Force-directed scheduling is a technique which schedules operations under time constraints in order to achieve schedules with a minimum number of resources. The worst case time complexity of the algorithm is cubic in the number of operations. This is due to the computation of the changes in the distribution functions needed for the force calculations. An incremental way to compute the changes in the distribution functions, based on gradual time-frame reduction, is presented. This reduces the time complexity of the algorithm to quadratic in the number of operations, without any loss in effectiveness or generality of the algorithm. Implementations show a substantial CPU-time reduction of force-directed scheduling, which is illustrated by means of some industrially relevant examples.< >