Abstract: A machine or apparatus simultaneously manufacutures a core-reinforced welded panel and assembles core strips in operative relationship with the face sheets of said panel. The machine includes a first welding head which is insertable in the space between the face sheets and has welding electrode means thereupon which internally weld securement portions of the core strips to adjacent inner surfaces of face sheets of any desired thickness. The welding head includes movable jaws mounting the welding electrodes to move the welding electrodes into engagement with the securement portions of the core strips and the welding electrodes are resilient to permit them to move independently of the movable jaws and each electrode provides an electrically isolated weld. A second welding head is provided which is capable of securing web portions of the core strips by weldments to one another after the weldment of the core strips at their securement portions has been accomplished by the first welding head.