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This article presents a new type of bi-material coin with a polymer centre and a metal ring. The polymer-metal coin is fabricated by combination of coin minting and joining by forming in a single die stroke. The design of the coin is based on an analytical model built upon plasticity theory and plastic instability of circular plates under uniform radial edge compression. The analytical model and the bi-material coin concept are supported and validated by means of finite element modelling and experimentation. Destructive tests for pushing the polymer centre out of the metal ring demonstrate the effectiveness of the mechanical joint resulting from the interface contact pressure between the polymer and the metal. The new bi-material coin was developed to obtain new aesthetic effects for the collection market, and its polymer core can additionally be used for other applications such as the incorporation of advanced security features in high-denomination coins.

Additive manufacturing is proposed as a novel alternative to coin blank’s production routes based on rolling, blanking and edge rimming. The presentation draws from laser powder bed fusion of cylinders, slicing into individual coin blanks by electro discharge machining and surface preparation by polishing, to coin minting in a laboratory press-tool system. Special emphasis is given to material deposition and coin minting due to the originality of producing coin blanks with complex intricate contoured holes and to the necessity of subjecting the additive manufactured coin blanks to extreme compressive stresses that are typical of coin minting. Numerical and experimental results confirm the excellent performance of the additive manufactured coin blanks. The new design layouts included in the additive manufactured coin blanks open the way to produce high value-added singular collector coins, which are disruptively different from those available in the market nowadays.