Explanations

hi Phil,

Ok, great, I guess you work on models with surfaces that are of organic or let's just say non-analytic shape. That's a pretty coarse accuracy you have there I'd say, even in millimeters.  Too high or too low accuracy (depends on how you look at it) usually leads to a lot of trouble with these compound surfaces when the data have to be used in different CAD/CAM/CAE system afterwards. Think of a simple surface, like a cylinder, cone or even a sphere, analytic shapes like these can be converted to other CADs easily cause the other CAD can figure out the topology of the surface even when the accuracy is bad. Not so often with spherical shapes, but cylindrical and conical shapes transfer really well. The real trouble comes with models that have multiple supposedly merged non-analytic surfaces, in cases like these the resulting import to another CAD system happens to be with alot of gaps or even bad surfaces that need to be completely replaced. Such models require alot of effort to be fixed and solidified, effort which brings in no additional value. That's why setting up accuracy to this high number is usually not recommended.