The present invention provides a mandrel tool and method for more efficiently and consistently forming various shapes of material. The depression pattern may be a rumble strip for alerting drivers who drift off a driving lane, or may be for other uses. The diode die is flipped so that it emits light through the face of the layer. The substantially laminar air flow assists in maintaining the air surrounding the die at a substantially constant temperature. A method for generating electrical energy is also disclosed. Also provided is a method for regenerating a digital signal from a frequency-modulated signal.