Project scheduling is an essential operational optimization task when precedence relations and the access to limited resources are problem inherent. In this work, a real-world production and logistics planning process of a steel manufacturer is modeled. Production activities have to be scheduled in a way such that real-world restrictions and objectives are considered. Therefore, the basis for this model is the well-known resource constrained project scheduling problem. However, for the consideration of all necessary real-world requirements, a new problem model with various extensions concerning project flexibility and the production of multiple lots is developed. Within a first step, the developed model is solved exactly for small instances by using IBM ILOG CPLEX. As a second step, for larger (real-world) instances which are not solvable within a reasonable time for real-world applications, a Constraint Programming model is developed and applied successfully for large real-world problem instances.