Rapid EDM electrodes manufacturing by metallization of rapid Prototypes.

The development of Rapid Prototyping techniques opens new perspectives for Rapid Tooling. The combination of RP and Metal Spraying has been already proofed to be successful in producing directly moulds for low melting point materials. The attempt to move this technique to the production of steel dies has generally failed. A research aimed to the investigation of indirect rapid tooling techniques has been started. The purpose is to obtain an EDM electrode from a prototype and then using it to manufacture the steel die by EDM. Rapid Prototyping process considered in the investigation is Laminated Object Manufacture (LOM). In first attempt a metallic coating has been applied to the prototype by thermal spraying. In this case the distortion of the prototype can be minimised and delamination can be eliminated by a proper choice of growing direction of the LOM prototype combined with a proper set-up of spraying process including inclination of nozzle, thickness of the layers and cooling. Considering the geometry of the coated prototype this method led to unsatisfactory results. The main reasons is the fact that thickness of the coating can not be controlled and, therefore the resulting geometry of the electrode is different from the initial geometry. An alternative technique has been proposed which in principle can produce a sound electrode combining metal spraying with metal casting. In this approach the LOM object is a copy of the die instead of the manufactured part. A first layer of metal is applied to the LOM object by thermal spraying and then is filled by metal casting. A sound electrode is therefore obtained a used to manufacture the steel die. In this preliminary work simple geometry electrodes have been considered and tested in EDM process. Material Removal Rate and wear of electrodes obtained with different materials and techniques (metal spraying, metal casting) have been evaluated and compared with those of conventional machined electrodes.