The quest for smarter manufacturing is motivating the need for operational decisions to be made in real-Time to adapt to uncertainties. Prevailing decision-making techniques typically consider each manufacturing function in isolation to reduce the complexity, which in turn leads to sequential decision-making where prior decisions become constraints for subsequent decisions. This paper proposes a unified approach for simultaneously controlling the timing of production events, the timing of maintenance events, and physical processing capacity. Moreover, the control algorithms can be fully distributed and exploit physics-based models for processes and remaininguseful-life of machinery components in real-Time decisionmaking. Fused Filament Fabrication (FFF) additive manufacturing process is used as an example in the paper to demonstrate the unified approach. Dynamics of the resulting unified control system is modeled using non-linear discontinuous differential equations. Computer simulations are used to illustrate dynamic interactions between production and maintenance functions. Benchmarking of the unified control approach for randomly generated datasets show superior performance compared to other commonly used scheduling heuristics by about 48%.