In this paper, a new method for offline programming part assembly operations with tight fittings is presented. More specifically, an assembly process trajectory generator with self programming capabilities is developed where the user needs to provide only very sparse and intuitive input. The presented system is added to the existing skill based robot software package VEROSIM. In VEROSIM, the trajectory generator is applied to an industrial test platform for assembling insulin injection devices at the Danish pharmaceutical company Novo Nordisk, where it is shown that the trajectories as expected are executable. Hence, the method is a strong alternative to online approaches such as programming by demonstration.