Modelling and simulation of formation resistance to excavation has become important in evaluating performance and designing efficient earthmoving equipment. Previous attempts at extending the passive earth theory to excavator dippers have only covered snap-shot estimates for a right-angled framed assembly. This work applies cable shovel kinematics and dynamics to estimate the dynamic cutting depth and angle, making it possible to apply the passive earth theory to model dipper dynamic formation resistance. Geometric simulation is applied to model the resistance due to the material payload. The models are then applied to simulate the formation resistance for a 17-yd³ dipper. The results show that the payload resistance (141-kN) is far more significant than the cutting resistance (between 16-kN and 31-kN).