Patent ID: 7238312

Claim:
A method of forming a plurality of apertures in a rigid panel made from a meltable plastic material having a cellular structure with a plurality of cells filled at least in part with air, said panel having a length, a width and a depth, said apertures being formed through said depth, and said depth defining a panel body between opposed first and second surfaces, said method comprising: moving said panel with said first and second surfaces oriented in a first orientation towards a plurality of heating elements in a first direction that is generally orthogonal to said first orientation, each of said heating elements having an elongated body portion formed in a generally U-shape with a rounded heating tip and being oriented about a longitudinal axis oriented in a second orientation that is generally parallel to said first direction, said heating elements each providing a thermal field around said body portion and around said tip, said heating elements not moving in relation to the environment, said panel moving toward and away from said heating elements without contacting said heating elements so that said first surface of said panel is heated by said plurality of heating elements to melt said plastic material at a plurality of locations without igniting the plastic material.