Method of making an air bag cover

A method of making an air bag cover for an inflatable air bag system, the air bag cover having front and back surfaces and having a tear seam visually imperceptible from the front surface, the method comprising the steps of:

• injecting molten thermoplastic into a mold having first and second mold halves defining a mold cavity corresponding to a shape of the air bag cover;
• moving an insert from a retracted position to an extended position within the mold cavity after the step of injecting but before the molten thermoplastic completely solidifies, wherein the insert has a tip portion having a predetermined width defining the tear seam and an elongated portion having a length substantially greater than the predetermined width, and wherein in the extended position the insert extends from within one of the first and second mold halves to within approximately 0.2 to 0.4 millimeters of the other one of the first and second mold halves so as to displace the thermoplastic along a substantially continuous line defining the tear seam;
• permitting the resulting air bag cover to cool to a temperature beneath the softening point of the plastic with the insert in its extended position;
• and
• removing the completed air bag cover from the mold.