AbstractThis study presents three thermal 3D models for bobbin tool Friction Stir Welding (FSW) implemented in Comsol and Matlab. The models use Thermal Pseudo Mechanical (TPM) heat sources and include tool rotation, an analytic shear layer model and ambient heat sinks like the machine and surrounding air. A new transient moving geometry approach has been implemented. It includes the full tool motion along the weld line, while the other two models use fixed geometry with and without moving heat source.The computational effort is small for all three models. The steady state model can be solved in approximately 5 minutes on a state of the art workstation. Experiments on the FlexiStir experimental welding unit have been carried out to validate the models’ outputs. The predictions of all models are in excellent agreement with each other and the experiment.