Several significant process and product developments have enabled single-sided projection welding of 6XXX-T4 automotive aluminum sheet (patent pending). Hem welding was performed on geometries typically encountered on door and hood applications using an enhanced version of the HY-PAK® technology. This process is unique because both electrodes approach from the same side of the component, enabling no visible weld mark on the opposing surface. An experimental design was developed to understand the influence of the major process variables (weld current, weld force, projection height) on the tensile shear and button peel performance. The DOE was performed on single-sided projection welds consisting of 0.8mm 6111-T4 aluminum sheet. The results indicate a range of acceptable process parameters that produced tensile shear strengths on the order of the Aluminum Association's T-10 recommended values for resistance welds of that gauge.