The thesis has been carried out in cooperation with Master Flow AB, Västervik owned by the EWEBE Group. The company produces and sells hot runner systems that are tailor made for the customers.The problem that MasterFlow AB has encountered is in the construction of complex hot runner systems in SolidWorks. With several different lengths, fronts and endcaps that builds the nozzles of the hot runner systems, is affecting the problems for MasterFlow AB. The purpose of this work is to automate the design of hot runner systems so it does not overload the CAD-system SolidWorks.To gain an understanding of the problem, there have been several studies and observations at the company, where the focus has been on how the work is done with the design of hot runner systems. By using help from the corporate management, enough information has been collected to find a solution to these problems.The implementation of design automation has been based on a flowchart that was created.