Adaptive welding for additive manufacturing due to dynamically oriented layer structure

• Applicants: Professorin Dr. Sigrid Brell-Cokcan; Professor Dr.-Ing. Uwe Reisgen
• Subject Area: Joining and Separation Technology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 455781630

Wire- and arc-based additive manufacturing (WAAM) is characterized by high production speeds and relatively low system costs and can be a key technology for resource-saving production chains. Here, arc welding processes are used to additively produce components by shape welding. One of the problems that WAAM processes are characterised by, is the high number of manual corrective interventions required during layer build-up. This is due to the high process dynamics combined with a relatively large molten pool. Varying thermal boundary conditions lead here to the fact that the applied welding beads solidify in different geometric characteristics despite constant welding parameters, whereby cumulative geometrical deviations arise with increasing layer build-up. On the one hand, these deviations lead to a poorer degree of material utilization due to the higher milling effort, on the other hand they require manual compensation by recreating the path planning of the printing process in order, to avoid collisions of the welding torch with the component. The aim of the project is to develop a manufacturing strategy for the WAAM process, which compensates geometrical deviations by dynamically oriented layer build-up and thus enables a fully autonomous process. The focus here is on two aspects to achieve the goal: on the one hand, the influence of gravity on the melt pool behaviour in combination with the thermal boundary conditions is to be taken into account in path planning. For this purpose, the equivalent contact surface is to be used to formulate an auxiliary variable that summarizes all thermal parameters relevant for geometric melt pool formation. On the other hand, suitable sensor technology should be used to detect geometric deviations of the structure to be manufactured and to enable a re-planning of the pressure paths on the basis of the determined geometric deviations. Within the scope of the project, a profound understanding of the thermal boundary conditions in the manufacturing process and their effects on geometrical errors is to be developed. It is expected that the project results will be transferable to other thermal additive manufacturing processes and will therefore have a broad field of interest. In particular, the dynamic layer structure represents a new aspect for additive manufacturing and can open up new research questions.

• DFG Programme: Research Grants