Method of correcting die model data
A die is produced based on die model data. The produced die is corrected. The corrected die is three-dimensionally measured by a measuring tool to produce measured three-dimensional die data. A polygonal surface represented by the measured three-dimensional die data and a model surface represented by the die model data are compared with each other. The polygonal surface is brought into proximity to the model surface, and the absolute values of the distances between a plurality of pairs of measuring points on the polygonal surface and corresponding points on the model surface are calculated. The die model data are corrected based on the absolute values of the distances.
1. A method of correcting die model data, comprising:
a first step of producing die model data based on a formed article model with a computer;
a second step of producing a die based on said die model data;
a third step of correcting said die;
a fourth step of measuring the corrected die to produce measured three-dimensional die data; and
a fifth step of comparing said measured three-dimensional die data with said die model data with a computer, bringing a first surface represented by said measured three-dimensional die data into proximity to a second surface represented by said die model data, calculating absolute values of distances between a plurality of pairs of measuring points on said first surface and corresponding points on said second surface, and correcting said die model data based on the absolute values of the distances.
2. A method according to claim 1 , wherein said fifth step comprises:
a first auxiliary step of calculating points of intersection between said die model data and average normal vectors to a plurality of surfaces having the measuring points of said measured three-dimensional die data;
a second auxiliary step of dividing straight lines extending from said measuring points to said points of intersection at a predetermined ratio, thereby establishing dividing points; and
a third auxiliary step of calculating points of intersection between said die model data and normal vectors from said dividing points to said die model data;
wherein said second auxiliary step and said third auxiliary step are carried out at least once, thereby defining the measuring points of said measured three-dimensional die data and the corresponding points of said die model data.
3. A method according to claim 2 , wherein said second auxiliary step comprises establishing polygons based on said dividing points, determining point representative vectors based on normal vectors to the polygons which are present in a predetermined range from said dividing points, and moving corresponding dividing points based on said point representative vectors.
4. A method according to claim 3 , wherein said point representative vectors are determined by weighting, depending on distances, the normal vectors to the polygons which are present in the predetermined range from said dividing points and averaging the weighted normal vectors.
5. A method according to claim 2 , wherein said first surface is corrected into a smooth surface by interconnecting central points of surfaces of polygons provided by said measuring points.