Cutting force modelling in green machining of polymer-based metallic feedstock

As a binder-based material composed of micro metallic particles and polymeric binder, the polymer-based metallic feedstock is largely adopted in Powder Metallurgy (PM) and emerging binder-based Additive Manufacturing (AM) to form green parts that then require sintering. Given the improved machinability of soft unsintered parts, green machining is beneficial with respect to machining hard sintered parts for reducing tool wear, improving productivity and energy consumption whilst enabling the creation of micro features and increased surface quality. This paper presents an innovative analytical orthogonal cutting force model of polymer-based steel feedstock that offers a physical deep understanding of the tool-material interaction and predicts the generated forces starting from the tool shape and the workpiece material characteristics. This paper fills a gap in the scientific literature regarding the analytical cutting force modelling of atomised metallic feedstock. The model includes the micro effects caused by the tool tip radius and computes the average forces (magnitude and direction) starting from the viscous interactions between the tool and the feedstock material. Cutting experiments, performed on different 316 L steel feedstocks, validate the model, and test its robustness versus the powder granulometry, the binder loading and the tool geometry. The presented findings open the way to further studies on hybrid AM techniques.