Design for Wire-Arc Additive Manufacturing : A feasibility study of WAAM-based serial production for load-bearing automotive components

Sammanfattning

Additive manufacturing (AM) offers significant potential for lightweighting and part consolidation across multiple industries compared to traditional manufacturing methods. However, most metal AM technologies are constrained by limited build volumes and relatively high costs, restricting their applicability for large, serially produced components. Wire-arcadditive manufacturing (WAAM) addresses these limitations through its high deposition rate, large build volume capability, and low material cost. Regardless, the feasibility of WAAM-based serial production for automotive components remains insufficiently explored, particularly in segments with moderate to high production volumes. This thesis evaluates the feasibility of designing a steering gear bracket (SGB) for a Scania bus using WAAM, selected as a representative case due to the moderate production volumes typical of bus manufacturing. A case study approach was employed, integrating design for additive manufacturing (DfAM), topology optimization, structural analysis, and supplier-based cost estimations to develop and assess a developed concept against a set of design criteria, as well as answering the following research questions: Research question 1: How can a load-bearing automotive part be designed for WAAM-based serial production? Research question 2: How does part feasibility differ when designing for WAAM compared to traditional manufacturing? To address these questions, an abductive research approach was employed, combining insight from literature, prior research and semi-structured interviews with metal AM suppliers. In addition, a single case study was conducted, following the initial stages of the product development process by Ulrich & Eppinger (2012). Based on the findings from the interviews, design for WAAM (DfWAAM) guidelines were established, and a hybrid manufacturing concept was selected for the SGB, by printing ER70S-6 carbon steel wire directly onto a S355 sheet metal base plate. A DfAM optimization process was developed and used for structured iteration, including TO, structural analysis and CAD-modeling for the creation of the initial 3D-printed SGB (3DPSGB) design concept. The 3DPSGB was then validated by a simulation engineer for strength and a WAAM supplier for manufacturability, who also provided a quotation of estimated costs for prototyping and serial production. The resulting design estimates significant performance improvements over the current solution, based on traditional sheet metal manufacturing, including weight reduction of approximately 30-40%, increased structural stiffness, and reduction of part count and fasteners. According to the available literature, the material performance of WAAM-produced carbon steel parts can be on par with traditional manufacturing methods. However, uncertainties regarding fatigue performance persist due to limited public availability of standards. The estimated manufacturing cost per unit of the WAAM component is higher than the traditional alternative. However, lifecycle factors such as reduced assembly effort, shorter lead times, shorter time-to-market, increased flexibility and improved functional performance demonstrate potential advantages of WAAM compared to traditional methods on a system level. The study concludes that WAAM could be a technically viable solution for load-bearing automotive components but requires established processes for validation and quality assurance to be considered anacceptable alternative manufacturing method. Its feasibility depends on application specific trade-offs and requires lifecycle-based cost evaluation to be properly assessed.