Auxetic metamaterials, or materials with a negative Poisson’s ratio, are characterized by a counterintuitive behaviour associated with advantageous macroscopic properties such as high shear stiffness and greater resistance to localised indentation. Despite extensive research into geometry-induced auxetic topologies, most materials are still developed through a reverse-engineering workflow, which derives mechanical properties from numerical and experimental testing of auxetic structures. Furthermore, the transposition of these auxetic geometric structures to additive manufacturing via material extrusion introduces additional constraints related to the characteristics of the printing equipment, the available materials, and the deposition technology used. This work presents a design-to-manufacturing strategy for controlled auxetic-isotropic materials via material-extrusion additive manufacturing, based on a fully discrete heuristic molecular model, in which a unit cell governs the macroscopic mechanical response. The approach makes use of a numerical code which implements the adopted theoretical model to simulate the macroscopic response of the designed material. Some selected materials have been produced using standard printers and polymer raw materials including auxetic-isotropic samples with different levels of auxeticity and distinct mechanical properties. Then, they have been tested experimentally, through uniaxial tensile tests combined with digital image correlation. The proposed workflow incorporates printing constraints into the parameterisation of unit cells, imposing limits on cell size and connection layout compatible with extrusion processes, while preserving the desired auxetic and isotropic behaviour. This approach reduces the discrepancy between numerical predictions and printed parts and improves repeatability for auxetic materials with predetermined mechanical performance.