Agile and flexible manufacturing systems make it mandatory that control programs have features such as agility, flexibility and reusability to meet fastchanging customer demands. Visual validation of control logics is one of the most sought-after ways to make the control logic more feasible for rapid product prototyping, concurrent engineering and flexible and agile manufacturing. This paper presents the development of virtual simulator to validate control programs (PLC) visually. For simplification, virtual cell is separated into generic model that resembles the operations and events of real cell and graphic model - a visualization module - which gives easy understanding of dynamic behavior of cell. The generic model is formalized using timed Finite State Automata. ROBOWORKS and IGRIP are used for graphic model. We developed tools for easy integration of proposed simulators with 3D graphic simulators and soft PLCs. We applied our system to real PLC applications and found that PLC programs can be easily validated by this system.