A bathtub system, including a tub with a bather access opening in one sidewall and a door mounted on that sidewall. In the same wiring layer as that of the wirings, a dummy pattern is formed so as to surround a formation region of the wirings and the diffused resistors. The method further includes angling the torch relative the planer surface of the work piece such that the torch is held at an angle of between about 1 and about 4 degrees from perpendicular with the planer surface to back burn a produced kerf such that a kerf edge is perpendicular relative the planer surface of the work piece.