrations of the method, as currently implemented on a FMS are provided.