In this paper, a lumped parameter model of a robotic fibre placement system consisting of a Motoman SK-120 robot, a force/torque sensor, a pneumatic actuator and a stiff workpiece holder is developed and experimentally verified for the purpose of predicting and characterising the dynamic behaviour of the fibre placement system. Special attention has been given to the dynamics of the actuator which is represented as a mass confined to move between two non-linear springs and dampers. The overall model containing manipulator, force sensor, pneumatic actuator and the workpiece holder dynamics is of the tenth order. Step response experiments were conducted to verify the model and to determine the approximate values of the parameters i%n the mathematical model. The results prove that the established model isccurate enough to explain the dynamic behaviour of the fibre placement system and it can be employed to quantify the influence of the dynamics of the pneumatic actuator on the constant force-based fibre placement. The well-known fact that the dynamics of the pneumatic actuator varies with the piston position has also been experimentally demonstrated.