The manufacturing domain can be characterized by the concepts of product, process and resource. The coordination of humans, machines and materials is needed to attain a desired product by using knowledge, time, money and energy optimally. Business processes define such coordination. Business Process Model and Notation (BPMN) is an industry standard for modeling business processes. This standard is not being applied to the manufacturing domain so far. In this paper, we propose BPMN extensions to support process modeling in the manufacturing domain, especially the modeling of production processes. We motivate and justify our proposed extensions by an exemplary assembly process.