## 3 Case Studies and Results
### Case Study 1: Jack Adapter of Heavy-Duty Prop  
This first case study refers to a product (heavy-duty prop) composed of several welded sub-assemblies (Figure 6). Heavy-duty props used in construction may consist of a girder beam body having a square section formed by four tubes at the corners held together by welded braces on the four sides. Usually, the total prop length can be changed by adding or eliminating extensions. At either end, the prop presents an adapter that concentrates the axial force on the four corner tubes onto another device, which can be a base plate, an adjustment jack, a hydraulic jack, etc. In this case study, a jack adapter is considered, i.e., an adapter capable of receiving the four corner columns and transmitting their axial load to a single jack, or threaded tube, acting on the adapter center. This solution is achieved by designing the adapter as a hollow box comprising two main faces, top and bottom, four tubes in the corner, apt for receiving the girder corner columns, and wall plates and strengthening gussets for holding them together and conferring to it the desired strength. Needs related mainly to on-site handling and costs, require the adapter to be as light as possible; hence, its design is based on thin plates and critical welding. In this study, only one welded sub-assembly has been analyzed in detail, with the aim to provide a global overview of the application of the methodology. The analyzed sub-assembly, called jack adapter, is the welded assembly at the base or at the top of the heavy-duty prop (see (Figure 6; framed in red). This item presents typical issues that can be highlighted in the early design phase of the product development process. The jack adapter is composed of 11 components made with the same material (carbon steel low grade). Some of them are commercial components (i.e., the center tube and the half sleeve), while others are machined with a laser cutting process. The CAD model and the bill of material of the jack adapter are presented in Figure 7. The welding process used to manufacture this assembly is the gas metal arc welding (GMAW) with manual operations. Starting with the feature recognition process, the following features were retrieved by the analysis of the welded product: (i) component features, (ii) geometric features, and (iii) welding features. The component features (Table 2) are related to the 11 parts which compose the assembly and only six parts are unique, as shown in Figure 7. Each component is made of the same material (carbon Steel S235 JR) with a similar weight (from 0,39 kg to 1,73 kg). For the sake of brevity, Table 3 only reports the geometric features of the component C002 (web plate) of the jack adapter, which are the ones connected to a non-validated rule. This component is a 4 mm thick sheet metal with a central fold of 65,65\({}^{\circ}\) (ID: G001). In the middle zone of the component, C002 is located a slot (ID: G002) (66 mm long, 7 mm wide, and 4 mm deep) needed for the subsequent welding with the component C005. Both features do not present specific PMI. Table 4 shows welding features of the assembly, which connect the components as follows:  
* W001: half sleeve with base plate and top cross plate;  
Figure 6: Heavy-duty prop product and application. Figure 7: CAD model of the first sub-assembly (jack adapter). * W002: web plate with base plate and top cross plate;
* W003: web plate with half sleeve;
* W004: web plate with center tube. The welds have different lengths and widths in the functions of connected components. Lengths vary from 135 mm to 263 mm, while welding widths vary from 3 mm to 4 mm according to the degree of mechanical strength required. By following the proposed approach, after reading the data related to the CAD feature recognition, an analysis of the features against the DFW guidelines was carried out. For the assembly analysis, only the set of DFW rules referring to arc welding technology calls, including the specific rule set of GMAW technology type was selected.