Process for manufacturing a mold using three-dimensional computer modelling

Claim 1

A process for manufacturing a mold from the shapes of a piece which it is desired to obtain by molding, by computer modelling of the fixed and mobile parts of a mold using a computer assisted design software for visualizing the piece in two and three dimensions, comprising at least the following steps: modelling and graphic representation of the piece in three dimensions, determination, from the shapes of the piece and/or of its model, of a zero joint plane which forms the main separation plane of the two parts of the mold, modelling and possible graphic representation of the negative of the piece, in three dimensions, within a cubic volume which may have the dimensions of the block of material from which the mold is formed, insertion of the model of the piece in the model of its negative, search for the unstrippable zones by simulating a relative movement between the model of the piece and the two parts of the model of its negative defined by the reference plane, along an axis perpendicular to said plane, and by determining the contact surfaces between the piece and said parts of the model of the negative, visualization of the contact surfaces by a graphic representation in at least one given plane, the systematic graphic representation, in planes perpendicular to the reference plane, of the sections of the model of the negative passing through the unstrippable zones and determination of the offset joint planes in successive slices of the model of the negative including said zones and of width equal to those of said zones, modelling of the mobile and fixed parts of the mold as a function of the established joint planes, manufacture of a mold whose fixed and mobile parts comprise joint planes and impressions according to the previously established models.