Geometric Accuracy Example(Cont’d)
Since CAD-X used a .003mm tolerance criteria for determining if a vertex in on an edge curve, a sphere of radius .003mm centered at A will contain “end segments” of e1, e4, and e5 as in Figure 3. Thus, A is on e1, e4, and e5 in CAD-X.
A STEP file is created containing the geometry and topology structures to define the solid. The STEP file is translated into CAD-Y which uses .001mm for determining vertex/edge curve relations. Now, a sphere centered at A of radius .001mm in CAD-Y does not contain points on e1, e4, or e5. Thus, CAD-Y indicates vertex A does not lie on any edge curves and the solid is invalid.