Current industrial practice, in automotive, aerospace, and other manufacturing industries, involves the creation of a number of physical product models. During the product development phase, both the product and the process are verified on these PMU�s. HW checks though cause tremendous time delays. Moreover, a late HW verification very often leads to respectively late design changes, which are cost intensive. The objective of DMU-PS has been to develop the technology, which allows the designer to model and simulate assembly, disassembly, service and maintenance processes within a digital mock-up environment. Such a technology enables the designer to take into account process knowledge already identified during the very early conceptual stage of the design process and throughout downstream product development. The result includes IT tools based on a well-defined conceptual structure. This structure consists of the Process Library, the Resource Library, the Knowledge Module, the Simulation Features, and the Integrated Framework. The main innovative aspects of the project are: -Library structure. -Concept of Experience database - for re-use of old processes, for embedding knowledge and for reference material and documentation of past and present projects. -Process Library-for standardisation of industrial and company processes and for embedding knowledge. -All the libraries deal with reorganisation of different types of data used in the lifecycle of product and its production development, which will help the product and process designers to access, easily and quickly, the relevant data and always share the latest information. Using this concept, the three prototypes of a process simulation system, consisting of problem specific solutions and based on present CAD/CAM technologies, have been developed, tested and refined. This means that the software available in the market today was influenced by the specifications from this project, utilising enhanced or new software. The benefits of that project are two-fold, depending on the view of the end users and of the IT vendors: The application of the results within user companies, like automotive and aerospace industries, as well as other industries, will achieve dramatic changes in the processes and the benefits from the resulting changes will be: -Dramatic reduction of the development time. -Product quality improvement. -Reduction of redesign costs. The economic benefits will accumulate within the next four to five years to: -Reduction of physical mock-ups-10%. -Reduction of costs due to late design changes-10%. -Reduction of scrapping volume-15%. -Reduction of resources and service tools not necessary-20%. On the other hand, the IT vendors gained from the user input of new ideas to enhance their existing products or develop new ones. Some parts of the evaluated prototype software are already available in the market. That means that the positions of those companies were already strengthened and will continue to be in the future.