The digital transformation of manufacturing introduces new security challenges as interconnected cyber-physical systems (CPS) and the Industrial Internet of Things (IIoT) expand the attack surface. This research presents FAST (Functions, Assets, Security Threats, and Treatments), a structured and adaptable security framework for automated manufacturing. FAST prioritises mitigations based on operational dependencies, balancing industrial functionality with security resilience. Developed through a design science methodology, it integrates literature review, regulatory analysis, simulation, and pilot implementations. Preliminary results show that FAST improves risk classification by linking threats to functional impact, bridging compliance requirements with practical application. It contributes a scalable, function-driven model to guide security decision-making in manufacturing contexts.