Abstract: Computer-aided method and apparatus for defining surfaces of a three-dimensional object on the basis of a three-dimensional wire-frame model, wherein a plurality of pairs of edges selected from edges which constitute the three-dimensional wire-frame model are sequentially pointed, each pointed pair consisting of two edges lying on the same plane, and a group of candidate edges is determined, the group consisting of the currently pointed pair of edges and at least one edge lying on the same plane as the edges of the currently pointed pair, so that those candidate edges of the determined group which cooperate to define a closed loop are determined as a set of closed-loop defining edges, and a surface of the three-dimensional object is defined on the basis of the set of closed-loop defining edges.

Abstract: This invention aims to shorten cycle time by allowing a robot to be operated with speed capability regardless of the shape of moldings. An extrusion molding apparatus has an extrusion molding machine which delivers an extrusion material which becomes a frame-shaped molding through a nozzle fore end, and a robot which holds a workpiece on which the molding is formed and whose working speed is set so as to make travel speed of workpiece rectilinear portions with respect to the nozzle fore end higher than travel speed of workpiece corner portions with respect to the nozzle fore end. Thus, changes in workpiece travel speed with respect to the nozzle fore end are allowed, and robot working speed is not restricted by the shape of moldings.