This research deals with the Planning of Operation on a two-machine cell consisting of: a) a (NC) turret-mounted multi-tool punch, b) a (NC) shear. The cell treats sheet metal. The three-stage Process Planning model treats in a coordinated way the following problems: i) the lay-out of rectangular pieces on the metal sheets, ii) the positioning of clamps and the positionings of the sheet on the punch table, iii) the sequencing of punch hits. The overall objective is to reach an efficient trade-off between material waste and throughput. The approach is based on Combinatorics and Mathematical programming. Some results about the implementation of the model will be presented.