Experimental investigation of the weld quality and strength during friction stir spot welding of PETG workpieces

Fabrication of functional parts from polymers is currently becoming more important due to the new possibilities offered by additive manufacturing processes. These advanced methods have enabled the creation of parts with more complex geometries and specialized features without requiring specialized tooling or multiple operations. However, the treatment of polymer parts is different from that of traditional engineering materials so thorough investigation of the suitable methods is required. In particular, in the case of joining processes, methods such as friction stir spot welding (FSSW) can be successfully used for polymer materials under appropriate conditions. The current work is focusing on an experimental study of two crucial parameters of FSSW process, namely plunge depth and dwell time and their effect on weld quality and strength. Experiments were carried out for Fused Filament Fabrication (FFF) printed polyethylene terephthalate glycol (PETG) thermoplastic polymer workpieces under different combinations of the process parameters and the welded workpieces are evaluated using appropriate testing methods. Afterwards, the results are analyzed and the effect of each parameter on the process outcome is identified, as well as the optimum values for obtaining higher quality of the weld and highest possible strength.