## 1 Introduction
For design engineers with no practical welding experience, a decision support system that can provide a set of manufacturing data would be a very helpful tool, if the welding process could be contemplated from the early design stages. Thus, two main research questions arise from the analysis of the state-of-art. 1. How welding knowledge can be translated into explicit knowledge to assist product designers during the development of 3D models of welded structures/products? 2. What is the set of information available from the investigation of the 3D CAD model (i.e., type of feature to recognize, parameter to query) necessary to develop a CAD-integrated DFW system and tool? By acknowledging the current gap, the goal of this paper is to describe a method to formalize welding engineering knowledge (rule-based approach) that is used as a repository for the development of a CAD-integrated decision support system (software platform) for welding-compliant products. The software platform uses, as input, geometrical data retrieved by the feature analysis of the 3D CAD model (feature recognition approach) and technical aspects related to manufacturing welding operations (DFW rules) previously collected through the knowledge-based system. In this manner, it will be possible to close the gap between the design and production departments, through the creation of a knowledge-based system. The latter can translate the tacit knowledge used during the development of welded products or structures into explicit and reusable knowledge. The outcome of this system does not concern the possibility to predict the welding parameters and avoid mandatory tasks (i.e., the welding procedure qualification), but rather the possibility to deliver a consistent product design (geometrical feature) in relation to the welding process. It is worth noting that the design issues refer to the product geometrical data connected with the welding operations (i.e., the type of welding, the material to weld, the geometry and the thickness of the weld plates, the geometry of the bevel, the location of the weld beam, the dimensions for weld beam, the possibility to use intermittent versus continuous weld, and the accessibility for the weld gun and fixture equipment) and not the welding process itself (i.e., the settings of welding parameters, current and voltage, the consistency of joint design with approved standards, the levels of distortion in the base material, the selection of the wire/rod material and diameter, the number of passes, and the welding speed), which needs a qualification procedure to fulfill the code requirements. The novel contribution of this study consists in the definition of a methodological framework that can be adopted for the development of a CAD-integrated DFW tool. This paper is structured as follows. After this introduction that recalls other studies on this topic and its main limitations, Section 2 describes the overall methodology, including materials and methods used for its development. Section 3 illustrates a sample of case studies where the proposed method was applied, and Section 4 discusses results and main limitations observed by the application of this methodology. Conclusions and final remarks are reported in Section 5.