A method of manufacturing an automotive instrument panel for eliminating distortion in an area of vibration welded air bags comprises: providing a weld fixture including at least one pre-stressor protrusion; placing the at least one pre-stressor protrusion against an instrument panel; generating a force to press the weld fixture against the instrument panel to create compression in a first surface of the instrument panel where the weld fixture contacts the instrument panel and to create tension in a second surface of the instrument panel, the second surface opposite to the first surface; and vibration welding an air bag chute to the instrument panel such that a weld bar of the air bag chute is welded to the second surface of the instrument panel.