
The generation of ink droplets in piezoelectric drop-on-demand printheads is governed by a tightly coupled multiphysics process involving electromechanical actuation, fluid dynamics and free-surface interactions. Conventional simulation approaches often treat these subsystems separately, limiting predictive fidelity for design optimization. In this work, we present a fully coupled three-dimensional fluid structure interaction (FSI) framework that integrates computational structural mechanics (CSM) that incorporates the piezoelectric effect with compressible multiphase computational fluid dynamics (CFD). The framework employs a partitioned solution strategy with strong interface coupling, enabling accurate capture of the dynamic interplay between actuator deformation and droplet ejection. The method is applied to recirculating inkjet printhead designs, utilizing volume-of-fluid (VOF) based free-surface modelling to resolve ink-air interactions and validate performance against benchmark structural and fluidic cases of the Seiko RC1536 printhead. Results demonstrate accurate prediction of droplet formation dynamics, capturing the influence of actuation waveforms, chamber geometry and surface tension effects. By combining high-fidelity electromechanical and fluidic models, this work advances predictive capabilities for inkjet printhead design and operation. The methodology lays the foundation for optimizing printhead architectures, tailoring actuation strategies and accelerating innovation in industrial and functional inkjet applications.