Computer aided design and manufacture of approximate rules surfaces

Techniques are developed for determining ruled surface that represent the best possible approximation to a given surface. A combined theoretical and experimental investigation of this technique applied to the design and manufacture of long-lead extruder screws is reported. The results show that it is possible, in some cases, to produce accurate surface geometries by treating the screw as an approximate ruled warped surface with a linear variation in the orientation of the generatrix as it moves along the directrices. It is believed that the proposed approach can be extended to the design and manufacture of other curved surfaces