Hybrid Additive Manufacturing of Silver Collector Coins: An Experimental and Numerical Case Study

This paper presents a new hybrid additive manufacturing approach to design and produce innovative collector coins from customized blanks with asymmetric, small, intricate holes that cannot be obtained from blanking, laser, or water jet cutting. The approach starts with the construction by laser powder bed fusion of the cylinders from where the individual blanks are obtained through wire electro-discharged machining. The individual blanks are subsequently polished and subjected to a coin minting operation to emboss the final letters, details and finishing of the designs. Experimental tests in a press-tool system and numerical simulations of the coin minting operation using an in-house finite element program were carried out with a case study developed in collaboration with the Portuguese Mint. The combined numerical and experimental investigation allows validating the developed approach by proving its feasibility for the production of high value-added silver collector coins aimed at redefining the standards of creativity and security in the numismatic market.