A typical methodology for product architecture design of complex products using Design Structure Matrix (DSM) uses a “bottom-up” approach where an algorithm suggests the ideal cluster of components. In the current research, we use a manual “top-down” approach to generate a modular product architecture for medium complexity product. We used a typical computational tool called IGTA for the “bottom-up” approach but found that the algorithm does not produce results which are practically applicable. A manual approach based on critical observation of the functional diagram of the product, product interactions, and verification of the modules using a Design Structure Matrix is more suitable. The paper compares the results of both approaches for the same product architecture considering a case study of a moving gantry based double-actuated Computer Numerical Control (CNC) milling machine. It is reported that manual “top-down” approaches are more suitable for medium complexity products than algorithmic bottom-up approaches.