Abstract: In the frame of concurrent engineering the design of the parts, the production planning, even the production system must be made quite simultaneously. So the design and development cycle is reduced and the manufacturing constraints are taken into account as soon as possible. The need of a short reconfiguration time leads to the concept of Reconfigurable Manufacturing Systems (RMS): using those systems, the manufacturer only uses elementary cells (such as milling cells, supports, tooling, etc ...) which can be easily and quickly replaced as soon as the demand changes. Besides, this higher reconfiguration speed can be improved by using Virtual Manufacturing: the manufacturer can design, draw and simulate the line and its evolution in terms of flows and costs. It is a powerful help to evaluate the best performance if several configurations are possible before the system is built, hence a gain of time. In the frame of virtual manufacturing of reconfigurable manufacturing systems, this paper will deal with creating and simulating machining systems based of an industrial part (a pump block in our case) and using a computer aided engineering software (DELMIA- Dassault Systemes).