COMIX (Configuring Mixing-Machines) is a knowledge-based system, which was designed to assist members of the distribution department in the configuration of mixing-machines. It's possible to configure a mixing- machine with COMIX with regard to aspects of process-engineering and mechanics or in respect of mechanics only. In the latter case, the user needs to know, what kind of mixing-machine he wants. The knowledge about physical objects, like the components of the mixing-machine, is represented in hierarchies of objects. On the one hand the mixing- machine with it's components takes place in a part-of hierarchy, on the other hand the machine and it's components are represented in different is-a-hierarchies. The knowledge about the process of configuration contains laws of mechanics and process-engineering, as well as industry- standards and heuristics. This knowledge is associated with the frames and instances by functions, relations or rule-sets, which are activated by methods of the objects. The process of configuration is a stepwise refinement of the structural model, until all values of parameters are defined. The process is guided by knowledge about causal dependencies. Alike constraint-propagation, the knowledge about causal dependencies is used, to find the next possible step in the configuration-process, i.e. which parameters can be determined. If there is a re-determination of a parameter with a different value, all values of parameters, which depend on the old parameter value, are retracted, alike a truth maintenance system. The first phase of developing the system is finished and the system will go under a (beta) -test at the company soon.