Been having some problems welding up punched holes. Last weekend I was replacing the Kickpanels in side the cab and I used a punch tool to make the holes along the edge. When I weld the holes up, I never seem to get the panel to stick to the flange under it. I have the panel clamped tiht and have tried several different settings on the MIG welder. The holes look very good when I finish but when I release the clamp, the weld don't hold. What am I doing wrong?