(Help Needed) Best-Fit Coordinate System from Surface

[[Ja...]]

Hello, 

I need help creating a best-fit of a surface to be used as a datum system for a profile callout. I am able to check a profile to itself and allow the surface to best fit. I am looking for a way to generate a datum system or coordinate system based off of the surface being best fit against itself in all six degrees of freedom. Are there any recommended methods for accomplishing this?

[[Ch...]]

Hello,

you can use surface in datum system callouts. For this purpose simply use one click-purpose inside the create datum system dialog and choose the needed surface on the CAD. The software will creating the needed nominal elements (a Patch Compound) and the needed actual element (a surface) and the measuring principle linking both together automatically:

Afterwards you have to specify a coordinate system inside the expert parameter section.

This will compute a transformation (according to chebyshev mathematics as told in the ISO standards) between the nominal and actual surface. Of course to get the heuristic running actual mesh and nominal cad have to be aligned to each other in a way that the maximum distance is not so big. The given coordinate system determine the origin of the datum system because the software can not extract automatically a plane, line and point from an arbitary surface. Please have an look into the online help of the datum system dialog. You will find a whole explanation what we are doing under the point "Coordinate system".

After construction this datum system can used as any other datum system inside the profile tolerance dialog.

Hope this helps

Christoph Schult

 

Edited November 7, 2023