## 4 Discussion  
In today's globally competitive market, the development of more challenging and complex products is pushing designers and engineers to shorten the design phase and to close the gap between design and manufacturing departments. To do so, computer-aided engineering and design tools are more and more important as they allow us to anticipate post-design concerns and manufacturing issues. Manufacturing knowledge is one of the most important assets of a company and the way to collect it and make it available for designers and engineers is a key topic. Thus, the proposed rule-based system for the design of welded structure aims to capture, retrieve and suggest design rules according to the given context of the welded assembly. The DFW method and tool proposition allows making accessible manufacturability knowledge within the design phase (3D modeling). The proposed approach enables the identification of design issues, analysis of the DFW rules \begin{table}
\begin{tabular}{c c} \hline \hline
**Component Model** & **Features** \\ \hline \hline  & ID: W003\_mod \\  & Type of feature: _Weld beam 03\_HE 180 A vs. Plate 3\_mod_ \\  & Coordinates of the welded parts involved in feature in reference with origin: \\  & \(\bullet\) & HE 180 coordinates: [0,0,0]; \\  & \(\bullet\) & Plates coordinates: [1124,00,0]; [1374,0]; [2299,0]; [2419,0]; [3329,0]; [3459,0] \\  & Coordinates of the welding in reference with origin (only for first plate): \\  & Welding: [1124,0,0]; \\  & Welding 2: [1133,5;0]; \\  & Welding 3: [1124,76;90]; \\  & Welding 4: [1124,\(-\)76;90]; \\  & Welding 5: [1133,5;\(-\)76;90]; \\  & Welding 6: [1133,5;\(-\)76;90]; \\  & Properties of the feature: \\  & Welding thickness: 4 mm \\  & Welding length (total): 6 \(\times\) 521,25 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Modified welding features (highlighted in orange) extracted by the 3D CAD model of the lateral frame. propagation in the CAD design environment, and distribution of \"know-how\" to designers in the context of their specific design activity (explicit knowledge). This activity is on the critical path of the engineering design process; thus, the developed method is supporting knowledge-intensive and prone to error engineering tasks, extending the current CAD capabilities. The adoption of the proposed approach highlights several outcomes. The first is related to the effort and time required for developing welded compliant products. With this approach, design review loops may be reduced, thus improving the product time-to-market by diminishing knowledge-intensive engineering practices. The advantages include the integration of concurrent engineering concepts in welding design and the possibility to improve the overall efficiency of design and manufacturing practices. The method developed in this study shows great potential for real-world reduction of product cost and lead time through the implementation of concurrent engineering and design for welding concepts in the early design stages in a complex welding environment. Another interesting outcome concerns the possibility to share manufacturing knowledge across members of a design team and reuse it each time it needs. Two case studies are proposed within this work to demonstrate the benefit introduced by the application of the proposed approach to real products made of few components. The two examples show how concerns can be detected by the adoption of the proposed approach and how design review steps can be skipped. However, for the time being, few limitations are observed. The first limitation deals with the fact that the method was applied to the welded assembly made of few components and simple geometries. Indeed, the feature recognition system works well for simple shapes and may fail for complex shapes (i.e., new feature types and additional properties to consider). This is strictly related to the new DFW rules that can be defined that may require the recognition of different feature types or interactions between features.