Nowadays faceted reflector design has become popular in automotive illumination systems. The advantage of a compound surface enables it to achieve the required hot spot intensity by directing more than 60% of the generated light towards the road, thereby largely illuminate the area through the aperture. The research is oriented to fabricating the mold insert on ultra-precision raster milling (Freeform 705G). In this paper, the tool path generation method for automotive headlamp reflectors is studied, and a practical gouging detection and avoidance algorithm is proposed. The surface roughness and form accuracy (peak-to-valley height) are then calculated theoretically using mathematical formulae. Through the tool path generation of a small but representative surface patch with a gap, a possible way is finally found to generate the tool path for such a class of freeform surface with special equipment.