The direction of travel and speed will effect the heat of the weld. If you use the "drag" technique with the gun dragging away from the weld, it will be "cooler". If you are using the "push" technique with the gun pushing into the weld it will produce a "hotter" weld. So, if you were to start on the left side of a seam and with the gun leaning to the right at 45 degrees welding from left to right, this would be "dragging". If you were to start on the right side of the seam with the gun leaning to the right as before and welding left, to the left side of the panel, that would be "pushing" the weld. I find that when welding sheet metal if I have a problem with burning through, changing to the pull technique will help most of the time.
