A device for positioning a workpiece for machining has a bench, which is mounted movably at a base and to which the workpiece can be fastened. A user may operate a plurality of selection switches to select the preset lighting modes and the lighting control programs from the memories. Next, arrange the series of low density strips to form a core panel and thread a continuous fibrous reinforcement sheet through the low density strips such that the fibrous reinforcement sheet is disposed between adjacent strips and adjacent to the major or minor faces of the low density strips.